Dissertations / Theses: 'Silicon Based Nanostructure'

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Ruminski, Anne Marie. "Manipulation of surface chemistry and nanostructure in porous silicon-based chemical sensors." Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3373085.

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Thesis (Ph. D.)--University of California, San Diego, 2009.
Title from first page of PDF file (viewed October 22, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 194-210).

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Ozdemir, Serdar. "Formation, characterization and flow dynamics of nanostructure modified sensitive and selective gas sensors based on porous silicon." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39541.

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Nanopore covered microporous silicon interfaces have been formed via an electrochemical etch for gas sensor applications. Rapid reversible and sensitive gas sensors have been fabricated. Both top-down and bottom-up approaches are utilized in the process. A nano-pore coated micro-porous silicon surface is modified selectively for sub-ppm detection of NH3, PH3, NO, H2S, SO2. The selective depositions include electrolessly generated SnO2, CuxO, AuxO, NiO, and nanoparticles such as TiO2, MgO doped TiO2, Al2O3, and ZrO2. Flow dynamics are analyzed via numerical simulations and response data. A general coating selection method for chemical sensors is established via an extrapolation on the inverse of the Hard-Soft Acid-Base concept.

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Seo, Michael. "Plasma-assisted nanofabrication of vertical graphene- and silicon-based nanomaterials and their applications." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12285.

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Scarcity of physical resources, increasing concerns for safety and hazardous waste disposal which affects the environment drove the current nanoscience research to focus on developing low-cost, green and environmentally friendly method of obtaining nanomaterials. Yet, developing such smart and innovative processes is at premature stage. Over a few decades, many nanomaterials have been found and investigated. Amongst many nanomaterials, carbon and silicon nanomaterials attracted immense attention due to their abundance, low cost, unique and tunable properties which are promising for many applications. However, making nanostructure with uniformity and desirable properties is often difficult due to a lack of precise control which inherits from fabrication process. Furthermore, many techniques cannot satisfy green and environmentally friendly synthesis of mentioned nanomaterials. Therefore, efficient, effective and environmentally friendly way to create mentioned nanostructures with tunable properties remains a major challenge. Over a few decades, many investigations demonstrated that plasma technique can create uniform nanostructure in an environmentally friendly way which holds great promise as a versatile nanofabrication tool. Therefore, in this thesis, I investigate the plasma aided fabrication of Nobel Prize winning graphene related material called vertical graphenes will be discussed in details. Vertical graphene features are expected to be promising for a host of applications, from energy storage devices to gas detection. Therefore, I will explore the potential of vertical graphenes in diverse applications. Furthermore, green way of creating vertical graphenes using natural precursors from different states of matter will also be investigated. Following on from investigation of vertical graphenes, I will also demonstrate controllable, green synthesis of silicon based nanostructures without hazardous silicon precursor material using plasma-assisted methods.

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Berencén, Ramírez Yonder Antonio. "Rare earth- and Si nanostructure-based light emitting devices for integrated photonics." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285453.

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This thesis presents experimental work on developing rare-earth ions and Si nanostructures as a material platform for light emitting devices (LEDs) in the visible and near-infrared range. The realization of the different electroluminescent devices, based on a single, bi- or tri-layer approach of silicon oxide and/or silicon nitride co-doped or not with rare earth ions, is successfully performed. Several complementary metal-oxide-semiconductor (CMOS) compatible fabrication techniques such as co-magnetron sputtering, plasma-enhanced chemical vapor deposition (PECVD), low-pressure chemical vapor deposition (LPCVD) and ion implantation are used. By using characterization techniques such as time of flight secondary ion mass spectrometry (TOF-SIMS), secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), energy-filtered transmission electron microscopy (EFTEM), focused ion beam (FIB) and ellipsometry, the structural and compositional properties of the studied active layers are determined. In addition, electro-optical properties at room and at high temperatures (25 0C – 300 0C) under quasi-static and dynamic regimes are studied in both visible and near-infrared spectral region. Typically, the used electro-optical techniques have been current-voltage, capacitance-voltage, charge to breakdown, electroluminescence (EL)-current, EL-voltage and time-resolved EL.
Esta tesis presenta un trabajo experimental en el desarrollo de iones de tierras raras y nanoestructuras de Si como plataforma de materiales para dispositivos de emisión de luz (LEDs) en el rango visible e infrarrojo cercano. Se han fabricado diferentes dispositivos electroluminiscentes basados en capas simples, dobles o triples de óxido de silicio y/o nitruro de silicio dopados o no con tierras raras. Para ello se han empleado varias técnicas de fabricación compatibles con la tecnología CMOS; a saber, depósito de vapor químico asistido por plasma (PECVD), pulverización catódica mediante magnetrón, depósito de vapor químico a baja presión (LPCVD) e implantación de iones. Así mismo, las propiedades estructurales y de composición de las capas fabricadas han sido determinadas mediante el uso de técnicas de caracterización tales como TOF-SIMS, SIMS, XPS, EFTEM, FIB y elipsometría. Además, a temperatura ambiente y altas temperaturas (25 0C – 300 0C) se han estudiado las propiedades electro-ópticas en los regímenes cuasi-estático y dinámico. Por lo general, las técnicas electro-ópticas empleadas fueron corriente-voltaje, capacitancia-voltaje, estudio de carga hasta la ruptura, electroluminiscencia (EL)-corriente, EL-voltaje y EL resuelta en tiempo.

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Jaffal, Ali. "Single photon sources emitting in the telecom band based on III-V nanowires monolithically grown on silicon." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI019.

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Une source de photons uniques (SPU) dans la bande télécom, épitaxiées sur un substrat de silicium (Si), est le Saint Graal pour réaliser des dispositifs CMOS compatibles pour les technologies de l'information optiques. Pour atteindre cet objectif, nous proposons la croissance monolithique de Boîte Quantiques-Nanofils (BQ-NFs) InAs/InP sur des substrats de silicium par épitaxie par jet moléculaire (EJM) en utilisant la méthode vapeur-liquide-solide (VLS). Au début, nous avons concentré nos efforts sur l'optimisation des conditions de croissance afin d'obtenir une densité de NF ultra-faible sans effort avant ou après la croissance, ce qui nous permet d'exciter optiquement un seul BQ-NF sur l'échantillon tel qu'il a été épitaxiées et de préserver la croissance monolithique sur le silicium. Par la suite, nous avons porté notre attention sur l'amélioration de l'extraction de la lumière de la BQ InAs du guide d'onde InP NF vers l'espace libre pour obtenir une source lumineuse avec un profil d'émission en Champ Lointain (CL) gaussien afin de coupler efficacement les photons individuels à une fibre optique monomode. Cela a été réalisé en contrôlant la géométrie de NF pour obtenir des NFs en forme d'aiguille avec un très petit angle de conicité et un diamètre de NF adapté pour supporter un guide d'onde monomode. Une telle géométrie a été produite avec succès en utilisant un équilibre induit par la température sur les croissances axiale et radiale pendant la croissance des NFs catalysée par l'or. Des mesures optiques ont confirmé la nature mono-photonique des photons émis avec g2(0) = 0,05 et un profil d'émission gaussien en CL avec un angle d'émission θ = 30°. Pour obtenir des performances optimales, nous avons ensuite abordé une question cruciale dans cette géométrie de NF représentée par l'état de polarisation inconnu des photons émis. Pour résoudre ce problème, une solution consiste à intégrer un seul BQ dans un NF avec une section asymétrique optimisée pour inhiber un état de polarisation et améliorer l'efficacité d'émission de l'autre. Une stratégie de croissance originale a été proposée, permettant d'obtenir des photons à haut degré de polarisation linéaire parallèle à l'axe allongé des NFs asymétriques. Enfin, l'encapsulation des BQ-NFs dans des guides d'ondes en silicium amorphe (a-Si) a ouvert la voie à la production des dispositifs des SPU entièrement intégrés sur Si dans un avenir proche
A telecom band single photon source (SPS) monolithically grown on silicon (Si) substrate is the Holy Grail to realize CMOS compatible devices for optical-based information technologies. To reach this goal, we propose the monolithic growth of InAs/InP quantum dot-nanowires (QD-NWs) on silicon substrates by molecular beam epitaxy (MBE) using the vapour-liquid-solid (VLS) method. In the beginning, we have focused our efforts on optimizing the growth conditions aiming at achieving ultra-low NWs density without any pre-growth or post-growth efforts allowing us to optically excite a single QD-NW on the as-grown sample and to preserve the monolithic growth on silicon. Subsequently, we have turned our attention on enhancing the InAs QD light extraction from the InP NW waveguide towards the free space to achieve a bright source with a Gaussian far-field (FF) emission profile to efficiently couple the single photons to a single-mode optical fiber. This was done by controlling the NW geometry to obtain needlelike-tapered NWs with a very small taper angle and a NW diameter tailored to support a single mode waveguide. Such a geometry was successfully produced using a temperature-induced balance over axial and radial growths during the gold-catalyzed growth of the NWs. Optical measurements have confirmed the single photon nature of the emitted photons with g2(0) = 0.05 and a Gaussian FF emission profile with an emission angle θ = 30°. For optimal device performances, we have then tackled a crucial issue in such NW geometry represented by the unknown polarization state of the emitted photons. To solve this issue, one solution is to embed a single QD in a NW with an asymmetrical cross-section optimized to inhibit one polarization state and to improve the emission efficiency of the other one. An original growth strategy was proposed permitting us to obtain highly linearly polarized photons along the elongated axis of the asymmetrical NWs. Finally, the encapsulation of the QD-NWs within amorphous silicon (a-Si) waveguides have opened the path to produce fully integrated SPSs devices on Si in the near future

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Guzman-Verri, Gian Giacomo. "Electronic Properties of Silicon-based Nanostructures." Wright State University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=wright1158515644.

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Lalic, Nenad. "Light emitting devices based on silicon nanostructures." Doctoral thesis, KTH, Electronic Systems Design, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-2943.

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Although silicon is the dominant semiconductor today, lightemitting devices are currently based on compound semiconductorsdue to their direct band-gap, which promotes fast radiativerecombination. However, in nanometer-size silicon structures,carrier confinement enhances the radiative recombination,while, at the same time, suppresses diffusion to non-radiativerecombination centra, resulting in a significant increase inlight emission efficiency. Moreover, the band-gap is wideningas the crystal size is reduced (quantum confinement), enablinglight emission in the visible range. In this work, twodifferent approaches to manufacture a light emitting diode(LED) in silicon have been investigated. The first type ofsilicon LED's is based on porous silicon (PSi) and manufacturedby electrochemical etching of a previously formed pn diodestructure. After optimizing the etching process, PSi LED's wereproduced with an external quantum efficiency of ~0.2% underpulsed excitation, more than an order of magnitude higher thanpreviously reported. Tunability of the emission wavelength inthe range 1.6-2eV was demonstrated by varying the etchingparameters. The EL wavelength is determined by the band-gap ofthe nanocrystals, i. e. their size, as evidenced by a lowerthreshold for longer EL wavelengths, due to lower barriers forinjection into larger crystallites. The EL decay after the biaspulse follows a stretched exponential shape, in agreement witha model involving exciton migration in partially interconnectednanocrystals. Under constant bias, the EL and forward currentare decreasing, due to charging, caused by carrier trapping inthe porous network. After the etching the hydrogen passivatedporous silicon surface is being gradually oxidized, resultingin increased barriers, permanent conductivity reduction and ELdegradation. To improve stability, the second LED approach,based on Si nanocrystals embedded in SiO₂, was studied. Nanocrystals were formed by theimplantation of Si into thermally grown SiO₂and by subsequent annealing at high temperatures(mostly 1100°C). Photoluminescence investigation showedthat luminescence properties are dependent on nanocrystal sizeand similar to those of PSi. However, decay shapes and timeconstants revealed a stronger isolation of the nanocrystalsthan in PSi. For the EL, good current transport properties werenecessary. That required a thin SiO₂layer and efficient injection, realized using anin-situ doped poly-Si cap layer. The Si nanocrystal LED's werestable, although the total light intensity was lower than inPSi, as a consequence of a thin active layer.

Key words: Electroluminescence, photoluminescence, lightemitting diode, porous materials, nanostructured materials,silicon, etching, anodized layers, ion implantation.

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Chau, Chien Fat. "A nanostructured porous silicon based drug delivery device." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/69237/.

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Targeted and controlled delivery of therapeutic agents on demand is pivotal in realising the efficacy of many pharmaceuticals. The design and fabrication of a novel, electrically-addressable, porous structure-based drug delivery device for the controlled release of therapeutic proteins and peptides, are described in this thesis. The initial prototype microdevice design incorporates a porous polysilicon (PPSi) structure as a drug reservoir. Two alternative methods were investigated to fabricate the PPSi structure: i) the chemical stain etching method; ii) a reactive ion etching (RIE) method through a masking template. Random pores, with irregular pore shape and size in the micro- to mesoporous regime (< 50 nm), were obtained using the stain etching method but this method suffered from poor reproducibility and non-uniformity. Two novel RIE approaches were investigated to fabricate ordered PPSi structures; two different masking templates were investigated – a porous anodic alumina (PAA) and a metal mask with hexagonally arranged holes produced by a novel nanosphere lithography (NSL) technique. A quasi-ordered PAA template with pore diameters in the region of 50 nm was fabricated but was not suitable for the subsequent proposed RIE process. By using the NSL technique, quasi-ordered PPSi structures with tapered pore profiles, were obtained. This is the first demonstration of the fabrication of PPSi with ordered pores of sizes in the macropore range of ~ 370 nm. A revised silicon-based prototype microdevice was designed and fabricated. The microdevice incorporates a nanostructured, quasi-ordered porous silicon (PSi) as a drug reservoir and an integrated heater and temperature sensor as an active control mechanism. The PSi structure was fabricated using a modified NSL technique and a Bosch-based RIE process. Hexagonally arranged cylindrical pores with diameters between ~75 nm and ~120 nm, and depths in the range of ~330 nm and 500 nm, were obtained. The novel fabrication techniques investigated here are simple and versatile; both p-type and n-type PSi structures have been successfully fabricated. Proof-of-concept studies, using the revised prototype drug delivery microdevices, suggested that the nanostructured PSi would be suitable for the passive release of an intermediate-sized (~23 000 Dalton) model protein. It is envisaged that the microdevice has the potential to deliver osteoinductive growthfactors, on demand, to the site of fracture, in a controlled and sustainable manner, as a first step to an intelligent therapeutic system for skeletal regeneration.

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Dohnalovà, Kater̆ina. "Study of optical amplification in silicon based nanostructures." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/DOHNALOVA_Katerina_2007.pdf.

