Dissertations / Theses: 'Photoresponses in thin films'

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Linsell, P. "Photoresponse of metal-SiO2Ì²-Si structures." Thesis, Coventry University, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378951.

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Liu, Fanmao. "Photoresponse of ferroelectric BaTiO3 thin films." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458535.

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BaTiO3 es un material de óxido ferroeléctrico sin plomo. BaTiO3 películas delgadas han sido ampliamente estudiados para aplicaciones de memoria debido a su efecto de memoria de carga resultante de su naturaleza ferroeléctrica. Hoy en día, la comunidad científica ha renovado su interés en BaTiO3, ya que posee características que son interesantes para áreas de rápido desarrollo como la fotovoltaica, la detección fotoeléctrica y la fotocatálisis. El objetivo principal de la presente tesis es estudiar los efectos fotoeléctricos de las películas delgadas BaTiO3 y dar luz sobre los mecanismos relevantes que las controlan. Los materiales ferroeléctricos muestran campos eléctricos internos intrínsecos, inevitables y exclusivos: campo eléctrico de impresión (Eimp) y campo eléctrico de despolarización (Edep). Así se pueden obtener distintos efectos fotoeléctricos debido a Eimp y Edep. En la presente tesis hemos estudiado en detalle el papel de Eimp y Edep en los efectos fotoeléctricos de películas BaTiO3. En particular, se muestra que se puede usar una configuración de medición apropiada para revelar y aislar su contribución. Como resultado, pueden obtenerse diferentes foto respuestas transitorias y constantes según se desee. De igual modo, se analiza su contribución a la dinámica de conmutación ferroeléctrica. La foto respuesta transitorio tiene su origen en el cribado de la carga superficial (fotograbado). Para modular su magnitud se ha realizado una caracterización detallada. Se concluye que la polarización de las fotos se rige por la presencia de agua adsorbida en la superficie, lo que permite su control. Sin embargo, se ha encontrado que la eficiencia fotoeléctrica está limitada por la baja generación de portadores por la luz, por lo que el efecto de O sustituido por N en la red BaTiO3, lo que debería dar lugar a un estrechamiento de banda, mejorando así la eficiencia fotoeléctrica , ha sido estudiado. Curiosamente, se encuentra que los tratamientos de amoníaco son eficientes para mejorar las respuestas fotoeléctricas, sin tener ninguna evidencia clara de la sustitución de N.
BaTiO3 is a lead-free ferroelectric oxide material. BaTiO3 thin films have been widely studied for memory applications due to its charge memory effect resulting from its ferroelectric nature. Nowadays, the scientific community has renewed its interest on BaTiO3, because it holds characteristics that is interesting for rapidly developing areas such as photovoltaics, photoelectric sensing and photocatalysis. The main goal of the present thesis is to study the photoelectric effects on BaTiO3 thin films and to give light on the relevant mechanisms that control them. Ferroelectric materials show intrinsic, unavoidable and exclusive internal electric fields: imprint electric field (Eimp) and depolarization electric field (Edep). Thus distinct photoelectric effects can be obtained due to Eimp and Edep. In the present thesis we have studied in detail the role of Eimp and Edep on photoelectric effects of BaTiO3 films. In particular, it is shown that appropriate measurement configuration can be used to disclose and isolate their contribution. As a result, different transient and constant photoresponses can be obtained as wish. By the same token, their contribution to the ferroelectric switching dynamics are also analyzed. The transient photoresponse finds its origin on the screening of surface charge (photoscreening). In order to modulate its magnitude detailed characterization has been performed. It is concluded that the polarization photoscreening is governed by the presence of water adsorbed at the surface, allowing it to be controlled. However, the photoelectric efficiency has been found to be limited by the low generation of carriers by light, that is the reason why the effect of O substituted by N in BaTiO3 lattice, which should result in band-gap narrowing, hence improving the photoelectric efficiency, has been studied. Interestingly, it is found that ammonia treatments are efficient to improve photoelectric responses, without having any clear evidence of N substitution.

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Hus, Saban Mustafa. "Physical Properties Of Cdse Thin Films Produced By Thermal Evaporation And E-beam Techniques." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607608/index.pdf.

