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Tesis sobre el tema "Surface electrical properties"

Autor: Grafiati
Publicado: 1 de marzo de 2025

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1

Pownall, P. G. "The surface electrical properties of calcium carbonate". Thesis, University of Bristol, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379592.

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2

Richardson, Stephen. "Sulphide ore minerals : surface chemical properties". Thesis, Aston University, 1988. http://publications.aston.ac.uk/8068/.

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The surfaces of iron-containing sulphide minerals were oxidised by a range of inorganic oxidants, and the resultant surface alteration products studied using various spectroscopic techniques. The characterisation of surface oxidation is relevant to the alteration of ores in nature and their behaviour during flotation and leaching, of importance to the metallurgical industry. The sulphides investigated included pyrite (FeS2), hexagonal pyrrhotine (Fe9S10), monoclinic pyrrhotine (Fe7Se), violarite (FeNi2S4), pentlandite ((FeiNi)9Se), chalcopyrite (CuFeS2) and arsenopyrite (FeAsS). The surfaces were oxidised by various methods including acid (sulphuric), alkali (ammonium hydroxide), hydrogen peroxide, steam, electrochemical and air/oxygen (in a low-temperature (150ºC) furnace), The surfaces were examined using surface sensitive chemical spectroscopic methods including x-ray photoelectron spectroscopy (ms), Auger electron spectroscopy (LES) and conversion electron Mössbauer spectroscopy (CEKS). Physical characterisation of the surfaces was undertaken using scanning electron microscopy (SM), spectral reflectance measurements and optical microscopy. Bulk characterisation of the sulphide minerals was undertaken using x-ray diffraction and electron microprobe techniques. Observed phases suggested to form in most of the sulphide surfaces include Fe204, Fe1-x0, Fe202, Fe00H, Fe(OH)3, with iron II & III oxy-sulphates. The iron sulphides show variable extents of oxidation, indicating pyrite to be the most stable. Violarite shows stability to oxidation, suggested to result from both its stable spinel crystal structure, and from the rapid formation of sulphur at the surface protecting the sub-surface from further oxidation. The phenomenon of sub-surface enrichment (in metals), forming secondary sulphides, is exhibited by pentlandite and chalcopyrite, forming violarite and copper sulphides respectively. The consequences of this enrichment with regard to processing and leaching are discussed. Arsenopyrite, often a hindrance in ore processing, exhibits the formation of arsenic compounds at the surface, the dissolution of which is discussed in view of the possible environmental hazard caused by the local pollution of water systems. The results obtained allow a characterisation of the sulphides in terms of their relative stability to oxidation, and an order of stability of the sulphide surfaces is proposed. Models were constructed to explain the chemical compositions of the surfaces, and the inter-relationships between the phases determined at the surface and in the sub-surface. These were compared to the thermo-chemically predicted phases shown in Eh/pH and partial pressure diagrams! The results are discussed, both in terms of the mineralogy and geochemistry of natural ores, and the implications for extraction and processing of these ore minerals.
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3

Oliveira, Junior Osvaldo Novais de. "Electrical properties of Langmuir monolayers and deposited Langmuir-Blodgett films". Thesis, Bangor University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236716.

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4

Pennington, R. C. "Spectral properties and modes of surface microcavities". Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/66438/.

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This thesis describes the experimental investigations into the transverse mode structure of nearly hemispherical microcavities. The nearly hemispherical niicrocavity structures are fabricated electrocemically through a template of self assembled latex spheres. Controlling the electrochemical parameters, such as the electrochemical solution and electrode potential. allows a wide range of uearly henuspherical rnicrocavities to be realised. The spatial intensity profiles arid resonant frequeucies of the transverse modes of nearly hemispherical nucrocavities are measured experimentally for a wide range of cavity lengths amid mirror curvatures. The experimental mode profiles are radially symmetric Gauss-Laguerre modes, but do not display the frequency degeneracies typical of large scale optical cavities. The nearly hemispherical mnicrocavity samples are compared to investigate how the cavity parameters. such as cavity length and mirror curvature, affect the experimental spatial intensity profiles and resonant frequencies of the transverse modes. Higher order modes are observed despite the fact that they are forbidden due to the symmetrical coupling geometry. rrhe symmetry breaking is shown to be produced by the surface roughness of the curved nnrror. The frequency degeneracy lifting which occurs in the nearly hemispherical niicrocavity structures can he explained and modelled by considering non-parabolic elements in the cavity. A nmnher of mathematical models for the cavity propagation are developed based on paraxial theory. rrliese models are analysed and the predictions made from the models are compared with the experimental profiles and frequencies. The basic agreement between theory and experinient shows that the paraxial theory is able to model the cavity modes. However, the spectrum and the mnode profiles are cpnte sensitive functions of the geometry of the cavity amid the surface roughness of the cavity mirrors. The nearly hemispherical mnicrocavities are structures which offer a new fabrication technique allowing inexpensive and a ummconmplicated method of fabrication. An important feature of the nearly hemispherical microcavities is the tunablity, and the ease in which this can be achieved. The structures are also empty, and this will allow them, in the future, to be easily filled with functional optical nmaterials such as liquid crystals.
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5

Azam, Sufyan. "Electrical Properties and Surface Characterization of Thin Copper Films Subjected to Mechanical Vibrations". Doctoral thesis, Universitat Rovira i Virgili, 2021. http://hdl.handle.net/10803/670604.

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Es van estudiar les característiques mecàniques i elèctriques de les pel·lícules fines de coure unides a laminats epoxi FR4, sota càrrega tèrmica i mecànica. A la 1a etapa, es van determinar paràmetres modals de manera experimental i analítica mitjançant un mètode d’elements finits per a quatre grups de mostres, per tal d’estudiar els efectes geomètrics i la presència d’un forat central de diferents diàmetres. S'ha comprovat que aquestes mides són adequades per utilitzar-se com a plaques de circuits electrònics que experimenten canvis de freqüència significatius que van des de 40 Hz fins a 1 kHz. Es va trobar que la freqüència de ressonància fonamental de tots els exemplars era inferior a 40 Hz i la influència d’un forat central no va ser significativa per afectar les propietats modals. Durant la segona etapa de la investigació realitzada, es va determinar l'efecte de les vibracions d'alta freqüència sobre les propietats elèctriques. Experimentalment, es va trobar que les tensions induïdes a les pel·lícules primes a causa de l’alta freqüència i el nombre de cicles afecten significativament la resistència de la làmina de material i altres propietats elèctriques com la resistivitat i la conductivitat. Aquestes càrregues mecàniques redueixen en última instància el rendiment elèctric de les pel·lícules fines de coure (PCB). Les imatges SEM van mostrar la formació d'esquerdes a prop de la zona d'alta tensió; aquestes esquerdes propaguen posteriorment la fallada de l'equip. El canvi de temperatura superficial de 25ºC a 45ºC va mostrar un petit canvi en la resistència de la làmina de les pel·lícules de coure primes. Aquesta tesi ha estat, doncs, una contribució a una millor comprensió de la relació entre l'acumulació de danys i el rendiment elèctric de les plaques PCB i MEMS i pot conduir a millores en la seva fabricació. Això fa que els resultats tinguin una gran importància pràctica i que la metodologia d’assaig desenvolupada es pugui estendre a altres pel·lícules primes.
Se estudiaron las características mecánicas y eléctricas de películas delgadas de cobre adheridas a laminados epoxi FR4, bajo carga térmica y mecánica. En la 1ª etapa se determinaron de forma experimental y analítica los parámetros modales como las frecuencias naturales y los ratios de amortiguamiento utilizando un método de elementos finitos para cuatro grupos de muestras, con el fin de estudiar los efectos geométricos y la presencia de un agujero central de diferentes diámetros. Se ha descubierto que estos tamaños son adecuados para su uso como placas de circuitos electrónicos que sufren cambios de frecuencia significativos que van desde 40 Hz a 1 kHz. Se encontró que la frecuencia de resonancia fundamental de todas las muestras era inferior a 40 Hz y la influencia de un orificio central no fue significativa para afectar las propiedades modales. Durante la segunda etapa de la investigación realizada, se determinó el efecto de las vibraciones de alta frecuencia sobre las propiedades eléctricas. Se encontró experimentalmente que las tensiones inducidas en las películas delgadas debido a la alta frecuencia y al número de ciclos afectan significativamente la resistencia de la hoja del material y otras propiedades eléctricas como la resistividad y la conductividad. Estas cargas mecánicas finalmente reducen el rendimiento eléctrico de las películas delgadas de cobre (PCB). Las imágenes SEM mostraron la formación de grietas cerca de la zona de alta tensión; estas fisuras propagan posteriormente la avería del equipo. El cambio de temperatura de la superficie de 25ºC a 45ºC mostró un pequeño cambio en la resistencia laminar de las películas delgadas de cobre. Por lo tanto, esta tesis ha sido una contribución a una mejor comprensión de la relación entre la acumulación de daños y el rendimiento eléctrico de las placas de PCB y MEMS y puede conducir a mejoras en su fabricación. Esto hace que los resultados sean de gran importancia práctica y la metodología de ensayo desarrollada se puede extender a otras películas delgadas.
Mechanical and electrical characteristics of thin copper films bonded to FR4 epoxy laminates, under thermal and mechanical loading, were studied. At the 1st stage modal parameters such as Natural frequencies and damping ratios were determined experimentally and analytically using a finite element method for four groups of samples, in order to study the geometric effects and the presence of a central hole of different diameters. It has been found that these sizes are suitable to be used as electronic circuit boards that undergo significant frequency changes ranging from 40 Hz to 1 kHz. The fundamental resonance frequency of all the specimens was found to be less than 40 Hz and the influence of a central hole was not significant to affect the modal properties. During the second stage of the accomplished research, the effect of high frequency vibrations on the electrical properties were determined. It was found experimentally that the stresses induced in the thin films due to high frequency and number of cycles significantly affect material sheet resistance and other electrical properties such as resistivity and conductivity. These mechanical loadings ultimately reduces electrical performance of thin copper films (PCBs). SEM images showed formation of cracks near the high stress zone; these cracks later propagates the failure of the equipment. The surface temperature change from 25ºC to 45ºC showed a little change in sheet resistance of thin copper films. This thesis has thus been a contribution to a better understanding of the relationship between damage accumulation and electrical performance of PCB boards and MEMS and may lead to improvements of their fabrication. This makes the results of great practical importance and the developed assay methodology can be extended to other thin films.
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6

Gittens, Ibacache Rolando Arturo. "The role of nanostructural and electrical surface properties on the osteogenic potential of titanium implants". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45975.

