Pour voir les autres types de publications sur ce sujet consultez le lien suivant : Nano crystal.
Thèses sur le sujet « Nano crystal »
Créez une référence correcte selon les styles APA, MLA, Chicago, Harvard et plusieurs autres
Consultez les 50 meilleures thèses pour votre recherche sur le sujet « Nano crystal ».
À côté de chaque source dans la liste de références il y a un bouton « Ajouter à la bibliographie ». Cliquez sur ce bouton, et nous générerons automatiquement la référence bibliographique pour la source choisie selon votre style de citation préféré : APA, MLA, Harvard, Vancouver, Chicago, etc.
Vous pouvez aussi télécharger le texte intégral de la publication scolaire au format pdf et consulter son résumé en ligne lorsque ces informations sont inclues dans les métadonnées.
Parcourez les thèses sur diverses disciplines et organisez correctement votre bibliographie.
1
Zhu, Rui. « Integrated nano-optomechanics in photonic crystal ». Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS258/document.
Texte intégralRésumé :
Les oscillateurs de référence de haute pureté sont actuellement utilisés dans un grand nombre d’applications allant du contrôle de fréquence aux horloges pour les radars, les GPS et l’espace... Les tendances actuelles dans ce domaine requièrent des architectures miniaturisées avec la génération de signaux directement dans la gamme de fréquences d’intérêt, autour de quelques GHz. Récemment, de nouvelles architectures basées sur les principes de l’optomécanique ont vu le jour dans ce but. De tels oscillateurs optomécanique génèrent non seulement des signaux hyperfréquences directement dans la gamme de fréquences GHz avec éventuellement un faible bruit de phase, mais permettent également un degré élevé d'intégration sur puce. Ce travail de thèse s'inscrit dans cette démarche. L’oscillateur optomécanique étudié se compose de cavités à cristaux photoniques suspendues couplées à des guides d’ondes silicium sur isolant intégrés dans une architecture tridimensionnelle. Ces cavités abritent des modes optiques fortement confinés autour de 1550nm et des modes mécaniques dans le GHz. De plus, ces structures présentent un recouvrement spatial entre phonon et photon élevé. Il en résulte un couplage optomécanique amélioré. Cette force de couplage optomécanique améliorée est ici sondée optiquement sur des structures à cristaux photoniques de conception optimisée. Ces cavités sont réalisées dans des matériaux semi-conducteurs III-V dont la piézoélectricité nous permet d'intégrer des outils supplémentaires pour sonder et contrôler les vibrations mécaniques via un pilotage capacitif, piézoélectrique ou acoustique. Ce contrôle total des modes mécaniques et de l’interaction optomécanique ouvre la voie à la mise en œuvre de circuits intégrés pour le verrouillage par injection et des boucles de rétroaction permettant de réduire le bruit de phase de l’oscillateurHigh purity reference oscillators are currently used in a wide variety of frequency control and timing applications including radar, GPS, space... Current trends in such fields call for miniaturized architectures with direct signal generation in the frequency range of interest, around few GHz. Recently, novel optomechanically-enhanced architectures have emerged with this purpose. Such optomechanically-driven oscillators not only generate microwave signals directly in the GHz frequency range with possibly low phase noise but also are amenable to a high degree of integration on single chip settings. This PhD work falls within this scope. The optomechanically-driven oscillator under study consists of suspended photonic crystal cavities coupled to integrated silicon-on-insulator waveguides in a three-dimensional architecture. These cavities harbor highly-confined optical modes around 1,55 µm and mechanical modes in the GHz and most importantly, feature a high phonon-photon spatial overlap, all resulting in an enhanced optomechanical coupling. This enhanced optomechanical coupling strength is here probed optically on photonic crystal structures with optimized design. These cavities are hosted in III-V semiconductor materials whose piezoelectricity enable us to integrate additional tools for probing and controlling mechanical vibrations via capacitive, piezoelectric or acoustic driving. This full control over the mechanical modes and optomechanical interaction, paves the way towards the implementation of integrated injection locking circuits of feedback loops for reducing the phase noise of the oscillator
2
Vizuete, Olivier. « Simulation study of phononic crystal structures ». Thesis, Uppsala universitet, Fasta tillståndets elektronik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-326118.
Texte intégralRésumé :
Thermoelectric materials are important in today’s society with a variety of applications. The material properties that determinate the efficiency of a thermoelectric device are mostly constants. In order to develop more efficient thermoelectric devices new materials and solutions need to be made. Minimizing the thermal conductivity in thermoelectric materials is of great interest to make them more effective. One effective way of lowering the thermal conductivity is to introduce holes in the lattice and create a phononic crystal. The main focus of this master thesis has been on how to place these holes and to optimize the geometry to minimize thermal conductivity. The method used in this report is based solely on simulations, which were done using Comsol Multiphysics 5.2a. The results are compared to already published results. Different geometries are tested to see how it affects the thermal conductivity and to optimize the phononic crystal. The Maxwell-Eucken model is also used to see how porosity affects the thermal conductivity and to analyze what the lowering in thermal conductivity depends on. The result showed a substantial reduction in thermal conductivity when creating a phononic crystal compared to bulk silicon. The simulated reduction compared to bulk silicon is up to 98.5% when introducing holes in the lattice, while Maxwell-Eucken only predicted a 74% reduction due to porosity. The conclusion is that by creating holes in a periodical pattern, phonon dispersion will occur, which lower the thermal conduction significantly.
3
Al-Zangana, Shakhawan. « Nano- and micro-particle doped liquid crystal phases ». Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/nano-and-microparticle-doped-liquid-crystal-phases(31dbb051-7d9c-4780-bda0-d58773846de0).html.
Texte intégralRésumé :
This thesis presents the investigation of the liquid crystal (LC) - particle suspensions. Particles from nano- to micro-size, spherical to two-dimensional shapes, with different functionality are dispersed into nematic and smectic phases. The aim is to create ordered nanoparticle (NP) assemblies and thereby modify the common properties of the liquid crystal, such as dielectric anisotropy and electro-optical, revealing any interaction between particles and LC properties. It is found that for concentrations (>0.5vol%), the ferroelectric NPs have increased the sensitivity of the nematic liquid crystal to the electric field through electro-optical responses, which is seen by an enhancement in the dielectric anisotropy. This could be induced by the coupling of the electrical dipole moments in the spherical NPs with the LC director field. The electro-optical properties of the chiral smectic (SmC*) phase (tilt angle Θ, switching time τ_s and spontaneous polarisation P_s) are found to be independent of the concentration and sizes of the doped NPs. The relaxation frequency f_R of the Goldstone mode is faster in the ferroelectric NPs suspensions of 2.0vol% compared to the paraelectric NPs. In the graphene oxide (GO) - nematic LC (5CB) suspensions, the small GO sizes of mean size 560 nm are more easily dispersible than larger flakes of 2.8 micro metre mean size. As the GO concentration is increased, each of the threshold voltage and splay elastic constant dramatically increases, reaching saturation at ≈1.0wt%. The field driven switching-on time is practically not affected, while the purely elastically driven switching-off time is strongly sped-up. Interestingly, thermotropic and lyotropic LC phases are exhibited in the GO-5CB suspensions when heating the thermotropic liquid crystal into its isotropic phase. The isotropic phase of 5CB acts as a solvent for the GO particles, forming a lyotropic nematic phase with largely reduced birefringence. It is found that the nematic to isotropic phase transition is shifted toward higher temperature for the GO-5CB system compared to the BaTiO3-5CB system. Dispersions of different sizes of GO flakes are prepared in isotropic and nematic fluid media. The dielectric relaxation behaviour of GO-dispersions was examined for a wide temperature range (25-60 ℃) and frequency range (100 Hz-2 MHz). The mixtures containing GO flakes were found to exhibit varying dielectric relaxation processes, depending on the size of the flakes and the elastic properties of the dispersant fluid. The relaxation frequencies in the isotropic media were lower compared to the nematic medium. Relaxation frequencies (~10 kHz) are observed in the GO-isotropic media, which are reduced as the size of the GO flakes are decreased, are anticipated to be inherited from GO flakes. However, the fast relaxations (~100 kHz) that are observed in the nematic suspensions could imply strongly slowed down molecular relaxation modes of the nematogenic molecules. Finally, the phase diagram of lyotropic LC as a function of the lateral dimensions of the GO flakes, their concentration, geometrical confinement configuration and solvent polarity was investigated. Polarising optical microscopy was used to determine isotropic-biphasic-nematic phase evolution. The confinement volume and geometry of the sample relative to the GO size are shown to be vital to the observation of the lyotropic phase. GO LCs have the potential for a range of applications from display technologies to conductive fibres. The confinement related LC phase transition is critical toward their applications. It is also found that the stability of the LC phase is higher for the solvent of higher dielectric constant.
4
Hurley, Evan Patrick. « A crystal engineering approach for the design of multicomponent crystals and assembly of nano-scale architectures ». Diss., Kansas State University, 2013. http://hdl.handle.net/2097/16004.