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CdSe thin films were deposited by thermal evaporation and e-beam evaporation techniques on to well cleaned glass substrates. Low dose of boron have been implanted on a group of samples. EDAX and X-ray patterns revealed that almost stoichiometric polycrystalline films have been deposited in (002) preferred orientation. An analysis of optical measurements revealed a sharp increase in absorption coefficient below 700 nm and existence of a direct allowed transition. The calculated band gap was around 1.7 eV. The room temperature conductivity values of the samples were found to be between 9.4 and 7.5x10-4 (&
#937
-cm)-1 and 1.6x10-6 and 5.7x10-7 (&
#937
-cm)-1for the thermally evaporated and e-beam evaporated samples respectively. After B implantation conductivity of these films increased 5 and 8 times respectively. Hall mobility measurements could be performed only on the thermally evaporated and B-implanted e-beam evaporated samples and found to be between 8.8 and 86.8 (cm2/V.s). The dominant conduction mechanism were determined to be thermionic emission above 250 K for all samples. Tunneling and v variable range hopping mechanisms have been observed between 150-240 K and 80- 140 K respectively. Photoconductivity &
#8211
illumination intensity plots indicated two recombination centers dominating at the low and high regions of studied temperature range of 80-400 K. Photoresponse measurements have corrected optical band gap measurements by giving peak value at 1.72 eV.

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Rossi, Leonardo. "Flexible oxide thin film transistors: fabrication and photoresponse." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14542/.

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Gli ossidi amorfi semiconduttori (AOS) sono nuovi candidati per l’elettronica flessibile e su grandi aree: grazie ai loro legami prevalentemente ionici hanno una mobilità relativamente alta (µ > 10cm^2/Vs) anche nella fase amorfa. Transistor a film sottile (TFT) basati sugli AOS saranno quindi più performanti di tecnologie a base di a-Si e più economici di quelle a base di silicio policristallino. Essendo amorfi, possono essere depositati a basse temperature e su substrati polimerici, caratteristica chiave per l’elettronica flessibile e su grandi aree. Per questa tesi, diversi TFT sono stati fabbricati e caratterizzati nei laboratori del CENIMAT all’Università Nova di Lisbona sotto la supervisione del Prof. P. Barquinha. Questi dispositivi sono composti di contatti in molibdeno, un canale semiconduttivo di ossido di zinco, gallio e indio (IGZO) e un dielettrico composto da 7 strati alternati di SiO2 e SiO2+Ta2O5. Tutti i dispositivi sono stati depositati mediante sputtering su sostrati flessibili (fogli di PEN). Le misure tensione-corrente mostrano che i dispositivi mantengono alte mobilità (decine di 10cm^2/Vs) anche quando fabbricati a temperature inferiori a 200°C. Si è analizzato il funzionamento dei dispositivi come fototransistor rilevando la risposta alla luce ultravioletta e in particolare la loro responsività e spostamento della tensione di soglia in funzione della lunghezza d’onda incidente. Questi risultati consentono di formulare ipotesi sul comportamento dei dispositivi alla scala microscopica. In particolare, indicano che i) la mobilità del canale non è influenzata dall’illuminazione, ii) sia l'IGZO sia il Ta2O5 contribuiscono al processo di fotoconduttività e iii) il processo di fotogenerazione non è adiabatico. La tesi contiene inoltre una descrizione del processo di ricombinazione e presenta un’applicazione pratica di tali dispositivi in un circuito per RFID. Infine, esplora la possibilità di migliorarne la flessibilità e le prestazioni.

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CHIPMAN, RUSSELL ATWOOD. "POLARIZATION ABERRATIONS (THIN FILMS)." Diss., The University of Arizona, 1987. http://hdl.handle.net/10150/184051.