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Dental and orthopaedic implants are currently the solutions of choice for teeth and joint replacements with success rates continually improving, but they still have undesirable failure rates in patients who are compromised by disease or age, and who in many cases are the ones most in need. The success of titanium (Ti) implants depends on their ability to osseointegrate with the surrounding bone and this, in turn, is greatly dependent on the surface characteristics of the device. Advancements in surface analysis and surface modification techniques have improved the biological performance of metallic implants by mimicking the hierarchical structure of bone associated with regular bone remodeling. In this process, damaged bone is resorbed by osteoclasts, which produce resorption lacunae containing high microroughness generated after mineral dissolution under the ruffled border, as well as superimposed nanoscale features created by the collagen fibers left at the surface. Indeed, increasing Ti surface roughness at the micro and sub-microscale level has been shown to increase osteoblast differentiation in vitro, increase bone-to-implant contact in vivo, and accelerate healing times clinically. Recently, the clinical application of surface nanomodification of implants has been evaluated. Still, most clinically-available devices remain smooth at the nanoscale and fundamental questions remain to be elucidated about the effect of nanoroughness on the initial response of osteoblast lineage cells. Another property that could be used to control osteoblast development and the process of osseointegration is the electrical surface charge of implants. The presence of endogenous electrical signals in bone has been implicated in the processes of bone remodeling and repair. The existence of these native signals has prompted the use of external electrical stimulation to enhance bone growth in cases of fractures with delayed union or nonunion, with several in vitro and in vivo reports confirming its beneficial effects on bone formation. However, the use of electrical stimulation on Ti implants to enhance osseointegration is less understood, in part because of the lack of in vitro models that truly represent the in vivo environment. In addition, an aspect that has not been thoroughly examined is the electrical implication of implant corrosion and its effect on the surrounding tissue. Implants are exposed to extreme conditions in the body such as high pH during inflammation, and cyclic loads. These circumstances may lead to corrosion events that generate large electrochemical currents and potentials, and may cause abnormal cell and tissue responses that could be partly responsible for complications such as aseptic loosening of implants. Consequently, Ti implants with tailored surface characteristics such as nanotopography and electrical polarization, could promote bone healing and osseointegration to ensure successful outcomes for patients by mimicking the biological environment of bone without the use of systemic drugs. The objective of this thesis is to understand how surface nanostructural and electrical characteristics of Ti and Ti alloy surfaces may affect osteoblast lineage cell response in vitro for normal tissue regeneration and repair. Our central hypothesis is that combined micro/nanostructured surfaces, as well as direct stimulation of Ti surfaces with fixed direct current (DC) potentials, can enhance osteoblast differentiation.
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7

Mantena, Keerthi Varma. "Electrical and mechanical properties of MWCNT filled conductive adhesives on lead free surface finished PCB's". Lexington, Ky. : [University of Kentucky Libraries], 2009. http://hdl.handle.net/10225/1084.

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Thesis (M.S.)--University of Kentucky, 2009.
Title from document title page (viewed on October 28, 2009). Document formatted into pages; contains: viii, 44 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 42-43).
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8

Agreda, Adrian. "Electrical control of the nonlinear properties of plasmonic nanostructures". Thesis, Bourgogne Franche-Comté, 2020. http://www.theses.fr/2020UBFCK010.

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Ce travail rassemble les technologies de nanoélectronique et de nano-photonique pour créer un dispositif électro-plasmonique dont les propriétés optiques linéaires et non linéaires sont contrôlées électriquement. Ici, nous présentons la première démonstration de la modulation de photoluminescence non linéaire par des moyens électriques dans un cas d'étude simple. A cette fin, les nanoantennes plasmoniques sont interfacées avec des connexions électriques induisant des régions localisées d’accumulation et de déplétion d'électrons et affectant ainsi la réponse optique. De plus, une analyse complète de la photoluminescence non linéaire dans les nanofils plasmoniques est réealisée. La délocalisation et le transport des non-linéarités apportées par de telles structures permettent l’activation à distance des signaux. Différents aspects, dont les mécanismes sous-jacents à la modulation électrique et les processus dictant la généeration de photoluminescence non linéaire, sont systématiquement explorés
This work brings nano-electronics and nano-photonics technologies together to create an electron- plasmon device whose linear and nonlinear optical properties are electrically controlled. Here, we present the first demonstration of nonlinear photoluminescence modulation by electrical means in an uncluttered configuration. To this purpose, plasmonic nanoantennas are interfaced with elec- trical connections inducing localized regions of electron accumulation and depletion and therefore affecting the optical response. Additionally, a complete analysis of the nonlinear photoluminescence in plasmonic nanowires is carried out. The delocalization and transport of nonlinearities provided by such structures allow the remote activation of the signals. Different aspects including the un- derlying mechanisms behind the electrical modulation and the processes dictating the nonlinear photoluminescence generation are systematically explored
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9

Johnson, Brady Allen. "A Methodology to Analyze Surface Recombination Velocity and Other Properties of Cadmium Telluride Using Time Resolved Photoluminescence". University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1448881819.

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10

Chan, Chi Lun. "Alp-CuInSe2 tunnel MIS Schottky diodes & surface properties of crystalline p-CuInSe2". Thesis, McGill University, 1989. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=61911.

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11

Mitin, V. F., P. M. Lytvyn, V. V. Kholevchuk, L. A. Matveeva, V. V. Mitin, O. S. Kulyk y E. F. Venger. "Ge/GaAs(100) Thin Films: Large Effect of Film Growth Rate and Thicknesses on Surface Morphology, Intrinsic Stresses and Electrical Properties". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35066.

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We found out and studied a profound effect of film growth rate on the electrical properties, intrinsic stresses and surface morphology of thin Ge films grown on GaAs(100). This effect is essential and has to be accounted for when developing and producing devices based on the Ge/GaAs heterostructure. All the Ge films under investigation were single-crystalline and epitaxially-grown on the GaAs(100) substrates. However, the transport phenomena in Ge films grown at low and high deposition rate differed drastically. Those obtained at low deposition rate were p-type and high resistant. They had a low concentration of free charge carriers and thermally activated conductivity, which is characteristic of heavily doped and strongly (in the limiting case, fully) compensated semiconductors. Although such films were single-crystalline, their conductivity was percolation-type. The Ge films obtained at high deposition rate were n-type and low resistant. They had high concentration of free charge carriers. The temperature dependence of conductivity in such films was weak or practically absent, which is characteristic of degenerate heavily doped semiconductors. Besides, the surface morphology cardinally differed for films obtained at low and high deposition rate. At low film growth rates, surfaces with developed relief were observed whose valleys and ridges formed grains of irregular shape with pronounced substructure. As the film thickness grew, the surface relief became essentially pronounced. At rather high film deposition rates, contrary to the above, the Ge film surface was fine-grained and smooth; the surface relief practically did not depend on the film thickness. As the deposition rate went down, the intrinsic stresses in films essentially decreased. The results obtained were analyzed from the viewpoint of formation of compositional and morphological inhomogeneities, and fluctuations of electrostatic potential at low growth rates. Such potential fluctuations modulate Ge energy bands leading to appearance of potential relief and deep tails of density of states in the Ge bandgap. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35066
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12

Fariza, Aqdas [Verfasser] y Armin [Gutachter] Dadgar. "Surface and electrical properties of GaN layers : impact on GaN/AlInN FETs / Aqdas Fariza ; Gutachter: Armin Dadgar". Magdeburg : Universitätsbibliothek Otto-von-Guericke-Universität, 2019. http://d-nb.info/121993691X/34.

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13

Hajimammadov, R. (Rashad). "Plasmonic, electrical and catalytic properties of one-dimensional copper nanowires:effect of native oxides". Doctoral thesis, Oulun yliopisto, 2018. http://urn.fi/urn:isbn:9789526218878.

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Abstract Recent advances in materials synthesis resulted in a rediscovery of the low cost copper in its one and two-dimensional forms and project newer applications of this metal in fields not considered before. In this thesis, one-dimensional copper, i.e. nanowires are synthesized by a hydrothermal route and explored for their chemical, electrical, catalytic and plasmonic properties with highlighted advantages, benefited from their size and shape compared to thin film and bulk copper. Characterization of copper nanowires and their native oxides were performed using a number of analytical techniques such as X-ray photoelectron and Auger spectroscopy, Raman spectroscopy, X-ray diffraction as well as scanning probe and electron microscopy techniques to elucidate the oxidation mechanism and to assess the feasibility of the oxidized materials for various applications. A few atomic layers of cuprous oxide seem to form on the surface of the nanowires instantly, maybe already during synthesis, which then slowly grows further when exposing the nanowires to ambient air leading to the appearance of cupric oxide as well. Because of the surface oxides, individual nanowires and their bundled networks exhibit semiconducting behavior, which complicates the direct use of such materials for interconnections in electronics. However, even with the presence of native oxides, copper nanowires hold promise in many other applications such as the ones explored here for plasmonics and heterogeneous catalysis. As demonstrated in this work, surface plasmon absorption properties of the nanowires can be exploited for chemical sensing of surface adsorbed molecules (model compound Rhodamine 6G) by efficiently amplifying its Raman spectrum without using any lithographically defined sensor template. Further, it is shown that phenol contamination in water may be efficiently eliminated by converting it to nontoxic polyphenol as well as to CO2 owing to the highly efficient catalytic property of the mixed oxide phases on the surface of the nanowires. The results published in this thesis contribute to the understanding of the chemical and physical behavior of copper nanowires and other low dimensional copper nanostructures that undergo rapid surface oxidation
Tiivistelmä Jatkuva elektronisten laitteiden ja anturien pienentäminen on hyvin linjassa teknologian kehittymisen kanssa. Pyrkimys monitoimisiin ja tehokkaisiin materiaaleihin on muuttanut tavanomaisten materiaalien käsitystä. Viimeisimmät edistysaskeleet materiaalisynteesissä ovat johtaneet edullisen kuparin uudelleenlöytämiseen sen yksi- ja kaksidimensionaalisissa muodoissa ennustaen metallille uusia sovellutuksia alueilla, joissa sitä ei ole aiemmin hyödynnetty. Tässä väitöstyössä on tutkittu hydrotermisesti syntetisoitujen yksiulotteisten kuparinanojohtimien kemiallisia, sähköisiä, katalyyttisiä ja plasmonisia ominaisuuksia sekä näiden pieneen kokoon ja muotoon perustuvia etuoja ohutkalvo- ja bulkkikupariin verrattuna. Kuparinanojohtimia ja niiden luonnollisia oksideja karakterisoitiin useilla analyysitekniikoilla kuten röntgenelektroni- ja Auger-eletronispektroskopialla, Raman-spektroskopialla, röntgendiffraktiolla sekä pyyhkäisykärki- ja elektronimikroskopialla selvittäen hapettumismekanismeja ja oksidien soveltuvuutta eri käyttötarkoituksiin. Muutaman atomikerroksen paksuinen kupari(I)oksidikerros havaittiin muodostuvan välittömästi, luultavasti jo materiaalisynteesin aikana nanojohtimien pinnalle. Nanojohtimien altistuessa ympäröivälle ilmalle oksidikerros kehittyi hitaasti johtaen kupari(II)oksidin muodostumiseen. Pintaoksidien johdosta yksittäiset nanojohtimet ja niistä yhteenkasautuneet verkostot käyttäytyvät puolijohdemaisesti mikä monimutkaistaa näiden materiaalien käyttöä sellaisenaan elektroniikan johtimissa. Luonnollisista oksideista huolimatta kuparinanojohtimet ovat lupaavia monissa muissa sovelluksissa, kuten tässä työssä tutkituissa plasmonisessa ja heterogeenisessä katalyysissä. Väitöstyössä osoitetaan, että nanojohtimen pintaplasmonisia absorptio-ominaisuuksia voidaan hyödyntää pintaan absorboituneiden molekyylien kemiallisessa havainnoinnissa (mallinnettu yhdiste rodamiini 6G) vahvistamalla Raman–spektriä käyttämättä lainkaan litografiapohjaista anturisapluunaa. Myöskin vesien fenolikontaminaatio voidaan tehokkaasti muuntaa myrkyttömiksi polyfenoleiksi ja hiiidioksidiksi hyödyntämällä nanojohtimien pinnalla olevia oksideja tehokkaana katalyyttinä (jopa parempi kuin kaupallisten kupariin pohjautuvat katalyytit). Tässä väitöstyössä julkaistut tulokset edistävät kuparinanojohtimien sekä muiden pienikokoisten ja nopeasti hapettuvien kuparinanorakenteiden kemiallisen ja fyysisen käytöksen ymmärtämistä. Tieteellisten kehitysaskeleiden lisäksi tämä väitöstyö voi myös toimia lähteenä pienirakenteisten yleisten metallien sovelluksille
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14

Mada, Mykanth Reddy Materials Science &amp Engineering Faculty of Science UNSW. "Fabrication and characterisation of SWCNT-PMMA and charcoal-PMMA composites with superior electrical conductivity and surface hardness properties". Awarded by:University of New South Wales. Materials Science & Engineering, 2009. http://handle.unsw.edu.au/1959.4/41831.