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Le but principal de ce travail fut de préparer un matériau photo-luminescent à base de nano-cristaux de Silicium dans une matrice de silice (SiO2) de qualité optique suffisante pour permettre l'observation d'un gain optique. Des nano-cristaux de silicium peu oxydés de tailles comprises entre 2 et 3 nm ont été obtenus par abrasion électrochimique de wafer de silicium. Les nano-cristaux avec une concentration variable permettant l'observation de leur émission stimulée sont dilués dans une matrice de silice obtenue par procédé sol-gel. Un dispositif optique dit "de zone à longueur variable" ("Variable Stripe Length" VSL) a été utilisé pour la mesure du gain optique des nano-cristaux. Cependant cette méthode seule reste peu fiable pour les matériaux à faible gain optiques tels que les nano-cristaux de silicium. Pour cette raison nous avons combiné la méthode VSL avec celle du "spot d'excitation déplacé " ("Shifting Excitation Spot" SES). Ceci nous permet d'observer des gains faibles qui n'auraient pas pu être atteint avec la méthode VSL seule. Nos résultats montrent clairement l'apparition d'un gain sous différentes conditions d'excitations. Pour préparer un laser il est nécessaire d'avoir un materiau, montrant du gain optique, mais il faut aussi appliquer une contra réaction optique suffisante. L'utilisation d'une cavité optique externe nécessite des échantillons de grande qualité optique. Ceci n'est pas compatible avec un gain élevé qui demande une concentration très forte en nano-cristaux de silicium. Pour cela nous avons construit un laser à "cavité à contra réaction distribuée" ("Distributed Feedback Laser" DFL). Dans ce type de cavité, la contra réaction est distribuée sur l'ensemble de l'échantillon. Le pas du réseau (166 nm) est inférieure aux variations moyennes de densité (≈0. 5-1. 0 μm) et peut être facilement modifié. Nous espérons ainsi obtenir un gain faible mais suffisant pour être observable. La cavité DFL est tout d'abord calibrée à l'aide de différents colorants dilués dans une solution de méthanol où nous avons observé des modes laser biens définis. Des modes d'émissions laser similaires (des pics plus larges et moins intenses que dans le cas des colorants) ont été obtenus dans nos échantillons Si-ncs/SiO2. Ceci est principalement dû à la moindre qualitéoptique de nos échantillons. Pour comprendre les précédentes observations, nous avons developpé un modèle théorique simple nous permettant de retrouver et d'expliquer les modes experimentaux en jouant sur la variation de densité et les caractéristiques des Si-ncs. L'effet de la contra réaction de la cavité DFL sur nos échantillons est clairement identifié par ce modèle. Ceci nous permet d'entrevoir de nouvelles perspectives pour la caractérisation optique et l'amélioration de nos échantillons
The aim of this work was to prepare light-emitting structure on the basis of silicon nanocrystals (Si-ncs) embedded in a silicon dioxide (SiO2) based matrix of a sufficiently good optical quality and stable emission properties, which exhibits positive optical gain and can be used as an active material in a laser cavity. The technique of sample preparation is based on a combination of the modified electrochemical etching of silicon wafers and the SiO2 based sol-gel processing. This method enables us to achieve relatively small oxidized Si-ncs (≈2-3 nm), embedded at virtually arbitrary volume fraction in a SiO2 based matrix, which is believed to be advantageous for easier stimulated emission (StE) onset observation. The optical gain coefficient was measured using the standard "Variable Stripe Length" (VSL) method, the application of which, however, is limited for low gain. Therefore we implemented a supplemental "Shifting Excitation Spot" (SES) method, enabling us to determine the optical gain coefficient even of such a small magnitude that will not be recognized by the VSL method itself. We observed a positive net gain coecient originating from the StE in dierent Si-ncs/SiO2 samples under different excitation and detection conditions. To prepare a laser system, a positive net gain observation is essential as well as a positive optical feedback. Using an external cavity as a resonator requires a high optical quality sample. This is, however, hardly achievable under the high Si-ncs volume fraction requirements for the StE onset. Because of that we decided to build an optically induced "Distributed Feedback Laser" (DFL) system, where the cavity is distributed over the whole sample volume and the cavity grating constant (≈166 nm) is lower than expected mean homogeneity length in our sample (≈0. 5-1. 0 μm). Therefore, a positive but low effect on the emission of Si-ncs is expected. Moreover, such type of DFL cavity is easily tuneable. The functionality of the DFL setup was tested using reference organic dye solutions in methanol, where a tuneable lasing action was successfully achieved. Similar tuneable cavity modes were also observed in different Si-ncs/SiO2 samples, however, of broader widths and less intense, compared to the organic dyes, which is mainly given by their lower optical quality. To understand and describe the mode selection in such a material, we developed a simple theoretical model, enabling us to determine the selected mode shape with respect to the sample homogeneity length and the character of the inhomogeneities. We proved the active feedback of the DFL cavity on the emission of our Si-ncs/SiO2 samples and proposed some further steps for future sample improvement

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Petukhou, Yu A., V. V. Uglov, N. T. Kvasov, A. V. Punko, I. L. Doroshevich, V. M. Astashynski, and A. M. Kuzmitski. "Formation of silicon-based nanostructures by compression plasma flows." Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20860.

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The use of compression flows (CPF) for the formation of metal and silicide nanostructures for data storage devices, thermoelectric materials and solar cells is presented. The action of CPF with injected metallic powder results in the formation of coatings composed of spherical clusters with complex structure: each submicron cluster (0,1-0,2 μm radius) is formed from a number of nanosized ones (10-25 nm radius). The action of CPF on binary “metal-silicon” systems provides formation of branched silicon dendrites (tip radius ~ 200 nm, primary spacing ~ 1,2 μm); interdendritic space is filled with nanostructured (50-100 nm) “silicide-silicon” and “monosilicide-disilicide” composite due to melting of the surface layer, rapid solidification (~ 10-3 m/s) and constitutional overcooling. Mechanisms of formation of nanostructured composites on silicon surface and in thick surface layers is discussed in terms of order parameter evolution and non-equilibrium solidification models. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/20860

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PACCOTTI, NICCOLO'. "SERS active Ag/silicon based nanostructures for biosensing applications." Doctoral thesis, Politecnico di Torino, 2020. http://hdl.handle.net/11583/2839849.

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Han, Tingting. "Highly active and efficient metal-decorated silicon-based nanostructured photoelectrodes for water splitting solar cells." Doctoral thesis, Universitat de Barcelona, 2020. http://hdl.handle.net/10803/670880.

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With the burning of large amounts of traditional fossil fuels, global environmental pollution is getting worse and worse, and energy crisis is becoming more serious for meeting human’s life demand. In order to solve these problems, it’s imperative to find renewable and clean energy sources. Although solar is one of the most abundant renewable energy on earth, it’s difficult to collect and store. As a non-polluting energy, hydrogen is a highly promising candidate to replace fossil fuels. Sunlight can be used to split water into hydrogen, producing chemical energy stored in hydrogen bonds. This easy way of producing clean fuels (hydrogen) has attracted the attention of both industry and academy. Photoelectrochemical (PEC) water splitting is one of the most promising methods to produce hydrogen by utilizing solar energy, due to the simple structure, low fabrication cost and good performance of the prepared cells. In these cells, a semiconductor photoelectrode is immersed in an electrolyte, and when illuminated, hydrogen and/or oxygen can be generated on its surface by electrolysis. To obtain better performance for PEC water splitting devices, it’s extremely significant to select proper semiconductors for absorbing light, catalysts for enhancing the PEC performance and electrolytes containing various ions. Silicon has garnered very much interest as semiconductor photoelectrodes due to its low cost and proper band gap (1.1 eV). However, the electrolyte can oxidize and/or corrode its surface, resulting in a reduction of its performance. Metal catalysts are often used to avoid the degradation of silicon photoelectrodes, and to enhance their activity in the electrolyte. However, the degree of protection can be reduced after some periods of time, and consequently the lifetime of the semiconductor photoelectrodes is still the main bottleneck of this PEC water splitting technology. Besides, tuning the pH of the electrolytes or the chemical composition of the electrolytes including special species could improve the activity and stability of the cells. In this PhD thesis I present a deep study about the ageing mechanisms of Ni layers with different thicknesses as protective and catalytic coatings on n-type Si photoanodes for PEC water splitting in strong alkaline condition. Before and after performed long-time PEC characterizations, we comprehensively analyzed the photoanodes at nano and atomic scales using atomic force microscopy (AFM) and electron microscopy. By investigating the morphology changes and the chemical composition of the photoanodes after long operation times, we find that the ageing mechanisms extremely rely on the thickness of the Ni coating layer. The activity of the 2 nm nickel coated silicon photoanode decays faster than thicker ones due to the formation of a thick interfacial SiOX film and the extensive penetration of potassium impurities into the NiOX layer. Whilst the photoanodes with more than 5 nm Ni coatings show longer stability, and the degradation is due to the formation of holes in the NiOX layer. Then, using 5 nm Ni-based n-Si photoanodes, we analyzed the effect of different alkaline electrolytes for PEC water splitting. Although the photoanodes show lower onset potential at high pH electrolyte, we also developed an advanced electrolyte (a mixture of potassium hydroxide (KOH) and lithium hydroxide (LiOH), pH 12.5) that shows good activity and stability for metal-based silicon photoelectrodes. Furthermore, we also designed, fabricated and tested n-3C-SiC/p-Si photocathodes for PEC water splitting in KOH, and observed an enhancement of PEC performance due to the catalytic and plasmonic resonance effects of the noble metal nanoparticles (NPs) introduced. By tuning the size and shape of Au NPs on the photocathodes, higher saturated photocurrent can be achieved. And Pt NPs coated n-3C-SiC/p-Si photocathodes show lowest onset potential and highest saturated photocurrent for PEC performance.
La quema de grandes cantidades de combustibles fósiles para satisfacer la demanda energética stá empeorando la contaminación ambiental cada vez más, y la crisis energética se está volviendo más grave. La división de agua mediante fotoelectroquímica (PEC, por sus siglas en inglés) utilizando luz solar es uno de los métodos más prometedores para producir combustible hidrógeno de forma limpia, debido a la estructura simple, el bajo costo de fabricación y el buen rendimiento. En las células fotoelectroquímicas, un fotoelectrodo semiconductor se sumerge en un electrolito y, cuando se ilumina, se puede generar hidrógeno y/u oxígeno en su superficie mediante electrólisis. Para obtener un mejor rendimiento, es extremadamente importante seleccionar semiconductores adecuados para absorber la luz, catalizadores para mejorar el rendimiento, y electrolitos que contienen varios iones. El silicio ha suscitado mucho interés debido a su bajo costo y a sus propiedades eléctricas (banda prohibida de 1.1eV). Sin embargo, debido a su inestabilidad en el electrolito, los catalizadores metálicos a menudo se usan para evitar la degradación de los fotoelectrodos de silicio y para mejorar su actividad en el electrolito. Dado que el grado de protección se puede reducir después de algunos períodos de tiempo, la vida útil de los fotoelectrodos de semiconductores sigue siendo el principal cuello de botella de esta tecnología de división de agua PEC. Además, ajustar el pH o la composición química de los electrolitos, incluidas las especies especiales, podría mejorar la actividad y la estabilidad de las células. En esta tesis, he estudiado el uso de niquel como capa protectora y catalizadora sobre fotoelectrodos de silicio, y hemos analizados su envejecimiento bajo condiciones de funcionamiento reales. También he desarrollado un electrolito avanzado (una mezcla de hidróxido de potasio [KOH] e hidróxido de litio (LiOH), pH 12.5) que muestra una buena actividad y estabilidad para los fotoelectrodos de silicio a base de metal. Además, también diseñamos, fabricamos y testeamos fotocatodos n-3C-SiC/p-Si cubiertos con nanopartículas de metales nobles para la división de agua PEC en KOH, y observamos una mejora en el rendimiento de PEC debido a los efectos de resonancia catalítica y plasmónica de las nanopartículas introducidas.

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Massoud, Mouhannad. "Experimental characterization of heat transfer in nanostructured silicon-based materials." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI063/document.

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Ce mémoire de thèse aborde la caractérisation expérimentale du transfert thermique à l’échelle nanométrique dans des matériaux compatibles avec les procédés de la micro-électronique. Pour cela deux techniques de caractérisation sont appliquées chacune à deux différents systèmes, le silicium mésoporeux irradié et les membranes de silicium suspendues. La première technique de caractérisation est la thermométrie micro-Raman. La puissance du laser chauffe l'échantillon exposé. La détermination de la conductivité thermique nécessite la modélisation de la source de chaleur par la méthode des éléments finis. Dans les cas considérés la modélisation de la source de chaleur repose sur différents paramètres qui doivent être soigneusement déterminés. La seconde technique de caractérisation est la microscopie à sonde locale (d’acronyme anglais SThM), basée sur le principe de la microscopie à force atomique (d’acronyme anglais AFM). Utilisée en mode actif, la sonde AFM est remplacée par une sonde résistive de type Wollaston qui est chauffée par effet Joule. Utilisée en mode AFM contact, cette technique permet une excitation thermique locale du matériau étudié. La détermination de la conductivité thermique nécessite l'analyse de la réponse thermique de la sonde au moyen d'échantillons d'étalonnage et également via la modélisation dans le cas des géométries complexes. L'effet de la position de la pointe sur le transfert de chaleur entre la pointe et l'échantillon est étudié. Une nouvelle méthode de découplage entre le transfert de chaleur entre la pointe et l'échantillon, respectivement à travers l'air et au contact, est proposée pour la détermination de la conductivité thermique des géométries complexes. Les résultats obtenus avec les deux techniques pour les échantillons de silicium mésoporeux irradiés à l’aide d’ions lourds dans le régime électronique sont en bon accord. Ils montrent la dégradation de la conductivité thermique du silicium mésoporeux suite à une augmentation dans la phase d’amorphe lorsque la dose d’irradiation croît. Les résultats obtenus sur les membranes de silicium suspendues montrent une réduction de la conductivité thermique de plus de 50 % par rapport au silicium massif. Lorsque la membrane est perforée périodiquement afin de réaliser une structure phononique de période inférieure à 100 nm, cette réduction est approximativement d’un ordre de grandeur. Un chapitre introduisant un matériau prometteur à base de silicium pour observer des effets de cohérence phononique conclut le manuscrit
This PhD thesis deals with the experimental characterization of heat transfer at the nanoscale in materials compatible with microelectronic processes. Two characterization techniques are applied to two different systems, irradiated mesoporous silicon and suspended silicon membranes. The first characterization technique is micro-Raman thermometry. The laser power heats up the exposed sample. The determination of the thermal conductivity requires the modeling of the heat source using finite element simulations. The modeling of the heat source relies on different parameters that should be carefully determined. The second characterization technique is Scanning Thermal Microscopy (SThM), an Atomic Force Microscopy (AFM)-based technique. Operated in its active mode, the AFM probe is replaced by a resistive Wollaston probe that is heated by Joule heating. Used in AFM contact mode, this technique allows a local thermal excitation of the studied material. The determination of the thermal conductivity requires the analysis of the thermal response of the probe using calibration samples and modeling when dealing with complicated geometries. The effect of the tip position on heat transfer between the tip and the sample is studied. A new method decoupling the heat transfer between the tip and the sample, at the contact and through air, is proposed for determining the thermal conductivity of complicated geometries. The results obtained from the two techniques on irradiated mesoporous silicon samples using heavy ions in the electronic regime are in good agreement. They show a degradation of the thermal conductivity of mesoporous silicon due to the increase in the amorphous phase while increasing the ion fluence. The results obtained on suspended silicon membrane strips show a decrease in the thermal conductivity of more than 50 % in comparison to bulk silicon. When perforated into a phononic structure of sub-100 nm period, the membrane thermal conductivity is about one order of magnitude lower than the bulk. A chapter introducing a promising silicon-based material for the evidence of phonon coherence concludes the manuscript

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Zhou, Di. "Conception and realization of solar cells based on silicon nanostructures." Thesis, Lille 1, 2013. http://www.theses.fr/2013LIL10160/document.

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Dans les cellules solaires planaires silicium, le matériau doit être assez épais pour que l’absorption des photons soit efficace, et dans le même temps, l’accroissement de l’épaisseur augmente les chances de recombinaison des porteurs. Afin d’avoir à la fois absorption et couche mince, des structures radiales (nanopiliers ou nanocones) peuvent être utilisées, qui ont des diamètres inférieurs à la longueur de diffusion des porteurs minoritaires, ce qui garantit une bonne collecte des porteurs. Ce travail présente la réalisation et la caractérisation de cellules solaires silicium bas coût, basées sur des nanostructures (piliers ou cônes). Pour la nanostructuration, l’usage d’un masqueur électronique est évité grâce à l’utilisation de microbilles de silice, déposées par technique Langmuir-Blodget et servant de masque à la gravure sèche des nanostructures. L’électrode face avant est en ZnO, obtenue par technique sol-gel. Avant la fabrication, une simulation des propriétés optiques des nanostructures en fonction de leur forme (densité, hauteur, diamètre,) a été réalisée à l’aide de calculs FDTD (Finite Difference Time Domain). La synthèse des films ZnO par sol gel a été optimisée (concentration des dopants, recuit thermique, hydrogénation, …) afin d’avoir la meilleure transparence optique et la plus faible résistivité. Finalement, des cellules solaires n+- i - p ont été réalisées, assemblant nanostructures et couche ZnO. Des étapes supplémentaires de passivation des défauts de surface et d’interfaces associés aux nanostructures ont été finalement menées
For planar p-n junction solar cell, the material must be thick enough to have enough absorption, whereas increasing the thickness leads to the increase of recombination of carriers. In order to decouple the requirement of light absorption and carrier collection, nanopillars (or nanocones) radial p-n junction are introduced. Nanopillars (or nanocones) have greater absorption and radial geometry offers minimal recombination if the diameter of nanopillars ( or nanocones ) is smaller than the minority carrier diffusion length. This work presents the realization and characterization of low-cost Si nanostructures (nanopillars and nanocones) solar cell with sol-gel derived ZnO transparent electrodes. In order to decrease the fabrication price, silica balls and Lamguir-Blodgett techniques are used as the substitutes of photoresist and electrical beam lithography, respectively. Besides, ZnO thin film transparent electrodes are synthesized by low-cost sol-gel methods For pursuiting high efficiency, first of all, we have tested the absorption of nanopillars and nanocones by varying their periods, diameters, lengths and sidewalls. Second, we have optimized the electrical properties of ZnO thin film by changing the synthesis parameters, such as doping concentration, baking temperature, anneal temperature and hydrogen treatment. In the end, solar cells were fabricated based on optimized Si nanostructures and optimized ZnO thin films. Due to their bad electrical properties associated with surface defects, surface passivation methods were performed to reduce the defects concentration in p-i-n junction and improve the efficiency of solar cells

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Buccafurri, Emanuela. "Analytical modeling of silicon based resonant tunneling diode for RF oscillator application." Lyon, INSA, 2010. http://theses.insa-lyon.fr/publication/2010ISAL0076/these.pdf.