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Polarization aberrations are the variations of amplitude, phase, polarization and retardance associated with ray paths through optical systems. This dissertation develops methods for calculating the polarization aberrations of radially symmetric systems of weak polarizers, systems like lenses, telescopes and microscopes. The instrumental polarization in these systems arises from weak polarization effects occurring near normal incidence at glass, metal and thin film coated interfaces. Polarized light and polarizers are treated using the Jones calculus. Weak polarizers, optical elements with small polarization effects, are treated by expanding the Fresnel equations and thin film equations into a Taylor series. Methods are given for calculating the Taylor series coefficients for a multilayer coated interface whose polarization performance is known, for example from a thin film design program. Equations are derived for the propagation of polarized light through optical systems. Weak polarizers are shown to be very weakly order dependent; this greatly facilitates the calculation of the effect of a sequence of weak polarizers. The dominant terms are order independent polarization terms which are readily calculated. The order dependent portion can be systematically evaluated as higher order terms. The instrumental polarization, being a function of angle of incidence, is different for different rays through the system. Thus an optical system is a spatially varying polarizer. The instrumental polarization associated with a single surface is often well approximated as a "parabolic" polarizer. The instrumental polarization function is calculated as a Taylor series Jones matrix about the optical axis as a function of object and pupil coordinates. The resulting spatial variations of the instrumental polarization function bear a strong resemblance to the wavefront aberrations, since both arise from fundamental geometrical considerations. In particular, there are terms in the weak linear polarization and in the weak retardance of radially symmetric systems which strongly resemble defocus, tilt and piston error. A polarization aberration expansion is defined to second order in the object and pupil coordinates. A method is derived for calculating the polarization aberration coefficients for a sequence of radially symmetric surfaces from the Taylor series representation of the polarization associated with the individual interfaces.

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Wallace, Anthony James. "Tin oxide thin films." Thesis, Brunel University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294556.

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Poulter, Mark W. "Pyroelectric organic thin films." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303623.

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Kamhawi, Khalid. "Transport in Thin Films." Thesis, Imperial College London, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.508624.

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Babkair, S. S. "Multilayer ferromagnetic thin films." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234564.

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Hu, Xiao. "Ultra-thin oxide films." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d7373376-84f1-459e-bffb-f16ce43f02b7.

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Oxide ultra-thin film surfaces have properties and structures that are significantly different from the terminations of the corresponding bulk crystals. For example, surface structures of epitaxial ultra-thin oxide films are highly influenced by the crystallinity and electronegativity of the metal substrates they grown on. Some enhanced properties of the novel reconstructions are related to catalysis, sensing and microelectronics, which has resulted in an increasing interest in this field. Ultra-thin TiO_x films were grown on Au(111) substrates in this work. Two well-ordered structures within monolayer coverage - honeycomb (HC) and pinwheel - were generated and investigated. Special attention has been paid to the uniform (2 x 2) Ti₂O₃ HC phase including its regular structure and imperfections such as domain boundaries (DBs) and point defects. Linear DBs with long-range repeating units have been observed; density functional theory (DFT) modelling has been used to simulate their atomic structures and calculate their formation energies. Rotational DBs/defects show up less frequently, however a six-fold symmetrical 'snowflake' DB loop stands out. Two types of point defects have been discovered and assigned to Ti vacancies and oxygen vacancies/hydroxyl groups. Their diffusion manners and pairing habits have been discussed within an experimental context. The results of growing NbO_x ultra-thin films on Au(111) are also presented in this thesis. An identical looking (2 x 2) HC structure to the Ti₂O₃ ultra-thin film has been formed; a stoichiometry of Nb2O3 is suggested. Another interesting reconstruction is a hollow triangle structure. Various sizes have been found, and sides of these equilateral triangles all show a double-line feature aligned along the { 1 ₁⁻ } directions of the Au(111) lattice. Chemical composition characterisations of NbO_x thin films are still required as is DFT modelling. Experimental techniques used in this thesis include scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), and X-ray photoelectron spectroscopy (XPS). Ultra-thin oxide films were created by physical vapour deposition (PVD) in ultra-high vacuum (UHV) systems.

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Campbell-Rance, Debbie. "Electrodeposited Silica Thin Films." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2123.

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Sol-gel derived silica thin film synthesis has gained prominence because of the mild processing conditions and widespread understanding of the chemistry of the process. Traditionally, silicate films are prepared by spin- and dip-coating but these materials lack the desired porosity for sensing, separations and catalysis applications. Electrochemical deposition was proposed to improve the porosity of silicate films. The main aims of this work were threefold. First we wanted to elucidate what parameters influenced film formation during electrodeposition. Then we wanted to understand how these parameters affected the morphology of the materials prepared. These films were characterized by profilometry, AFM, and SEM-EDX. Films electrodeposited via cathodic potentials are particle-like, thicker and rougher than spin-coated films. The final goal was to pattern a substrate with silica using photolithography, sol-gel process and electrodeposition. Successful patterning was hindered by the deposition of silica on glass, especially when the gap between ITO bands was smaller than the diffusion layer thickness of the electroactive species.