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Fabrication of SWCNT-PMMA and Activated Charcoal- PMMA composites was carried out by the compression moulding technique. Then Mechanical and Electrical properties of the composites were investigated. The morphological studies of composites showed a) good dispersion of fillers and b) good interaction between fillers and matrix. Electrical conductivity of SWCNT-PMMA composites was increased by 9 orders of magnitude (at 0.8 % volume fraction of SWCNT) and that of AC-PMMA composites increased by 16 orders of magnitude (at 17 % volume fraction of AC). The percolation threshold of both composites turned out to be lower compared to the theoretical values. A significant improvement in mechanical properties was obtained ??? particularly in AC-PMMA composites which showed a 400 % improvement in Vickers microhardness ??? raising the polymer matrix abrasion property literally to that of Aluminium alloys (Dobrazanski et al 2006). In conclusion, it is to be noted that Activated Charcoal - PMMA composites have a great potential for cost effective conducting polymer composite production by the use of cheap filler: In addition, the compression moulding technique shows good potential for cost effective fabricating technique for amorphous polymers with high electrical and mechanical properties.
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15

Gao, Yan 1970. "Surface electrical properties of goethite and adsorption of phosphate and arsenate on iron oxyhydroxides in high ionic strength solutions". Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36934.

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Iron oxyhydroxides are ubiquitous in natural systems and have been recognized as strong adsorbents for Group V elements, such as arsenic and phosphorus. Consequently, the mobility and bioavailability of phosphate and arsenate in the marine environment are mostly regulated by the fate of iron oxyhydroxides. However, to this day, the majority of adsorption studies of phosphate and arsenate were performed in low ionic strength solutions. In this study, phosphate and arsenate complexation on goethite in a 0.7 M NaCl solution and seawater was characterized over a pH range of 3.0 to 10.0 in batch adsorption experiments. Phosphate complexation is described using electric double layer models which consider the presence of three monodentate surface complexes, each characterized by an intrinsic formation constant. Arsenate shows a similar adsorption pattern on goethite but a higher affinity than phosphate. A model including three surface complexes describes the arsenate adsorption at relatively high initial concentrations (i.e., 23 and 34 mumol/l) but overestimates the adsorption at a lower concentration (i.e., 8.8 mumol/l). The equilibrium model derived by combining the formation constants obtained in the single oxyanion subsystems predicts the shape of the competitive adsorption data but fails to reproduce it quantitatively. In competitive experiments, phosphate adsorption is underpredicted whereas arsenate adsorption is overpredicted.
Magnesium, calcium and sulphate complexation on goethite was studied in a 0.7 M NaCl solution at 25°C and a pH range of 3.0 to 10.0 and their surface complexation constants were derived. Phosphate adsorption in a 0.7 M NaCl solution increases slightly in the presence of Mg and Ca and decreases at low pH upon the addition of SO4. In contrast, arsenate adsorption is not affected by the presence of Mg or Ca. Phosphate adsorption in seawater is reduced at low pH and enhanced at neutral pH relative to 0.7 M NaCl whereas arsenate adsorption is identical in both solutions except for a decrease at low pH in seawater. The equilibrium model derived by combining the single adsorbate subsystems predicts phosphate and arsenate adsorption in the PO 4-SO4-goethite and AsO4-Ca-goethite systems well, but fails to accurately reproduce the adsorption data in the PO4-Ca-goethite, PO4-Mg-goethite, PO4-seawater-goethite, AsO4-Mg-goethite and AsO4-seawater-goethite systems. The inclusion of ternary surface complexes >FeOMgHPO4-, >FeOMgH2PO 40, >FeOCaHPO4-, >FeOCaH 2PO40, >FeOMgHAsO4- and >FeOMgH2AsO40 in the latter systems improves model fits significantly. Phosphate adsorption in the competitive experiments in seawater is identical to that in the 0.7 M NaCl solution whereas arsenate adsorption in seawater is greater at pH > 7. In competitive experiments in seawater, phosphate adsorption is underpredicted at pH < 6.5 whereas arsenate adsorption is reproduced well using the Constant Capacitance Model (CCM) with the inclusion of the ternary surface complexes.
Phosphate and arsenate adsorption by ferrihydrite, in both 0.7 M NaCl and artificial seawater solutions, was studied at particle concentrations of 0.24 g/l and 0.025 g/l between pH 3.0 and 10.0. Both phosphate and arsenate surface complexation can be described using a model comprising three surface intrinsic constants which decrease with decreasing particle concentration. Ferrihydrite is a stronger adsorbent of PO4 and AsO4 on a per mass basis whereas goethite is a stronger sorbent in terms of chemical affinity. The CCM is able to predict PO4 and AsO4 adsorption on a mixture of goethite and ferrihydrite by combining the complexation constants derived from the single adsorbent subsystems. There is no evidence that adsorbed PO4 and AsO4 is released to solution when ferrihydrite is converted to hematite, an iron oxide with a much lower affinity for these oxyanions. The coprecipitation of both PO4 and AsO4 with hematite during the conversion may be responsible for these observations.
Finally, the surface complexation constants reported in this thesis may be incorporated into other models and contribute to the development of an experimental and thermodynamic database for marine geochemical systems.
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16

Andrä, Michael Tobias [Verfasser], Joachim [Akademischer Betreuer] Mayer y Rainer [Akademischer Betreuer] Waser. "Chemical control of the electrical surface properties of n-doped transition metal oxides / Michael Tobias Andrä ; Joachim Mayer, Rainer Waser". Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://nbn-resolving.de/urn:nbn:de:101:1-2020081914254831384617.

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17

Andrä, Michael Tobias Verfasser], Joachim [Akademischer Betreuer] [Mayer y Rainer [Akademischer Betreuer] Waser. "Chemical control of the electrical surface properties of n-doped transition metal oxides / Michael Tobias Andrä ; Joachim Mayer, Rainer Waser". Aachen : Universitätsbibliothek der RWTH Aachen, 2019. http://d-nb.info/1216202079/34.

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18

Cordoba, Erazo Maria Fernanda. "Near-field Microwave Microscopy for Surface and Subsurface Characterization of Materials". Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5930.

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This dissertation presents an investigation on the capabilities of Near-Field Microwave Microscopy (NFMM) for the characterization of surface and subsurface materials. Subsurface characterization refers to the detection, differentiation and imaging of dielectric, and metallic features that are coated with an insulating layer. The design, simulation and modeling, and testing of a dielectric resonator (DR)-based NFMM and a coaxial transmission line resonator-based NFMM are discussed in detail in this work. Additionally, materials differentiation and imaging capabilities of each microscope are examined using several bulk samples, liquids, GaAs MMIC circuits, and gold/glass testing patterns. The 5.7 GHz DR-based NFMM uses a microwave probe that consists of a commercial gold-coated probe tip coupled to a DR through a non-resonant microstrip line. The probe is enclosed in an aluminum cavity to preserve the quality factor of the probe (Q=986) and therefore to enhance its sensitivity. The development of a lumped-element model of this DR-based probe is discussed in this work. Characteristics of this design are its high Q and the ability to resolve differences in permittivity (E’r) of insulting bulk samples and liquids as small as ∆E’r =1.75 and ∆E’r =0.04, respectively. The imaging capabilities of this design were verified using a GaAs MMIC phase shifter. It was found that a 10 um wide microstrip line is successfully resolved and that the spatial resolution of the microscope is 50 um when using a tungsten tip with an apex radius of 25 um. Additionally, measurement of the electrical resistance of an additive manufactured resistor was measured using the DR-based NFMM without the need of contacts. The percent difference between the electrical resistance measured using the DR-based NFMM and a four-point probe is 9.6%. Furthermore, the DR-based NFMM allows simultaneous imaging of topography and RF electrical conductivity of rough thick films without the need of an additional distance sensor; this ability is demonstrated for a rough CB028 thick film. The 5GHz coaxial resonator transmission line-based NFMM employs a half-wavelength coaxial transmission line resonator terminated in a sharp tungsten tip as the microwave probe. A quartz-tuning fork based distance following feedback system is integrated with the microwave probe in order for the NFMM to operate in non-contact mode. The Q of the probe is degraded by 30% (Q=55) due to the presence of the quartz tuning fork. Despite the low Q, this NFMM is able to differentiate several insulating bulk samples (3.8 < E’r < 25) even if they are coated with an insulating layer of thickness similar to the apex radius of the tungsten tip. Finally, the coaxial resonator transmission line-based NFMM is able to image subsurface permittivity distribution of a flexible polymer-composite PDMS-Ba0.55Sr0.45TiO3 49% which is coated with 10 um thick parylene-C layer. Measurements performed at a tip-sample distance of 100 nm reveal that within an area of 50 um x 50 um, the relative permittivity of the polymer-composite is not constant but varies between 6.63 and 11.78.
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19

Maillard, Alexis. "Structuration des propriétés électriques d'une surface vitreuse appliquée au contrôle de l'orientation d'une mésophase nématique". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0490.