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Since the introduction in microelectronics of the MOS transistor, the trend has been to reduce the size of each device, in order to increase density and performance, and to reduce costs. Devices nowadays are in a range of dimensions governs by Quantum Physics. At the nano scale, it may be smarter to integrate new devices operating according to the law of quantum physics rather than to classical Physics. In this context, resonant tunneling diodes (RTDs) present interesting characteristics. Its maximum operating frequency is in the Terahertz range and offers a wide range of applications, in analog (analog-digital converter ADC, frequency divider or multiplier, oscillator as well as digital (“multi-value” logic) circuits. Its I-V characteristics present an unusual negative differential resistance (NDR). Such negative differential resistance is usually achieved by a circuit involving more devices, and significant power consumption. Like most of the other tunnel devices, the first RTD was realized on III-V materials. Nevertheless, difficulty to integrate III-V materials on silicon, pushed to find silicon compatible solution for RTD. In this work, an alternative option to integrate these innovative devices in a silicon process, exploiting the vertical transport (gate to gate) in a double gate MOSFET has been considered. The aim of this work is thus to estimate by the means of an original analytical models, the theoretical expected performances of silicon based RTDs (static and dynamic behavior) and to compare them with conventional heterostructures. The high operating frequency of RTD is one of the major advantages of this device, for this reason an accurate frequency analysis has been carried out in collaboration with the Universidad Autonoma de Barcelona in the Xavier Oriols team. Finally, this model has been introduced in a circuit simulator (CADENCE), and used to estimate the performances of RF oscillators based on silicon RTD
La diminution incessante de la taille des composants semi-conducteurs permet d’envisager une rupture en associant ou remplaçant les composants conventionnels par des composants nanométriques avec un transport des charges de nature quantique ou balistique. La diode tunnel résonante (RTD) présente des caractéristiques très intéressantes et peut répondre à un grand nombre d’attentes: sa fréquence de coupure intrinsèque élevée doit permettre de travailler à de très hautes fréquences (possibilité d’atteindre la valeur théorique du THz), sa caractéristique atypique présente une Résistance Différentielle Négative (NDR) et permet d’envisager une diminution très importante en nombre de composants utilisés pour une fonction électronique donnée (électronique faible consommation). L’objectif de ce travail de thèse a été d’évaluer les performances théoriques de la RTD sur silicium avec des barrières d’oxyde de forte permittivité et de faible épaisseur (comme par exemple HfO2) et d’analyser son utilisation dans une application oscillateur radiofréquence. Pour atteindre cet objectif, les travaux ont concerné: la modélisation physique des dispositifs RTD, la validation du modèle analytique par comparaison à des simulations numériques, et enfin la simulation du comportement du dispositif et de son application: l’oscillateur radiofréquence. La partie sur l’étude temporelle de la structure a été approfondie et validée par des simulations temporelles basées sur les trajectoires de Bohm dans le cadre d’une collaboration avec l’Universidad Autonoma de Barcelona, dans l’équipe du Dr. Xavier Oriols. Par rapport aux travaux existant, notre modèle est suffisamment compact pour être introduit dans un simulateur circuit (formulation analytique) et considère des variables calculées su une base totalement physique sans aucun paramètre d’ajustement. L’originalité de ce projet repose sur une démarche globale, allant de la simulation physique du dispositif à la simulation de circuit pour une application ciblée (oscillateur), la principale retombée concerne le modèle analytique de RTD

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Bock, Lorenz [Verfasser]. "Nanostructured Catalysts Based on Mesoporous Silica / Lorenz Bock." Tübingen : Universitätsbibliothek Tübingen, 2020. http://d-nb.info/1218073616/34.

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Hamdana, Gerry [Verfasser]. "MEMS piezoresistive force sensors based on micro-/ nanostructured silicon components / Gerry Hamdana." München : Verlag Dr. Hut, 2019. http://d-nb.info/1176251112/34.

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Nguyen, Thanh Tra. "Sillicon photonics based on monolithic integration of III-V nanostructures on silicon." Phd thesis, INSA de Rennes, 2013. http://tel.archives-ouvertes.fr/tel-01065999.

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This thesis focuses on the heterogeneous growth optimization of III-V nanostructures on Si (001) substrate displaying a miscut toward [110]. The main purpose concerns the integration of efficient light sources on Si substrate for high-speed optical interconnects inter-and intra-chip, as a cornerstone for the development of optoelectronic integrated circuits (OEIC).First, this study focuses on the optimisation of nitrogen incorporation in GaPN on GaP(001) substrate, while reachingthe lattice-matching condition with Si. This study is also interesting for the growth of any GaPN-based dilute nitridecompounds, such as GaAsPN, which are very attractive for long wavelength laser applications and high-efficiency photovoltaic applications on Si substrates. In a second step, we studied the growth of an active layer based on (In,Ga)As quantum dots (QD) on GaP (001) substrate. These QD display a high density and good uniformity in size. Room temperature photoluminescence is also obtained on these QD, which is very promising for the fabrication of integrated optoelectronic sources on a silicon substrate. In the third part, this study focuses on the homoepitaxial growth of Si by UHV/CVD necessary to bury residual contaminants initially present on the Si surface, and to obtain a Si surface suitable for the subsequent heteroepitaxial growth of optimal structural quality GaP layer. This includes the formation of double atomic steps, by step bunching and favors by the substrate miscut, in order to limit the structural defects. Finally, the GaP/Si interface is optimized, while obtaining a flat GaP surface and a minimum defects density. A methodology to quantify the structural defects (anti-phase domains, micro-twins) by X-ray diffraction using Synchrotron and laboratory sources is presented. This study reveals an anisotropic behavior of the micro-twins, linked to the miscut direction of the Si substrate, and a dramatic reduction of the micro-twins density at high growth temperature. The growth of thin GaP layers on Si substrates, with thickness less than the critical one and obtained with a purposely dedicated growth cluster composed of a Si UHV/CVD chamber connected under UHV with a III-V MBE chamber, shows a significant reduction of the structural defects and provides a GaP/Si pseudo-substrate with a flat surface suitable for subsequent growth of efficient light sources.

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Karman, Cheryl. "Génération électrochimiquement assistée de films sol-gel nanostructurés orientés : fonctionnalisation par « chimie click », caractérisation et applications." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0218/document.

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Dans ce travail, plusieurs applications des films minces à base de silice mésoporeuse fonctionnalisée, générés par auto-assemblage électrochimiquement-assisté (EASA), organisés et orientés, ont été développées. Au préalable, avant de se concentrer sur les films fonctionnalisés proprement dits, nous avons caractérisé les propriétés de perméabilité de tels films vis-à-vis de sondes redox en solution différemment chargées (neutre, Fc(MeOH)2, positive, Ru(NH3)63+, négatives, Fe(CN)63-/4-), démontrant une limitation électrostatique pour les anions. Ceci nous a amené à étudier l'amplification de la réponse électrochimique des sondes électroactives anioniques (Fe(CN)63-/4-) en présence d’un film de silice chargé négativement sur la surface de l’électrode en ayant recours à des médiateurs neutres ou chargés positivement. La fonctionnalisation de ces films minces de silice a été effectuée en combinant la méthode EASA pour obtenir un film de silice fonctionnalisé par de groupements azoture avec une réaction de couplage avec un groupe alcyne (l’éthynyl-ferrocène dans ce cas). La réponse électrochimique obtenue pour ces films isolants fonctionnalisés par des groupes ferrocene électroactifs est due à un mécanisme de saut d’électrons entre les sites électroactifs adjacents. L'oxydation électrochimique du ferrocène en ion ferricinium génère des charges positives qui sont compensées par l'entrée d'anions permettant une éventuelle détection ampérométrique indirecte d'anions non électroactifs. L’injection d’anions non-électroactifs dans une cellule électrochimique constituée par une électrode de travail fonctionnalisée par ces films de silice porteurs de groupements ferrocène, soumise à l’imposition d’un potentiel positif (+0,5 V), a donné lieu à une réponse ampérométrique proportionnelle à la concentration d'anions. La régénération de l’électrode par réduction du ferricinium était nécessaire afin d’éviter la diminution du signal électrochimique dû à la consommation progressive du ferrocène par des multiples analyses successives. Cette régénération a été réalisée in situ par une méthode ampérométrique à onde carrée. Le films mésoporeux orientés peuvent également être fonctionnalisés par des complexes à base de ruthénium du type [Ru(bpy)2(bpy')]2+ en adaptant la méthode décrite auparavant. Le succès de la fonctionnalisation est vérifié par électrochimie et aussi par spectroscopie UV-Vis au travers de la bande MLCT caractéristique du complexe immobilisé. Une étude plus approfondie est effectuée lors du transfert de charge (saut d'électrons le long des sites adjacents) et le transport de masse de l’anion compensateur de charge au travers des canaux mésoporeux en faisant varier la vitesse de balayage en potentiel. Les propriétés de luminescence de ces films ont été étudiées en présence et en absence d’oxygène, évaluant la possibilité d'utiliser ce type de film pour des applications telles que l'électrochimiluminescence ou la détection d’oxygène. Finalement, ces films à base silice orientés ont été utilisés pour la croissance de nanofilaments de polyaniline (PANI). Ces nanofilaments de polyaniline ordonnée sont générés par voie électrochimique de manière contrôlée. Etant donnée la taille des mésopores (2 nm de diamètre), des chaînes PANI quasi-uniques sont vraisemblablement produites. À partir d'expériences de chronoampérométrie, sur base de films de différentes épaisseurs (100-200 nm), il est possible de prouver l’existence de plusieurs étapes d'électropolymérisation. Chaque étape de la formation du polymère (période d'induction, croissance de la polyaniline au sein et en dehors des canaux mésoporeux) est clairement identifiée. La génération de nanofilaments de polyaniline isolés est démontrée par l'amélioration de la réversibilité entre les états conducteurs et non-conducteurs de la polyaniline. La possibilité de contrôler et d'adapter la croissance des nanofilaments polymères conducteurs offre de nombreuses possibilités [...]
In this work, we exploited the vertically-aligned mesoporous silica thin films generated by electro-assisted self-assembly (EASA). First of all, we present a study about the amplification of charge transfer of a repulsed anionic redox probes [i.e. Fe(CN)63-/4-] through the negatively charged silica film by using neutrally or positively charged redox probes [Fc(MeOH)2 or Ru(NH3)63+ respectively] through redox mediating processes. Furthermore, the functionalization can be conducted by combining EASA method to obtain azide-functionalized silica film and further letting it react with an ethynyl-bearing reactant (e.g. ethynyl-ferrocene) according Huisgen click chemistry. The resulting ferrocene-functionalized silica films are electroactive, involving an electron hopping mechanism between adjacent ferrocene moieties. The electrochemical oxidation of ferrocene into ferricinium ion generates positive charges that are compensated by the ingress of anions into the film, opening the door to possible indirect amperometric detection of non-electroactive anions by flow injection analysis. Operating in an electrolyte-free flow, each injection of an anion (e.g., NO3-) at an electrode biased at a suitable positive potential (i.e., +0.5 V) gave rise to an amperometric response proportional to the anion concentration. However, to avoid the decrease of the electrochemical signal due to the progressive consumption of ferrocene in multiple successive analyses, it was necessary to regenerate the electrode by reduction of ferricinium moieties, which can be achieved in-situ by square wave amperometry. The feasibility to apply such indirect amperometric detection scheme in suppressed ion chromatography (for detecting anions in mixture) was also demonstrated. The oriented mesoporous film can also be functionalized with ruthenium(II)bipyridyl complex [Ru(bpy)2(bpy’)]2+ using the same method. Optimization of the functionalization level is controlled electrochemically by cyclic voltammetry (CV) and monitored through the UV-vis spectra. Further study is conducted upon the charge transfer (electron hopping along the adjacent sites) and the mass transfer of the compensating counter anion through the mesochannels by varying the CV potential scan rate. The emission of the [Ru(bpy)2(bpy’)]2+-functionalized film and its quenching in the presence of oxygen are evidenced in both aqueous and organic solvent, giving opportunities to apply the film for different application, such as electrochemiluminescence sensor and oxygen detection. Lastly, the vertically-aligned mesoporous silica film is used as a hard template to grow polyanilinine nanofilaments. The growth of ordered polyaniline nanofilaments is controlled by potentiostatic polymerization. In such small pore template (2 nm in diameter), quasi-single PANI chains are likely to be produced. From chronoamperometric experiments and using films of various thicknesses (100−200 nm) it is possible to evidence the electropolymerization transients, wherein each stage of polymerization (induction period, growth, and overgrowth of polyaniline on mesoporous silica films) is clearly identified. The advantageous effect of mesostructured silica thin films as hard templates for the generation of isolated polyaniline nanofilaments is demonstrated from enhancement of the reversibility between the conductive and the nonconductive states of polyaniline and the higher electroactive surface areas displayed for all mesoporous silica/PANI composites. The possibility to control and tailor the growth of conducting polymer nanofilaments offers numerous opportunities for applications in various fields including energy, sensors and biosensors, photovoltaics, nanophotonics, or nanoelectronics

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Noé, Pierre-Olivier. "Elaboration et caractérisation de matériaux nanostructurés à base de silicium comme source de lumière pour la photonique." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY006.