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Morris, Gareth David Morte. "Particle stabilised thin films." Thesis, Imperial College London, 2010. http://hdl.handle.net/10044/1/6206.

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Froth flotation is widely used by the mining industry to concentrate low grade metal ores. It uses the differences in surface properties between particles of the desired mineral and waste material to separate them using a mineralised froth. The properties of this particle stabilised mineralised froth impact on the efficiency of the separation process. Due to its dynamic and unstable nature it is difficult to study and remains relatively poorly understood. A deeper insight into the fundamental froth properties can be gained by using computer modelling techniques. Here a series of models are developed using the Surface Evolver (Brakke 1992). They are used to investigate the effects of particle shape, hydrophobicity and packing arrangement on the critical capillary pressure of thin films. Three dimensional simulations of uniformly spaced spherical particles in the film are compared to existing two dimensional (2D) analytical models. It is shown that 2D models over predict the capillary pressure required to rupture the film. The models are developed further to simulate randomly distributed particles in a periodic film. The results are then used to derive an expression for film stability based on particle packing density and contact angle. The different possible failure modes of double layers of particles are also investigated and the conditions under which they occur identified. A versatile model for simulating non-spherical particles in an interface or film is also derived and used to find the energetically stable orientations of orthorhombic particles at an interface. This information is then used to investigate the effect of particle orientation on the capillary pressure required to rupture the film. It is shown that the combination of contact angle and shape affect the particle orientation. Certain orientations are then shown to reduce the critical capillary pressure of the film by up to 70 %.

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Rycroft, Ian M. "Electric, magnetic and optical properties of thin films, ultra thin films and multilayers." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318142.

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Dürr, Arndt Christian. "Growth and structure of DIP thin films and Au contacts on DIP thin films." [S.l. : s.n.], 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10277647.

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Kobler, Johannes. "Thin Films from Porous Nanoparticles." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-98694.

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Serral, Serra Maria. "Modeling of thin polymer films." Doctoral thesis, Universitat Rovira i Virgili, 2015. http://hdl.handle.net/10803/306133.