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Les travaux de cette thèse se sont axés sur le développement d’un système photonique hybride regroupant un nouveau matériau vitreux possédant une fonction électrique de surface et une mésophase nématique de cristaux liquides.Principal élément du système hybride, le matériau fonctionnalisé est un verre commercial sodo-calcique dont le potentiel électrique de surface est structuré via un traitement de poling thermoélectrique assisté par plasma. Dans un second temps, le substrat vitreux à la fonction électrique structurée spatialement est utilisé dans la conception d’un système photonique simple, une cellule à cristal liquide. Ces cellules sont conçues de manière à pouvoir observer l’alignement induit par le verre polé sur les molécules. À ce stade, l’objectif est de mieux comprendre l’origine de l’alignement des cristaux liquides sur les verres polés, ceci passe par une caractérisation multimodale du système hybride qui se décompose en deux axes principaux :• L’étude de la structure et des propriétés électriques de surface du verre fonctionnalisé• L’étude de l’organisation et de la dynamique des molécules au contact du substrat polariséLe premier axe est réalisé en menant une analyse spectroscopique poussée sur le substratfonctionalisé. Des techniques de microscopie en génération de second harmonique polarisée, microscopie Raman polarisée et une analyse de composition par microsonde électronique permettent d’établir un lien clair entre la fonction électrique du matériau et sa structure atomique. Le deuxième axe sur l’organisation des molécules est réalisé en utilisant des techniques de microscopie en lumière polarisée et de spectroscopie Raman polarisée permettant de mesurer l’orientation des molécules. De plus, l’application d’un modèle de distribution d’orientation permet de comparer l’alignement moléculaire entre les échantillons mais aussi avec une cellule de référence à alignement planaire.Les premiers travaux effectués dans la thèse ont visé à reproduire des résultats obtenus précédemment sur des systèmes similaires, puis à augmenter la taille des structures obtenues lors de la mise en contact des cristaux liquides avec le substrat. Dans ce cadre le verre a été traité avec une électrode sous forme de grille microstructurée. Les résultats montrent que la fonction électrique obtenue est contrôlable en position et en orientation. Les cristaux liquides s'alignent suivant la fonction électrique en formant des motifs triangulaires avec un degré d'alignement similaire pour des tailles de motifs variant d'un ordre de grandeur.Dans un deuxième temps, l’étude de la structure du verre polé montre un lien fort entre l’apparition d’une charge d’espace planaire et la production de plasma pendant le traitement. L’origine de la charge d’espace est d’ailleurs discutée sur la base des mesures Raman. Finalement, la conception de cellule dynamiques In-plane-Switching (IPS) permet de caractériser la dynamique de réalignement des cristaux liquides et par comparaison avec une cellule de référence fabriquée à partir de substrats commerciaux de quantifier l'énergie d'ancrage des cristaux liquides sur la surface de verre polarisée
The work performed in this thesis focused on the development of a hybrid photonic system combining a novel functionalized vitreous material and a nematic mesophase of liquid crystals.The main component of the hybrid system is a commercial soda-lime glass, whose surface potential is structured via a plasma-assisted thermoelectric poling treatment. This is made possible through the use of a microstructured electrode. In a second phase, the electrically structured vitreous substrate is used to produce a simple photonic system that is a liquid crystal cell. These cells are designed to observe the alignment induced by the poled glass on the molecules. At this stage, the goal is to better understand the origin of the liquid crystal alignment on poled glass, which involves a multimodal characterization of the hybrid system, broken down into two main axis:• A structural study of the functionalized glass• A study of the molecular organization in contact with the poled substrateThe first axis is achieved through a thorough spectroscopic analysis of the poled substrate. Techniques such as polarized second harmonic generation microscopy, polarized Raman microscopy, and composition analysis by electron microprobe establish a clear link between the electrical function of the material and its atomic structure. The second axis, concerning molecular organization, is conducted using polarized light microscopy and polarized Raman spectroscopy techniques to measure molecular orientation. Furthermore, the application of an orientation distribution model allows for a comparison of molecular alignment between samples and with a reference planar alignment cell.The initial work of the thesis aimed to reproduce results previously obtained on similar systems, then to increase the size of the structures formed when liquid crystals come into contact with the substrate. In this context, the glass was poled using an electrode in the form of a microstructured grid. The results show that the obtained electrical function is highly oriented on the glass and that the liquid crystals follow this alignment by forming triangular patterns, with similar molecular flatness relative to the substrates for two poling grid sizes.These preliminary studies led to the use of a new wire-shaped electrode. The study of the poled glass structure shows a strong link between the appearance of a planar space charge and plasma production during the treatment. The origin of the space charge is further discussed based on Raman measurements. Subsequently, when poled glasses with wire anodes are brought into contact with liquid crystals, homogeneous alignment domains in the form of bands are produced. A strong correlation between domain size and poling voltage was observed, while the molecular alignment remained the same for all treatments. Finally, the design of dynamic In-plane Switching (IPS) cells with poled substrates allows for the comparison of the anchoring of molecules on the surface with a reference cell designed with commercially available substrates
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20

Picollet, Martine. "Contribution à l'étude de l'imprimabilité des papiers LWC en héliogravure édition". Grenoble INPG, 1997. http://www.theses.fr/1997INPG0038.

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Dans ce travail, nous etudions l'imprimabilite des papiers lwc en heliogravure edition. Les proprietes de surface, la permeabilite et les proprietes electriques des papiers vierges sont caracterisees a l'aide de diverses techniques de mesure. Une relation entre la structure de la couche et la permeabilite du papier couche est mise en evidence. D'autre part, la technique de la chromatographie inverse en phase gazeuse appliquee aux papiers couches permet de determiner de facon satisfaisante leur energie de surface. Les points manquants, les vaguelettes, la transvision et le rendu densitometrique ont ete retenus comme criteres de qualite d'impression. Ils sont analyses visuellement et a l'aide d'appareils de mesure. Grace aux resultats obtenus, il est possible d'identifier les caracteristiques du papier ayant une influence preponderante ainsi que leur importance relative. L'etat de surface du papier mais aussi ses proprietes electriques determinent le nombre de points manquants. Les vaguelettes dependent essentiellement de la regularite de la couverture de couche sur le support fibreux. Les problemes de transvision sont causes principalement par une opacite trop faible du papier. Des experiences complementaires realisees au laboratoire permettent d'ameliorer la comprehension des phenomenes d'interaction encre - papier, qui determinent notamment le rendu densitometrique. Nous montrons l'existence d'une competition entre la penetration de l'encre, liee a la permeabilite du papier, et l'etalement a la surface, qui depend de la mouillabilite mais aussi de la rugosite.
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21

Fragneaud, Benjamin. "Synthesis and characterization of polymer/carbon nanotubes composites : impact of polymer grafting on the surface of CNx MWNTs on the electrical and mechanical properties of the nanocomposites". Lyon, INSA, 2006. http://theses.insa-lyon.fr/publication/2006ISAL0124/these.pdf.

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New hybrid materials from the grafting of polystyrene on the surface of nitrogen doped carbon nanotube were synthesized. These chemically modified nanotubes were further used in the fabrication of polymer based nanocomposites. In these works, we studied the impact of the polymer grafted nanotubes on the electrical and mechanical properties of a polystyrene (PS) and a poly (butadiene-co-styrene) (PSBS) matrices. The grafted nanotubes have a better dispersion in a PS matrix as compared to the as received ones. Nevertheless, this kind of functionalization does not lower the percolation threshold since the grafted polymer layer electrically isolates the nanotubes each others. On the other hand, the mechanical reinforcement (PS matrix) increases when the nanotubes are polymer grafted. Furthermore, a stronger mechanical reinforcement is observed for large strain deformation. Concerning the nano-structured PSBS matrix, we observed a stronger mechanical reinforcement as compared to the PS matrix. The PS grafted nanotubes permit to connect the PS nano-domains of the matrix and consequently forms a percolating rigid network with a very low threshold (PC<0. 05 vol. %)
ADes nouveaux matériaux hybrides, provenant du greffage de polystyrène à la surface de nanotubes de carbone dopés azote (CNx MWNTs) ont été synthètisés et utilisés dans l’élaboration de nano-composites à matrice polymère. Dans ces travux de recherche nous avons étudiés l’impacte de ces nanotubes de carbone greffés polystyrène sur les propriétés mécaniques et électriques de matrices polystyrène (PS et poly (butadiène-co-styrène) (PSBS). Les nanotubes greffés ont une meilleure dispersion dans une matrice de polystyrène que les nanotubes sans traitement chimique. Cependant, ce type de fonctionnement ne permet pas de baisser le seuil de percolation électrique, puisque le greffage tend à isoler électriquement les nanotubes. Par ailleurs, nous avons observé une sensible augmentation de l’effet de renfort mécanique de la matrice PS quand les tubes sont greffés ; particulièrement quand les composites sont soumis à de grandes déformations. Dans le cas particulier d’une matrice nano structurée comme le PSBS, nous avons observé un effet de renfort mécanique beaucoup plus important quand les nanotubes étaient greffés. En effet, la couche de PS à la surface des CNx MWNTs connecte les domaines de PS du copolymère, permettant l’apparition d’un réseau percolant rigide avec un seuil de percolation très bas (PC <0. 05 vol%)
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22

Fragneaud, Benjamin Cavaillé Jean-Yves Terrones Maldonado Mauricio Gonzalez Montiel Alfonso. "Synthesis and characterization of polymer/carbon nanotubes composites impact of polymer grafting on the surface of CNx MWNTs on the electrical and mechanical properties of the nanocomposites /". Villeurbanne : Doc'INSA, 2007. http://docinsa.insa-lyon.fr/these/pont.php?id=fragneaud.

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23

Abou, Taha Mohammad. "Reversible modification of the surface properties of silica incorporated in ultra high molecular weight polyethylene : application to batteries separators". Electronic Thesis or Diss., Lyon, 2020. http://www.theses.fr/2020LYSE1299.

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Malgré la croissance du marché des batteries lithium-ion, les batteries plomb-acide offrent toujours des avantages que les nouvelles ne sont pas en mesure d'assimiler, notamment en termes de coût, de procédés de fabrication et des besoins réels du marché. Dans ce contexte, l'objectif de ce travail est de valoriser les propriétés des séparateurs PE de batteries plomb-acide qui dominent 90% du marché des séparateurs de batteries plomb-acide. Ces membranes poreuses sont principalement constituées de silice précipitée, un squelette de polyéthylène haute masse molaire (UHMWPE) et elles sont élaborées par un procédé de séparation de phase induite thermiquement (TIPS) avec de l'huile naphténique qui est ensuite extraite. La porosité résultante est ensuite infiltrée avec l'électrolyte de la batterie. Cependant, en raison de la mouillabilité limitée des pores de la membrane par l'électrolyte polaire, seule une fraction de la porosité disponible est efficace. Cette thèse se concentre sur l'amélioration d'une telle porosité mouillable par l'électrolyte afin de réduire la résistivité électrique du séparateur. La mouillabilité des pores n'est pas seulement liée à la présence de silice mais également à la nature de sa surface. Paradoxalement, la silice hydrophobe favorise la qualité du mélange et la dispersion des agrégats; tandis que la silice hydrophile favorise la mouillabilité de la porosité par l'électrolyte. Pour remplir ces critères et obtenir un matériau le plus homogène possible avec une porosité maximale accessible, une modification réversible de la surface de la silice a été réalisée par imprégnation physique de tensioactifs ou par modification chimique avant le procédé d’élaboration de la membrane. Dans un premier temps, des mesures rhéologiques des suspensions de silice dans l’huile, les isothermes de sorption, l’angle de contact et d'autres techniques ont été utilisées pour évaluer le changement des propriétés de surface de la nouvelle silice. Ensuite, les silices préparées ont été dispersées dans les membranes et la porosité, l’état de dispersion, la structure, les propriétés électriques et mécaniques ont été étudiées
Notwithstanding the growth of the market of the new lithium-ion batteries, lead-acid batteries still offer advantages that the new ones are not able to equate especially in terms of cost, manufacturing base and the actual market need. In this context, the aim of this work is to enhance the properties of lead-acid batteries PE- separators that predominate 90% of the market of lead-acid batteries separators. These porous membranes consist mainly of precipitated silica, a backbone of ultra-high molecular weight Polyethylene (UHMWPE) and they are processed using a thermally induced phase separation process (TIPS) with naphthenic oil that is subsequently extracted. The resulting porosity is thereafter infiltrated with the electrolyte of the battery. Yet, due to the limited wettability of the pores of the membrane by the polar electrolyte, only a fraction of the available porosity is efficient. This thesis focuses on the enhancement of such wettable porosity by the electrolyte in order to reduce the electrical resistivity of the separator. The wettability of the pores is not only related to the presence of silica but also to the nature of silica surface. Paradoxically, hydrophobic silica favors the blend and the dispersion of aggregates; while hydrophilic silica promotes the wettability of the porosity by the electrolyte. To fulfill these criteria and obtain a material as homogeneous as possible with maximum accessible porosity, a reversible modification of the surface of silica was realized by physical impregnation of surfactants or by chemical modification before the blending and the dispersion in the membrane. Therefore, rheological characterization of the suspensions, contact angle and sorption isotherms and other techniques were used to evaluate the change in the surface properties of the new silica. Then, these tuned silica were dispersed in membranes and the prorosity, the structure, the electrical and mechanical properties were investigated
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24

Yesil, Sertan. "Processing And Characterization Of Carbon Nanotube Based Conductive Polymer Composites". Phd thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/3/12611984/index.pdf.