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Le silicium est reconnu comme étant un mauvais émetteur de lumière à cause de son gap indirect. Diverses stratégies ont été développées pour améliorer son rendement d'émission, le Si constituant le matériau de choix pour la photonique. Ce manuscrit présente l'élaboration et la caractérisation de matériaux originaux à base de silicium afin de proposer des solutions alternatives pour améliorer les propriétés d'émission de lumière du Si. Ce travail est divisé en 4 parties avec tout d'abord une revue de l'état de l'art de l'émission de lumière dans le Si et les bases sur les mécanismes de recombinaison dans le Si. Une seconde partie se concentre sur l'élaboration et l'étude de dispositifs électroluminescents à base de Si comportant un réseau de dislocations enterrées un niveau d'une jonction PN obtenu par collage moléculaire. L'émission de lumière située vers 1,1 et 1,5 µm (1,1 et 0,8 eV) est attribuée à la recombinaison des porteurs sur les états piège induits par des précipités de bore et d'oxyde dans le voisinage de dislocations (E^phonon_Bore vers 1.1eV et Dp~0.8eV) et des états de défauts localisés à l'intersection du réseau carré de dislocations vis (D1~0.8eV). Une troisième partie traite de l'élaboration et des propriétés optique d'ions Er3 + couplés avec des nanostructures de Si dans des films minces de SRO (Silicon-Rich Oxide) obtenus par co-évaporation de SiO et d'Er. Dans cette matrice, l'efficacité d'excitation indirecte de l'Er à 1,5 µm via les nanostructures est démontrée par la mesure de sections efficaces effectives d'excitation de l'Er entre 2x10-16 cm2 et 5x10-15 cm2 en fonction du flux d'excitation et des paramètres d'élaboration. Le principal résultat est la forte diminution avec la température de recuit de la fraction d'ions Er3+ émetteurs susceptible d'être inversée. Des expériences EXAFS révèlent que ce comportement est en corrélation avec l'évolution de l'ordre chimique local autour des atomes d'Er. Dans une dernière partie est présentée l'élaboration de nanostructures de Si de type nanofils cœur-coquille Si/SiO2. Ces structures cœur-coquille sont obtenues par trois méthodes différentes. Les structures obtenues par dépôt d'oxyde sur la surface de nanofils de silicium CVD catalysées avec de l'Au présentent une émission autour de 500 nm efficace à température ambiante due à la recombinaison des porteurs photo-générés au niveau des états de défauts dans la couche d'oxyde et à l'interface Si/SiO2. L'intensité de PL collectée est de plus d'un ordre de grandeur supérieure à celle mesurée sur des films minces de SiO2 similaires déposés sur des substrats de Si. En outre, la passivation des nanofils de Si CVD par un procédé d'oxydation thermique permet de neutraliser les états de surface qui dominent dans de telles structures. La mesure des vitesses de recombinaison de surface semble indiquer que ces nanofils ainsi passivés présentent des propriétés électroniques de volume similaires à celles du Si standard de microélectronique. Enfin, une nouvelle méthode pour l'élaboration in situ de nanofils cœur-coquille Si/SiO2 basée sur l'évaporation d'une source solide SiO avec l'Au et le Cu comme catalyseurs est détaillée. La croissance des fils catalysés par l'Au se produit dans le mode de croissance VLS (Vapor-Liquid-Solid comme en CVD) donnnat des nanofils présentant un cœur de Si cristallin et une coquille amorphe d'oxyde. En revanche, la croissance des nanofils catalysée par le Cu semble se produire préférentiellement à plus basse température en mode VSS (Vapeur-Solide-Solide) expliquant pourquoi ces NFs présentent une forte densité de défauts cristallins dans la cœur de Si contrairement aux fils catalysés Au
Silicon is known as a poor light emitter due to its indirect band gap. Various strategies have been developed to overcome its poor emission efficiency since it is the material of choice for photonics. In this manuscript are detailed the elaboration and characterization of original silicon-based materials in order to propose alternatives solutions to improve Si light emission properties. This work is divided in 4 parts with a first one describing the state of the art of light emission in Si and the basics of recombination mechanisms in Si. A second part focuses on the elaboration and study of electroluminescent devices based on bulk Si with a buried dislocation network at a PN junction obtained by wafer bonding. The light emission near 1.1 and 1.5 µm (1.1 and 0.8 eV) is attributed to the recombination of carriers on trap states induced by boron and oxide precipitates in the vicinity of dislocations (E^phonon_Bore near 1.1eV and Dp~0.8eV) and defects traps at the intersection of the square network of screw dislocations (D1~0.8eV). In a third part is showed the elaboration and the optical properties of Er3+ ions coupled with Si nanostructures in Si-Rich Silicon Oxide (SRO) thin films obtained by co-evaporation of SiO and Er. We demonstrate the efficient indirect excitation of Er at 1.5 µm with high effective cross sections between 2x10-16 cm2 and 5x10-15 cm2 as a function of the excitation flux and the elaboration parameters. The main result is the drastic decrease of the number of Er3+ emitting ions coupled to Si with the annealing temperature. EXAFS experiments revealed that this behavior is correlated with the evolution of the local chemical order around Er atoms. In a last part is presented the elaboration of Si nanostructures based on core-shell Si/SiO2 nanowires. These core-shell structures are obtained by three different methods. Core-shell nanowires obtained by oxide deposition on the surface of CVD Au-catalyzed Si nanowires exhibit an efficient room temperature emission around 500 nm due to the recombination of photo generated carriers in defects states in the oxide layer and at the Si/SiO2 interface. The collected PL intensity is more than one order of magnitude higher than similar SiO2 thin films deposited on Si substrates. Moreover, the passivation of CVD-growth Si nanowires by a thermal oxidation procedure allows neutralizing the surface states which are predominant in such structures. As a result, the measurement of surface recombination velocities seems to indicate that such passivated nanowires present similar volume electronic properties than standard microelectronic bulk Si. Finally, a new method for the elaboration of in situ core-shell Si/SiO2 nanowires based on the evaporation of a solid SiO source with Au and Cu as catalysts is presented. The Au-catalyzed growth occurs in the VLS mode (Vapor-Liquid-Solid like in CVD-growth) leading to the growth of nanowires with a crystalline Si core surrounded by an amorphous oxide shell. But Cu-catalyzed nanowires growth seems to appear preferentially at lower temperatures in the VSS (Vapour-Solid-Solid) mode explaining why these nanowiress exhibit a high density of crystalline defects in the Si core compared to Au-catalyzed wires

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Palacios, Higueras Raquel. "Fabrication and characterization of polymer micro- and nanostructures by template-based method." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8478.

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La fabricación de micro- y nanoestructuras orgánicas ha recibido un creciente interés debido a sus potenciales aplicaciones en campos como los sensores, las células solares y los diodos emisores de luz. En este trabajo, se ha desarrollado la técnica "template-based method", la cual consiste en la infiltración de un polímero en un molde poroso para obtener una estructura que sea su replica inversa. Dicha técnica ha sido utilizada empleando diferentes condiciones experimentales. El silicio macroporoso y la alumina nanoporosa han sido utilizados como moldes. Se fabricaron micro- y nanoestructuras orgánicas y se caracterizaron por microscopia electrónica de barrido, absorción, fotoluminiscencia, difracción de rayos X y espectroscopia Raman. Se analizó la morfología, las propiedades ópticas y la estructura cristalográfica de las micro- y nanoestructuras obtenidas. Finalmente, se estudió la influencia del disolvente, la estructura y del método experimental en la ordenación de las cadenas del polímero dentro de los nanoporos.

Fabrication and characterization of polymer micro- and nanostructures by template-based method
The fabrication of polymer micro- and nanostructures has received an increasing interest due to its potential applications in fields such as sensors, solar cells and light-emitting diodes. In this thesis, we have developed the template-based method, which consists on the infiltration of a specific material into a cavity (called template) to obtain the inverse replica of the template. This method has been studied using different experimental conditions. Macroporous silicon and self-ordered nanoporous alumina have been employed as templates. Polymer micro- and nanostructures were prepared and characterized by scanning electron microscopy, UV-Vis absorbance, photoluminescence, X-ray diffraction and Raman spectroscopy. Then, the morphology, optical properties and the degree of crystallinity of the micro- and nanostructures were analysed. Finally, the influence of the solvent, the structure and the experimental method in the conformation of the polymer chains inside the nanopores were studied.

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Hosatte, Mikaël. "Nanostructured silicon-based metamaterial and its process of fabrication for applications in optoelectronics and energy." Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAD019.

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Des nanostructures basées sur des différences de cristallinité ont été insérées dans des cellules test en silicium par des techniques d’amorphisation innovantes. Un nouveau mécanisme de multiplication de porteurs a ainsi été observé. Cet effet peut provenir des niveaux d’énergie électronique introduits par de grandes densités locales de bi-lacunes. Un principe de fonctionnement impliquant des mécanismes à niveaux d’énergie multiples et un transport électronique rapide au sein de la bande d’énergie des atomes de phosphore non-ionisés a également été proposé. Cela conduit à une asymétrie favorable entre la génération et la recombinaison des porteurs libres.L’énergie nécessaire à un photon pour enclencher le procédé s’est révélée plus petite que deux fois celle de la bande interdite. L’amélioration du rendement photovoltaïque devient donc concevable et une nouvelle génération de cellules solaires à haute efficacité pourrait ainsi émerger de cet effet de multiplication à faible-énergie
Nanostructures based on differences of crystallinity have been embedded into all-silicon test devices by innovative amorphization techniques and a new carrier multiplication mechanism was observed. This effect can indeed originate from the electron energy levels resulting from the high densities of divacancies localized at the crystalline/amorphous interfaces.An operating principle involving multiple energy level mechanisms and fast electronic transport within the unionized phosphorus energy band was also advanced. It led to a favourable asymmetry between generation and recombination of free carriers.Besides, contrary to other carrier multiplication effects, photon energy lower than twice the band gap was found sufficient to initiate the process. The enhancement of photovoltaic yields becomes therefore conceivable and propositions of prototypes are made. A new generation of high efficiency solar cells may then emerge from this Low-Energy Electron Multiplication effect

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Khumalo, Zakhelumuzi Mesuli. "Growth and characterisation of platinum and palladium catalysed silicon based nanostructures for nano-device fabrication." Doctoral thesis, University of Cape Town, 2018. http://hdl.handle.net/11427/29422.

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This thesis first describes the application of ion beam techniques for the analysis of synthesised metal silicide nano-droplets which are used to synthesis silicon nanowires. This analysis was performed for both Molecular Beam Epitaxy (MBE) and Electron Beam Evaporator (EBE) deposited metal coated silicon substrates. The formation of platinum silicide phases as a function of annealing temperature and time was investigated using in situ real-time Rutherford Backscattering Spectrometry (RBS). In situ real-time RBS revealed the reaction of platinum and silicon to start at about 200 °C and 230 °C, for MBE and EBE coatings respectively, forming platinum silicide phases (Pt2Si and PtSi) in sequence. Further analysis on the EBE deposited coatings using a scanning electron microscope confirmed the formation of droplets at 800 °C. Particle induced X-ray emission analysis showed the variation of platinum concentration, in droplets regions, between 1600 and 2000 counts. The surrounding regions were left almost uncovered due to platinum coating dewetting. Work was then carried out to investigate the growth of silicon nanowires from the produced droplets. Silicon nanowires were observed to form at 800 °C and 1000 °C using pulsed laser ablation and thermal annealing techniques, respectively, for the EBE deposited coatings. Furthermore, MBE was shown to produce self-aligned platinum silicide (PtSi) nanoclusters and nanowires on Si (111) substrates near the eutectic point (T = 978 °C and 67 at% Si) of the platinum silicon system. With an added silicon source in the MBE annealing chamber, the formation of two different silicon steps (straight and wave-like) is reported. The steps determine the position and the shape of the thermomigrating PtSi droplets. Nanoclusters preferentially form in the triple point of the wave-like steps while nanoclusters that form on the straight steps combine and grow into silicide nanowires. We report, for the platinum (MBE deposited) catalysed core-shell silicon nanowires, a reproducible method for eliminating hazardous acids during lithography device preparation with the use of silicide forming metal. With regard to palladium coatings, self-aligned polycrystalline palladium-silicide nanowires and palladium catalysed crystalline core-amorphous shell silicon nanowires were synthesised. The catalyst (palladium) was deposited on a silicon substrate using MBE. As a result of thermal annealing in the silicon flux, self-aligned and fully crystalline palladium-silicide nanowires were synthesised while crystalline core-amorphous shell silicon nanowires were grown when an argon gas was introduced. These results highlight the mechanisms to synthesise specific types of nanowires to be used in a variety of electronic devices depending on their applications. Furthermore, for the application of the produced core-shell nanowires in nanodevice fabrication, we present two approaches to reduce the oxidation of the nanowires during the thermal annealing growth method. The ratios of the amorphous shell to crystalline core on the nanowires produced, from the two methods, are compared and show a remarkable drop in oxide thickness when compared to nanowires fabricated using the current techniques available. In addition, focused ion beam was utilised to contact the oxide reduced nanowires, without first removing the thin oxide shell, for transport measurements. The oxygen reduced core-shell silicon nanowires showed very low electrical resistivity (4×10-1 Ω.cm). The techniques employed presents a new alternative to the production of low cost, high yield, high conducting silicon nanowires that will find use in a range of semiconductor based technology.

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Pandey, Bimal. "Synthesis, Characterization, Structural, and Optical Properties of Zinc Oxide Nanostructures Embedded in Silicon Based Substrates." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500222/.

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Structural and optical properties of ZnO nanostructures synthesized by low energy ion implantation technique were examined. ZnO molecular ions were implanted into Si/SiO2 substrates at room temperature and then furnace annealed under different temperatures and environments. In all as-implanted samples only Zn nanostructures with varying diameters distributed into the Si/SiO2 matrices were observed. No trace of ZnO was found. The distributions of Zn nanostructures in Si/SiO2 closely matched results from Stopping and Range of Ions in Matter (SRIM) simulations. During annealing at 750 oC, Zn diffused both toward and away from the surface of the substrate and combine with oxygen to form ZnO nanostructures. At higher annealing temperatures ZnO bonding started to break down and transfer to zinc silicate (Zn2SiO4), and at 900 oC the ZnO was completely converted into Zn2SiO4. The average sizes of Zn/ZnO nanostructures depended on the ion fluence. If the fluence increased the average sizes of nanostructures also increased and vice versa. For room temperature photoluminescence (RT-PL), band-edge emission in the ultraviolet (UV) region was observed from all samples annealed at 700 oC/750 oC and were slightly blue shifted as compare to bulk ZnO. Donor-bound exciton (D,X) and acceptor-bound exciton (A,X) transitions were observed in low temperature photoluminescence (PL). The lifetime of both donor-bound excitonic emission (D, X) and acceptor-bound excitonic emission (A, X) were found to be in the picosecond (ps) range.

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Usenko, A., V. V. Khovaylo, A. I. Voronin, A. V. Korotitsky, D. Yu Karpenkov, and O. N. Maradudina. "Study of Compacting Methods for Nanostructured Thermoelectric Materials Based on Si-Ge and Half -Heusler Alloys." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35514.

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Recent methods of compacting nanopowders of thermoelectric materials of silicon germanium and Half-Heusler (HH) compounds based on Ni(Ti,Zr,Hf)Sn are presented. Half-Heusler alloys are known to be intermetallic compounds with quite large Seebeck coefficient and semiconducting transport properties. This makes them a potential candidate for thermoelectric applications. In this study we compare compacting methods applied to raw materials as a function of crystal structure. The results suggest that the thermal conductivity can be reduced by increasing the phonon scattering via nanostructuring. The effect of spark plasma sintering (SPS) and hot pressing on Gleeble system was analyzed by TEM and SEM methods. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35514

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Demoulin, Rémi. "Etude structurale et cartographie du dopage dans des oxydes nanostructurés à base de sillicium." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMR086/document.

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La modification des propriétés optiques et électriques du silicium apportée par la réduction en taille, notamment due aux effets de confinement quantique des porteurs de charges, est aujourd'hui bien connue et a permis le développement de nouveaux systèmes en optoélectronique. Comme dans le cas du silicium massif, le dopage devrait permettre d'optimiser les propriétés du silicium nanostructuré. Cependant, les caractéristiques du dopage dans le silicium nanostructuré sont encore mal comprises et de nombreux questionnements, concernant la localisation des impuretés ainsi que leur état d'activation, restent en suspens. De plus, l'environnement des impuretés semble avoir une influence majeure sur l'ensemble des propriétés. Cette thèse vise à mieux comprendre les caractéristiques structurales du dopage à l'échelle atomique en fonction de la nature de l'impureté, de la matrice hôte et de la technique d'élaboration. Pour cela, nous avons étudié deux types de système en sonde atomique tomographique. Le premier concerne un dopage aux ions de terres rares dans les silicates d'hafnium. Nous avons mis en évidence que la formation de nano-grains de HfO2 cristallisés sous la forme cubique permet un transfert d'énergie efficace vers les ions praséodyme. Le second porte sur les dopages de type n et p de nanocristaux de silicium insérés dans la silice. Nous avons démontré l'introduction des impuretés de type n (As, P) au cœur des nanocristaux, indépendamment de la technique d'élaboration, permettant de réaliser des forts dopages. Un comportement différent a été mis en évidence pour les impuretés de type p, avec l'accumulation de Bore aux interfaces entre les nanocristaux et la matrice
The change of silicon optical and electrical properties induced by size reduction, due to the quantum confinement of charged carriers, is a well-known effect and allowed to develop new optoelectronic devices. As in bulk silicon, doping should allow to optimize these properties in nanostructured silicon. However, the characteristics of doping of nanostructured silicon still misunderstood and many questions, concerning the location of impurities and their activation state, remain unanswered. Moreover, in these materials, the environment of impurities seems to inuence strongly all of their properties. The purpose of this thesis is to get a better understanding of structural characteristics of doping at the atomic scale in function of the nature of the impurity, the host matrix, and the elaboration technic. In this way, we have investigated two di_erent systems using atom probe tomography. The first concerns a rare earth doping of hafnium silicates. We have evidenced that the clustering of HfO2 nano-grains crystallized in their cubic form induced an efficient energy transfer with praseodymium ions. The second system concern the n and p type doping of silicon nanocrystals embedded in silica. We have demonstrated the important introduction of n type impurities (As, P) in the core of every nanocrystals, independently of the elaboration technic. This introduction of impurities should allow the formation of highly doped silicon nanocrystals. A different behavior has been observed in the case of p type doping, represented by the aggregation of Boron at the interface between the nanocrystals and the silica matrix

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González, Fernández Alfredo A. "Studies and integration of Silicon-based light emitting systems." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285863.