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Aquest treball es centra en l’estudi de dos sistemes diferents de films polimèrics. En primer lloc, s’analitza experimentalment la resposta viscoelàstica dels films polimèrics multicapa (sandvitxos) de polietilè lineal de baixa densitat (LLDPE) i etilen-vinil-alcohol (EVOH). A partir de les dades experimentals es troba que la resposta mecànica dels sandvitxos estudiats es pot predir mitjançant una regla additiva utilitzant les dades dels components purs, quan aquests han estat processats en les mateixes condicions. Per tant, la resposta no depèn del gruix de les capes individuals, ni dels efectes interfacials, sinó només de la fracció volumètrica d’EVOH i LLDPE en el sistema. Es proposa addicionalment un model més mesoscòpic per la resposta viscoelàstica dels films de LLDPE i EVOH purs i els sandvitxos. Aquest es basa en el model de Maxwell Generalitzat que correspon a l’analogia mecànica de la resposta complexa del material. Mitjançant l’ajust del model a les dades experimentals podem obtenir informació sobre l’espectre dels temps de relaxació, els quals ens donen coneixement sobre l’estructura microscòpica del sistema. Finalment, el segon sistema que s’investiga és completament diferent a l’anterior. Aquest sistema consisteix en films de “diblock-copolymers” que formen esferes i que estan sotmesos a influències externes. Per l’estudi s’utilitza una implementació numèrica de la dinàmica del sistema en una xarxa que es coneix com “Cell Dynamics Simulation”. A través de les simulacions demostrem que podem obtenir formacions de dominis esfèrics altament ordenats en films prims sobre una superfície químicament decorada amb bandes paral•leles. No obstant, l’ordre de llarg abast, requerit en aplicacions nanoscòpiques, depèn de la commensurabilitat de l’estructura amb la periodicitat de les bandes i el gruix del film, i la seva adequada selecció permet tenir una disposició d’esferes hexagonal o bé quadrada, que correspondria a un empaquetament cúbic centrat (BCC).
Este trabajo se centra en el estudio de dos sistemas diferentes de films poliméricos. En primer lugar, se analiza experimentalmente la respuesta viscoelástica de los films poliméricos multicapa (sándwiches) de polietileno lineal de baja densidad (LLDPE) y etilen-vinil-alcohol (EVOH). Partiendo de los datos experimentales se encuentra que la respuesta mecánica de los sándwiches se puede predecir mediante una regla aditiva utilizando los datos de los componentes puros, cuando éstos han sido procesados en las mismas condiciones. Por consiguiente, la respuesta no depende del grosor de las capas individuales, ni de los efectos interfaciales, sino que depende de la fracción volumétrica de EVOH y LLDPE en el sistema. Se propone adicionalmente un modelo más mesoscópico para la respuesta viscoelástica de los films de LLDPE y EVOH puros y los sándwiches. Éste se basa en el modelo de Maxwell Generalizado que corresponde a la analogía mecánica de la respuesta compleja del material. Mediante el ajuste del modelo a los datos experimentales podemos obtener información sobre el espectro de los tiempos de relajación, que nos dan conocimiento sobre la estructura microscópica del sistema. Finalmente, el segundo sistema que se investiga es completamente diferente al anterior. Este sistema consiste en filmes de “diblock-copolymers” que forman esferas y se someten a influencias externas. Para el estudio se utiliza una implementación numérica de la dinámica del sistema en una red conocida como “Cell Dynamics Simulation”. Por medio de las simulaciones demostramos que se pueden obtener formaciones de dominios esféricos altamente ordenados en films delgados sobre una superficie químicamente decorada con bandas paralelas. El orden de largo alcance depende de la conmensurabilidad de la estructura con la periodicidad de las bandas y del grosor del film, y su adecuada selección permite tener una disposición de esferas hexagonal o bien cuadrada, correspondiente a un empaquetamiento cúbico centrado (BCC).
This work is focused on the study of two different systems of thin polymeric films. In the first place, the viscoelastic response of multilayer polymeric films (sandwiches) of linear low-density polyethylene (LLDPE) and ethylene vinyl alcohol (EVOH) copolymer has been experimentally analyzed. From experimental data we find that the mechanical response of the studied sandwiches can be predicted through a mixing rule using the data of the pure constituents when they have been processed under the same conditions. Then, the response does not depend on the individual layer thickness, neither on the interfacial effects, but only on the volume fraction of the EVOH and LLDPE in the system. We additionally propose a more mesoscopic model for the viscoelastic response of the solid LLDPE and EVOH films and sandwiches. The model is formally a Generalized Maxwell (GM) model, which corresponds to a mechanical analog of the complex response of the material. Through the fitting of the model to the experimental data one can get information on the spectra of relaxation times, which bear information on the microscopic structure of the system. Finally, the second system investigated is completely different to the previous one. This system studied consists of films of sphere-forming diblock copolymers under external influences. For the study we use a numerical implementation of the dynamics of the system on a lattice that is referred to as Cell Dynamics Simulation. Using 3-Dimensional CDS we demonstrate that on patterned surfaces with chemically attractive parallel stripes, arrays of spherical domains with long-range order, required for nanoscopic applications, can be obtained. The long-range order depends on the commensurability of the structure with both the band periodicity and slit thickness, and their proper selection permits the system to switch from a hexagonal packing to a square packing corresponding to a body-centered orthohedron.

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Hänni-Ciunel, Katarzyna. "Interactions in thin aqueous films." [S.l.] : [s.n.], 2006. http://opus.kobv.de/tuberlin/volltexte/2006/1432.

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Huang, Bin. "Mechanical characterization of thin films /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?MECH%202005%20HUANG.

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Song, Gang. "Hydrogen in thin niobium films." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=961906529.

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Kedsongpanya, Sit. "Nanolaminated Thin Films for Thermoelectrics." Thesis, Linköping University, Linköping University, Department of Physics, Chemistry and Biology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-56699.