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The aim of this study was to improve the mechanical and electrical properties of conductive polymer composites. For this purpose, different studies were performed in this dissertation. In order to investigate the effects of the carbon nanotube (CNT) surface treatment on the morphology, electrical and mechanical properties of the composites, poly(ethylene terephthalate) (PET) based conductive polymer composites were prepared by using as-received, purified and modified carbon nanotubes in a twin screw extruder. During the purification of carbon nanotubes, surface properties of carbon nanotubes were altered by purifying them with nitric acid (HNO3), sulfuric acid (H2SO4), ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2) mixtures. Electron Spectroscopy for Chemical Analysis (ESCA) results indicated the removal of metallic catalyst residues from the structure of carbon nanotubes and increase in the oxygen content of carbon nanotube surface as a result of purification procedure. Surface structure of the purified carbon nanotubes was also modified by treatment with sodium dodecyl sulfate (SDS), poly(ethylene glycol) (PEG) and diglycidyl ether of Bisphenol A (DGEBA). Fourier Transformed Infrared Spectroscopy (FTIR) spectra of the carbon nanotube samples indicated the existence of functional groups on the surfaces of carbon nanotubes after modification. All composites prepared with purified and modified carbon nanotubes had higher electrical resistivities, tensile and impact strength values than those of the composite based on as-received carbon nanotubes, due to the functional groups formed on the surfaces of carbon nanotubes during surface treatment. In order to investigate the effects of alternative composite preparation methods on the electrical and mechanical properties of the composites, in-situ microfiber reinforced conductive polymer composites consisting of high density polyethylene (HDPE), poly(ethylene terephthalate) and carbon nanotubes were prepared in a twin screw extruder followed by hot stretching of PET/CNT phase in HDPE matrix. Composites were produced by using as-received, purified and PEG treated carbon nanotubes. SEM micrographs of the hot stretched composites pointed out the existence of in-situ PET/CNT microfibers dispersed in HDPE matrix up to 1 wt. % carbon nanotube loadings. Electrical conductivity values of the microfibrillar composites were higher than that of the composites prepared without microfiber reinforcement due to the presence of continuous PET/CNT microfibers with high electrical conductivity in the structure. To investigate the potential application of conductive polymer composites, the effects of surfactant usage and carbon nanotube surface modification
on the damage sensing capability of the epoxy/carbon nanotube/glass fiber composite panels during mechanical loadings were studied. Surface modification of the carbon nanotubes was performed by using hexamethylene diamine (HMDA). 4-octylphenol polyethoxylate (nonionic) (Triton X-100) and cetyl pyridinium chloride (cationic) (CPC) were used as surfactants during composite preparation. Electrical resistivity measurements which were performed during the impact, tensile and fatigue tests of the composite panels showed the changes in damage sensing capabilities of the composites. Surface treatment of carbon nanotubes and the use of surfactants decreased the carbon nanotube particle size and improved the dispersion in the composites which increased the damage sensitivity of the panels.
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25

Park, So Jeong. "Propriétés électriques et modélisation des dispositifs MOS avanvés : dispositif FD-SOI, transistors sans jonctions (JLT) et transistor à couche mince à semi-conducteur d'oxyde amorphe". Phd thesis, Université de Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-00954637.

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Selon la feuille de route des industriels de la microélectronique (ITRS), la dimension critiqueminimum des MOSFET en 2026 ne devrait être que de 6 nm [1]. La miniaturisation du CMOS reposeessentiellement sur deux approches, à savoir la réduction des dimensions géométriques physiques etdes dimensions équivalentes. La réduction géométrique des dimensions conduit à la diminution desdimensions critiques selon la " loi " de Moore, qui définit les tendances de l'industrie dessemiconducteurs. Comme la taille des dispositifs est réduite de façon importante, davantage d'effortssont consentis pour maintenir les performances des composants en dépit des effets de canaux courts,des fluctuations induites par le nombre de dopants.... [2-4]. D'autre part, la réduction des dimensionséquivalentes devient de plus en plus importante de nos jours et de nouvelles solutions pour laminiaturisation reposant sur la conception et les procédés technologiques sont nécessaires. Pour cela,des solutions nouvelles sont nécessaires, en termes de matériaux, d'architectures de composants et detechnologies, afin d'atteindre les critères requis pour la faible consommation et les nouvellesfonctionnalités pour les composants futurs ("More than Moore" et "Beyond CMOS"). A titred'exemple, les transistors à film mince (TFT) sont des dispositifs prometteurs pour les circuitsélectroniques flexibles et transparents.
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26

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

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The objective of this study is to examine core-shell type plasmonic metamaterials aimed at the development of materials with unique electromagnetic properties. The building blocks of metamaterials under study consist of gold as a metal component, and silica and precipitated calcium carbonate (PCC) as the dielectric media. The results of this study demonstrate important applications of the core-shells including scattering suppression, airborne obscurants made of fractal gold shells, photomodification of the fractal structure providing windows of transparency, and plasmonics core-shell with a gain shell as an active device. Plasmonic resonances of the metallic shells depend on their nanostructure and geometry of the core, which can be optimized for the broadband extinction. Significant extinction from the visible to mid-infrared makes fractal shells very attractive as bandpass filters and aerosolized obscurants. In contrast to the planar fractal films, where the absorption and reflection equally contribute to the extinction, the shells' extinction is caused mainly by the absorption. This work shows that the Mie scattering resonance of a silica core with 780 nm diameter at 560 nm is suppressed by 75% and only partially substituted by the absorption in the shell so that the total transmission is noticeably increased. Effective medium theory supports our experiments and indicates that light goes mostly through the epsilon-near-zero shell with approximately wavelength independent absorption rate. Broadband extinction in fractal shells allows as well for a laser photoburning of holes in the extinction spectra and consequently windows of transparency in a controlled manner. Au fractal nanostructures grown on PCC flakes provide the highest mass normalized extinction, up to 3 m^2/g, which has been demonstrated in the broad spectral range. In the nanoplasmonic field active devices consist of a Au nanoparticle that acts as a cavity and the dye molecules attached to it via thin silica shell as the active medium. Such kind of devices is considered as a nano-laser or nano-amplifier. The fabricated nanolasers were studied for their photoluminescence kinetic properties. It is shown that the cooperative effects due to the coupling of dye molecules via Au nanoparticle plasmons result in bi-exponential emission decay characteristics in accord with theory predictions. These bi-exponential decays involve a fast superradiant decay, which is followed by a slow subradiant decay. To summarize, this work shows new attractive properties of core-shell nanoparticles. Fractal Au shells on silica cores prove to be a good scattering suppressor and a band pass filter in a broadband spectral range. They can also be used as an obscurant when PCC is used as the core material. Finally, gold nanoparticles coated with silica with dye results in bi-exponential decays.
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27

Burr, Tracey Alexandra 1967. "Electrical properties of silicon surfaces and interfaces". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9689.

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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1998.
Includes bibliographical references (p. 159-168).
This work addresses two scientific challenges associated with diminishing device size. First, alternative surface passivation chemistries are investigated to meet the narrowing process tolerances for high quality silicon surfaces. Second, Si-based light emitting devices are studied to address a longer-term move towards photons instead of electrons for data transfer. A concerted effort is made to engineer environmentally benign solutions to these challenges. Highly effective Si( 100) surface passivation is achieved by immersing wafers in very dilute solutions of methanolic iodine. The electrical quality of Si surfaces is monitored in terms of surface recombination lifetime, employing radio frequency photo conductance decay (rfPCD) measurements. J/methanol treated surfaces are shown to have higher lifetimes and greater air stability than hydrogen terminated surfaces, while retaining comparable planarity and smoothness. Using XPS, UPS, and ATR-FTIR, the identity of the primary passivating surface species is ascertained to be a methoxysilane (Si-OCH3), and the most plausible passivation mechanism is deduced. Our results clearly illustrate the relationship between chemical passivation and electrical passivation. Thin films of visibly emitting silicon nanoparticles are fabricated using a pulsed laser ablation supersonic expansion technique. The electrical and electroluminescence characteristics of devices containing these films are shown to be controlled by carrier transport through the nanoparticulate silicon layer. A conduction mechanism encompassing both geometric and electronic effects most effectively relates the high resistivity with structural properties of the films. The observed temperature dependent PL, EL, and I-V characteristics of the devices are consistent with a model in which carrier transport is controlled by space-charge-limited currents or tunneling through potential barriers on a percolating lattice.
by Tracey Alexandra Burr.
Ph.D.
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28

Dalla, Francesca Kevin. "Exfoliation du graphène par voie liquide en vue d'une application aux contacts électriques". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS134/document.

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Le graphène est un matériau carboné exceptionnel de par ses propriétés électriques (mobilité électronique à température ambiante de 200 000 cm²V-¹s-¹), mécaniques (module d'Young de 1,5 TPA) et sa capacité à protéger un substrat de l’atmosphère. Cela en fait un candidat idéal comme revêtement de protection pour les dispositifs de connexion dont la partie active (le contact électrique) peut subir des dégradations sévères au cours du temps.. Un tel revêtement de protection doit en effet avoir des propriétés de robustesse et de conduction la plupart du temps antinomiques. La première étape de ce travail a consisté à mettre en œuvre un procède d’exfoliation en phase liquide afin de produire des suspensions de graphène ou de matériaux de type graphène. Différents type de caractérisations structurelles et électriques à l’échelle microscopique ont permis de déterminer des conditions d’exfoliation favorables en variant la nature du solvant et les conditions de sonication. Il s’est agi ensuite d’évaluer différents modes de dépôts permettant d’obtenir un revêtement de protection à partir de feuillets individuels. Les méthodes de trempé, évaporation, spray et filtration ont été caractérisées et ont montré leurs avantages et inconvénients. La méthode de filtration donne les films les plus couvrants mais pose le problème du transfert vers la surface à protéger : on a mis en évidence une contamination résiduelle difficile à éliminer. Les premiers résultats avec une méthode de spray industriel sans buse ont montré une grande réduction du frottement mais aussi la complexité des mécanismes régissant la qualité des dépôts. Les limites des différentes méthodes de dépôt pourraient être dépassées par l’utilisation de films composites polymère-graphène
Graphene is a special carbon material due to its electrical properties (electron mobility at room temperature 200 000 cm²V-¹s-¹), mechanical (Young modulus of 1.5 TPA) and ability to protect a substrate of atmosphere. This makes it an ideal candidate as a protective coating for connecting devices including the active portion (electrical contact) may suffer severe damage over time .. Such a protective coating must indeed have properties and robustness conducting most of the contradictory time. The first step of this work was to implement an exfoliation proceeds in the liquid phase to produce suspensions of graphene and graphene-like materials.Different types of structural and electrical properties at the microscopic scale have determined favorable conditions for exfoliation by varying the nature of the solvent and conditions of sonication. He then acted deposits evaluate different methods to obtain a protective coating from individual sheets. The methods of dip coating, drop casting, spray and filtration have been characterized and have shown their advantages and disadvantages. The filtration method gives the most covering films, but the problem of the transfer to the surface to be protected: it showed residual contamination difficult to remove. The first results with an industrial spray without nozzle method showed a large reduction in friction but also the complexity of the mechanisms governing the quality of deposits. Limitations of different deposit methods could be exceeded by the use of graphene-polymer composite films
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29

Gondran, Chantal. "Transfert des ions Na+ à l'interface NASICON/électrolyte : application à l'acquisition de signaux bioélectriques à la surface de la peau". Grenoble INPG, 1994. http://www.theses.fr/1994INPG0106.