Texte intégralRésumé :
Doctor of PhilosophyDepartment of Chemistry
Christer B. Aakeroy
The work presented in this thesis has demonstrated that supramolecular synthons can be used to make multicomponent crystals, and various synthons can be combined to make supermolecules. The synthons can also be used to construct nanoscale assemblies. Molecules containing single and multiple hydrogen-bond (HB) and halogen-bond (XB) acceptor sites have been synthesized in an effort to carry out supramolecular synthesis in order to establish a reliable hierarchy for intermolecular interactions. Pyrazole-based molecules have been made, combined with various carboxylic acids, and characterized using infrared (IR) spectroscopy to give a success rate of 55-70%. Reactions that gave a positive result were converted to solution experiments, and crystals were grown and characterized using single-crystal X-ray diffraction (XRD). The co-crystals display infinite 1-D chains with the intended stoichiometry and structural landscape on 6/6 occasions. The salts, on the other hand, display unpredictable stoichiometry and structural landscape on 5/5 occasions. Furthermore, the electrostatic charge on the primary hydrogen-bond acceptor, N(pyz), can be altered by adding a nitro, R-NO2, covalent handle to the backbone of the pyrazole molecule. Addition of a strongly electron withdrawing group significantly lowered the charge on the pyrazole nitrogen atom and, in turn, lowered the supramolecular yield to 10%. Ditopic molecules containing pyrazole and pyridine on the same molecular backbone were synthesized and characterized using 1H NMR. The molecules were co-crystallized with carboxylic acids, and the resulting solids were characterized using IR spectroscopy. The solids could then be classified as co-crystal or salt using specific markers in the IR spectrum. Single-crystal XRD was used to observe the intermolecular interactions in the co-crystals and salts, and the co-crystals were assigned to two groups: Group 1 (2) and Group 2 (2). The salts (4) show more unpredictability with stoichiometry and structural landscape. A library of ditopic molecules containing triazole and pyridine acceptor sites were synthesized and characterized using 1H and 13C NMR. The molecules were co-crystallized with carboxylic acids and the resulting solids were characterized using IR spectroscopy which demonstrated a 100% supramolecular yield whenever a pyridine moiety was present, consistent with results from Chapter 3. Single-crystal XRD was used to identify the intermolecular interactions in the co-crystals (2) and salt (1), and the results show that triazole can compete with pyridine for hydrogen bond donors. A library of ditopic molecules was also used for halogen-bonding (XB) studies with a series of activated iodine and bromine-based donors. The results show that iodine donors have a higher success rate range (12.5-75%) compared to bromine donors (16.7-50%) based on results obtained from IR spectra. Furthermore, the results from the XRD show that pyrazole nitrogen atoms can compete with pyridine for forming XB, and two groups of supramolecular synthons were observed. Finally, relatively weak non-covalent interactions, HB and XB, can influence the assembly of nanoparticles based on IR spectroscopy and TEM images. The assembly of the particles is influenced by specific capping ligands, which were synthesized and characterized using 1H, 13C and 19F NMR. The results demonstrate that relatively weak non-covalent interactions based on HB and XB interactions can influence nanoparticle assembly.
5
Mei, Shan. « Novel Three Dimensional C3v Symmetric Nano-molecules Based on Polyhedral Oligomeric Silsesquioxanes (POSS) Nano-atoms ». University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1367361671.
Texte intégral
6
Brunstein, Maia. « Nonlinear Dynamics in III-V Semiconductor Photonic Crystal Nano-cavities ». Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00606315.
Texte intégralRésumé :
L'optique non linéaire traite les modifications des propriétés optiques d'un matériau induites par la propagation de la lumière. Depuis ses débuts, il y a cinquante ans, des nombreuses applications ont été démontrées dans presque tous les domaines de la science. Dans le domaine de la micro et nano-photonique, les phénomènes non linéaires sont à la fois au cœur d'une physique fondamentale fascinante et des applications intéressantes: ils permettent d'adapter et de contrôler le flux de lumière à une échelle spatiale inferieure à la longueur d'onde. En effet, les effets non linéaires peuvent être amplifiés dans des systèmes qui confinent la lumière dans des espaces restreints et avec de faibles pertes optiques. Des bons candidats pour ce confinement sont les nanocavités à cristaux photoniques (CPs), qui ont été largement étudiées ces dernières années. Parmi la grande diversité des processus non linéaires en optique, les phénomènes dynamiques tels que la bistabilité et l'excitabilité font l'objet de nombreuses études. La bistabilité est bien connue pour ces applications potentielles pour les mémoires et les commutateurs optiques et pour les portes logiques. Une réponse excitable typique est celle subjacente dans le déclanchement du potentiel d'action dans les neurones. En optique, l'excitabilité a été observée il y a une quinzaine d'années. Dans ce travail, nous avons étudié les régimes bistables, auto-oscillants et excitables dans des nanocavités semiconductrices III-V à CP. Afin de coupler efficacement la lumière dans les nanocavités, nous avons développé une technique de couplage par onde évanescente en utilisant une microfibre optique étirée. Grâce à cette technique, nous avons démontré pour la première fois l'excitabilité dans une nanocavité à CP. En parallèle, nous avons accompli la première étape vers la dynamique non linéaire dans un réseau de cavités couplées en démontrant le couplage optique linéaire entre nanocavitités adjacentes. Ceci a été réalisé en utilisant de mesures de photoluminescence en champ lointain. Un ensemble de résonateurs non linéaires couplés ouvre la voie à une famille de phénomènes dynamiques non linéaires très riches, basés sur la rupture spontanée de symétrie. Nous avons démontré théoriquement ce phénomène dans deux cavités couplées par onde évanescente. Les premières études expérimentales de ce régime ont été menées, établissant ainsi les bases pour une future démonstration de la rupture spontanée de symétrie dans un réseau de nanocavités non linéaires couplées.
7
Marseglia, Luca. « Nano-structures coupled to optically active defects in diamond ». Thesis, University of Bristol, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.573911.
Texte intégral
8
Reinke, Charles M. « Design, simulation, and characterization toolset for nano-scale photonic crystal devices ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33932.
Texte intégralRésumé :
The objective of this research is to present a set of powerful simulation, design,
and characterization tools suitable for studying novel nanophotonic devices. The
simulation tools include a three-dimensional finite-difference time-domain code adapted
for parallel computing that allows for a wide range of simulation conditions and material
properties to be studied, as well as a semi-analytical Green's function-based complex
mode technique for studying loss in photonic crystal waveguides. The design tools
consist of multifunctional photonic crystal-based template that has been simulated with
nonlinear effects and measured experimentally, and planar slab waveguide structure that
provides highly efficient second harmonic generation is a chip-scale device suitable for
photonic integrated circuit applications. The characterization tool is composed of a
phase-sensitive measurement system using a lock-in amplifier and high-precision optical
stages, suitable for probing the optical characteristics of nanoscale devices. The high
signal-to-noise ratio and phase shift data provided by the lock-in amplifier allow for
accurate transmission measurements as well as a phase spectrum that contains
information about the propagation behavior of the device beyond what is provided by the
amplitude spectrum alone.
9
Liang, Hong. « Crystal plasticity modelling of lengthscale effects in deformation and nano-indentation ». Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496995.
Texte intégral
10
Pendergast, Megan. « Environmental effects on nano-wear of gold and KBr single crystal ». [Tampa, Fla.] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002306.
Texte intégral
11
Shi, Xiaohua. « Design, fabrication and characterization of one dimensional photonic crystal devices ». Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.485957.
Texte intégralRésumé :
Photonic crystals (PhCs) are periodically structured electromagnetic media, generally characterised by not permitting light of defined ranges of frequency to propagate through the structure. These disallowed ranges of frequency are known as photonic band gaps. The intentional introduction of defects into the crystal gives rise to localized electromagnetic states that provide a mechanism for the control of the propagation of photons through PhCs. In the case of one dimensional (1-D) PhCs, the introduction of a single defect into a finite PhC results in the formation of a resonant cavity structure, a so-called microcavity. The ease of fabrication and scope for integration make 1-D PhCs good candidates for the future applications of PhCs in light transmission systems and, as such, these structures are the focus of the research reported here. The aim of this thesis is to report a practical study of passive 1-D PhC devices and thereby extend the base of measurements that support and extend the results of theory and simulation. Various types of 1-D PhC structures have been fabricated using electron beam lithography and inductively coupled plasma technologies in a clean-room environment. The fabricated structures in effect demonstrate a first or primitive level of integration of 1-D PhCs with another optical device, namely a ridge waveguide. Measurements were performed by butt-coupling from a single mode fibre taper of the transmission characteristics of the resulting integrated waveguides, whilst a Side-band measurement method for very high resolution (0.2pm) microcavity characterisation was invented during the measurement process. A multiple wavelength transmission optical filter transmitting at the telecommunication wavelengths of 1310nm and 1550nm, and which could be used in a WDM system was demonstrated. The effect of introducing mode matching structures to minimize II the scattering loss and boost the quality factor value was investigated. Optimum positioning of the tapers produced a significant enhancement of Q. Finally, a narrow pass band filter constructed from coupled cavities was fabricated and characterised. A quasi-flat transmission peak with a pass band width of just 4nm was observed.
12
Chen, Yan. « SINGLE CRYSTAL ENGINEERING OF AMORPHOUS-CRYSTALLINE BLOCK COPOLYMERS CRYSTALLIZATION, MORPHOLOGY AND APPLICATIONS ». University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1133226076.
Texte intégral
13
Chen, Zhihui. « Light manipulation in micro and nano photonic materials and structures ». Doctoral thesis, KTH, Teoretisk kemi och biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-94081.
Texte intégralRésumé :
Light manipulation is an important method to enhance the light-matter interactions in micro and nano photonic materials and structures by generating usefulelectric field components and increasing time and pathways of light propagationthrough the micro and nano materials and structures. For example, quantum wellinfrared photodetector (QWIP) cannot absorb normal incident radiation so thatthe generation of an electric field component which is parallel to the original incident direction is a necessity for the function of QWIP. Furthermore, the increaseof time and pathways of light propagation in the light-absorbing quantum wellregion will increase the chance of absorbing the photons.The thesis presents the theoretical studies of light manipulation and light-matter interaction in micro and nano photonic materials and structures, aiming atimproving the performance of optical communication devices, photonic integrateddevices and photovoltaic devices.To design efficient micro and nano photonic devices, it is essential to knowthe time evolution of the electromagnetic (EM) field. Two-dimensional and three-dimensional finite-difference time-domain (FDTD) methods have been adopted inthe thesis to numerically solve the Maxwell equations in micro and nano photonicmaterials and structures.Light manipulation in micro and nano material and structures studied in thisthesis includes: (1) light transport in the photonic crystal (PhC) waveguide, (2)light diffraction by the micro-scale dielectric PhC and metallic PhC structures(gratings); and (3) exciton-polaritons of semiconductor quantum dots, (4) surfaceplasmon polaritons at semiconductor-metallic material interface for subwavelengthlight control. All these aspects are found to be useful in optical devices of multiplebeam splitter, quantum well/dot infrared photodetectors, and solar cells.QC 20120507
14
Sigdel, Krishna P. « Phase transition studies of liquid crystal colloids with solvents and nano-solids ». Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-dissertations/137.