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This project presents the study of luminescent devices and materials based on silicon for its use in the fabrication of an optical system that integrates light emitter, waveguide, and light sensor in a single chip obtained by the use of standard CMOS techniques and materials. The atomic and structural characteristics of the materials are analysed and related to its luminescent response. Taking into account the results from the active material characterization, the design, fabrication, and characterization of electroluminescent devices based on such materials is presented. Finally, the design, fabrication and characterization of a complete CMOS compatible Integrated Optical System consisting of a transceiver, is discussed and analysed. The active materials used for light emission were different Silicon Rich Silicon Dioxide(SRO) and SRO-Si3 N4 bi-layers, obtained by a variety of CMOS compatible techniques and fabrication parameters. Two contributing mechanisms to photoluminescence in SRO were identified in all cases, respectively linked to the presence of radiative defects, and to Quantum Confinement phenomena. It is proposed and tested a model to describe the latter, based on the effective mass approximation, and the relation between the amount of Si-Si links and the volume of nano-agglomerates present in the material. In bi-layer samples, an additional luminescence band was observed, found to be generated in the transition material between silicon nitride and dioxide, and related to energy states introduced by defects. Samples with SRO thickness ten times higher than that of nitride, presented a clear dominance of the photoluminescence related to the dioxide. The centres responsible for electroluminescence in the electronicd evices were found to be fundamentally the same as those for photoluminescence despite the differences in measured spectra, and it was concluded that the influence of the architecture on the light output is of significant importance. It was shown that bi-layered devices delivered better results in terms of efficiency, light emission control, distribution and stability. The carrier transport mechanisms observed in the devices were dominated by material breakdown in single-layered devices, and Trap-assisted Tunnelling in the bi-layers. The Optical System integrating the light emitter, a waveguide, and a light detector, was designed and fabricated based on the results from the fabrication and analysis of the stand alone light emitting devices. During the design stage, it was corroborated by computer simulations that the characteristics of thelight emittedby thedevices thatpresented thehighest e.ciency and reliability, were suitable for its transmission trough the proposed waveguide architecture. The detection capabilities of the designed light sensors were also theoretically corroborated to be appropriated for the detection of the emitted light type. The proper functioning of the elements conforming the finally fabricated system was probed. Differences were found in the operation of the stand alone light emitting devices and those integrated, but the resulting luminescence was within the boundaries of the transmittable spectrum. The operation of the Integrated Optical System was tested and preliminarily studied, obtaining positive results in its stimulus-detection response, fulfilling the main objective of the work, and opening the door for further studies which can lead to the optimization of the design for particular applications.
Este proyecto aborda el estudio de dispositivos y materiales luminiscentes basados en silicio para su uso en la fabricación de un sistema óptico que integre emisor de luz, guía de ondas, y sensor en un solo chip obtenido mediante el uso de técnicas y materiales estándar para la fabricación CMOS. Las características atómicas y estructurales de los materiales son analizados y relacionados con su respuesta luminiscente. Considerando los resultados de la caracterización del material activo, se presenta el diseño, fabricación, y caracterización de dispositivos electroluminiscentes basados en dichos materiales. Finalmente, se discute y analizan el diseño, fabricación, y caracterización de un transceptor como Sistema Óptico Integrado. Los materiales activos para la emisión de luz fueron distintos Dióxidos de Silicio enriquecidos con Silicio (SRO por sus siglas en inglés) y bi-capas SRO-Si3 N4, obtenidos mediante una variedad de técnicas compatibles con los procesos CMOS y distintos parámetros para los mismos. Se identificaron dos mecanismos que contribuyen a la fotoluminiscencia del SRO en todos los casos, relacionados con defectos radiativos y fenómenos de Confinamiento Cuántico, respectivamente. Se sugiere y pone a prueba un modelo para describir este último, basado en la aproximación de la masa efectiva y la relación entre la cantidad de enlaces Si-Si y el volumen de nano-aglomerados. En muestras bi-capa, se observó una banda adicional de luminiscencia, cuya generación fue identificada en el material de transición entre el nitruro de silicio y el óxido, y relacionada con estados de energía introducidos por defectos. Muestras con un espesor de SRO diez veces mayores a aquel del nitruro presentaron una clara dominación de la luminiscencia relacionada con el óxido. Se halló que los centros responsables por la electroluminiscencia en los dispositivos electrónicos son fundamentalmente los mismos que los responsables de la fotoluminiscencia a pesar de las diferencias en los espectros medidos, y se concluyó que la influencia de la arquitectura sobre el espectro de salida es de importancia significativa. Se mostró que dispositivos bi-capa entregan mejores resultados en términos de eficiencia, control sobre la luz emitida, distribución de la misma, y estabilidad en el funcionamiento. Se observó que los mecanismos de transporte de carga hallados en los dispositivos están dominados por ruptura del material en el caso de dispositivos de una sola capa, y Tuneleo Asistido por Trampas en el caso de dispositivos bi-capa. El Sistema Óptico que integra el emisor, una guía de ondas, y el detector de luz, fue diseñado y fabricado con base en los resultados de la fabricación y análisis de los dispositivos emisores de luz aislados. Durante la etapa de diseño, se corroboró mediante simulaciones por computadora que las características de la luz emitida por los dispositivos que presentaron la máxima eficiencia y fiabilidad fueran apropiadas para su transmisión a través de la guía de ondas propuesta. También se corroboró teóricamente que las capacidades de detección de los sensores diseñados fuera la adecuada para el tipo de luz emitida. Se exploró el apropiado funcionamiento de los elementos del sistema finalmente fabricado. Se encontraron diferencias en la operación de los dispositivos emisores de luz aislados y aquellos integrados, pero la luminiscencia resultante se halló dentro de los límites del espectro transmisible. La operación del Sistema Óptico Integrado fue probada y estudiada de manera preliminar, con la obtención de resultados positivos en su respuesta estímulo-detección, cumpliendo así con el objetivo principal del trabajo, y abriendo la puerta para estudios posteriores que pueden guiar a la optimización del diseño del sistema para aplicaciones particulares.

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Thissandier, Fleur. "Elaboration de micro-supercondensateurs à base d'électrodes en silicium nanostructuré : des nanomatériaux aux dispositifs." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENV031/document.

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Depuis les années 1990, l'électronique portable connait un véritable essor. De plus en pluscomplexes, ces appareils requièrent des besoins énergétiques croissants en termes de puissance,d'autonomie et de durée de vie. De nouveaux dispositifs de stockage pouvant être assemblés au plusproche du circuit micro-électronique et dans l'idéal directement sur la puce doivent donc être développés.Les micro-supercondensateurs représentent une solution prometteuse. Constitués principalementd’électrodes en carbone ou oxydes métalliques, leur fabrication sur les puces de micro-électroniques restedifficile. Cette intégration serait facilitée avec des électrodes à base de silicium. L’objectif de cette thèse estl'élaboration de micro-supercondensateurs constitués d’électrodes en silicium nanostructuré. Leursperformances peuvent être améliorées en travaillant à la fois sur les électrodes et sur l’électrolyte.L’électrode doit être stable en présence de l’électrolyte et avoir une grande surface développée.L’électrolyte doit permettre d’atteindre une tension élevée. Ce travail démontre que seules les électrodes ensilicium fortement dopées avec un traitement de surface adapté ont un comportement capacitif. La surfacedes électrodes est augmentée via la croissance de nanostructures par CVD catalysée par de l’or. L’étude del’influence des paramètres de croissance sur la morphologie des nanostructures a permis d’optimiser leprocédé pour obtenir des nano-arbres fortement dopés longs, denses, hyperbranchés et avec plusieursgénérations de branches ont pu être obtenus. L’utilisation du chlorure d’hydrogène permet de contrôlerprécisément le dopage des nanofils. Les paramètres clés des nanostructures pour obtenir de meilleurescapacités ont été identifiés : dopage, longueur, densité, branches. Les performances des microsupercondensateurs(Tension maximale, Energie, Puissance, Stabilité) avec des électrodes en siliciumnanostructurée ont été évaluées dans différents électrolytes. L’utilisation de liquide ionique (EMI-TFSI)permet d’augmenter la tension maximale et donc l’énergie et la puissance. Des pistes d’amélioration ont étéétudiées : traitement de surface, nouvelles architecture de dispositifs. La compatibilité des procédés utilisésavec ceux de micro-électronique a aussi été vérifiée
Since 1990, portable electronics is a thriving field. Devices gather more and more functions and thusrequire more and more efficient energy sources in terms of power, autonomy and lifespan. Such sourcesshould be fixed as close as possible from the micro-electronic circuit, ideally directly on chip. Microsupercapacitorsare a promising solution. Due to the electrodes materials (carbon or metallic oxide), theirfabrication directly on chip is still difficult. It should be easier with silicon based electrodes. The aim of thiswork is the elaboration of micro-supercapacitors with nanostructured silicon based electrodes. Theirperformances can be improved by working on the electrode and the electrolyte. The electrode must bestable in the electrolyte and have a high developed surface. The electrolyte must lead to high voltage. Thiswork demonstrates that only highly doped silicon electrodes with an adapted surface treatment have acapacitive behavior. The electrode surface can be increased via nanostructures growth of by gold-catalyzedCVD. Thanks to the study of the influence of growth parameters on the nanostructures morphology, theprocess has been optimized to get highly doped, dense, long and hyperbranched nano-trees with severalbranches generations. Their doping level is precisely monitored thanks to the use of HCl. Doping, length,density and branches are the key parameters to improve the electrode capacity. Micro-supercapacitorsperformances (maximum voltage, energy, power, stability) with such electrodes have been evaluated inseveral electrolytes. Higher voltage, and thus higher energy and power can be reached in ionic liquids.Several improvement trails are investigated: surface treatment, new device design. Our processcompatibility with micro-electronics one has been checked

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Moulin, Nelly. "Cellules solaires à haute tension de fonctionnement à basede Silicium ultra mince nanostructuré." Thesis, Lyon, 2021. http://www.theses.fr/2021LYSEI002.

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Les technologies actuelles sont marquées par une augmentation exponentielle du nombre d’objets connectés. Ceux-ci sont intégrés dans tous les domaines et s’accompagnent d’un enjeu de taille : leur approvisionnement en énergie. Dans cette thèse, on propose une nouvelle architecture de cellule solaire en Silicium pouvant s’intégrer facilement dans le design d’un objet connecté. Cette cellule est constituée de plusieurs sous-cellules mises en série par des jonctions tunnels verticales. La jonction tunnel a été étudiée analytiquement par le développement de deux nouveaux modèles sur sa caractéristique I(V). Par la suite, un procédé de fabrication a été mis en place pour la réalisation de jonctions tunnels verticales auto-alignées. Un premier démonstrateur de cellule solaire a été réalisé et a produit 200 mV de tension de sortie pour une cellule de 18 µm de large. L’effet de cascade de sous-cellules a également pu être montré sur des cellules contenant jusqu’à 10 jonctions tunnels. Par ailleurs, des options d’améliorations ont été proposées ainsi que des études sur la diminution des sources de résistance dans la cellule. Cette thèse étudie les phénomènes physiques interagissant dans une cellule à jonctions tunnels verticales de manière analytique, par simulation optique, physique et électrique ainsi que de manière expérimentale
Current technologies see an exponential increase in the number of connected objects. These objects are integrated in every domain and come along with an important challenge: their energy supply. In this thesis, we propose a new Silicon solar cell architecture that is easy to integrate in a chip design. This solar cell is composed of several subcells connected in series by vertical tunnel junctions. We study the tunnel junction from an analytical point of view and develop two new models on the I(V) characteristic. Then, we develop a new process flow to fabricate auto-aligned vertical tunnel junctions. With this process flow, a first prototype shows 200 mV output voltage for an 18 µm wide cell. We could also demonstrate the impact of series connection on cells containing up to 10 tunnel junctions. Several optimisations solutions have been proposed and investigated, notably on the resistance sources. This thesis studies physical phenomena interacting in a vertical tunnel junction solar cell from an analytical point of view, with optical, physical and electrical simulations along with experiments

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Liu, Huanhuan. "A novel optical bio-chemical sensor based on hybrid nanostructures of Bowtie nanoantennas and Fabry-Perot Interferometer." Phd thesis, Ecole Centrale de Lyon, 2013. http://tel.archives-ouvertes.fr/tel-01064196.

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Nowadays, the increasing concern for environmental analysis and food quality control, as well as medical needs such as fast diagnosis in case of emergency events, leads to a growing need for new generations of chemical and biological sensors. These devices should have high sensitivity and reliability, perform specific detection of molecules and enable multiple parallel sensing, while being cheap, portable, fast and easy to use. Thus, a general trend tends towards bio-chemical sensors which are on-chip integrated, label-free, and compatible with standard micro-technologies. Photonic dielectric devices based on porous silicon and metallic nanostructures based on plasmon resonances are good candidates to fulfill the above requirements. Porous silicon is a biocompatible material, with a huge specific surface providing a sensitivity enhancement by several orders of magnitude compared to bulk materials; furthermore, its refractive index and thickness can be easily tuned, enabling for the realization of a large variety of photonic designs. Metallic nanostructures provide high confinement and strong field enhancement in sub-wavelength regions, leading to high sensitivities; combined with fluorescence or other sensing mechanisms such as Raman or IR spectroscopy, they have already demonstrated increased sensing potential. The realization of a hybrid device combining both elements would be highly interesting, since it could yield the advantages of both elements, and the photonic structure could shape the plasmonic resonance to develop ultrasensitive devices with narrow resonance linewidth and increased sensing depth. In this context, we realized and studied a novel hybrid photonic / plasmonic device exploiting the coupling between the surface plasmon resonance of a bowtie nano - antenna (NAs) array and the photonic modes of porous silicon (PSi) interferometer. We designed and fabricated a NAs array with resonance wavelength ~ 1.3μm on a homogeneous PSi interferometer. A thin spacing silica layer with controllable density protects the pores of PSi layer and provides a smooth surface for the fabrication of NAs. The coupling mechanisms of two elements - NA array and interferometer, are studied with 2 models, which are interferometer approach and resonator approach. The interferometer approach is focused on studying the influence of NAs array as a homogeneous layer on the fringes shift of the interferometer. For resonator approach, the coupled mode theory is applied. With these models, strong coupling between both elements are discovered: splitting. In the case of viii smaller environment variation, the hybrid device gains 5-10 fold sensitivity enhancement vs. 2 elements alone. The controllable SiO2 layer allows us to sense the index variation within PSi interferometer. This opens a route towards double parallel sensing. The development of the theoretical models under different environment is ongoing, which is expected to utilize the strong coupling for the sensing. A further investigation of the sensing potential of the hybrid device would be expected. And the 2 elements constituting the hybrid structure - the interferometer and the NA array - could be modified in order to enlarge the study to a wider family of devices with greater properties and performances. This work was performed within the framework of the program "Groups of Five Ecoles Centrales" between China Scholarship Council (CSC) and Lyon Institute of Nanotechnologies (INL, CNRS UMR 5270). The project has been supported by the Nanolyon technology platform at INL.