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Ce travail a ete consacre a la caracterisation de l'interface nasicon/electrolyte par spectroscopie d'impedance. L'interface se comporte comme un circuit rc parallele. La resistance varie fortement avec la nature de l'electrolyte. Elle a ete attribuee au transfert des ions na#+ a l'interface. Une correlation entre la resistance d'interface et la conductivite de l'electrolyte a ete mise en evidence. La capacite est independante de l'electrolyte etudie et a ete reliee a l'existence d'une couche compacte resultant de la distance minimale d'approche des ions na#+ dans le nasicon. Lorsque l'electrolyte contient des protons, la resistance d'interface augmente au cours du temps. Cette evolution est reliee a la protonation de la surface du nasicon. Ces resultats ont ete utilises pour realiser des electrodes a base de nasicon destinees a l'acquisition de signaux bioelectriques a la surface de la peau. L'interet de ces electrodes reside dans la possibilite de les utiliser, sur de longues durees et pour de nombreux essais, sans gel de contact a la surface de la peau. Le comportement electrique (impedance et bruit) des electrodes en solution de chlorure de sodium a ete etudie. L'interface electrode peau a aussi ete caracterisee. L'electrode a base de nasicon est peu polarisable. En solution, l'impedance est essentiellement due a la membrane nasicon. Un bruit electrochimique en exces au bruit thermique a pu etre mis en evidence. Sur la peau, l'impedance a pu etre reliee au taux d'hydratation de la peau. Un bruit electrochimique variant avec la frequence en f#-#2 a ete mesure. Des signaux bioelectriques acquis avec ces electrodes sont donnes
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30

Al-Milli, Zain. "Electrical and mechanical properties of molecular junctions and nano surfaces". Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/84693/.

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The behaviour of two graphene based structures has been theoretically investigated and analysed by using one or more tools. This tool kit consists firstly of SIESTA, a density functional theory software package, secondly Gollum, a non-equilibrium Green’s function code, and finally the tight binding approach. The first project considers the variation of the thermoelectric properties of a graphene-graphene junction functionalised by the amino-silane molecule. The second project studies the mechanical properties of the interface between a silicon-carbide substrate and monolayer graphene. The results of these two projects are summarised in the next paragraphs. The calculation of the thermoelectric properties of a graphene-silane-graphene junction reveals a number of interesting results. The most important result is that silane hinders the cross-plane electron transmission and thermal conductance. Such properties have effective applications through controlling the heat flow in the electronic chip. Furthermore, the silane molecule enhances the figure of merit of the junction which refers to the ability to convert heat. To sum up, silane-functionalized graphene has an improved heat mediation over a non-functionalised junction. The second project analyses the mechanical properties of the silicon-carbide/graphene junction. The study of this junction focuses on the trends in terms of stiffness and work function as the hydrogen concentration intercalating the interface and the number of graphene sheets on top of the silicon-carbide substrate varies. As a result of this study I have found that the effect of increasing the number of penetrating hydrogen atoms is to reduce the stiffness and to enhance the work function. The same situation is found for the stiffness when the number of graphene layers is increased. However the work functions shows two completely opposing behaviours; the first one can be seen in the quasi-free standing graphene layer type 1 and type 2, where the work function has increased, while it has decreased for as-grown interface. An additional property can be deduced is that a certain amount of hydrogen atoms at the interface of approximately 33%, can dramatically change the characteristics of the interface. Another feature is that the junctions exhibit three distinct values of stiffness depending on the hydrogen concentration. The highest value is calculated for the directly attached graphene sheet to the silicon-carbide, while the softest junction is obtained when the concentration of hydrogen atoms passivates more than 50% of the surface silicon atoms. The last value has been shown for the graphene-graphene layer.
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31

La, Spina Léa. "Ondes élastiques guidées hautes fréquences dans des films minces de niobate de lithium sur saphir". Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://indexation.univ-fcomte.fr/nuxeo/site/esupversions/c6ae7a0b-2092-4108-95d2-d34cd889ce9d.

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Cette thèse fait partie du projet ANR MAXSAW qui vise à développer des nouveaux composants fonctionnant dans le domaine RF, adaptés aux nouvelles fréquences 5G. Les filtres à ondes acoustiques de surface (SAW) sont largement utilisés pour distinguer les différentes fréquences des signaux RF. Malheureusement, la fréquence des filtres SAW classiques est limitée à 3,7 GHz. Les couches minces épitaxiales de LiNbO3 sur du saphir accueillent des ondes acoustiques guidées qui répondent à la demande d'atteindre des fréquences et une efficacité plus élevées. Nous avons tout d’abord produit des couches minces de LiNbO3 sur des substrats de saphir. Des films minces de bonne qualité cristalline ont été obtenus. Nous avons aussi étudié leurs propriétés acoustiques par le biais de simulations et confirmé les fréquences pouvant être atteintes avec ces structures. Puis, nous avons simulé, conçu et caractérisé des résonateurs SAW basés sur les couches minces de LiNbO3 déposées sur saphir et les avons comparés à l’état de l’art. Des dispositifs acoustiques prometteurs ont été obtenus. Pour finir, une application au projet MAXSAW est présentée
This thesis is part of the ANR MAXSAW project, which aims to develop new components operating in the RF domain, adapted to the new 5G frequencies. Surface acoustic wave (SAW) filters are widely used to distinguish the different frequencies of RF signals. Unfortunately, the frequency of conventional SAW filters is limited to 3.7 GHz. Epitaxial thin films of LiNbO3 on sapphire host guided acoustic waves that meet the demand for higher frequencies and efficiency. We first produced LiNbO3 thin films on sapphire substrates. Thin films of good crystalline quality were obtained. We also studied their acoustic properties using simulations, and confirmed the frequencies achievable with these structures. The, we simulated, designed and characterized SAW resonators based on LiNbO3 thin films deposited on sapphire, and compared them with the state of the art. Promising acoustic devices were obtained. Finally, an application to the MAXSAW project is presented
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32

Plachinda, Pavel. "Electronic Properties and Structure of Functionalized Graphene". PDXScholar, 2012. https://pdxscholar.library.pdx.edu/open_access_etds/585.

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The trend over the last 50 years of down-scaling the silicon transistor to achieve faster computations has led to doubling of the number of transistors and computation speed over about every two years. However, this trend cannot be maintained due to the fundamental limitations of silicon as the main material for the semiconducting industry. Therefore, there is an active search for exploration of alternate materials. Among the possible candidates that can may [sic] be able to replace silicon is graphene which has recently gained the most attention. Unique properties of graphene include exceedingly high carrier mobility, tunable band gap, huge optical density of a monolayer, anomalous quantum Hall effect, and many others. To be suitable for microelectronic applications the material should be semiconductive, i.e. have a non-zero band gap. Pristine graphene is a semimetal, but by the virtue of doping the graphene surface with different molecules and radicals a band gap can be opened. Because the electronic properties of all materials are intimately related to their atomic structure, characterization of molecular and electronic structure of functionalizing groups is of high interest. The ab-inito (from the first principles) calculations provide a unique opportunity to study the influence of the dopants and thus allow exploration of the physical phenomena in functionalized graphene structures. This ability paves the road to probe the properties based on the intuitive structural information only. A great advantage of this approach lies in the opportunity for quick screening of various atomic structures. We conducted a series of ab-inito investigations of graphene functionalized with covalently and hapticly bound groups, and demonstrated possible practical usage of functionalized graphene for microelectronic and optical applications. This investigation showed that it is possible [to] produce band gaps in graphene (i.e., produce semiconducting graphene) of about 1 eV, without degrading the carrier mobility. This was archived by considering the influence of those adducts on electronic band structure and conductivity properties.
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33

Coria, Garcia Jose Conrado. "SURFACE ENHANCED RAMAN SCATTERING OF INTERFACIAL HALIDE IONS AND WATER AT SILVER ELECTRODES IN THE PRESENCE OF LEAD (SERS, ADSORPTION, DEPOSITION)". Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275414.

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34

Gullu, O., S. Ruzgar, S. Asubay, E. Ozerden, T. Kilicoglu y A. Turut. "Electrical Properties of Al/p-Si Structures with Colchicine Organic Thin Film". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35140.

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In this study, we have fabricated an Al/Colchicine/p-Si structure and have investigated its current– voltage (I–V) and capacitance–voltage (C–V) characteristics at room temperature. The barrier height and ideality factor values of 0.68 eV and 3.22, respectively, have been obtained from the I-V plot. The value of the barrier height was compared with the barrier height value of 0.50 eV of a conventional Al/p-Si diode. This was attributed to the Colchicine organic film modifying the effective barrier height by affecting the space charge region of the inorganic Si semiconductor substrate. By using C – 2-V characteristics the diffusion potential value has been extracted as 1.32 V. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35140
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35

Klein, Katherine. "Electromagnetic properties of high specific surface minerals". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20699.

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36

Wells, Andrea Dawn. "Deposition, surface chemistry, and electrochemistry of YBa₂Cu₃O₇₋(subscript delta) materials". Access restricted to users with UT Austin EID, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3036611.

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37

Ringer, Eric. "The energetis, dynamics and transport properties of CaF₂ : surface superionic conductivity". Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/31029.

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KUPFER, JOHN CARLTON. "A SEARCH FOR CHANGES IN THE BAND STRUCTURE OF EXTREMELY STRAIN-FREE MAGNESIUM-CADMIUM CRYSTALS AS A FUNCTION OF ALLOYING, IN THE DILUTE LIMIT (DE HAAS-VAN ALPHEN, FERMI SURFACE)". Diss., The University of Arizona, 1985. http://hdl.handle.net/10150/187953.

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We report here a study of a specific doublet of de Haas-van Alphen frequencies in pure Mg and very dilute Mg(Cd) alloys with the magnetic field aligned with the c-axis. The work involved three stages. First, the use of extremely strain-free crystals, temperatures down to 40 millidegree Kelvin, large amplitude modulation, and the fast Fourier transform allowed the components of this doublet to be well resolved. This resolution allowed measurement of the changes in the cross-sectional area as a function of magnetic field orientation to verify the assignment of this doublet to the cap and monster arm junction at the top of the Brillouin zone. Third, with the magnetic field aligned with the c-axis, the splitting of this doublet offered a direct and sensitive indication of any symmetry breaking changes in the 0001 Fourier component of the ionic lattice potential in Mg upon the introduction of Cd. C. B. Friedberg's analysis of his electron interference lineshape data from the quantum interferometer in Mg had indicated that the energy of this band gap should increase by 40% with the introduction of 15 ppm Cd. Our data indicate that any change in the energy of the band gap must be at least three orders of magnitude smaller than that indicated by Friedberg. Our data are, in fact, consistent with there being no changes in the electronic band structure or the Fermi surface of Mg(Cd) alloys (with up to 0.02% (At) Cd), from that of pure Mg.
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39

Badard, Mathieu. "Optimisation et contrôle de la transition dynamique de percolation au sein de matériaux nonostructurés : expérience et modélisation". Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI093.