Texte intégralRésumé :
Liquid crystals (LCs) are anisotropic fluids that exhibit numerous thermodynamically stable phases in between an isotropic liquid and a three-dimensionally ordered solid. In their simplest ordered phase, the nematic, LCs show orientational order due to molecular self assembly and at the same time maintaining fluid flow properties. In the smectic phase, they show both orientational and partial translational order characterized by a 1-d density wave. Liquid crystalline substances have been extensively studied due to their applications and as important physical models of self-assembly. The effect of the disorder and impurities on LC systems is an important and challenging problem to the fundamental understanding of phases ordering or self-assembly and continually attracts the attention of researchers. The disordered systems often display complex and rich phenomena, being the generalization of the pure (ideal) systems. Disorder can dramatically alter the physical properties of multi-component, composite systems. In particular, the effect of disorder on phase transitions is important as the disorder typically couples to the order parameter, which can be usefully described as a random local field that is conjugate to the order parameter. This is usually realized in systems with random inclusions in a phase ordering media, e.g., a colloidal dispersion of solids in a complex fluid. Another form of disorder is presented by dilution effects, which imposes instead the random breaking or weakening of intermolecular bonds or interactions responsible for the phase ordering. Exploring a good physical system representing random dilution effects in a controlled manner offers a physical probe to unresolved problems in the understanding of mesophasic order. This Dissertation presents a series of studies of dilution and different form of disorder effect on liquid crystal phase transitions. We have used high-resolution AC-calorimetry, dielectric spectroscopy as well as polarizing microscopy to characterize the effects of solvent such as hexane, acetone, decane, and nanomaterials such as multiwall carbon nanotubes and ferroelectric nanoparticles on the phase transitions of several liquid crystals. The liquid crystals of interest are: pentylcyanobiphenyl (5CB), octylcyanobiphenyl (8CB), and decylcyanobiphenyl (10CB). Studies have been carried out as a function of solvent, nanotube, and nanoparticles concentration and temperature spanning the isotropic to nematic (I-N), nematic to smectic-A (N-SmA), and isotropic to smectic-A (I-SmA) phase transitions.
15
Miller, Max. « An Integrated Experimental and Simulation Study on Ultrasonic Nano-Crystal Surface Modification ». University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378394103.
Texte intégral
16
Chang, Hyung-Jun. « Analysis of nano indentation size effect based on dislocation dynamics and crystal plasticity ». Grenoble INPG, 2009. http://www.theses.fr/2009INPG0134.
Texte intégralRésumé :
Ce mémoire de thèse concerne une étude expérimentale et numérique de l'essai d'indentation dans des monocristaux de cuivre. Des essais d'indentation sont réalisés sur différentes orientations du monocristal. L'effet de l'orientation de l'axe d'indentation est quantifié sur la modification de la courbe de charge et sur la forme de l'empreinte résiduelle observée par microscopie à force atomique. On observe un effet de taille pour de faibles profondeurs de pénétration de l'indenteur. Les simulations sont réalisées en utilisant un modèle de plasticité cristalline à variables internes qui prend en compte la densité de dislocations sur les différents systèmes de glissement. Le modèle est implémenté dans le logiciel ABAQUS à la fois en mode explicite et implicite. La valeur de certains paramètres du modèle est déterminée en comparant les résultats de simulations 3D d'indentations avec les expériences. L'effet de taille en indentation est reproduit en utilisant un modèle simplifié de plasticité à gradient. Finalement, le cas de l'indentation suivant l'axe (111) est simulée en utilisant une approche multiéchelle fondée sur la dynamique de dislocations dicrètes. Cette modélisation utilise des résultats de dynamique moléculaire spécifiant le procédé de germination de dislocations sous indenteurThis thesis deals with experiments and simulations of nanoindentation in copper single crystals. Indentation experiments are performed with different orientations of the indentation axis and both the load-displacement curve and the surface imprint observed by atomic force microscopy are analysed and compared. Indentation size effect is observed for low penetration of the indenter. Simulations are then performed using crystal plasticity finite element modelling. ABAQUS user subroutines are specially developed in order to account for the physics of dislocation activity in the twelve glide systems of copper crystals. 3D simulations are then performed and comparisons with the experiments give access to key parameters of the constitutive equations. The indentation size effect is reproduced using a simplified size effect theory implanted in the finite element modelling. Finally, a multiscale approach based on discrete dislocation dynamics is used to reproduce (111) indentations of copper single crystals. Molecular dynamics simulations give details of dislocation nucleation beneath the indenter. Dislocation dynamics simulations are then performed and the indentation size effect is addressed
17
Hui, Pui Chuen. « Optomechanics and nonlinear mechanics of suspended photonic crystal membranes ». Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13068536.
Texte intégralRésumé :
The recent demonstration of strong interactions between optical force and mechanical motion of an optomechanical structure has led to the triumphant result of mechanical ground-state cooling, where the quantum nature of a macroscopic object is revealed. Another intriguing demonstration of quantum physics on a macroscopic level is the measurement of the Casimir force which is a manifestation of the zero- point energy. An interesting aspect of the Casimir effect is that the anharmonicity of the Casimir potential becomes significant when the separation of microscale objects is in the sub-100nm regime. This regime is readily accessible by many of the realized gradient-force-based optomechanical structures. Hence, a new avenue of probing the Casimir effect on-chip all-optically has become available. We propose an integrated optomechanical platform, consisting of a suspended photonic crystal membrane evanescently coupled with a silicon-on-insulator substrate, for (i) measuring the Casimir force gradient and (ii) counteracting the attractive force by exerting a resonantly enhanced repulsive optical gradient force. This thesis first presents the full characterization of the optomechanical properties of the system in vacuo. The interplay of the optical gradient force (optomechanical coupling strength \(g_{om}/2\pi=- 66GHz/nm\)) and the photothermal force manifested in the optical spring effect and dynamic backaction is elucidated. Static displacement by the repulsive force of 1nm/mW is also demonstrated.
In the second part of the thesis, the nonlinear mechanical signatures upon a strong coherent drive are reported. By resonantly driving the photonic crystal membrane with a piezo-actuator and an optical gradient force, we observed mechanical frequency mixing, mechanical bistability and non-trivial interactions of the Brownian peak with the driving signal. Finally we present our recent progress in establishing electro- static control of individual photonic crystal membranes to reduce and calibrate the electrostatic artifact which plagues Casimir measurements.
The results discussed in this thesis point towards an auspicious future of a complete realization of a Casimir optomechanical structure and novel applications with nonlinearity afforded by the Casimir force and the optical gradient force.Engineering and Applied Sciences
18
Li, Jianyou. « Oligonucleotide guanosine conjugated to gallium nitride nano-structures for photonics ». Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9065/.
Texte intégralRésumé :
In this work, I studied the hybrid system based on self-assembled guanosine crystal (SAGC) conjugated to wide-bandgap semiconductor gallium nitride (GaN). Guanosine is one of the four bases of DNA and has the lowest oxidation energy, which favors carrier transport. It also has large dipole moment. Guanosine molecules self-assemble to ribbon-like structure in confined space. GaN surface can have positive or negative polarity depending on whether the surface is Ga- or N-terminated. I studied SAGC in confined space between two electrodes. The current-voltage characteristics can be explained very well with the theory of metal-semiconductor-metal (MSM) structure. I-V curves also show strong rectification effect, which can be explained by the intrinsic polarization along the axis of ribbon-like structure of SAGC. GaN substrate property influences the properties of SAGC. So SAGC has semiconductor properties within the confined space up to 458nm. When the gap distance gets up to 484nm, the structure with guanosine shows resistance characteristics. The photocurrent measurements show that the bandgap of SAGC is about 3.3-3.4eV and affected by substrate properties. The MSM structure based on SAGC can be used as photodetector in UV region. Then I show that the periodic structure based on GaN and SAGC can have photonic bandgaps. The bandgap size and the band edges can be tuned by tuning lattice parameters. Light propagation and emission can be tuned by photonic crystals. So the hybrid photonic crystal can be potentially used to detect guanosine molecules. If guanosine molecules are used as functional linker to other biomolecules which usually absorb or emit light in blue to UV region, the hybrid photonic crystal can also be used to tune the coupling of light source to guanosine molecules, then to other biomolecules.
19
Makles, Kevin. « Nano-membranes à cristal photonique pour l'optomécanique ». Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066457/document.
Texte intégralRésumé :
Dans ce manuscrit, nous présentons le développement d'un résonateur optimisé pour observer des effets quantiques du couplage entre un resonateur mécanique et le champ electromagnétique via la pression de radiation. Celui-ci doit combiner une réflectivité élevée, une faible masse, ainsi qu'un facteur de qualité mécanique élevé. Le résonateur consiste en une membrane suspendue de quelques centaines de nanomètres d’épaisseur, et de quelques dizaines de microns de côté, présentant une réflectivité importante grâce à l'utilisation de cristaux photoniques. Après une étude détaillée de la physique d'un cristal photonique en incidence normale, nous présentons les résultats expérimentaux, en bon accord avec des simulations optiques, notamment lorsque la membrane est utilisée comme miroir de fond d’une cavité Fabry-Perot. Dans un second point, nous passons en revue les mécanismes d'amortissement mécanique à l’œuvre dans les micro-résonateurs. Nous montrons ensuite comment l'introduction de contraintes peut améliorer leur facteur de qualité. Nous finissons la caractérisation mécanique par l'étude de non-linéarités apparaissant lors des grandes amplitudes de mouvement. Puis nous présentons le montage expérimental permettant l'observation du bruit thermique de ces resonateurs. Celui-ci a également permis d'obtenir des résultats préliminaires sur le refroidissement de leur bruit thermique par friction froide et par effet photothermique. Enfin, nous présentons le développement d’un système de couplage capacitif entre la membrane et un circuit électrique, constituant la première étape de la réalisation d’un transducteur optomécanique entre photons optiques et micro-ondesThe field of optomechanic consists in studying the coupling induce by the radiation pressure between a mechanical resonator and a light field, it has expended over the last fifteen years. In this memoir we present the developpement of a resonator optimised to observe quantum effect of the optomechanical coupling. On the one hand, it has to combine a high reflectivity and a low mass to enhance its coupling with the light field. On the other hand it should exhibit high mechanical quality factor in order to minimize its interaction with the environment. This resonator is a suspended membrane, whose thickness is about hundreds of nanometers, and whose reflectivity is achieved thanks to a photonic crystal. After a study of the photonic crystal physic in normal incidence, we present the experimental results including those in the end mirror of a Fabry-Pérot cavity configuration, which are in good agreement with the optical simulations. In a second point, we list the dissipation mechanisms in micro-resonator. Then we show how the stress introduction in such resonators can improve the quality factor. We finish the mechanical characterisation by studying mechanical non-linearities which appears in the case of large amplitude of motion. Then we present the experimental set-up developed to observe the thermal noise of the resonators. We also obtain some preliminary results about the cooling of the thermal noise using active cooling and photothermal effect. Last we present the development of a capacitive coupling between the membrane and a electrical circuit. This device is the first step toward the realisation of an optomechanical transducer between optical and micro-wave photons
20
Clarke, Colin. « Development of an automated identification system for nano-crystal encoded microspheres in flow cytometry ». Thesis, Cranfield University, 2008. http://dspace.lib.cranfield.ac.uk/handle/1826/4036.