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Dhoubhadel, Mangal S. "Synthesis and Characterization of Ion Beam Assisted Silver Nanosystems in Silicon Based Materials for Enhanced Photocurrent Collection Efficiency." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc799502/.

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In recent years a great deal of interest has been focused on the synthesis of transitional metal (e.g. Ag, Cu, Fe, Au) nanosystems at the surface to sub-surface regions of Si and SiO2 matrices for fundamental understanding of their structures as well as for development of technological applications with enhanced electronic and optical properties. The applications of the metal nanoparticle or nanocluster (NC) systems range from plasmonics, photovoltaic devices, medical, and biosensors. In all of these applications; the size, shape and distribution of the metallic NCs in the silicon matrix play a key role. Low energy ion implantation followed by thermal annealing (in vacuum or gas environment) is one of the most suitable methods for synthesis of NCs at near surfaces to buried layers below the surfaces of the substrates. This technique can provide control over depth and concentration of the implanted ions in the host matrix. The implanted low energy metal ions initially amorphizes the Si substrates while being distributed at a shallow depth near the substrate surface. When subject to thermal annealing, the implanted ions agglomerate to form clusters of different sizes at different depths depending upon the fluence. However, for the heavier ions implanted with high fluences (~1×1016 - 1×1017 atoms/cm2), there lies challenges for accurately predicting the distribution of the implanted ions due to sputtering of the surface as well as redistribution of the implants within the host matrix. In this dissertation, we report the investigation of the saturation of the concentration of the implanted ion species in the depth profiles with low energies (< 80 keV) metal ions (Ag and Au) in Si (100), while studying the dynamic changes during the ion implantation. Multiple low energies (30-80 keV) Ag ions with different fluences were sequentially implanted into commercially available Si wafers in order to facilitate the formation of Ag NCs with a wide ion distributions range. The light absorption profile according to different sizes of NCs at the near-surface layers in Si were investigated. We have investigated the formation of Ag NCs in the Si matrix as a function of implantation and thermal annealing parameters. The absorbance of light is increased in Ag implanted Si with a significant increase in the current collection in I-V (current-voltage) photo switching measurements. The experimental photovoltaic cells fabricated with the Ag implanted Si samples were optically characterized under AM (air mass) 1.5 solar radiation conditions (~1.0 kW/m2). An enhancement in the charge collection were measured in the annealed samples, where prominent Ag NCs were formed in the Si matrix compared to the as-implanted samples with the amorphous layer. The characterization techniques such as Rutherford Backscattering Spectroscopy, XPS-depth profiling, transmission electron microscopy, optical absorption, and I-V (current-voltage) photo switching measurements were employed to understand the underlying science in the observed properties. The results of these investigations are discussed in this research.

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Peiris, Thelge Manindu Nirasha. "Development and characterization of silica and titania based nanostructured materials for the removal of indoor and outdoor air pollutants." Diss., Kansas State University, 2012. http://hdl.handle.net/2097/14891.

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Doctor of Philosophy
Department of Chemistry
Kenneth J. Klabunde
Solar energy driven catalytic systems have gained popularity in environmental remediation recently. Various photocatalytic systems have been reported in this regard and most of the photocatalysts are based on well-known semiconducting material, Titanium Dioxide, while some are based on other materials such as Silicon Dioxide and various Zeolites. However, in titania based photocatalysts, titania is actively involved in the catalytic mechanism by absorbing light and generating exitons. Because of this vast popularity of titania in the field of photocatalysis it is believed that photocatalysis mainly occurs via non-localized mechanisms and semiconductors are extremely important. Even though it is still rare, photocatalysis could be localized and possible without use of a semiconductor as well. Thus, to support localized photocatalytic systems, and to compare the activity to titania based systems, degradation of organic air pollutants by nanostructured silica, titania and mixed silica titania systems were studied. New materials were prepared using two different approaches, precipitation technique (xerogel) and aerogel preparation technique. The prepared xerogel samples were doped with both metal (silver) and non-metals (carbon and sulfur) and aerogel samples were loaded with Chromium, Cobalt and Vanadium separately, in order to achieve visible light photocatalytic activity. Characterization studies of the materials were carried out using Nova BET analysis, DR UV-vis spectrometry, powder X-ray diffraction, X-ray photoelectron Spectroscopy, FT-IR spectroscopy, Transmission Electron Microscopy, etc. Kinetics of the catalytic activities was studied using a Shimadzu GCMS-QP 5000 instrument using a closed glass reactor. All the experiments were carried out in gaseous phase using acetaldehyde as the model pollutant. Kinetic results suggest that chromium doped silica systems are good UV and visible light active photocatalysts. This is a good example for a localized photocatalytic activity. In contrast, our xerogel system shows comparatively high visible light photocatalytic activity for the titania based system, showing the importance of non-localized nature of photocatalysis. The Cobalt doped silica system shows interesting dark catalytic activity towards acetaldehyde and several other pollutants. Thus, in summary, based on the different activities we observed during our studies these materials could be successfully used to improve the quality of both indoor and outdoor air.

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Bange, Romain. "Réalisation et optimisation de biocapteurs à base de nanostructures SiC pour la détection électrique d’ADN." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT007/document.

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La détection de faibles concentrations d’acides nucléiques est essentielle pour certaines applications comme la biologie médicale, où elle permet le diagnostic d’une multitude de pathologies par l’identification de biomarqueurs spécifiques. Par rapport aux techniques traditionnelles de détection par voie biochimique, la détection électrique par effet de champ présente l’avantage d’être une mesure directe, sans marquage, et à réponse rapide. Les transistors à nanofils semiconducteurs sont des dispositifs prometteurs qui permettent potentiellement d’atteindre des limites de détection très basses et une sensibilité élevée, grâce à leur grand rapport surface/volume et leurs propriétés électroniques uniques. Le carbure de silicium (SiC) est un matériau semiconducteur dont les qualités le rendent particulièrement adapté aux applications visées, telles que sa très grande stabilité physico-chimique et biocompatibilité.Dans cette thèse, des transistors à effet de champ à base de nanofils de Si et SiC ont été conçus dans une approche descendante pour être fabriqués par photolithographie. Un procédé de fabrication basé sur la filière silicium a été développé et optimisé afin de réaliser des dispositifs à nanofils et à nanorubans de Si de manière reproductible. Une étude détaillée a permis de démontrer la stabilité chimique supérieure des nanofils de SiC par rapport aux nanofils de Si en conditions physiologiques. Fort de ce résultat, nous avons exploré deux approches pour l’élaboration d’une couche mince de SiC autour de ces nanostructures de Si, pour leur conférer cette résistance chimique en milieu liquide. Ces dispositifs cœur-coquille Si/SiC reproductibles ont finalement été fonctionnalisés et intégrés dans un système microfluidique complet afin de réaliser des premières mesures novatrices de détection de pH et d’ADN en temps réel et en milieu liquide
Sensing of low concentrations of nucleic acids is essential to a variety of applications such as bio-medical analysis, in which case it allows the diagnosis of pathologies by identifying specific biomarkers. Compared to traditional sensing techniques based on biochemistry, the advantage of electrical field-effect detection is that it relies on a direct, label-free, and fast-response measurement. Transistors based on semiconducting nanowires are promising devices that theoretically enable very low detection limits and a high sensitivity, thanks to their high surface-to-volume ratio and unique electronic properties. Silicon carbide (SiC) is a semiconductor material with qualities such as very high physical and chemical stability and high biocompatibility, which make it particularly suited for aforementioned applications.In this thesis, field-effect transistors based on Si and SiC nanowires were designed with a top-down approach to be fabricated using photolithography techniques. The Si-based process was developed and optimized in order to fabricate reproducible devices made of nanowires and nanoribbons. A detailed study was conducted to demonstrate the superior chemical stability of SiC nanowires over Si nanowires under physiological conditions. Based on these results, we investigated two ways of elaborating a thin SiC layer around these Si nanostructures to provide them with its chemical resistance in liquid medium. These reproducible core-shell Si/SiC devices were eventually functionalized and integrated into a microfluidic system in order to achieve novel measurements of DNA detection in real time and in liquid media

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Ollivier, Maelig. "Elaboration de nanostructures à une dimension à base de carbure de silicium." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI095/document.

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Le carbure de silicium est pressenti comme un matériau prometteur dans plusieurs domaines de l’électroniquetels que la nano-électronique, l’électronique de puissance ou les capteurs travaillant en milieuxhostiles (hautes températures, milieux corrosifs, milieux biologiques) du fait de ses propriétés physicochimiquessupérieures à celles du silicium, notamment. Cependant, parmi les différentes méthodesd’élaboration par voie descendante ou ascendante permettant de fabriquer des nano-objets à 1D enSiC, aucune n’a pour l’instant permis d’obtenir du SiC d’excellente qualité cristalline.Le travail de cette thèse a porté sur la démonstration de l’élaboration de nanostructures 1D àbase de SiC, à savoir nanofils coeur-coquille Si-SiC, nanofils de SiC et nanotubes de SiC, par unprocédé original de carburation de nanofils de silicium, eux-mêmes élaborés par gravure plasma. Cettedémonstration a été possible grâce au contrôle de la pression de carburation, ce qui permet la maîtrisede l’exodiffusion des atomes de silicium à travers le carbure de silicium.À pression atmosphérique l’exodiffusion des atomes de silicium est restreinte ce qui permet d’élaborerdes nanofils coeur-coquille Si-SiC avec une coquille de SiC monocristalline et entièrement recouvrante.En se servant de la biocompatibilité du SiC et du bon contrôle électronique dans le silicium, ilest possible d’envisager l’utilisation de ces nanofils coeur-coquille Si-SiC pour des bio-nano-capteurs.En diminuant la pression au cours de la carburation, il est possible d’augmenter l’exodiffusion etainsi d’obtenir des nanotubes de SiC cubique de très bonne qualité cristalline avec des parois denses.Ces nanotubes de SiC sont largement modulables en termes de dimensions, et la faisabilité de leurouverture a été démontrée, permettant ainsi l’utilisation du fort rapport surface sur volume de telsnano-objets pour des capteurs électroniques notamment.Un premier pas a été franchi vers les applications des nanofils coeur-coquille Si-SiC et des nanotubesde SiC, puisque les mesures électriques réalisées sur des nano-transistors à effet de champ utilisant cesdeux types de nano-objets comme canal sont prometteurs
Due to their superior physical and chemical properties —such as high breakdown field, high thermalconductivity and biocompatibility— compared to other semiconductors, silicon carbide is forseento be a promising materials for power electronics, bio-nano-sensors and nano-electronics in harsh environments.However, among the numerous top-down or bottom-up methods used to synthesise siliconcarbide 1D nano-objects, none has been able yet to produce SiC with a high cristalline quality.The aim of this project is to demonstrate the synthesis of silicon carbide- based 1D nanostructures—e.g. core-shell Si-SiC nanowires, SiC nanowires and SiC nanotubes— through an original processbased on the carburization of plasma-etched silicon nanowires. This demonstration is based on thecontrol of the pressure during the carburization process, which leads to the monitoring of the outdiffusionof silicon atoms through silicon carbide.Thus if the pressure is kept at the atmospheric pressure, the out-diffusion of silicon is limited andSi-SiC core-shell nanowires can be synthesized with a single-crystalline cubic SiC shell. Thanks to thebiocompatibility of the SiC shell and the good electronic transport into the Si core, bio-nano-sensorscan be considered.If the pressure is decreased during the carburization process, the outdiffusion of silicon atomsthrough SiC is enhanced, and leads to SiC nanotubes synthesis. SiC nanotubes sidewalls are dense,with an excellent crystalline quality. These original SiC nanotubes have a high surface to volume ratioand thus can be used for sensors or storage devices.The first step for direct applications has also been demonstrated since first results on electricalperformances of nano-field effect transistors, with these nano-objects as channel, are promising

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Wang, Jianren. "Nanostructured Redox-Active Mesoporous Silica Films Based on An Electron-Hopping Mechanism : Charge Transfer Behaviors And Energy Storage Potentials." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0216.

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Un nouveau type de matériaux de stockage d'énergie à base de silice fonctionnant avec un mécanisme de saut d'électrons a été préparé en combinant une méthode d'auto-assemblage électrochimique (EASA) et une réaction de clic d'azide-alcyne catalysée par le cuivre (CuAAC). Les centres actifs redox (molécules de ferrocène ou de cobaltocénium) répartis à la surface du film de silice peuvent directement commuter les électrons par le biais du processus de saut d'électrons. Les résultats démontrent que ce mécanisme de transfert de charge est capable de fournir un taux de transfert d'électrons rapide même sur le substrat de silice isolant, ce qui se traduit par une performance de taux supérieure par rapport aux matériaux faradiques traditionnels. La haute densité des molécules redox et la voie de diffusion des contre-ions lisses ont été identifiées comme jouant un rôle essentiel pour assurer le processus de saut d'électrons rapide. En outre, l'assemblage à grande échelle du système de saut d'électrons a été réalisé en générant le film de silice fonctionnalisé au ferrocène sur une électrode autoportante en mousse de graphène, présentant une densité de capacité 100 fois plus élevée que celle générée sur une électrode ITO, tout en maintenant la performance de taux élevé. Enfin, une tentative a été faite pour assembler la silice fonctionnalisée au ferrocène sur un dispositif planaire flexible, et les résultats préliminaires ont prouvé la faisabilité de l'idée que nous proposons. Globalement, dans cette thèse, l'étude systématique du potentiel du processus de saut d'électrons dans le domaine du stockage de l'énergie, qui pourrait ouvrir une nouvelle voie pour la construction de matériaux de stockage de l'énergie
A new type of silica-based energy storage materials operating with electron-hopping mechanism has been prepared by combining electrochemically-induced self-assembly method (EASA) and a copper-catalyzed azide-alkyne click (CuAAC) reaction. The redox active centers (ferrocene or cobaltocenium molecules) distributed on the surface of the silica film can directly commute electrons via the electron-hopping process. The results demonstrate this charge transfer mechanism is able to deliver a fast electron transfer rate even on the insulating silica substrate, resulting in a superior rate performance in comparison to the traditional faradic materials. The high density of redox molecules and the smooth counter ions diffusion pathway have been identified playing a pivotal role to ensure the fast electron-hopping process. Besides, the large-scale assembly of the electron-hopping system has been achieved by further generating the ferrocene functionalized silica film on a free-standing graphene foam electrode, exhibiting a 100-times higher capacity density, in comparison to that generating on ITO electrode, while maintaining the high rate performance. Finally, an attempt has been tried to assemble the graphene-supported ferrocene-functionalized silica into a flexible planar device, and the preliminary results has proved the feasibility of our proposed idea. Overall, in this thesis, the systematical study for the potential of the electron-hopping process in the energy storage field, which may pave a new way for the construction of energy storage materials

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Ternon, Céline. "Nanostructures luminescentes à base de silice et de silicium : de l'élaboration par pulvérisation magnétron réactive à la modélisation de la photoluminescence." Caen, 2002. http://www.theses.fr/2002CAEN2057.

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Ce travail présente le développement d'une méthode originale d'élaboration basée sur la pulvérisation magnétron réactive d'une cible de silice pour l'obtention de matériaux luminescents à base de silicium. Les paramètres d'élaboration (gaz et température) permettent le contrôle de la composition du matériau déposé (SiO2, composite Si-SiO2 ou Si). Deux types de structures ont été élaborés et étudiés : Les composites Si-SiO2 où des nanocristaux de silicium sont noyés dans une matrice de silice : Un processus expérimental est développé afin d'accroître l'intensité de photoluminescence de ces matériaux. Les multicouches où alternent couches de silicium de quelques nanomètres et couches de silice d'une dizaine de nanomètres : Une étude expérimentale et théorique de la photoluminescence, en corrélation avec la microstructure du silicium, nous a permis de déterminer l'origine de l'émission, à savoir les structures nanométriques et la présence d'une région interfaciale entre silicium et silice.