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L'émergence des nanotubes de carbone a ouvert de nouveaux champs d'application dans le domaine des matériaux polymères. L'ajout de ces charges carbonées au sein de polymères permet la mise en œuvre de composites aux propriétés électriques optimisées. La conductivité de ces matériaux dépend en grande partie de l'organisation des charges dans la matrice, notamment de la présence de réseaux percolants. L'objectif du présent travail de thèse est de comprendre les mécanismes de structuration des nanotubes de carbone au sein de différents milieux. L'architecture de ces réseaux de charges a principalement été révélée par le biais de mesures électriques et diélectriques. L'originalité de nos travaux réside dans l'utilisation de matrices liquides, notamment des huiles de silicone, afin de s'affranchir des contraintes présentes dans les plastiques d'une part, et de simplifier les processus de mise en œuvre d'autre part. Le manuscrit de thèse est articulé autour de six chapitres. Une première partie bibliographique aborde les propriétés des nanotubes de carbone ainsi que les phénomènes que sont la percolation et la percolation dynamique. Le second chapitre, matériel & méthode, présente les matériaux employés ainsi que les différentes techniques de caractérisation utilisées au cours de la thèse. Le troisième chapitre de la thèse aborde, à travers des mesures de conductivité, la percolation dynamique des nanotubes de carbone sein d'huiles de silicone. Le chapitre 4 propose une modification la loi de puissance de Kirkpatrick, afin de décrire la conductivité en fonction du temps et du taux de charge. L'exposant critique de percolation, caractérisant la transition isolant conducteur, se révèle être un indicateur de l'état de dispersion des nanotubes à travers la matrice. Le chapitre 5 démontre la possibilité de contrôler l'organisation des charges par l'application d'un champ électrique. L'application d'un champ élevé permet une augmentation de plusieurs ordres de grandeur de la conductivité ainsi qu'une diminution des charges nécessaire à la formation d'un réseau percolant. Nous avons notamment déterminé des seuils de percolation de l'ordre de 0.005% massique en nanotube de carbone. Enfin, l'influence des propriétés intrinsèques de la matrice, telles la viscosité et la tension de surface, est étudié dans le chapitre 6. La dispersion des nanotubes de carbone s'avère être favorisée au sein de liquides ayant des tensions de surface proches de celle des tubes. Au contraire, une agrégation de charge est rapidement observée dans le cas ou la différence de tension de surface charge-matrice est importante. Nous avons également observé que la percolation des nanotubes est défavorisée au sein de milieux visqueux
The rise of carbon nanotube has open possibility for composites polymers. Mixing this carbonaceous filler with polymer medias leads to an optimization of the electrical properties. Then, conductivity mainly depends of the filler architecture, especially the presence of percolating networks. The objective of this work is to understand the percolation mechanisms of the carbon nanotubes in different media. During this study, filler network has been revealed by the mean of electrical and dielectrical measurements. The originality of our work lies in the use of liquid matrices, such as silicone oils, in order to overcome the stresses in the plastic on the one hand, and to simplify the processing in other hand. This thesis is organized around six chapters. The first bibliographic part discusses the carbon nanotubes properties as well as percolation and dynamic percolation phenomena. The second chapter, matériel & méthode, presents the materials used and the different characterization techniques employed. The third chapter of the thesis talks about dynamic percolation of carbon nanotubes in silicone oil, probed by conductivity measurements. Chapter 4 provides a change of the power law Kirkpatrick to describe the conductivity as a function of time and filler content. The critical exponent of percolation is proving to be an indicator of the dispersion state of nanotubes throughout the matrix. In the Chapter 5, electric field is depicted as a tool to control the organization of fillers. The application of a high field increases the conductivity of several orders of magnitude and decreases the percolation threshold. Percolation thresholds close to 0.005 wt % have been determined. At last, the influence of the intrinsic properties of the matrix, such as viscosity and surface tension, is discussed in Chapter 6. Carbon nanotubes dispersion appears to be favored if the difference of surface tension between filler and liquid is low. In contrast, a filler aggregation is rapidly observed in the case where the difference in surface tension is important. We also observed that the percolation of the nanotubes is favored in viscous media
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40

Lao, Changshi. "Transport Properties and Nanosensors of Oxide Nanowires and Nanobelts". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19744.

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ZnO is one of the most important materials for electronics, optoelectronics, piezoelectricity and optics. With a wide band gap of 3.37eV and an exiton binding energy of 60meV, ZnO 1D nanostructures exhibit promising properties in a lot of optical device applications. It is also an important piezoelectric material and has applications in a new category of nanodevices, nano-piezotronics. Demonstrated prototype of devices includes nanogenerators, piezoelectric-FET, and a series of evolutive devices based on the concept of nanogenerator. This is based on working principle of a semiconductor and piezoelectric coupled property. This thesis is about the growth, characterization and device fabrication of ZnO nanowires and nanobelts for sensors and UV detectors. First, the fundamental synthesis of ZnO nanostructurs is investigated, particularly polar surface dominated nanostructues, to illustrate the unique growth configurations of ZnO. Detail study in this part includes nanobelts, nanorings, nanocombs, nanonetworks, and nanodiskettes synthesis. Important factors in driving the nanostructure synthesis mechanism are analyzed, such as the chemical activities of different surface of ZnO and the polar surface dominated effects. Then, the devices fabricated methods using individual nanowires/nanobelts and their electrical transport properties were carefully characterized. In this part, dominant factors which are critical for nanobelt device performance are investigated, such as the contact properties, interface effects, and durability testing. Also, a metal doping method is studied to explore the controlling and modification of nanowire electric and optical properties. Further more, I will present the surface functionalization of nanobelt for largely improving its electrical, optoelectronic and chemical performance. Surface functionalization of nanobelts is proven to be an effective method in enhancing the semiconductor and metal contact. Piezoelectric field-effect transistors will be demonstrated as a powerful approach as chemical sensors. Finally, a technique is illustrated for functionalizing the surfaces of ZnO nanobelts for enhancing its UV sensitivity by over five orders of magnitude. This demonstrates an effective approach for fabricatiing ultrasensitive UV detectors. The research results presented in this thesis have made great contribution to the growth, device fabrication and novel applications of ZnO nanostructures for photonics, optoelectronics and sensors.
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41

Patitsas, Stathis Nikos. "Electron wavefunctions at crystal interfaces". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/29738.

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A one dimensional analysis of the boundary conditions of the electron energy eigenfunc-tion at a sharp interface between two crystals was made. An attempt to evaluate these conditions in terms of known band structure was made. It was concluded that this cannot be done in general. It was shown, however, that if the interface has the proper symmetry properties, the boundary conditions can be expressed in terms of only one unknown, energy-dependent parameter. It was concluded that setting this parameter equal to one gives boundary conditions which, though more general, are equivalent to the commonly used effective mass boundary conditions when they are applicable. It was concluded from numerical results for the transmission coefficient of the symmetric interface, that in general, these boundary conditions, which depend only on known band structure, do not give a good approximation to the exact answer. Since the energy dependence of the parameter mentioned above is described quite well qualitatively using the nearly free electron approximation or the tight-binding approximation, the applicability of any boundary conditions depending only on band structure can be predicted using these simple theories. The exact numerical results were calculated using the transfer matrix method. It was also concluded that the presence of symmetry in the interface either maximizes or minimizes the transmission coefficient. A tight-binding calculation showed that the transmission coefficient depends on an interface parameter which is independent of band structure. The transmission coefficient is maximized when this parameter is ignored. It was concluded that the effective mass equation is of little use when applied to this problem. Some transfer matrix results pertaining to the barrier and the superlattice were obtained.
Science, Faculty of
Physics and Astronomy, Department of
Graduate
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42

Nanthakumar, Alaganandan 1958. "PHOTOELECTROCHEMISTRY AND ELECTROCHEMISTRY OF ELECTROACTIVE LAYERED MOLECULES ON PHTHALOCYANINE AND METAL ELECTRODE SURFACES". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/277248.

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43

Dubourdieu, Catherine. "Étude de la microstructure et de l'impédance de surface de films supraconducteurs de YBa2Cu3O(7-x) élaborés par dépôt chimique en phse vapeur". Université Joseph Fourier (Grenoble ; 1971-2015), 1995. http://www.theses.fr/1995GRE10221.

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Des couches minces supraconductrices d'yba#2cu#3o#7#-#x ont ete deposees par depot chimique en phase vapeur a partir de precurseurs organometalliques sur des substrats de mgo (001), srtio#3 (001), laalo#3 (012) et yalo#3 (001). Nous avons etudie l'influence de la nature du substrat, de la pression partielle d'oxygene pendant le depot et de la composition des films sur les proprietes microstructurales, electriques et sur l'impedance de surface des films. Les films elabores sont fortement textures, avec l'axe c perpendiculaire au plan du substrat. Une relation d'epitaxie particuliere a ete mise en evidence sur yalo#3: une seule direction de maclage est observee au lieu de deux comme sur mgo, laalo#3 et srtio#3. L'orthorhombicite du substrat favorise l'alignement des directions 110 ou 10 d'ybco selon la direction 010 d'yalo#3. L'impedance de surface des films a ete mesuree par une technique de cavite resonnante en cuivre a 87 ghz et par une technique de resonateur coplanaire a 8 ghz. Les meilleurs films cvd elabores sur mgo ou laalo#3 presentent une temperature critique t#c#r 90 k (mesure de resistivite), une densite de courant critique j#c superieure a 10#6 a/cm#2, une profondeur de penetration a 0 k de 155 nm, et une resistance de surface comprise entre 15 milliohms et 20 milliohms a 77 k et 87 ghz (soit r#s de l'ordre de 0. 2 a 0. 3 milliohms a 77 k et 10 ghz et 10 ghz si r#s f#2). Ces performances sont equivalentes a celles des meilleurs films elabores par les techniques pvd (ablation laser, pulverisation et co-evaporation). Nous avons mis en evidence une correlation entre: la resistance de surface a 0. 85 t#c et la fraction de grains orientes axe-a dans le film, la resistance de surface et la densite de courant critique mesurees a 0. 85t#c, la resistance de surface a 0. 85 t#c et la profondeur de penetration a 0 k, la profondeur de penetration a 0 k et la resistivite dans l'etat normal
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44

Jada, Amane. "Etude de la structure et de la dynamique de microemulsions eau dans huile". Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13101.

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Etude des microemulsions qui sont des solutions transparentes constituees de fines gouttelettes d'eau dispersees dans une phase continue riche en huile. Determination par declin de fluorescence, diffusion de lumiere et conductivite electrique de l'influence de la nature de l'huile, de la temperature et de la structure du tensioactif sur la taille des gouttelettes et les processus d'echange de matiere entre gouttelettes
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45

Mirkhalaf, Fakhradin. "Electrochemical, optical and metal ion sensing properties of dithizone derivatised electrodes". Thesis, University of Liverpool, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367270.

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46

Patryarcha, Lukas [Verfasser]. "Experiments and simulations on the structural and electrical properties of nano- and microstructures on graphite surfaces produced by ion beam lithography / Lukas Patryarcha". Dortmund : Universitätsbibliothek Technische Universität Dortmund, 2011. http://d-nb.info/1018124373/34.

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47

Augustine, Robin. "Electromagnetic modelling of human tissues and its application on the interaction between antenna and human body in the BAN context". Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00499255.