Texte intégralRésumé :
Quantum dot encoded microspheres (QDEMs) offer much potential for bead based identification of a variety of biomolecules via flow cytometry (FCM). To date, QDEM subpopulation classification from FCM has required significant instrument modification or multiparameter gating. It is unclear whether or not current data analysis approaches can handle the increased multiplexed capacity offered by these novel encoding schemes. In this thesis the drawbacks of currently available data analysis techniques are demonstrated and novel classification methods proposed to overcome these limitations. A commercially available 20 code QDEM library with fluorescent emissions at 4 distinct wavelengths and 4 different intensity levels was analysed using flow cytometry. Multiparameter gating (MPG) a readily available classification method for subpopulations in FCM was evaluated. A support vector machine (SVM) and two types of artificial neural networks (ANNs), a multilayer perceptron (MLP) and probabilistic radial basis function (PRBF) were also considered. For the supervised models rigorous parameter selection using cross validation (CV) was used to construct the optimum models. Independent test set validation was also carried out. As a further test, external validation of the classifiers was performed using multiplexed QDEMs solutions. The performance of MPG was poor (average misclassification (MC) rate = 9.7%) was a time consuming process requiring fine adjustment of the gates, classifications made on the dataset were poor with multiple classifications on single events and as the multiplex capacity increases the performance is likely to decrease. The SVM had the best performance in independent test validation with 96.33% accuracy on the independent testing (MLP = 96.12%, PRBF = 94.38%). Furthermore the performance of the SVM was superior to both MPG and both ANNs for the external validation set with an average MC rate for MLP = 6.1% and PRBF = 7.5% whereas the SVM MC rate was 2.9%. Assuming that the external test solutions were homogenous the variance between classified results should be minimal hence, the variance of correct classifications (CCs) was used as an additional indicator of classifier performance. The SVM demonstrates the lowest variance for each of the external validation solutions (average σ 2 = 31479) some 50% lower than that of MPG. As a conclusion to the development of the classifier, a user friendly software system has been developed to allow construction and evaluation of multiclass SVMs for use by FCM practitioners in the laboratory. SVMs are a promising classifier for QDEMs that can be rapidly trained and classifications made in real time using standard FCM instrumentation. It is hoped that this work will advance SAT for bioanalytical applications.
21
SALOMONI, MATTEO. « Boosting scintillation based detection ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2019. http://hdl.handle.net/10281/241285.
Texte intégralRésumé :
Durante il mio dottorato di ricerca ho studiato in modo approfondito I cristalli scintillanti, trovando diversi limiti legati all’emissione di luce, proprietà ottiche e stabilità chimica. Sono stati sviluppati diversi banchi di lavoro specifici per le caratterizzazioni presentate nella tesi e molto lavoro è stato dedicato alla finalizzazione dei programmi di simulazione necessari alla descrizione del sistema scintillatore-photorivelatore.
Uno studio della maggior parte degli Approcci classici, sul tema dell’ottimizzazione degli scintillatori, ha portato a confermare come si sia arrivati ad un compromesso tra prestazioni e costi, mentre per migliorare il meccanismo di scintillazione viene proposto cambio di paradigma. Questa tesi di dottorato ha esplorato l’utilizzo di strutture diffrangenti e quantum dots per superare rispettivamenti i limiti legati alla presenza di un angolo critico e alla ricombinazione classica elettrone-lacuna.
I cristalli fotonici utilizzati come reticoli di diffrazione depositati sulla superficie di lettura di scintillatori inorganici hanno mostrato risultati promettenti dal punto di vista di risoluzione energetica e temporale. I modi di diffrazione creati dalla nano-strutturazione periodica creano nuovi gradi di libertà per la luce incidente, entro I quali, con l’utilizzo di programmi di simulazione, si possono trovare soluzioni con un guadagno relativo alla configurazione classica. Un miglioramento è stato dimostrato sperimentalmente per scintillatori misurati in diverse configurazioni.
Nanocristalli sono stati invece utilizzati per migliorare lo stato dell’arte per quanto riguarda le caratteristiche temporali della rivelazione, portando a tempi di decadimento dell’ordine dei picosecondi. L’utilizzo di quatum dots ha permesso di ottimizzare I processi di ricombinazione in scintillatori semiconduttori, portando all’inibizione di canali non radiativi e ad un incremento dell’emissione di dipolo.During this Ph.D., state-of-the-art scintillating materials have been intensively studied with several constraints found regarding their light emission, optical properties, and chemical stability. Different characterization benches were developed specifically for the measurements presented in the thesis and extensive work has been dedicated to fine tune the simulations framework that describes scintillators and photo-detectors. Classical approaches were found to be already at a good trade-off between performances and costs while to really boost scintillation detection a shift in paradigm was needed, moving away from classical ray tracing concepts and scintillation mechanism. This Ph.D. work explored the use of diffraction and quantum dots to break the limit of critical angle and classical e-h recombination, respectively. \newline Photonic crystals were used as diffracting layer deposited on the read-out face of inorganic scintillators and showed promising results from the point of view the crystal's time and energy resolution. The additional modes provided by the periodical nano-structuration of the read-out face add several degrees of freedom where simulations could find new optimal solutions. An enhanced extraction of scintillation light was demonstrated in different crystal configurations.\newline Nanocrystals, on the other hand, pushed the state-of-the-art of scintillation timing properties down to the ps scale, bringing innovative ideas for future fast detectors. The use of quantum dots allowed to tune the recombination mechanism of scintillating semiconductors leading to inhibited non-radiative channels and enhance dipole emission from the emitting centers.
22
Cyganok, Pavel. « Judrios magnetofotoninės sistemos nano dalelė – skystasis kristalas magnetooptinės savybės ». Master's thesis, Lithuanian Academic Libraries Network (LABT), 2008. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2008~D_20080924_182935-73352.
Texte intégralRésumé :
Šiame darbe tiriamos skystojo kristalo su integruotomis kobalto nanodalelėmis optinės savybės. Panaudotos medžiagos: skystasis kristalas 5CB (penkiakomponentis cianobifenilas) ir kobalto nanodalelės kurių dydis 10nm. Tiriami pavyzdėliai su skirtingomis kobalto koncetracijomis (0,05%, 0,092%, 1,04%) skystajame kristale. Išmatuoti sugerties ir LD intensyvumo spektrai bangų ruože nuo 250 iki 700nm.In this work I studied optical and manetooptical features of liquid crystal (LC) with integrated magnetic particles in magnetic field. I observed three different samples of LC with cobalt nanoparticles. Samples were made of LC pentyl-cyanobifenyl (5CB) and ferromagnetic (cobalt) particles of about 10nm. Each sample has a different concentration of cobalt nanoparticles (0,05%, 0,092%, 1,04%). All observations were made with Perkin-Elmer UV-VIS-NIR lambda 19 and Jasco spectrometer at room temperature and wavelength ranges from 250 to 700nm. My results show that low magnetic field till 0,2T is required to change cobalt-LC suspension optical features. Shift to IR region a: 17nm, 28nm and 31nm depending from cobalt concentration are detected. Different magnetic field makes unequal influence to samples with various concentrations of cobalt nanoparticles. From experiment I found that increasing of magnetic field till 0,2T, it shifts the absorption line to longer wavelength. From results follows that the magnetically controlled optical characteristic is very promising for magnetically controlled LC devices and information processing.Pavel Cyganok Magnetooptical features of flexible system, nanoparticle – liquid crystal.
23
Ren, He. « Crystal Engineering of Giant Molecules Based on Perylene Diimide Conjugated Polyhedral Oligomeric Silsesquioxane Nano-Atom ». University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1461014185.
Texte intégral
24
Swinteck, Nichlas Z. « Phase-Space Properties of Two-Dimensional Elastic Phononic Crystals and Anharmonic Effects in Nano-Phononic Crystals ». Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228156.
Texte intégralRésumé :
This dissertation contains research directed at investigating the behavior and properties of a class of composite materials known as phononic crystals. Two categories of phononic crystals are explicitly investigated: (I) elastic phononic crystals and (II) nano-scale phononic crystals. For elastic phononic crystals, attention is directed at two-dimensional structures. Two specific structures are evaluated (1) a two-dimensional configuration consisting of a square array of cylindrical Polyvinylchloride inclusions in air and (2) a two-dimensional configuration consisting of a square array of steel cylindrical inclusions in epoxy. For the first configuration, a theoretical model is developed to ascertain the necessary band structure and equi-frequency contour features for the realization of phase control between propagating acoustic waves. In contrasting this phononic crystal with a reference system, it is shown that phononic crystals with equifrequency contours showing non-collinear wave and group velocity vectors are ideal systems for controlling the phase between propagating acoustic waves. For the second configuration, it is demonstrated that multiple functions can be realized of a solid/solid phononic crystal. The epoxy/steel phononic crystal is shown to behave as (1) an acoustic wave collimator, (2) a defect-less wave guide, (3) a directional source for elastic waves, (4) an acoustic beam splitter, (5) a phase-control device and (6) a k-space multiplexer. To transition between macro-scale systems (elastic phononic crystals) and nano-scale systems (nano-phononic crystals), a toy model of a one-dimensional chain of masses connected with non-linear, anharmonic springs is utilized. The implementation of this model introduces critical ideas unique to nano-scale systems, particularly the concept of phonon mode lifetime. The nano-scale phononic crystal of interest is a graphene sheet with periodically spaced holes in a triangular array. It is found through equilibrium molecular dynamics simulation techniques, that phonon-boundary collision effects and coherent phononic effects (band-folding) are two competing scattering mechanisms responsible for the reduction of acoustic and optical phonon lifetimes. Conclusions drawn about the lifetime of thermal phonons in phononic crystal patterned graphene are linked with the anharmonic, one-dimensional crystal model.
25
Laurens, Gaétan. « Laser generation of nanoparticles in liquids : new insights on crystal structure control and colloidal stability ». Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1161/document.