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Bisson, Antoine. "Syntèse et étude de matériaux nanostructurés à base de silice pour la superisolation thermique." Paris, ENMP, 2004. http://www.theses.fr/2004ENMP1245.

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Skolem, Lotte Maria Beate. "Biosynthesis and characterization of Ti-doped silica-based Nanostructures formed by the Diatoms Pinnularia sp. and Coscinodiscus wailesii." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for bioteknologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-14143.

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The metabolic insertion of titanium into the biosilica frustules of the pennate diatom Pinnularia sp. and the centric diatom Coscinodiscus wailesii was explored in the present study. A total of five titanium incorporation experiments were conducted on Pinnularia, in addition to five control experiments. Titanium dissolved in HCl was co-delivered with silicate dissolved in NaOH to silicate replete and silicate deplete Pinnularia cultures over a 10 hour delivery period. Cell number, silicate and titanium concentration, Quantum Yield, Instantaneous Chlorophyll Fluorescence and pH was measured regularly throughout the experiments. The diatoms were left to consume the delivered silicate/titanium for 62 hours after delivery was completed before they were harvested and rinsed to remove the organic material. The resulting biosilica frustules were analyzed with (Scanning) Transmission Electron Microscopy to investigate the frustule structure, Inductively Coupled Plasma Mass Spectrometry to measure the elemental composition of the frustules and Energy Dispersive Spectroscopy to determine the location of the elements in the frustules. Quantum Yield measurements were conducted to obtain information about the Pinnularia photo system condition, and high Quantum Yield values were interpreted as an indication of a good overall physiological state of the cell. It was found that a combination of high Quantum Yield values and silicate depleted cultures produced the highest titanium content in the Pinnularia frustules (1.3 wt% relative to silicon). Furthermore, EDS analysis revealed that titanium was not evenly distributed throughout the biosilica frustule. The relative titanium content in the Pinnularia frustules was higher in the biosilica at the base of the large pores covering the frustule surface than in the biosilica between the pores. This was in accordance with findings reported in literature. The observed inhomogeneous distribution trend was found to apply also to phosphorous and iron present in the titanium-doped frustules. This observation has not been previously reported.Cell aggregation of the Pinnularia cultures was observed upon silicate/titanium addition. Based on results from control experiments there was reason to believe that the aggregation was triggered by titanium, but the explanation for this cellular response as well as its effect on titanium uptake and incorporation was not determined. Three titanium incorporation experiments were conducted in the proof on concept study on Coscinodiscus . Titanium dissolved in HCl and silicate dissolved in NaOH was co-delivered with a pipette once a day for three, five and seven days. On the day following the final addition, the diatoms were harvested and rinsed before they were analyzed in the same manner as Pinnularia. The experiments on Coscinodiscus revealed that metabolic insertion of titanium into the frustule biosilica was possible, but due to the small maximal titanium content achieved (0.03 wt% relative to silicon) and the slow growth rate, Coscinodiscus was not considered an optimal choice of diatom species for titanium incorporation purposes.It was not possible to rule out whether the frustule structure in any of the two species had been altered or impaired as a consequence of titanium exposure. Structural flaws were observed in frustules with and without titanium incorporated. A faint irregular pattern on the nanoscale was observed in Pinnularia frustules containing titanium. No such pattern was observed in titanium free frustules.The amount of boron measured in the frustule biosilica was higher than the regular dopant concentration in boron-doped silicon. The boron content in Pinnularia was found to be on average 0.1 wt% or 0.28 atomic % relative to Si, while the average in Coscinodiscus was nearly twice as high. Without further manipulation, this high boron natural boron concentration makes diatom frustules unusable for doped semiconductor purposes.Future work should involve reproduction of the obtained results with more replicates, as well as larger culture volumes and, in the case of Coscinodiscus in particular, longer time scale. Titanium uptake and incorporation studies should if possible be performed on single Coscinodiscus cells. Multiple continuous silicate starvation and titanium/silicate delivery cycles should be tested to determine if it is possible to incorporate titanium into a larger fraction of the culture population, as well as to increase the maximum amount of titanium incorporated into one frustule.Aggregation of Pinnularia diatoms should be further investigated to determine reason for the observed reaction, the effects on titanium uptake/incorporation and possible strategies to prevent it from occurring. Pinnularia frustules unexposed to titanium should be inspected in order to determine if the iron and phosphorous distribution pattern observed in the titanium-doped frustules is present in titanium-free frustules as well.A completely artificial culture medium and plastic cultivation containers should be applied to explore how the boron content of diatom frustules can be tailored by controlled delivery of boron to the culture medium.

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Krawczyk, Nastaran [Verfasser]. "Effect of nanostructured silica filler material on ionic liquid-based lithium electrolytes - systematic characterization of liquid and gellified electrolytes / Nastaran Krawczyk." Gießen : Universitätsbibliothek, 2014. http://d-nb.info/1068874481/34.

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LORENZI, ROBERTO. "Silica based functional materials: - Charge transport in nanostructured SnO2: SiO2 thin films. - Second harmonic generation in niobium potassium silicate glasses. - Tapered silica optical microfibres for gas sensors." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2010. http://hdl.handle.net/10281/10933.

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"Charge transport in nanostructured SnO2:SiO2 thin films": Silica based nanostructured thin films grown on silicon substrates are promising materials for novel light emitter devices. In particular, tin dioxide is a wide band gap n-type semiconductor (Eg=3.6 eV) with an expected band-to-band emission centered in the ultraviolet (344 nm) region of the electromagnetic spectrum. Our group succesfully demonstrated UV emission from such systems, but at the beginning of my work many issues in charge transport processes needed to be explained. Aim of this project was to clarify electric transport and charge trapping mechanisms. As a result of a materials science approach we can now interpret the experimental data through specific relationships between synthesis conditions, clustering morphology (nanoparticle (NP) size distribution and volumic concetration, interphase substoichiometry, film thickness), and electric response. The observed phenomena have been analyzed within the percolation theory. Main results concern: electric transport of both holes and electrons is sustained by NP-to-NP hopping events and dielectric enhancement results from oscillating charges (holes) on NPs. "Second Harmonic Generation in potassium niobium silicate glasses": Second harmonic generation (SHG) is a non linear optical process largely employed in current laser technology and photonics. However in almost every application the material employed for these purposes are single crystals. Therefore the possibility to achieve large SHG in amorphous systems may lead to devices with innovative configurations. SHG may occur only if the system is non-centrosymmetric, therefore for glasses it is forbidden due to intrinsic isotropy. The inversion symmetry can be broken up with poling treatments. They consist in applying strong electrostatic field while the sample is stressed by external perturbation (typically heat, electron beam or laser light). We have explored the effect of thermal poling treatment on potassium niobium silicate glasses on inducing non linear optical properties. The results have revealed a strong SHG associated with structural modifications. The proposed mechanism involves a rearrangement of niobium oxide groups mediated by non bridging oxygen and potassium ion transport across the glass. These new charge arrangements form a non-centrosymmetric region underneath the anodic contact responsible of the detected SH signal. "Tapered silica optical microfibres for gas sensors": In the last years, tapered silica fibres have attracted much interest in photonic research, because of peculiar properties emerging in waveguides with lateral dimensions of the same order of the guided modes. In particular, in these structures the large evanescent field enables some interesting properties, such as microfluidic sensors and high Q optical resonators (coiling the tapered fibre), non-linear effects and supercontinuum generation. In this project, carried out at the University of Southampton (UK) in the group of Dr. Gilberto Brambilla, we have explored the feasibility of an innovative optical absorption device, based on ring down spectroscopy. In this case we are interested in a sensor for in-line application: a fluidic channel wrapped with tapered fibre in which the analyte can flow. The large power fraction outside the fibre interacts with the flowing medium and any change in the surrounding optical properties (refractive index or absorption coefficient) leads to a modification of the recorded light intensity propagating in the fibre. The idea is to exploit ring down time of a silica tapered microcoil resonator as an indicator of the absorption coefficient of a gas (or a liquid) flowing in the channel.

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Tremblay, Ronan. "Propriétés structurales, optiques et électriques de nanostructures et alliages à base de GaP pour la photonique intégrée sur silicium." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0026/document.

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Ce travail de thèse porte sur les propriétés structurales, optiques et électriques de nanostructures et alliages à base de GaP pour la photonique intégrée sur silicium. Parmi les méthodes d’intégration des semi-conducteurs III-V sur Si, l’intérêt de l’approche GaP/Si est tout d’abord discuté. Une étude de la croissance et du dopage de l’AlGaP est présentée afin d’assurer le confinement optique et l’injection électrique dans les structures lasers GaP. Les difficultés d’activation des dopants n sont mises en évidence. Ensuite, les propriétés de photoluminescence des boites quantiques InGaAs/GaP sont étudiées en fonction de la température et de la densité d’excitation. Les transitions optiques mises en jeu sont identifiées comme étant des transitions indirectes de type-I avec les électrons dans les niveaux Xxy et les trous dans les niveaux HH des boites quantiques InGaAs et de type-II avec les électrons dans les niveaux Xz du GaP contraint. Malgré une modification notable de la structure électronique de ces émetteurs, une transition optique directe et type I n’est pas obtenue ce qui reste le verrou majeur pour la promotion d’émetteurs GaP sur Si. La maitrise de l’interface GaP/Si et de l’injection électrique est par ailleurs validée par la démonstration de l’électroluminescence à température ambiante d’une LED GaPN sur Si. Si l’effet laser n’est pas obtenu dans les structures lasers rubans GaP, un possible début de remplissage de la bande Гdans les QDs est discuté. Enfin, l’adéquation des lasers à l’état de l’art avec les critères d’interconnections optiques sur puce est discutée
This PhD work focuses on the structural, optical, electrical properties of GaP-based nanostructures and alloys for integrated photonics on silicon. Amongst the integration approaches of III-V on Si, the interest of GaP/Si is firstly discussed. A study of the growth and the doping of AlGaP used as laser cladding layers (optical confinement and electrical injection) is presented. The activation complexity of n-dopants is highlighted. Then, the photoluminescence properties of InGaAs/GaP quantum dots are investigated as a function of temperature and optical density. The origin of the optical transitions involved are identified as (i) indirect type-I transition between electrons in Xxy states and holes in HH states of quantum dots InGaAs and (ii) indirect type-II with electrons in Xz states of strained GaP. Despite an effective modification in the electronic structure of these emitters, a direct type I optical transition is not demonstrated. This is the major bottleneck in the promotion of GaP based emitters on Si. This said, the control of the GaP/Si interface and electrical injection are confirmed by the demonstration of electroluminescence at room temperature on Si. If no laser effect is obtained in rib laser architectures, a possible beginning of Г band filling in QDs is discussed. Finally, the adequacy of state of the art integrated lasers with the development of on-chip optical interconnects is discussed

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Letant, Sonia. "Transfert d'excitation dans les nanocomposites à base de silicium poreux." Université Joseph Fourier (Grenoble), 1998. http://www.theses.fr/1998GRE10117.

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Ce travail a ete consacre a l'etude du transfert d'excitation dans les nanocomposites a base de silicium poreux. Le but etait d'etudier le couplage des porteurs photogeneres dans les nanocristaux de silicium avec leur environnement, liquide, solide ou gazeux. Nous presentons ici l'investigation par des methodes de luminescence continue et resolue dans le temps, de trois structures composites : * le silicium poreux dans sa solution acide de formation : un processus de photodissolution des couches poreuses sous lumiere est mis en evidence et caracterise ; dans ce cas, les porteurs fuient physiquement les cristallites pour participer a la reaction photochimique permettant le passage des atomes de silicium dans la solution. * le silicium poreux impregne de colorants laser : il est demontre que les couches poreuses peuvent etre utilisees comme matrice d'accueil passive (excitation directe des molecules) ou active (transfert d'excitation de la matrice vers les molecules via un couplage dipolaire). * le silicium poreux couvert de liaisons si-h : une conversion de l'energie optique en energie vibrationnelle via un couplage dipolaire entre les porteurs et les vibrations de surface a lieu. Le role important de la surface specifique est alors mis en evidence malgre l'origine quantique de l'emission. Il ressort de cette etude que le silicium poreux, malgre sa faible efficacite quantique, est une bonne matrice d'accueil, grace a sa porosite ouverte et a sa grande surface specifique, et qu'il possede les proprietes d'un donneur d'excitation.

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De, Silva Vashista C. "Core-Shell Based Metamaterials: Fabrication Protocol and Optical Properties." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1062904/.

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The objective of this study is to examine core-shell type plasmonic metamaterials aimed at the development of materials with unique electromagnetic properties. The building blocks of metamaterials under study consist of gold as a metal component, and silica and precipitated calcium carbonate (PCC) as the dielectric media. The results of this study demonstrate important applications of the core-shells including scattering suppression, airborne obscurants made of fractal gold shells, photomodification of the fractal structure providing windows of transparency, and plasmonics core-shell with a gain shell as an active device. Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction. Significant extinction from the visible to mid-infrared makes fractal shells very attractive as bandpass filters and aerosolized obscurants. In contrast to the planar fractal films, where the absorption and reflection equally contribute to the extinction, the shells' extinction is caused mainly by the absorption. This work shows that the Mie scattering resonance of a silica core with 780 nm diameter at 560 nm is suppressed by 75% and only partially substituted by the absorption in the shell so that the total transmission is noticeably increased. Effective medium theory supports our experiments and indicates that light goes mostly through the epsilon-near-zero shell with approximately wavelength independent absorption rate. Broadband extinction in fractal shells allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. Au fractal nanostructures grown on PCC flakes provide the highest mass normalized extinction, up to 3 m^2/g, which has been demonstrated in the broad spectral range. In the nanoplasmonic field active devices consist of a Au nanoparticle that acts as a cavity and the dye molecules attached to it via thin silica shell as the active medium. Such kind of devices is considered as a nano-laser or nano-amplifier. The fabricated nanolasers were studied for their photoluminescence kinetic properties. It is shown that the cooperative effects due to the coupling of dye molecules via Au nanoparticle plasmons result in bi-exponential emission decay characteristics in accord with theory predictions. These bi-exponential decays involve a fast superradiant decay, which is followed by a slow subradiant decay. To summarize, this work shows new attractive properties of core-shell nanoparticles. Fractal Au shells on silica cores prove to be a good scattering suppressor and a band pass filter in a broadband spectral range. They can also be used as an obscurant when PCC is used as the core material. Finally, gold nanoparticles coated with silica with dye results in bi-exponential decays.

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Souza, Jair Fernandes de. "Desenvolvimento de materiais e métodos de fabricação de sensores químicos/bioquímicos baseados em silício e nanoestruturas de carbono (ISFET, CNTFET e GraFET) = Development of materials and methods of fabrication of chemical/biochemical sensors based on silicon and carbon nanostructures (ISFET, CNTFET and GraFET)." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/261064.