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Energy harvesting is an interesting topic for today since we face running out of energy source, a serious problem in the world. Thermoelectric devices are a good candidate. They can convert heat (i.e. temperature gradient) to electricity. This result leads us to use them to harvest waste heat from engines or in power plants to generate electricity. Moreover, thermoelectric devices also perform cooling by applied voltage to device. This process is clean, which means that no greenhouse gases are emitted during the process. However, the converting efficiency of thermoelectrics are very low compare to a home refrigerator. The thermoelectric figure of merit (ZT_m) is a number which defines the converting efficiency of thermoelectric materials and devices. ZT_m is defined by Seebeck coefficient, electrical conductivity and thermal conductivity. To improve the converting efficiency, nanolaminated materials are good candidate.

This thesis studies TiN/ScN artificial nanolaminates, or superlattices were grown by reactive dc magnetron sputtering from Ti and Sc targets. For TiN/ScN superlattice, X-ray diffraction (XRD) and reciprocal space map (RSM) show that we can obtain single crystal TiN/ScN superlattice. X-ray reflectivity (XRR) shows the superlattice films have a rough surface, supported by transmission electron microscopy (TEM). Also, TiN/ScN superlattices grew by TiN as starting layer has better crystalline quality than ScN as starting layer. The electrical measurement shows that our superlattice films are conductive films.

Ca-Co-O system for inherently nanolaminated materials were grown by reactive rf magnetron sputtering from Ca/Co alloy target. The XRD shows we maybe get the [Ca₂CoO₃]_xCoO₂ phase, so far. The energy dispersive X-ray spectroscopy (EDX) reported that our films have Al conmination. We also discovered unexpected behavior when the film grown at high temperature showed larger thickness instead of thinner, which would have been expected due to possible Ca evaporation. The Ca-Co-O system requires further studies.

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Ma, Fuyuan. "Electrochemically active organic thin films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0020/NQ44501.pdf.

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Pradhan, Sailesh. "Tensile testing of thin films /." Available to subscribers only, 2006. http://proquest.umi.com/pqdweb?did=1203573161&sid=10&Fmt=2&clientId=1509&RQT=309&VName=PQD.

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Thesis (M.S.)--Southern Illinois University Carbondale, 2006.
"Department of Mechanical Engineering and Energy Processes." Includes bibliographical references (leaves 73-84). Also available online.

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Music, Denis. "Boron suboxide based thin films /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek835s.pdf.

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Yim, Sanggyu. "Structure of phthalocyanine thin films." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405780.

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Mohd, Yatim Yazariah. "Unsteady flows of thin films." Thesis, University of Strathclyde, 2010. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=14374.

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Bunce, Christopher Edward. "Magnetisation dynamics in thin films." Thesis, University of York, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495860.

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Lin, Keng-Yu. "Thin films for thermoeletric applications." Thesis, Linköpings universitet, Tunnfilmsfysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-109106.

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Global warming and developments of alternative energy technologies have become important issues nowadays. Subsequently, the concept of energy harvesting is rising because of its ability of transferring waste energy into usable energy. Thermoelectric devices play a role in this field since there is tremendous waste heat existing in our lives, such as heat from engines, generators, stoves, computers, etc. Thermoelectric devices can extract the waste heat and turn them into electricity. Moreover, the reverse thermoelectric phenomenon has the function of cooling which can be applied to refrigerator or heat dissipation for electronic devices. However, the energy conversion efficiency is still low comparing to other energy technologies. The efficiency is judged by thermoelectric figure of merit (ZT), defined by Seebeck coefficient, electrical conductivity and thermal conductivity. In order to improve ZT, thin film materials are good candidates because of their structural effects on altering ZT. Ca3Co4O9 thin films grown by reactive radio frequency magnetron sputtering followed by post-annealing process is studied in this thesis. Structural properties of the films with the evolution of elemental ratio (Ca/Co) of calcium and cobalt have been investigated. For the investigations, three samples having elemental ratio 0.82, 0.72, and 0.66 for sample CCO1, CCO2 and COO3, respectively, have been prepared. Structural properties of the films have been investigated by X-ray diffraction (XRD) θ-2θ and pole figure analyses. Surface morphology of the films has been investigated by scanning electron microscopic (SEM) analyses. The highly oriented and phase pure epitaxial Ca3Co4O9 thin films were obtained in the end. Mixing of ScN and CrN to obtain ScxCr1-xN solid solution thin films by DC magnetron sputtering is the other task in this thesis. Growth of ScN and CrN thin films were studied first in order to get the best mixed growth conditions. The phase shifts between ScN (111) and CrN (111) peaks were observed in mixed growth films by XRD θ-2θ measurements, indicating the formation of ScxCr1-xN. Surface morphology of the films were investigated by SEM. The (111)-oriented ScxCr1-xN thin films with decent surface smoothness grown by DC magnetron sputtering at 600 °C in pure nitrogen with bias were developed.