Texte intégralRésumé :
L’engouement pour l’originalité des propriétés physiques des nanoparticules s’est accompagné d’un développement de nombreuses méthodes de synthèse depuis un demi siècle. Parmi elles, l’ablation laser en liquide permet de produire des nanoparticules avec des surfaces libres de tout contaminant et ce pour une multitude de combinaisons de matériaux et de solvants. Cependant, la simplicité apparente de cette technique dissimule la complexité des mécanismes physico-chimiques, ce qui entraîne actuellement un manque de contrôle des objets synthétisés. Tout d’abord, nous nous sommes intéressés à la cinétique des bulles pour laquelle les conditionsextrêmes d’ablation laser en liquide présentent des cas originaux de cinétique dans le domaine de la mécanique des fluides. Puis, ce travail de thèse vise à donner de plus amples perspectives quant à une meilleure maîtrise de la structure cristalline des nanoparticules et de la stabilité colloïdale. Une manière plus directe de contrôler la taille, la phase cristalline et la stabilité colloïdale des solutions contenant des nanoparticules est d’ajouter des ligands. Nous avons donc étudié les mécanismes de stabilisation de ces solutions en utilisant des ions qui se complexent aux nanoparticules d’or. Nous avons aussi réussi à synthétiser des nanoparticules de rubis (alumine dopée chrome). La stabilisation de ces nanoparticules dans une phase métastable en utilisant des ligands organiques a été expliquée par une étude théoriqueLaser generation of nanoparticles in liquids : new insights on crystal structure control and colloidal stability The great interest of nanoparticles for their original physical and an chemical properties has been supported by the development of numerous methods of synthesis. In the nineties, laser generation of nanoparticles in liquids appeared, including Pulsed Laser Ablation in Liquids (PLAL). The PLAL technique enables to produce surface free particles for plenty of material and solvent combinations. However, the apparent simplicity of its implementation hides complex physico-chemical mechanisms resulting in a lack of control of the final products. We firstly investigated the dynamics of the laser-generated bubbles for which the PLAL extreme conditions present new studied cases of bubbles dynamics not encountered in the field of fluid mechanics. Then, we aim to bring new insights into better control of the nanoparticles morphology and their colloidal stability. A straight way to tune sizes, crystal structures and the colloidal stability consists in the addition of stabilizing agents. Hence, we investigated the mechanisms of stabilization of colloidal gold using complexing ions. We also succeed to synthesis nano-rubies, i.e. chromium doped corundum alumina nanoparticles, unexpected at nanoscale. The stabilization of the metastable crystal structure using ligands is explained thanks to a comprehensive theoretical approach
26
蔡紫珊 et Tsz-shan Jacqueline Choy. « Enhancing the sensitivity and specificity of piezoelectric quartz crystal sensor by nano-gold amplification and molecularly imprintingtechnologies ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558575.
Texte intégral
27
Goubet, Nicolas. « Nano et supracristaux d'or : sur l'influence de la nanocristallinité ». Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066119/document.
Texte intégralRésumé :
Cette thèse porte sur l'influence des défauts cristallins des nanocristaux d'or. Elle traite de la synthèse et de l'assemblage de nanocristaux d'or dont la taille et le taux de défauts cristallins sont contrôlés. Au cours de ce travail, une méthode permettant de séparer des nanocristaux de même taille mais soit mono-, soit polycristallines a été mise au point pour ensuite les utiliser comme graines de croissance cristalline afin d'étendre le contrôle de taille de 5 à 13 nm. Les propriétés plasmoniques ainsi que vibrationnelles de ces nanocristaux d'or ont pu ainsi être étudiées en fonction de la présence ou non de défauts cristallins. Les nanocristaux synthétisés lors de cette thèse présentent une distribution de taille suffisamment faible pour permettre leur auto-assemblage en réseau ordonné à trois dimensions, appelés supracristaux. L'apparition de supracristaux inverses et de surfaces vicinales a pu être observée dans certaines conditions d'assemblage. De plus, il est aussi possible d'obtenir des supracristaux de taille submillimétrique ne contenant que des nanocristaux mono- ou polycristallines, et pouvant être étudiés individuellement par diffraction de rayons X. Il a ainsi été possible de corréler l'ordre orientationnel et translationnel des nanocristaux dans le réseau supracristallinThis thesis deals with the influence of crystal defects of gold nanocrystals, especially on the synthesis and self-assembly of gold nanocrystals whose crystal defects and size are controlled. During this work, a method have been developed to separate single and polycrystals with similar size using crystalline segregation. Then, these nanocrystals have been used as seeds for a second crystal growth in order to expand their size from 5 nm to 13 nm in diameter. The plasmonic and vibrational properties of these gold nanocrystals have also been studied. The obtained nanocrystals exhibit low size distribution that allows their self-assemblies into three dimensional ordered lattice, called supracrystals. Negative supracrystals and vicinal surfaces have been observed under specific self-assembly conditions. Moreover, it is possible to obtain supracrystals with submillimeter size containing only either single or polycrystals and study them in an individual way by X-ray diffraction. It has also been possible to correlate the translational and orientational order of gold nanocrystals within the supracrystalline lattice
28
Kodumuri, Pradeep. « IN-SITU GROWTH OF POROUS ALUMINO-SILICATES AND FABRICATION OF NANO-POROUS MEMBRANES ». Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243304850.
Texte intégral
29
Choy, Tsz-shan Jacqueline. « Enhancing the sensitivity and specificity of piezoelectric quartz crystal sensor by nano-gold amplification and molecularly imprinting technologies ». Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558575.
Texte intégral
30
Sidhu, Kuldeep S. « Residual Stress Enhancement of Additively Manufactured Inconel 718 by Laser Shock Peening and Ultrasonic Nano-crystal Surface Modification ». University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535464760914267.
Texte intégral
31
Moille, Grégory. « Non-Linear Dynamics in Semiconductor Nano-Structures for Signal Processing ». Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS174/document.
Texte intégralRésumé :
Cette thèse porte sur la numérisation de signaux hyperfréquences en utilisant une horloge optique, possédant une gigue temporelle très faible en comparaison des horloges électroniques. Une faible gigue est un facteur clé de l’échantillonnage à haute performance, car l’horloge commande l’ouverture d’une “porte” qui extrait les échantillons du signal à intervalles réguliers. Cette thèse décrit deux approches originales : l’échantillonnage purement optique et l’échantillonnage électro-optique.Une porte électro-optique se constitue d’une ligne coplanaire transportant le signal électrique. Cette ligne présente une discontinuité qui devient conductrice sur commande optique grâce à un matériau photoconducteur. Les alliages semi-conducteurs du groupe III-V sont souvent utilisés car la mobilité de ces porteurs photo-générés est suffisamment élevée, ce qui est favorable à une bonne conductivité à l’état “on”. Le GaAs, en particulier, présente l’avantage d’une conductivité faible à l’état “off” du fait de la largeur de la bande interdite électronique. Cela explique l’intérêt de ce matériau, cependant, cela impose aussi une contrainte sur la longueur d’onde de la source laser, expliquant l’utilisation de sources autour 800 nm.Dans cette thèse l’utilisation de sources laser à verrouillage de modes à fibre, développées dans le domaine des Télécoms, donc plus facilement accessibles, tout en gardant le GaAs comme matériaux actif est explorée. Cela est possible en exaltant l’efficacité de l’absorption à deux photons, effet faible dans la plupart des structures. L’approche suivie porte sur l’utilisation d’une cavité à cristaux photoniques. Le très fort confinement et le très faible volume occupé par le mode optique se traduit en une très forte absorption non linéaire. De plus, la nano-structuration du semi-conducteur réduit de manière considérable le temps de vie des porteurs, ce qui permet un retour suffisamment rapide à l’état “off”. L’étude se conclut par la démonstration de la fonction d’échantillonnage.La même fonction a été étudiée dans le cas ou le signal hyperfréquence se trouve sur une porteuse optique. La fonction porte “tout optique” est réalisée par un résonateur à cristaux photoniques. La génération de porteurs par absorption à deux photons induit un déplacement spectral de la résonance, ce qui est exploité pour moduler la transmission du dispositif. Une porte optique rapide, capable en principe de traiter des signaux dépassant les 50 GHz à été montrée. Cette porte requiert une puissance de commande de l’ordre de 200 fJ/impulsion, ce qui est suffisamment faible pour utiliser des sources lasers compactes (diode laser) et, de ce fait, outre sa très faible taille, peut être intégrée facilementThis thesis is focused on the digitalization of radio-frequency signal using optical clock, allowing a low time jitter compared to electronic clocks. A low jitter is a key factor for high performance sampling, as the clock commands the “gate” opening which extracts the signal samples at regular intervals. This thesis describes two original approaches: all-optical sampling and electro-optics one.An electro-optic gate is based on radio-frequency transmission strip-line carrying the electric signal. A discontinuity in this strip-line occurs which become conductive, thanks to the optical command provided by the clock, due to a photo-conductive material. Semiconductor alloys from the III-V groups are widely used thanks to the high mobility of the photo-generated carriers allowing a high “on” state. In particular, GaAs present a good “off” state due to its band-gap energy. However, this restrains the optical clock wavelength explaining the use of optical sources around 800 nm.In this thesis, the focus was made on using mode-locked lasers in the Telecom range, thus using the improvement made on these sources during the past decades, while keeping GaAs as the active material in the electro-optic sampler. This is made possible by exalting the efficiency of two-photon absorption, which is usually weak in common structures. The approach followed here is to use a photonic crystal cavity. Thanks to its high optical mode confinement, non-linear absorption becomes efficient enough to generated carriers to modify the resistivity of the material. In addition, the nano-structuration of the material reduce tremendously the carrier lifetime, owing to switch from an “on” to “off” state fast enough to sample high frequency signals.The same function has been studied in the case where the signal is not carried electrically but optically. The all-optical gate function is realized using two photonic crystal resonators coupled together. The carrier generation by two-photon absorption induces a spectral shift of the resonance, used to modulate the transmission of the device. A fast all-optical gate, enabling signal processing up to 50 GHz is demonstrated here. The gate only requires a control power of about 200 fJ per pulses, which is low enough to use integrated optical sources (laser diodes) and, thanks to the small footprint, be easily integrated
32
Gryn, Iryna. « Auto-assemblage de défauts structurels et de nano-objets dans des films cristaux liquides ». Thesis, Paris 6, 2015. http://www.theses.fr/2015PA066710.