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Orientadores: Peter Jürgen Tatsch, José Alexandre Diniz
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-21T00:22:30Z (GMT). No. of bitstreams: 1 Souza_JairFernandesde_D.pdf: 13128989 bytes, checksum: 25325c1093f208d379ae77adc08c90ff (MD5) Previous issue date: 2012
Resumo: Este trabalho teve como objetivo o desenvolvimento de materiais e métodos avançados de fabricação de sensores químicos/bioquímicos. Utilizando equipamentos disponíveis no Centro de Componentes Semicondutores da UNICAMP, foram desenvolvidos e caracterizados filmes finos de alta constante dielétrica e filmes metálicos. Os materiais desenvolvidos foram empregados na fabricação de sensores baseados em transistores de efeito de campo sensíveis a íons (ISFET) e em dispositivos de efeito de campo que incorporam nanoestruturas de carbono como elemento funcional [grafeno (GraFET) e nanotubos de carbono (CNTFET)]. A aplicação dos materiais como camada sensível, dielétrico de porta e eletrodos, assim como a utilização de nanoestruturas, tem por objetivo aumentar a sensibilidade e a biocompatibilidade dos dispositivos, construir dispositivos robustos que possam ser empregados em ambientes agressivos e obter sensores com resposta linear e estável com o tempo e temperatura. Foram fabricados, caracterizados e encapsulados ISFET's com camada sensível constituída por filmes finos de nitreto de silício (SiNx)/nitreto de alumínio (AlN) e com eletrodos formados por filmes metálicos de alumínio. Filmes finos de óxido de titânio (TiOx) e óxido de tântalo (TaOx), cujas características são de interesse para aplicação como filme sensível em determinadas aplicações, também foram estudados. Os filmes foram obtidos pelas técnicas de deposição química em fase vapor (LPCVD), sputtering dc e oxidação térmica rápida (RTO). Foram desenvolvidas técnicas de fabricação de dispositivos de efeito de campo baseados em grafeno e nanotubos de carbono, utilizando como dielétrico de porta os filmes finos desenvolvidos para formar a camada sensível dos ISFET's. Entretanto, os eletrodos foram construídos empregando-se filmes finos de nitreto de tântalo (TaN) depositados por sputtering dc. Filmes sensíveis de SiNx são quimicamente estáveis e tornam os sensores robustos com sensibilidade em tensão próxima ao limite de Nernst (59 mV/pH). Entretanto, a grande sensibilidade em tensão obtida (50 mV/pH) não é transformada em alta sensibilidade em corrente (1,35 ?A/pH), devido ao baixo valor de transcondutância observado (19 ?S). Por outro lado, quando se utiliza AlN depositado a temperatura ambiente, tem-se um baixo valor de sensibilidade em tensão (20 mV/pH) que é transformado em uma alta sensibilidade em corrente (28 ?A/pH), em razão da alta transcondutância dos dispositivos (329 ?S). GraFET's e CNTFET's demonstraram a modulação da corrente entre os eletrodos de fonte e dreno pela ação do campo elétrico perpendicular, aplicado com o auxílio do eletrodo de porta. Entretanto, o efeito de campo observado é ambipolar, ou seja, existem dois regimes possíveis de operação dos dispositivos, um regime dominado pelo transporte de lacunas e outro dominado pelo transporte de elétrons. A característica ambipolar possibilita a detecção de moléculas carregadas positiva e negativamente, enquanto que o baixo coeficiente de temperatura do filme de TaN possibilita a utilização dos dispositivos em processos realizados em altas temperaturas
Abstract: The main aim of this work is the development of advanced materials and methods for the fabrication of chemical/biochemical sensors. By using equipments available in the Center of Semiconductor Components of UNICAMP, high dielectric constant thin films and metallic films have been developed and characterized. The materials developed were employed in the fabrication of sensors based on ion-sensitive field effect transistors (ISFET) and in field-effect devices incorporating carbon nanostructures as functional elements [Graphene (GraFET) and carbon nanotubes (CNTFET)]. The application of these materials as sensitive layer, gate dielectric and electrodes, as well as the use of nanostructures, aims to increase the sensitivity and biocompatibility of the devices, to build robust devices that can be used in harsh environments and obtain sensors with linear and stable response over time and temperature. ISFET's with sensitive layer consisting of thin films of silicon nitride (SiNx)/aluminum nitride (AlN) and with electrodes formed by aluminum metallic films were fabricated, characterized and packaged. Thin films of titanium oxide (TiOx) and tantalum oxide (TaOx), whose characteristics are interesting in certain applications, were also studied. The films were obtained by chemical deposition techniques in vapor phase (LPCVD), dc sputtering and rapid thermal oxidation (RTO). Techniques have been developed for manufacturing field effect devices based on graphene and carbon nanotubes, the thin films developed to form the ISFET's sensitive layer were used as gate dielectric. However, the electrodes were built by using thin film of tantalum nitride (TaN) deposited by dc sputtering. SiNx sensitive films are chemically stable and make sensors robust with sensitivity in voltage near to the Nernst limit (59 mV/pH). However, the great sensitivity in voltage (50 mV/pH) is not transformed into high current sensitivity (1.35 ?A/pH), due to the low value of transconductance (19 ?S). On the other hand, when AlN deposited at room temperature is used, a low voltage sensitivity value is obtained (20 mV/pH) that is transformed into a high sensitivity in current (28 ?A/pH), due to high transconductance of the devices (329 ?S). GraFETs and CNTFETs demonstrated the current modulation between the source and drain electrodes by the action of perpendicular electric field, applied with the aid of the gate electrode. However, the field effect observed is ambipolar, in other words, there are two possible operation regime, a regime dominated by the transport of holes and another dominated by transport of electrons. The ambipolar feature enables the detection of positively and negatively charged molecules, while the low temperature coefficient of TaN film allows the use of devices in processes carried out at high temperatures
Doutorado
Eletrônica, Microeletrônica e Optoeletrônica
Doutor em Engenharia Elétrica

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45

El, Fouhaili Bandar. "Development of hydrophobic/superhydrophobic anti-fouling photopolymer coatings for PVC reactor." Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH6191.

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Lors de la polymérisation en suspension du chlorure de vinyle, il se forme sur les parois un dépôt de polychlorure de vinyle (PVC). Ce phénomène, nommé encroûtement, génère des problèmes car il limite la production de PVC et affecte la qualité du produit final. Dans ce contexte, un projet FUI (Fond Unique Interministériel) intitulé «Ecoating», a été financé dans le cadre d’une collaboration entre plusieurs partenaires industriels et universitaires (INEOS ChlorVinyls, Mäder Research, Avenir Group, LPIM, ESPCI-ParisTech). Deux thèses ont vu le jour au LPIM, avec pour but de développer un revêtement (photo)polymère aux propriétés anti-encroûtement durables qui permettrait d’améliorer la qualité du PVC produit, d’augmenter les quantités produites et ainsi d’améliorer la compétitivité des usines de PVC. Cette thèse s’inscrit dans le développement d’un vernis photopolymère répondant au cahier des charges. Pour éviter l’encroûtement des réacteurs, il est nécessaire de stopper une étape du mécanisme d’encroûtement comme l'adsorption sur les parois du réacteur d’un copolymère nommé Acvagen Graft Copolymer (AGC). Ce copolymère est très actif dans le phénomène d’encroûtement (site de nucléation) et se trouve principalement dans la phase aqueuse du milieu réactionnel. La stratégie de recherche élaborée dans ce projet a été basée sur le développement d'un revêtement photopolymère présentant une faible affinité pour l'eau et devant adhérer à la surface des réacteurs pour éviter la formation de croûte. Les polymères à base de fluoroacrylates ont été les premiers candidats choisis dans cette étude du fait que leurs propriétés exceptionnelles (faible énergie de surface, stabilité chimique et haute hydrophobicité...) pouvaient éviter l'adsorption de l'AGC sur les parois du réacteur, et par conséquent le développement de la croûte. Une recherche bibliographique a été réalisée pour comprendre le comportement particulier de ces molécules qui migrent vers la surface du film et s’organisent en surface pour donner des surfaces hydrophobes. Des mélanges de résines fluoroacryliques modèles ont été testés pour évaluer le caractère hydrophobe du revêtement, comprendre la migration des molécules de fluor vers l’interface en fonction de la nature de substrat et aussi déterminer l’influence de l’ajout d’additifs fluorés au mélange sur les propriétés globales du film. Cette étude nous a permis de comprendre l’influence de l’additif fluoré sur les propriétés chimiques et physiques du film. À l’échelle du laboratoire des tests d’immersion de ces revêtements déposés sur l’acier inoxydable ont étés réalisés dans l’eau chaude (80°C) afin de caractériser leur caractère hydrophobe en fonction du vieillissement dans l’eau chaude ainsi que l’adhésion du film au substrat. Nous avons observé une diminution de l'hydrophobicité de la surface du film au cours du temps lors d’une immersion. [...]
Our scientific approach has explored different strategies to develop a durable UV-cured coating with antifouling properties to prevent the crust formation. Firstly, the potential of fluoroacrylate photocurable coatings was exhaustively investigated. Indeed, their outstanding properties (low surface energy, chemical stability and high hydrophobicity...) could limit the adsorption of the AGC on the reactor walls and further encrusting. A bibliographic research highlighted the behavior of fluorinated monomers on film surface and the parameters affecting the hydrophobic properties. Different fluorinated monomers were selected. At low concentration, they provide hydrophobic surfaces on 316L stainless steel, the reference substrate. However, a decrease of the films surface hydrophobicity in hot water was observed with time, and was attributed to a disorganization of the fluorinated chains on the coating surface. An optimization of the amount of fluoroacrylate monomer was performed by confocal Raman microscopy (CRM) to promote the fluorinated chains stability on the surface before and after immersion in hot water at 80°C. The beneficial effect was found maximal at a concentration ranging from 1 to 1.8 wt%. However, even after this optimization, a decrease of the film surface hydrophobicity was observed for increased immersion time in hot water. Therefore, optimized fluoroacrylate monomer concentration was combined with alternated thermal/immersion post-treatment and has conducted to more stable photocured films. This result was attributed to a rigidification of the fluorinated chains on the film surface limiting thus, the extent of their disorganization. After this study realized at a laboratory scale, we tested the photocured coating in the VCM pilot reactor. A surface cleaning, an increase of the stainless steel roughness by shot blasting and the use of alkoxysilanes as coupling agents were implemented in order to enhance the adhesion properties of the photopolymer film on stainless steel. In addition, the use of a fluorinated monomer containing a heteroatom improved the rigidification when associated with the alternated thermal/immersion post-treatment. The crust formation was limited during four successive polymerizations in the VCM pilot reactor. A durable anti-fouling UV-coating could be not obtained due to some swelling phenomena resulting from the lack of coating adhesion or some abrasion occurring from small PVC pellets during the PVC polymerization.A second part of this project was dedicated to superhydrophobic coatings. Indeed, reducing interaction with water should lead to a better protection of the substrate. A literature review on the superhydrophobic surfaces has shown that the contact with hot water generally strongly affects their antiwetting properties and induces a large contact angle decrease. [...]

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Ho, Chi-Yin, and 何技殷. "Synthesis and characteristic of the silicon-based nanostructure." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/83108432480455178326.

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碩士
國立臺灣科技大學
光電工程研究所
97
In this research, the silica nanowires (SiOx NWs) were synthesized on silicon substrate via a thin gold catalytic reaction by the thermal chemical vapor deposition system. The XeF excimer laser with different energy was adapted as the pretreatment and post-treatment technique for silica nanowires. The FE-SEM and FTIR and XPS were used for silica nanowires characteristic. Furthermore, It was observed that the I-V characteristic of patterned silica nanowires was improved. To investigate the potential application for the bundles of silicon nanowires in solar cell anti-reflection, the anti-reflection properties for the bundles of silicon nanowires were studied with different length. The reflectance is lowest (<5%) in the visible region as the nanowires length increased. Regardless, the reflectance was increased after the CF4 and H2 plasma post-treatment. The photoluminescence characteristic for the bundles of silicon nanowires by EMD process is inferior to those by the chemical vapor disposition (CVD) technique. The photoluminescence intensity for the bundles of silicon nanowires is low. The photoluminescence intensity was enhanced as the nanowires length increased. It was found that the photoluminescence intensity is strongest after the CF4 plasma post-treatment for 400 sec. However, there was no obvious variation for the H2 plasma post-treatment. It was observed that turn-on field was approximately 14.6 V/μm for the bundles of silicon nanowires in the field emission measurement. The high turn-on field could be a result of screen effect due to the high density of nanowires getting to close to each other. After CF4 plasma post-treatment, it was found that the lowest turn-on field and highest β factor were 14.2 V/μm、645, respectively.

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Chen, Chun-Yi, and 陳俊毅. "A Silicon-Based Hollow Nanostructure produced by Electrospinning process." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/c55722.

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碩士
義守大學
材料科學與工程學系
107
In this study, the silicon-base net-like hollow nano- structure were prepared using single-nozzle electrospinning and heat treatment process. Firstly, a precursor solution is prepared by dissolving an appropriate amount of Polyvinyl- pyrrolidone (PVP) and Tetraethyl orthosilicate (TEOS) in ethanol and spinning the nanofibers using a single -nozzle electrospinning. Secondly, the morphology of electrospi- nning nanofibers was controlled, the temperature profile was designed to prepare hollow nanofibers, and the morphology and properties of nanofibers were explored. Molding with traditional methods, such as rapid freezing, 3D printing, and sintering. It is almost impossible to prepare fibers with diameters less than 1 μm. The electrospinning technology is simple in its production process and cab increase the hollow, high length, uniform 　　diameter, and diverse components of the nano-fiber. Finally, The characteristic of nanofibers, following instrum- ents were used:Field Emission Scanning Electron Microscope (FE-SEM), Photoluminescence (PL), X-ray Diffract-ion(XRD).Using FE-SEM system is to explore the morphology, diameter of nanofibers, and hollow nanofiber.The electrospinning technique followed by sub-sequent heat treatment is well developed so that we can successfully prepare silicon-base oxide nanofibers with the hollow structure. Thus, the microstructure and morphology of electrostatic spinning silicon-base oxide hollow nanofib- ers were explored, and also their crystalline properties and crystal structure were identified.

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Zhan, Jun-Yu, and 詹竣宇. "Nanostructure-enhanced Broadband Photodetector Based on Graphene/CdSe Quantum Dot/Silicon Multiple Junctions." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/83937728306479422712.

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碩士
國立臺灣海洋大學
光電科學研究所
102
The thesis studies the fabrication of efficient broadband(380 nm ~ 940 nm) photodetector(PD) base on graphene/CdSe QDs/Si multiple junctions. At 2 V bias for the graphene side, the external quantum efficiency(EQE) up to 218 % at 510 nm and the responsivity as high as 0.9 A/W for the range from 520 nm to 660 nm were achieved. The response time and recovery time are 0.24 ms and 0.28 ms, respectively. Under bias of -2 V for the graphene side, the dark current, photocurrent and on/off ratio was fou- nd to be 1.77#westeur024#10-6 A, 2.06#westeur024#10-4 A and ~10+2, respectively. It was found that when CdSe QDs were added, the EQE and responsivity of graphene/CdSe QDs/Si PD with respect to that of graphene/Si PD were enhanced together with the increase in the absorption band of the detector ranging from ultraviolet to near-infrared. Thus the graphene/CdSe QDs/Si multiple junctions can form the efficient broadband phtodetector.

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Chen, Ting-Gang, and 陳亭綱. "Fabrication and Analysis of Nanostructure on Silicon-Based Homo- and Hetero- Junction Photovoltaic Devices." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/ww4r7z.

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博士
國立交通大學
光電工程學系
101
Wafer-based silicon photovoltaics are currently dominating the solar cells industry, and they are likely to continue dominate the market share due to the mature technology. However, the price of silicon photovoltaics is necessary to further decrease to accelerate the wide-spread use. Therefore, new techniques to save the material usage and to reduce the fabrication costs are essential. In this thesis, we firstly introduced the nano-technology and its applications on silicon photovoltaics. Then, we presented solar cells based on silicon nanohole arrays which employ polystyrene nanosphere lithography and reactive-ion etching (RIE) techniques for large-area processes. Moreover, optical modeling has been established to perform the wafer thickness dependence of active layer absorption. The SiNH arrays reveal great potential for efficient light harvesting in thin silicon photovoltaics with a 95% of material saving compared to a typical cell thickness of 200 μm. To address the goal of simplifying the fabrication procedures in silicon photovoltaics, we developed hybrid heterojunction solar cells based on a conjugate polymer directly spun-cast on micro-textured n-type crystalline silicon wafers. Moreover, we presented solution-processed silver-nanowire meshes which uniformly cover the micro-textured surface of hybrid heterojunction solar cells to enable efficient carrier collection for large device area. A remarkable power conversion efficiency of 10.1% is achieved with a device area of 1×1 cm2. A one-dimensional drift-diffusion model is then developed based on fitting the device characteristics with experimentally determined PEDOT:PSS parameters and projects an ultimate efficiency above 20% for organic/inorganic hybrid photovoltaics. The simulation results reveal the impacts of defect densities, back surface recombination, doping concentration, and band alignment.

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Dohnalová, Kateřina. "Study of Optical Amplification in Silicon Based Nanostructures." Doctoral thesis, 2007. http://www.nusl.cz/ntk/nusl-289628.

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