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Karl, Werner Josef. "Piezomagnetic thin-films and devices." Thesis, University of Sheffield, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425487.

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Adamjee, Admil. "Ormosil thin films for waveguides." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301907.

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Logan, Randy. "Optical metrology of thin films." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/46094.

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Song, Ohsung. "Magnetoelastic coupling in thin films." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/28083.

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Aessopos, Angelica. "Surfactant instabilities on thin films." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/88902.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2005.
"June 2005."
Includes bibliographical references (pages 89-92).
The deposition of a surfactant drop over a thin liquid film may be accompanied by a fingering instability. In this work, we present experimental results which identify the critical parameters that govern the shape and extend of the fingering phenomena. It was found that the normalized wavelength, [lambda]/t, scales with Marangoni number, Ma=[Delta][gamma]t/[mu]D, to the -1 exponent for any Marangoni higher than 4.3 · 10⁷. On the other end, for Marangoni < 4.3 · 10⁷ the normalized wavelength scales with Ma to the -0.4 but becomes in addition a funcion of the Prandtl number, Pr=[upsilon]/D, which demonstrates the critical significance of bulk diffusion on the spreding behavior. Finally, we present a numerical implementation of a mathematical model which is capable of reproducing the experimentally observed trends.
by Angelica Aessopos.
S.M.

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Marshall, J. M. "Thin lead zirconate titanate films." Thesis, Cranfield University, 2006. http://dspace.lib.cranfield.ac.uk/handle/1826/10743.

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The subject of study was the growth and nucleation of sol-gel deposited lead zirconate titanate (PZT) films of composition Pb(Zr0_52,Ti0_4g)O3 (PZT52/48). This particular composition is on a phase boundary between titanium-rich tetragonally structured PZT and the zirconium-rich rhombohedral phase. The coexistence and relative instability of these phases is thought to be one of the origins of high piezoelectric coefficients exhibited by films of this composition. The aims of this study were to investigate variables affecting the piezoelectric coefficients in sol-gel deposited PZT52/48 thin films. Control of preferred orientation if PZT52/48 films on platinum-coated substrates was accomplished by manipulating processing conditions, specifically pyrolysis temperature. Corona poling was investigated as an alternative to contact poling. Attempts were made to find a set of poling parameters which yielded consistent results. Piezoelectric coefficients are highly dependant on poling conditions, with coefficient being lower in insufficiently poled films or those damaged by field induced sample cracking. It was observed that (001)/(100)-oriented samples with small grains had significantly lower piezoelectric coefficients and were harder to pole than coarser-grained (00l)/(l00)- oriented samples. Samples with a more irregular grain structure and a wide distribution of grain size had the lowest piezoelectric coefficients, irrespective of preferred orientation. The impact of grain size on piezoelectric coefficients was confirmed using the FWHM of the (200) reaction. Films with more irregular grain structures had higher FWHM than those with more uniform grains and had lower d33,f and e31,f. Values of e31,f and d33f were plotted against (001) intensity a determined from xray diffraction. It was difficult to determine any correlation between piezoelectric coefficients and (001) intensity. I comparison, there was a definite inverse correlation between d33,f, e31,f and FWHM, indicating that defect concentration has much more of an impact on piezoelectric coefficients in polycrystalline thin films than (001) intensity as a result of defect-induced domain pinning.

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Shu, Rui. "Nonstoichiometric Multicomponent Nitride Thin Films." Licentiate thesis, Linköpings universitet, Tunnfilmsfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-170529.