Texte intégralRésumé :
Un intérêt scientifique croissant dans les cristaux liquides (LC) est née de leur capacité à guider l'assemblage des colloïdes1,2 et des nanoparticules (NPs)3-8 en configurations spatiales bien définies. Dans cette thèse, nous avons étudié les LC smectiques A (SmA) qui produisent 1D et 2D modèles de défauts de taille nanométrique9 avec sub-micrométrique périodicité et sont capables d'assembler des NP dans des structures ordonnées par défaut/NP interactions. La thèse a été axé sur deux tâches principales: l'élaboration d'une méthode fiable pour motifs de défaut de la création avec la symétrie et la périodicité prédéfinie qui peut être réglé par des champs électriques appliqués; assemblage NPs de nature différente, la taille et la forme en structures ordonnées dans accordable LC tableaux de défauts. Dans ce mémoire, nous avons montré que les modèles de défauts 1D et 2D peuvent être créés soit par variation de l'épaisseur du film à cristaux liquides en l'absence de champ électrique externe, ou en appliquant le champ à une épaisseur donnée. La morphologie de motif est déterminée par l'épaisseur de la région confinée, où le directeur de LC de rotation perpendiculaire à l'orientation parallèle à des substrats. Dans les cellules hybrides SmA/NP NPs anisométriques alignent le long de la directrice en l'absence de défauts, mais alignent parallèle à la ligne des défauts10 dans le noyau de défaut. Un champ électrique appliqué à la ligne normale de défaut de contestation de l'interaction des particules anisotropes défaut et peut conduire à une orientation perpendiculaire, en fonction du type et de la taille des particules. Ajout sphériques NPs d'or à SmA LCs conduit à la déstabilisation des domaines de défauts linéaires, la stabilisation de bandes striées et empêche l'agrégation même pour une grande concentration de NPs d'or dans les cellules hybridesAn increasing scientific interest in liquid crystals (LCs) has arisen from their ability to guide the assembly of colloids and nanoparticles (NPs) into well-defined spatial patterns. In this thesis we have studied the smectic A (SmA) LCs which produce 1D and 2D patterns of nanometer size defects with sub-micrometer periodicity and are capable to assemble NPs into ordered structures via defect/NP interactions. The dissertation was focused on two main tasks: developing a reliable method for creation defect patterns with predefined symmetry and periodicity which can be tuned by applied electric fields; assembling NPs of different nature, size and shape into ordered structures within tunable LC defect arrays. In this thesis we have shown that 1D and 2D defect patterns can be created either by varying the LC film thickness in the absence of external electric field, or by applying the field at a given thickness. The pattern morphology is determined by the thickness of the confined region, where the LC director rotates from normal to parallel to the substrates orientation. In SmA/NPs hybrid cells anisometric NPs align along the director in the absence of defects but align parallel to line defects within the defect core. An electric field applied normal to the defect line challenges the anisotropic particle-defect interaction and may lead to perpendicular orientation, depending on the particle type and size. Adding spherical gold NPs (GNPs) to SmA LCs leads to destabilization of linear defect domains, stabilization of striated stripes and prevents aggregation even for a large concentration of GNPs in hybrid cells
33
Tulli, Domenico. « Micro-nano structured electro-optic devices in LiNbO3 for communication and sensing ». Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/81118.
Texte intégralRésumé :
A material that is enabling integrated optics is the ferroelectric crystal Lithium Niobate (LiNbO3), which has excellent electro-optical, acousto-optical and nonlinear optical properties. Moreover, it can be doped with laser-active ions and allows for simple fabrication of low-loss optical waveguides.
The broad aim of this work is to develop and introduce advanced micro- and nano-fabrication techniques for LiNbO3 and a new class of integrated based telecommunication and sensing devices. The techniques developed include precise micro-domain inversion, etching, bonding and thin film fabrication.
From a device point of view, domain inversion is used to improve the electro-optic response of LiNbO3 waveguide modulators in terms of bandwidth and driving voltage. With respect to standard single-domain structures, larger bandwidths and lower driving voltages can be obtained, thus achieving figure of merits for the electro-optic response that are up to 50% larger. As a demonstration, a chirp-free modulator, having ~2V switching voltage and bandwidth of 15 GHz, was fabricated by placing the waveguide arms of a Mach-Zehnder interferometer in opposite do- main oriented regions. The modulator could be driven in a single-drive configuration with inexpensive low-voltage drivers, e.g. a SiGe based RF amplifier, typically used for electro-absorption devices.
A further aspect of this work focuses on the development of devices for the precise measurement of strong electric fields, which are typically generated in power stations and transmission lines. Therefore, two new integrated electric field sensors are proposed, each of which exploits the aforementioned micro-fabrication techniques. The first device is based on a proton-exchange waveguide at cut-off, centered on a few microns wide domain-inverted region in a z-cut LiNbO3 substrate. The sensor’s performance is demonstrated by detecting DC fields up to 2.6 MV/m and high-frequency (1.1 GHz) fields ranging from 19 V/m to 23 kV/m. The second proposed device is fabricated by direct bonding a z-cut LiNbO3 substrate on top of a cut-off proton-exchanged waveguide centered on the domain-inverted region. It is possible to detect electric fields as high as 2 MV/m at low frequency with improved sensitivity compared to the previous device. These features make the devices suitable for use in high electric field and harsh conditions without endangering the operator. The conclusions section of the Thesis presents possible future developments which will contribute to increase the impact of the work in the optical telecommunication and sensing industries.
After a brief introduction, the second chapter describes the basic properties of the material used in the thesis work: Lithium Niobate (LiNbO3). This includes the properties related to its ferroelectric crystal structure and the subsequent applications. Chapter three presents the micro-fabrication techniques, over 3 inch LiNbO3 wafers, developed at ICFO during this work. The chapter begins with a description of waveguides fabrication by Annealed Proton Exchange (APE). The mid-part of the chapter outlines the fabrication procedure for domain inversion using electric field poling technique and liquid electrodes while the last part describes the bonding technique to permanently join LiNbO3 with different substrates, namely Si, SiO2 and another LiNbO3. Moreover, lapping and polishing techniques for thin plate fabrication are presented. The forth chapter firstly introduces the
fundamentals and main characteristics of travelling-wave LiNbO3 Mach-Zehnder modulators. Secondly, a new modulator design is proposed. It is based on domain inverted LiNbO3, with improved performance with respect to existing devices. The modulator characterization and the results obtained from the new design are presented. The chapter five begins with a literature review about DC and low frequency electric field optical sensors. Afterwards, two novel all-optical electric field sensors are presented. Both devices are based on a proton-exchange, domain inversion and bonding techniques. The sensors characterization, including the test set-up and the performance results are discussed. Finally, in chapter six, several conclusions on the thesis work and possible future work directions are presented.Uno de los materiales que permite el avance de la tecnología de dispositivos ópticos integrados es el niobato de litio (LiNbO3). Se trata de un cristal ferro-eléctrico, con excelentes propiedades electro-ópticas, acusto-ópticas y no lineales. Además, es posible fabricar guías de onda de bajas pérdidas mediante las técnicas de intercambio protónico (PE) y difusión de titanio. El objetivo principal de este trabajo es el desarrollo y la introducción tanto de las técnicas avanzadas de micro-nano fabricación para el niobato de litio como de nuevos dispositivos ópticos integrados para las comunicaciones ópticas y la detección de campo eléctricos de alto voltaje. La técnicas de fabricación desarrolladas incluyen inversión de dominios mediante la técnica de poling de alto voltaje, grabado, bonding y capas delgadas. Desde el punto de vista de los dispositivos, la inversión de dominios ha sido utilizada para mejorar la respuesta electro-óptica de los moduladores en LiNbO3 en términos de ancho de banda (BW) y voltaje de control (Vπ). En comparación con los moduladores comerciales actuales de un único dominio, con esta técnica es posible obtener mayores anchos de banda y menores voltajes de control resultando en un aumento del 50% del producto BW·Vπ. Para demonstrar la eficacia de la técnica desarrollada, se ha fabricado un modulador Mach-Zehnder chirp-free poniendo los brazos del interferómetro en dos regiones de dominios opuestos. De las mediciones efectuadas se han obtenidos valores de voltaje de control de 2V y ancho de banda de 15 GHz. Estos resultados muestran que los dispositivos desarrollados pueden reducir el coste total de funcionamiento, ya que permiten el uso de controladores económicos de Si-Ge que operan en el rango de los 2V. Otro aspecto de este trabajo se enfoca en el desarrollo de dispositivos para medir, de forma exacta, altos campos eléctricos, que normalmente son generados en las centrales eléctricas y en las líneas de transmisión. Por este motivo, se han desarrollado dos sensores de campo eléctrico mediante las técnicas de micro-fabricación anteriormente mencionadas. El primer dispositivo está basado en una guía fabricada mediante intercambio protónico en LiNbO3 z-cut, diseñada a la frecuencia de corte y centrada en una región de dominio invertido de 10 micras de ancho y 10mm de largo. El rendimiento del dispositivo se ha demostrado detectando campos a baja frecuencia con amplitudes de hasta 2.6MV/m y campos a la frecuencia de 1.1GHz con amplitudes desde 19V/m hasta 23kV/m. El segundo dispositivo se ha fabricado mediante bonding directo de un sustrato de LiNbO3 encima de una guía PE diseñada a la frecuencia de corte y centrada en una región de dominio invertido de 10 micras de ancho y 10mm de largo. El dispositivo se ha caracterizado a baja frecuencia y ha sido posible medir campos eléctricos de hasta 2MV/m con un aumento de sensibilidad comparado con el primer dispositivo fabricado sin la técnica del bonding. Estos resultados muestran que los dispositivos desarrollados pueden ser utilizados para mediciones de campos eléctricos intensos en condiciones peligrosas sin ningún riesgo para el operador. Después de una breve introducción en el Capítulo 1 de esta Tesis, las propiedades del LiNbO3 se discuten en el Capítulo 2, prestando especial atención a sus características ópticas y electro-ópticas. El Capítulo 3 presenta las técnicas de micro fabricación desarrolladas durante este trabajo sobre sustratos de 3 pulgadas. En particular, se presentan las técnicas de fabricación de guías mediante intercambio protónico, de inversión de dominios mediante poling de alto voltaje, de bonding de LiNbO3 con diferentes sustratos (LiNbO3 , SiO2, Si) y la fabricación de capas delgadas. El Capítulo 4 ofrece una introducción sobre los moduladores interferométricos Mach-Zehnder de onda propagada, presentando sus principales características. Además se presenta una nueva estructura de modulador basada sobre inversión de dominios y los resultados obtenidos. El Capítulo 5 empieza con una introducción sobre los sensores de campo eléctrico y después se presentan dos nuevos sensores de campo eléctrico completamente ópticos fabricados en LiNbO3 z-cut. Los dispositivos están basados en las técnicas de intercambio protónico, inversión de dominios y bonding directo. Finalmente, en el Capítulo 6 se presentan las conclusiones y posibles desarrollos futuros que pueden contribuir al aumento del impacto de este trabajo en las industrias de comunicaciones ópticas y de detección.