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Les réseaux BAN (Body Area Network) révolutionnent le concept de la surveillance et de la prise en charge à distance de la santé du patient. Le BAN fournit des informations sur l'état de santé du patient en temps réel quelque soit l'endroit où il se trouve. Dans le « télé monitoring », des capteurs de mouvement, de respiration ou du rythme cardiaque placés à l'intérieur ou sur le corps humain transmettent des données via le réseau sans fil constituant le BAN, une antenne étant associée à chaque nœud du réseau. La communication peut être in/on, on/on ou on/off selon que les antennes sont placées à l'intérieur, sur ou à l'extérieur du corps. Le développement des BAN nécessite la réalisation de modèles (ou fantômes) simulant au mieux les propriétés électromagnétiques du corps humain. Des antennes portables, miniaturisées doivent être réalisées avec des contraintes d'intégration d'une part (aux vêtements, à des objets type montre ou badge), des contraintes de résistance ou de prise en compte de l'influence du corps d'autre part. La réduction de l'impact des antennes sur les tissus en terme de SAR (Specific Absorption Rate) doit également être considérée. Dans ce travail, l'objectif est de développer des fantômes valables pour les communications dans et sur le corps. Les matériaux de base sélectionnés sont d'origine biologique (biocéramiques et biopolymères) avec des propriétés proches de celles des tissus humains. Ces fantômes étant biocompatibles, ils sont essentiellement non toxiques alors que les fantômes usuels le sont en général. D'autre part, différents types d'antennes conformables, fonctionnant dans la bande ISM 2.4 GHz ont été développées et étudiées dans la perspective du BAN. Les antennes voient leur adaptation et leur efficacité chuter au contact ou à proximité du corps, ce qui constitue un écueil majeur pour établir une bonne communication. Différentes méthodes permettant de réduire l'influence du corps (plan de masse à l'arrière, surface haute impédance, feuille de ferrite polymère) sont testés et leurs avantages et inconvénients développés. Des mesures de SAR permettent aussi de démontrer l'efficacité de ces méthodes sur la réduction de la puissance absorbée par les tissus. Au final, ce travail apporte une contribution à l'étude théorique et expérimentale de l'interaction entre corps humain et antenne dans le cadre des réseaux BAN appliqués à la télésurveillance de la santé
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48

Talbi, Abderazek. "Effect of ultra-short laser nanostructuring of material surfaces on the evolution of their thermoelectric properties". Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2053/document.

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Aujourd’hui, les énergies renouvelables comme l’énergie éolienne, l’énergie solaire, l’énergie hydroélectrique et la thermoélectricité jouent un rôle essentiel dans la couverture de nos besoins en énergie. Parmi ces différentes sources d’énergie, la thermoélectricité, qui permet de convertir la chaleur en électricité ou inversement, attire une grande attention grâce à son large champ d’application. Les actuelles avancées dans la recherche thermoélectrique visent l’amélioration du rendement de conversion des modules thermoélectriques, à travers l’optimisation des propriétés thermoélectriques intrinsèques des matériaux utilisés (coefficient de Seebeck, conductivité électrique et conductivité thermique). Pour cela, différentes approches ont été étudiées (dopage, nouveau alliages, nanostucturation …). Parmi ces approches, la nanostructration des matériaux a été largement étudiée pour mener à bien cet objectif. Dans ce travail de thèse, nous nous sommes intéressés à étudier l’effet de la nanostructuration de surface des matériaux (silicium mesoporeux et oxyde de titane déposé en couches minces) par faisceaux laser ultra-court (picoseconde et femtoseconde) sur l’évolution de leurs propriétés thermoélectriques. Dans un premier temps, nous nous sommes focalisés sur l’étude des différents phénomènes physiques impliqués durant l’interaction laser-matière ainsi que sur la formation des différentes nanostructures résultantes (en forme de ripples, spikes, dots et autres) en fonction de la dose laser appliquée (la fluence et le nombre de pulses). La formation de ces nanostructures a été étudiée suivant deux régimes (stationnaire et dynamique). Après l’optimisation des paramètres conduisant à la formation de ces nanostructures, la caractérisation du coefficient de Seebeck et la conductivité électrique avant et après la nanostructuration de ces matériaux a été réalisée grâce à un nouveau dispositif de mesure (ZT-meter) développé au laboratoire GREMI. Les résultats de mesures montrent une importante amélioration du coefficient de Seebeck et la conductivité électrique après la nanostrucutration. Un facteur d’augmentation de la puissance thermoélectrique a été observé pour les deux matériaux étudiés ; notamment dans le cas de couches minces d’oxyde de titane (jusqu’à 500 fois)
Today, renewable energies such as wind, solar, hydropower and thermoelectricity play an essential role to cover our energy needs. Among these different sources of energy, thermoelectricity, which offers the ability to convert a heat into electricity or vice versa, has attracted a great attention due to its wide field of potential applications. The current advances in thermoelectric research are focusing on the improvement of the conversion efficiency of thermoelectric devices through optimizing and improving the thermoelectric properties of the thermoelectric materials (Seebeck coefficient, electrical conductivity and thermal conductivity). For this, different approaches (doping, new materials, nanostucturing...) have been investigated in the literature. Among these approaches, nanostructuring of materials is the most studied in the literature in order to improve the thermoelectric properties of materials. In this thesis work, we aimed to study the effect of surface nanostructuring of materials (mesoporous silicon and titanium oxide deposited in thin film) by ultra-short laser beams (picosecond and femtosecond) on the evolution of their thermoelectric properties. First, we focused on the study of various physical phenomena involved during the laser-matter interaction that yield to the formation of very different nanostructures in form of ripples, spikes, dots and others as function of the applied laser dose (fluence and number of pulses). The formation of these nanostructures has been studied in two regimes (stationary and dynamic). After optimizing the laser parameters leading to the formation of such nanostructures, a characterization of Seebeck coefficient and the electrical conductivity before and after the nanostructuring of these materials was carried out by using a new experimental setup (ZT-meter) designed and validated in GREMI laboratory. The results of measurements showed an important improvement of Seebeck coefficient and electrical conductivity after nanostructuring. This important improvement observed with the both materials leaded to a strong increase in the thermoelectric power factor (reaching roughly 50000%)
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49

Hausgen, Paul E. "A thermal analysis of an alkali metal thermal to electric converter with geometrically designed interior surfaces exhibiting directionally dependent radiative properties". Diss., Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/16701.

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Возний, Андрій Андрійович, Андрей Андреевич Возный y Andrii Andriiovych Voznyi. "Структурні, оптичні та електрофізичні властивості плівок SnxSy та гетероперехідних структур на їх основі". Thesis, Сумський державний університет, 2019. http://essuir.sumdu.edu.ua/handle/123456789/72936.

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Дисертаційна робота присвячена дослідженню полікристалічних плівок SnxSy як матеріалу для створення приладових структур, а саме тонкоплівкових гетероперехідних сонячних елементів (СЕ); вивченню впливу фізико-технологічних умов нанесення плівок SnS та SnS2, одержаних у квазізамкненому об’ємі, та впливу термічного і лазерного оброблення шарів SnS2 на їх структурні, субструктурні, оптичні, електрофізичні властивості та елементний склад для використання в приладових структурах; визначенню оптимальних режимів одержання однофазних плівок SnS і SnS2 та створенню СЕ з конструкціями "Substrate" та "Superstrate" на їх основі; моделюванню фізичних процесів у СЕ на основі плівок сульфіду олова та з’ясуванню параметрів, що обмежують ефективність виготовлених фотоперетворювачів (ФЕП). Установлені взаємозв’язки між фізико-технологічними умовами одержання плівок SnS та SnS2, післяростовими відпалюваннями (термічним і лазерним) та структурними, субструктурними, оптичними, електрофізичними властивостями, елементним складом можуть бути використані для підвищення ККД існуючих СЕ і створення нових підходів до виготовлення ефективних та економічних плівкових ФЕП.
Диссертационная работа посвящена исследованию поликристаллических пленок SnxSy как материала для создания приборных структур, а именно тонкопленочных гетеропереходных солнечных элементов (СЭ); изучению влияния физико-технологических условий нанесения пленок SnS и SnS2, полученных в квазизамкнутом объеме и влиянию термической и лазерной обработки слоев SnS2 на их структурные, субструктурные, оптические, электрофизические свойства и элементный состав для использования в приборных структурах; определению оптимальных режимов получения однофазных пленок SnS, SnS2 и созданию СЭ с конструкциями "Substrate" и "Superstrate" на их основе; моделированию физических процессов в СЭ на основе пленок сульфида олова и выявлению параметров, ограничивающих эффективность полученных фотопреобразователей (ФЭП). Установленные взаимосвязи между физико-технологическими условиями получения пленок SnS и SnS2, послеростовым отжигом (термическим и лазерным) и структурными, субструктурными, оптическими, электрофизическими свойствами, элементным составом могут быть использованы для повышения КПД существующих СЕ и создания новых подходов для изготовления эффективных и экономичных пленочных ФЭП.
The dissertation is devoted to the following aspects: (i) investigation of the influence of growth conditions of SnS and SnS2 films obtained by the close spaced sublimation (CSS) method and exploring the effect of thermal and laser post-growth treatment of SnS2 layers on structural, substructural, optical, electrical properties and chemical composition for thin film solar cell application; (ii) determination of the optimal conditions for production a single-phase SnS and SnS2 films and formation of solar cells based on "Substrate" and "Superstrate" device architecture; (iii) numerical simulation of the physical processes in solar cells based on tin monosulfide films and evaluation of the parameters that limit efficiency of the produced devices. In the first stage, we have studied in detail the influence of grown conditions on structural and electrical properties, phase composition and surface morphology of polycrystalline SnS2 and SnS thin films. It was found that obtained samples are single-phase and have good crystal quality. This result open new possibility for application of close spaced sublimation method for deposition of high quality and low cost SnS2 and SnS thin films. Also, the parameters of localised states (LS) in the band-gap of SnS2 thin films were determined from analysis of current-voltage characteristic and temperature-dependent conductivity measurements. For this purpose, for the first time, the method of injection spectroscopy for the analysis of trap centers in SnS2 thin films was used. Lastly, based on optimal growth conditions of SnS films, the heterojunction solar cells were fabricated and tested. The next stage of this work is post-growth treatment of initial SnS2 samples. In case of thermal annealing, we demonstrate a simple approach to fabricate pure-phase SnS thin films. In particular, the thermally-induced SnS2-SnS phase transition was observed. The modification of the chemical composition and hence phase transition was confirmed by the EDS, XRD and Raman spectroscopy methods. It was clearly shown that amount of SnS2 and Sn2S3 phases decreased with the increasing of annealing time and temperature. The measurements of optical reflectance and transmission spectra reveal substantial decreasing in band gap energy of material which indicates the transition from wide band gap SnS2 to narrower band gap SnS. Finally, the heterojunction solar cell based on a SnS thin film, obtained from the initial SnS2 layer, was fabricated and tested. These results can be used for improvement of SnxSy-based optoelectronic devices using thermal annealing. In case of laser annealing, we report the modification of surface, chemical and phase composition of SnxSy thin film. In particular, for the first time, the laser-induced transition from SnS2 to SnS phase was observed. It was established that the phase transition is due to evaporation of sulfur from the surface under intensive laser irradiation. The electrical measurements of the irradiated samples show diode behavior of the current-voltage dependencies. This was considered as the evidence of formation of the two-layer n-SnS2/p-SnS heterojunction structure by the laser irradiation of initial single-phase SnS2 thin film. Thus, these results open up a new possibility for producing n-SnS2/p-SnS heterojunction structures and improvement of SnxSy-based optoelectronic devices using laser radiation. Finally, in order to predict the main limiting factors affecting performance of SnS based photovoltaic devices, we performed device simulations in SCAPS 1-D software. Our modelling showed that reducing defects in SnS layer and at buffer/absorber interface are the primary issues for overcoming the record efficiency of 4.4 %.
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