34
Lu, Yi Ju, et 呂易儒. « Effects of Liquid Crystal Polymer and Nano-particles on the Liquid Crystal Displays ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/03495349417163763005.
Texte intégralRésumé :
碩士長庚大學
電子工程學系
99
For LCD display module, pre-tilt angles is a very important parameter, and the pre-tilt angle represents the angle of LC molecules and alignment layer (Polyimide, PI).Because of this angle, by applying voltage to the LC molecules can twist toward the consistent direction. In addition, this could also prevent create reverse twist which could defect the alignment when applying voltage to cell. We proposed two methods of controlling the pre-tilt angles, and we also compared and contrasted how these two methods have effects to LCD display module. One method is by directly rubbing alignment on the substrate with coating Indium Tin Oxide(ITO), and we will also utilize the characteristics of horizontal and vertical LCP on ITO. By controlling the different concentrations of horizontal and vertical LCP, it could produce net force (also called resultant force). Another method is to apply different concentrations of SiO2 nano-particles (AE130) doped in horizontal alignment PI and then be coating on ITO substrate to control the pre-tilt angles. The experiment demonstrates, by having different concentrations of horizontal and vertical LCP , the LC cell without coating alignment layer could also control the pre-tilt angles to be 17.45°,32.59°,and 46.52°, respectively. On the other hand, different concentrations of nano-particles doped in PI could induce the pre-tilt angles to be in the range of 2.3~10.5°, and in this condition, pre-tilt angles are inverse with concentrations of nano-particles.
35
Jia-FangZhang et 張嘉芳. « Study on synthesis and magnetism of nano-hematite, nano-magnetite and nano-maghemite with different crystal morphologies ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/85525405426568850014.
Texte intégralRésumé :
碩士國立成功大學
地球科學系
102
The objective of this study is to investigate the magnetic properties of nano-hematite, nano-magnetite, and nano-maghemite with morphologies of nano-particle, nano-rod, nano-tube, and nano-ring. Four crystal morphologies of nano-hematite are synthesized by a hydrothermal method. Nano-magnetite is prepared via nano-hematite by using carbon reduction method. Nano-maghemite is obtained by oxidation of nano-magnetite. The particle-shaped nano-hematite has a granular morphology with aparticle size of 45~85 nm; the nano-rod is 50~100 nm in width and 250~350 nm in length; nano-tube has a inner-diameter of 40~85 nm width and 150~300 nm length; nano-ring shows a inner-diameter of 20~45 nm and outer-diameter of 70~100 nm. The particle size and morphology of nano-magnetite and nano-maghemite are almost the same as nano-hematite. It exhibits that all nano-hematites have a weak ferro-magnetism with multi-domains, however, all nano-magnetites and nano-maghemites are ferri-magnetic with pseudo-single-domain measured by superconducting quantum interference device magnetometer. The spatial distribution of magnetism are characterized by magnetic force microscopy (MFM). The MFM phase images show bright and dark areas, implying ferro-magnetic domains for nano-magnetite and nano-maghemite. Moreover, it reveals a complicated magnetic arrangement for nano-magnetite and nano-maghemite with crystal shapes of rod, tube and ring. Nano-magnetite and nano-maghemite with particle-shape both have a single-domain. This suggests the crystal structure and morphology have an impact on magnetic properties. The MFM technique could be applied in the explaination of paleomagnetism and environmental implications of fault zones.
36
Lin, Yu-hsuan, et 林育璇. « The Study of Optical Properties of Nano Crystal Silicon ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/kss698.
Texte intégralRésumé :
碩士國立中山大學
光電工程研究所
96
In this thesis, using Micro-Photoluminescence (μ-PL), continuous-wave time-resolved photoluminescence (CWPL/TRPL) and Fourier transform infrared (FTIR) analysis, silicon rich nc-Si (nano-crystal Silicon) samples with various emission wavelength (760 30 nm and 390 10 nm) are investigated to understand the proper explanation of the emission mechanism. The model of increasing Si－O －Si bondings during thermal process by enhancing the annealing or deposition time, induced blue shifts in PL spectrums and increased the rate of Schockley-Read-Hall recombination which resulted in the enhancement of its fluorescence is provided.
37
Wu, Kuan-Ju, et 吳冠儒. « Unique properties of semiconductor and liquid crystal nano composites ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/05964410063982002830.
Texte intégralRésumé :
碩士國立臺灣大學
物理研究所
95
Abstract In this thesis we report the study of optical and electrical properties on the composites based on liquid crystals and CdS nanorods. Quite interesting results have been obtained from our studies, which are very useful for the understanding as well as application of these materials. They are presented as follow. The novel nanocomposite device reveals a very unique and useful behavior that the polarization of the emission from semiconductor nanorods can be controlled by an external bias. The large magnitude of polarization anisotropy of 0.63 can be quantitatively interpreted very well in terms of the dielectric contrast between semiconductor and liquid crystal. Our approach is quite general, which is applicable to other nanomaterials, and it utilizes the currently mature liquid crystal display technology. The results open up new possible applications for one-dimensional semiconductor nanostructures in smart optoelectronic applications, including optical switches, integrated photonic devices, as well as electrochromatic gadgets in the near future.
38
Pay-YuLee et 李培裕. « The Synthesis and Photoelectrochemical Applications of Nano Cu2ZnSnSe4 Crystal ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/90806124403734572947.
Texte intégralRésumé :
博士國立成功大學
微電子工程研究所
102
In this work, we report a systematic study of the growth and evolution mechanism of quaternary Cu2ZnSnSe4 (CZTSe) nanocrystals (NCs) in a polyetheramine solvent. Pure-phase CZTSe NCs were synthesized by a facile one-pot heating process. High-quality CZTSe NCs were easily obtained by mixing the precursors and simply heating them to the reaction temperature. Synthesis parameters, including reaction temperature, reaction time, and precursor concentration, which influence the morphology, size, and monodispersity of CZTSe NCs, were studied in detail. Time- and temperature-dependent experiments were performed to observe the growth of CZTSe NCs. The final CZTSe NCs were evolved from triangle-like Cu2Se crystals to pure spherical crystals. On the basis of detailed time-dependent shape and elemental composition evaluations, a possible asynchronous doping growth and formation mechanism is proposed. Moreover, the optical and electrical properties of pure CZTSe NCs were also investigated. The band gap of CZTSe was approximately 1.57 eV, which is close to the optimum value for solar photoelectric conversion. The precipitated NCs were redispersed in toluene to form ink solutions for characterization. The properties of thin films of these inks were investigated as a function of the chemical compositions of the inks. The Cu/(Zn+Sn) ratio of the inks was varied from 0.7 to 1.0, while the Zn/Sn ratio was kept constant at 1. Photodetectors (PDs) with a Au/CZTSe/soda-lime glass structure were fabricated. The PD corresponding to a Cu/(Zn+Sn) ratio of 0.70 exhibited excellent photoresponsivity, and its dark current was 7.65 × 10−7 A when a bias of 10 V was applied. In the chemical applications, the sensing membrane of an extended-gate field-effect-transistor (EGFET) pH sensor with CZTSe nanoparticles was fabricated on a glass substrate through a solution-based method. The resulting EGFET pH sensors with CZTSe nanocrystals exhibited good sensing performances owing to the large sensing surface-to-volume ratio. The pH sensitivity calculated from the linear relation between the drain-source current and the pH value was 7 μA/pH, and that calculated from the linear relation between the reference voltage and the pH value was 9 mV/pH. By controlling the Zn-to-Sn ratio, the resulting CZTSe particle films exhibited a photoresponse of n-type and p-type semiconductor photoelectrodes in an aqueous solution containing NaCl as an electron scavenger. The comparison between n-type and p-type CZTSe photoelectrochemical (PEC) property are demonstrated, athe pplication of CZTSe thin film photoanodes in PEC results in the value of ηc = 2.81% was found in n-type. The lower ηc = 0.42%, obtained from p-type CZTSe photoanodes, the flat band potential of the n-type and p-type CZTSe in 1 M NaCl were obtained to be -0.55 and 0.48V, the net carrier concentration of the n-type and p-type calculated from Mott–Schottky plot were 3.38 x1018 and 2.73 x1018 cm-3, respectively. Keyword: Cu2ZnSnSe4; Synthesis; Photoelectrochemical
39
Chen, Guan-Hua, et 陳冠華. « The study of nano-sphere assembled photonic crystal slab ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/20966264409547032999.
Texte intégralRésumé :
碩士國立彰化師範大學
光電科技研究所
99
In this thesis, the fabrication and optical properties of nano-sphere assembled photonic crystal slab (PCS) have been investigated experimentally and theoretically. The experiment includes two parts: (1) the fabrications of single-layer close-packed nano-sphere array and silver shell on silicon nitride (SiN) membrane; (2) the studies of guiding-mode resonance and surface plasma resonance (SPR). In the simulation, the bend structures have been studied by utilizing plane wave method (PWM). In the fabrication part, the substrate was surface modified by reactive ion etching (RIE). The surfactant Triton X-100 is mixed with IPA by the ratio 1:400, and then the mixture mixed with nano-sphere solution by the ratio 1:1. After Spin-coating onto the substrate with spin rate 600 rpm, the single, uniformly nano-sphere arrays can be take. By Sputtered silver onto the nano-sphere array, the silver nano shell can be take. In the transmittance measurement, the spectrums were measured. By utilizing RSoft BandSolve, the band structure has been studied, and it matches with the measurement results.
40
Wu, Kuan-Ju. « Unique properties of semiconductor and liquid crystal nano composites ». 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-0607200717320500.
Texte intégral
41
Huang, Tai-wei, et 黃泰瑋. « Two-Dimensional Photonic Crystal Devices Fabricatedby Nano-Imprint Lithography ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/01484942222603627441.
Texte intégralRésumé :
碩士國立中央大學
電機工程研究所
95
In this study, photonic crystal wavelength division multiplexer (WDM) and polarization filter based on SOI substrate have been demonstrated. The WDM is used to separate the electromagnetic wave at the wavelength of 1.55μm and 1.31μm. The polarization filter can be applied to leach the optical signal of TM polarization in the range of wavelength 1.3μm ~2.1μm. We use the plane wave expansion method (PWE) to simulate the band-gap distribution of the periodical arrayed structure and used finite-differential time-domain (FDTD) method to study the steady state electromagnetic wave propagation simulation. The WDM was fabricated by e-beam lithography and polarization filter was processed by a novel technology “nano-imprint lithography” which has several extremely ascendant advantages: simple process, low production cost and high throughput efficiency. Waveguide measurement system was used in this experiment. The measurement result shows that the performance of the WDM and the polarization filter are both good. So it means that the design of the devices structure and devices process are successful in this study. And it is expectable that more and more nano-scale devices can be fabricated by E-beam lithography and NIL process by consulting the process parameters in this study.
42
Tse-JenWang et 汪澤仁. « Study of liquid crystal alignment based on periodic nano-wedgy structures via nano-imprint lithography ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/40263816512483897213.
Texte intégralRésumé :
碩士國立成功大學
光電科學與工程學系
100
In this study, we used the nanoimprint lithography (NIL) to fabricate the periodic nano-wedges groove for vertical alignment. The incline slope from nano-wedges can control LC raising-up direction on applied voltage. The periodic triangle structure was made on silicon wafer by Electron beam lithography, then we chose perfluoropolyether(PFPE) as a mold to replicate the periodic triangle structure on silicon master. A photoresist material of SU-8 used as an imprint material was coated on the ITO glass, and Poly(dimethylsiloxane) (PDMS) used as an vertical alignment layer by an external hydrophobic property. For the contrast, we also fabricated the periodic nano-rectangular groove with 1μm pitch to assemble VA LC cell by some processes. It demonstrated that the LC cell of periodic nano-wedges structure has better optical symmetry than the periodic nano-rectangular groove and prevent reverse-twist domains.
43
游信強. « Application of novel lithography and nano-crystal technique in the fabrication of nano-devices and memories ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/38469779404664908255.
Texte intégral
44
Yu, Ming-Wei, et 余明韋. « Effects of Nano-Particles-Doped Polyimide on Liquid Crystal Cells ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/09458583288470443109.
Texte intégralRésumé :
碩士逢甲大學
電機工程所
93
The purpose of this thesis is to study effects of nano-particle-doped polyimide on liquid crystal cells, to understand influence of nano-particle-doped polyimide on liquid crystal cells of interface trapped ions. The purpose of this thesis is including that 1. When high voltage static electricity is input on liquid crystal cells, image sticking is induced by Electro-Static Discharge. 2. The ions accumulate on the interface between polyimide and LC that can induce the phenomenon interface trapped ions in LC, this will influence the optical and electric property of liquid crystal cells. In our Experimental results, we found that 1. When nano-particle-doped concentration increase, the phenomenon interface trapped charge is less that can improve the duration of image sticking caused by ESD but can not influence voltage holding ratio and residual DC. 2. There doesn’t find any relations between threshold voltage of nano-particle-doped different concentrations. 3. From optical and electric measurement we establish the model of interface trapped ions in LC.
45
Shie, Wun-Yi, et 謝文逸. « Study on Liquid Crystal Cells Doped with Nano-ITO Particles ». Thesis, 2008. http://ndltd.ncl.edu.tw/handle/43555129031062658258.
Texte intégralRésumé :
碩士逢甲大學
電機工程所
96
In this study, it was found that nano-conductive powders doped in liquid crystal cells can significantly and effectively reduce the image sticking effect for the display suffering a short pulse of electro-static discharge (ESD) stress. Nano-scaled Tin-doped Indium Oxide (ITO) powders were uniformly solved in the LC cells to form a suspension solution. Both electrical and optical characteristics for the doped cells and those without intentional doping were compared. According to the measurement results from the normal voltage holding ratio (VHR), lower frequency of VHR, voltage-transmittances (V-T), enhance molecular reorientation (EMR), depressed molecular reorientation (DMR), EMR+DMR and ion density, it was shown that there is no difference between the two types of LC cells. This was shown that ion effect didn’t increase. And doping nano-ITO in LC wouldn’t have more ion effect from these measurement results. However, the capability of suffering high-voltage stress was profoundly improved for the doped cells in the ESD test. The possible reason for this finding will be discussed according to the breakdown theory of suspended particles in liquid. In order to demonstrate the possible reason, we measured induction charges of the cells by the capacitance in ESD stress. And induction charges of doping nano-ITO cells were lower than without intentional doping cells. With the results, it can be expected that the LC cells doped with conductive nano-particles would survive in worse environments while keeping their displaying characteristics unaffected. Further, a new model that conducting nanoparticles move in the liquid crystal after ESD stressing can be successfully built and explained for these results in the study.
46
Tsai, Shou-Chi, et 蔡守騏. « Mechanical behaviors of LiAlO2 single crystal in micro/nano scales ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/91083837352365665159.
Texte intégralRésumé :
碩士國立中山大學
材料與光電科學學系研究所
103
The deformation behavior and mechanical properties of phase lithium aluminate LiAlO2 (-LAO) single crystal under various loading conditions were investigated in the present study. The theoretical Young’s modulus and Poisson ratio of -LiAlO2 were firstly extracted from elastic constant for subsequent comparison with the experimentally measured data. The experimental micro-scaled mechanical properties were obtained by microcompression testing. The nano-scaled mechanical properties, such as Young’s modulus, hardness and yield stress, were measured by using the nanoindentation system and fit by the Hertzian contact theory. The experimental micro-scaled and nano-scaled data were compared. The deformation microstructures were characterized by various techniques, including scanning electron microscopy (SEM), and electron backscattered diffraction (EBSD). By using the nanoindentation test with Berkovich indenter at room temperature, the measured modulus, hardness and yield stress values (in nano scale) are 167 GPa, 12 GPa and 10 GPa for the c-plane (001) surface, and 132 GPa, 9 GPa and 9 GPa for the a-plane (100) surface. By measuring the 2 m micropillars under microcompression, the measured modulus and yield stress values (in micro scale) are 153 GPa and 5 GPa for the c-plane (001) surface, and 111 GPa and 3 GPa for the a-plane (100) surface. The higher nano-scale values are due to the small volume constraint effect.
47
-Mao, Ho Chih, et 何志茂. « The Fabrication of Photonic Crystal based on Nano-Imprint Technology ». Thesis, 2011. http://ndltd.ncl.edu.tw/handle/90254897696443058630.
Texte intégralRésumé :
碩士華梵大學
機電工程學系博碩專班
99
Abstract Nanotechnology has become very popular in recent years. It influences not only on a single type of industry but wide range of applications. However the traditional semiconductor manufacturing processes involved in nanotechnology manufacturing technology encountered bottleneck due to the resolution limit of the photolithography and nanoimprint technology provides an good alternative which is suitable for manufacturing nano-level precision components. This paper mainly tries to establish the soft PDMS mold to the UV nanoimprint process to make photonic crystal film, the photonic crystal helps raise the efficiency of the LED light. We repeat the molding process to make a series of photonic crystal structural and then test the integrity of the PDMS molds. Meanwhile we compared several ways of cleaning the residual PDMS on the Silicon mold.. After using UV nano-imprint machine with PDMS soft mold imprinting the photonic crystal structure can be realized. We then analyze some key parameters to improve the molding by nanoimrpint process. The test on LED with photonic crystal structure showed improved luminous flux of LED light.
48
Chang, Chi-Peng, et 張志鵬. « Studies of liquid crystal Fresnel lenses doped with nano particles ». Thesis, 2013. http://ndltd.ncl.edu.tw/handle/77890551103566082335.
Texte intégralRésumé :
碩士國立中山大學
物理學系研究所
101
A simple method to make a controllable liquid crystal Fresnel lens with bistable state is proposed based on a surface of polymerization and the characteristic of nanoparticles. The sample is fabricated by a homogeneous aligned substrate and a vertical aligned one of coating polymer film. However, it has low diffraction efficiency. We improve the patterned electrode type with etching electrode structure. Experimental results reveal that liquid crystal Fresnel lens which ITO etching pattern using the nanoparticles doped with liquid crystals has bistable state and high diffraction efficiency.
49
Chen, Jian-Chuen, et 陳建淳. « Hydrothermal Synthesis Nano-Size BaTiO3 Used Solvent to Control Crystal Growth ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/j4447q.
Texte intégralRésumé :
博士國立臺北科技大學
材料科學與工程研究所
102
In this study, the particle size of barium titanate was controlled by different concentration of methanol, ethanol, propa-1-ol, isopropanol and tret-butanol under hydrothermal condition. Experiences results showed by several analysis, using X-Ray diffractometer analyzed the barium titanate crystal phase, and scanning electron microscopy observed the microstructure for particle morphology, and Raman spectroscopy analyzed the residual TiO2 、lattice stress and OH- defects. Other results included particle size distribution, phase transformation of non-thermal activation and internal defects and lattice constant variation. The results showed that tetragonal structure transformed to cubic structure against nano particle size. And the OH- defects of structure caused the lattice constant larger than theoretical value slightly. For the results showed the barium titanate crystal had internal stress for OH- defects induced. The results showed the stress of crystal lattice increased with decreased particle size. The two important results of uniform particle size distribution and crystal type obtained by using alcohol as part of solvent to form nano size barium titanate in hydrothermal synthesis.
50
Jhao, Hong-Jyun, et 趙竑鈞. « Analysis of Defect Modes of Two-Dimensional Photonic Crystal Nano-Cavities ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/36361224210576618415.
Texte intégralRésumé :
碩士國立交通大學
光電工程系所
93
In this thesis, defect modes of two-dimensional photonic crystal nano-cavity are analyzed. The defect is formed by removing a single air hole from array of air holes of hexagonal lattice arrangement on a dielectric slab. First, the finite difference time domain method with various boundary conditions is introduced. Second, symmetry analysis of defect modes and design rules for high quality factor cavities are presented. Finally, techniques of the simulation and the results of the simulation, like photonic band structures, resonant frequencies, mode profiles, and quality factors are exhibited.