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High entropy ceramics have rapidly developed as a class of materials based on high entropy alloys; the latter being materials that contain five or more elements in near-equal proportions. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical, electrical and chemical properties. In this thesis, high entropy ceramic films, (TiNbZrTa)Nx were deposited using reactive magnetron sputtering with segmented targets. The stoichiometry x was tuned with two deposition parameters, i.e., substrate temperature and nitrogen flow ratio fN, their effect on microstructure and mechanical, electric, and electrochemical properties were investigated. Understoichiometric MeNx (Me = TiNbZrTa, 0.25 ≤ x ≤ 0.59) films were synthesized at a constant fN when substrate temperature was varied from room temperature (RT) to 700 °C. For low-temperature deposition, the coatings exhibited fcc solid-solution polycrystalline structures. A NaCl-type structure with (001) preferred orientation was observed in MeN0.46 coating deposited at 400 ºC, while an hcp structure was found for the coatings deposited above 500 ºC. The maximum hardness value of 26 GPa as well as the highest ${H/E_r}$ and ${H^3}$ ${/E_r^2}$ values (0.12 and 0.34 GPa) were obtained for the MeN0.46 coating. These films exhibited low RT electrical resistivities. In 0.1 M H2SO4 aqueous solution, the most corrosion resistant film was MeN0.46 featured dense structure and low roughness. The MeNx films (x=0, 0.57 < x ≤ 0.83) were deposited with different fN. The maximum hardness was achieved at 22.1 GPa for MeN0.83 film. Their resistivities increased from 95 to 424 μΩcm with increasing nitrogen content. The corrosion resistance is related to the amount of nitrogen in the films. The corrosion current density was around 10-8 A/cm2, while the films with lower nitrogen contents (x < 0.60) exhibited a nearly stable current plateau up to 4.0 V, similar to the metallic films, while the films with a higher nitrogen content only featured a plateau up to 2.0 V, above which a higher nitrogen content resulted in higher currents. The reason was that the oxidation of these films at potentials above about 2.0 V vs. Ag/AgCl resulted in the formation of porous oxide layers as significant fraction of the generated N2 was lost to the electrolyte. Hence, these observed effects of deposition temperature and nitrogen content on the overall properties of nonstoichiometric MeNx films provide insights regarding protective multicomponent nitride films, e.g. as corrosion resistant coatings on metallic bipolar plates in fuel cells or batteries.

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JOTHIMUTHU, PREETHA. "Photodefinable Polydimethylsiloxane (PDMS) Thin Films." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1212181335.

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Qureshi, Uzma. "Host thin films incorporating nanoparticles." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1446050/.

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The focus of this research project was the investigation of the functional properties of thin films that incorporate a secondary nanoparticulate phase. In particular to assess if the secondary nanoparticulate material enhanced a functional property of the coating on glass. In order to achieve this, new thin film deposition methods were developed, namely use of nanopowder precursors, an aerosol assisted transport technique and an aerosol into atmospheric pressure chemical vapour deposition system. Aerosol assisted chemical vapour deposition (AACVD) was used to deposit 8 series of thin films on glass. Five different nanoparticles silver, gold, ceria, tungsten oxide and zinc oxide were tested and shown to successfully deposit thin films incorporating nanoparticles within a host matrix. Silver nanoparticles were synthesised and doped within a titania film by AACVD. This improved solar control properties. A unique aerosol assisted chemical vapour deposition (AACVD) into atmospheric pressure chemical vapour deposition (APCVD) system was used to deposit films of Au nanoparticles and thin films of gold nanoparticles incorporated within a host titania matrix. Incorporation of high refractive index contrast metal oxide particles within a host film altered the film colour. The key goal was to test the potential of nanopowder forms and transfer the suspended nanopowder via an aerosol to a substrate in order to deposit a thin film. Discrete tungsten oxide nanoparticles or ceria nanoparticles within a titanium dioxide thin film enhanced the self-cleaning and photo-induced super-hydrophilicity. The nanopowder precursor study was extended by deposition of zinc oxide thin films incorporating Au nanoparticles and also ZnO films deposited from a ZnO nanopowder precursor. Incorporation of Au nanoparticles within a VO: host matrix improved the thermochromic response, optical and colour properties. Composite VC/TiC and Au nanoparticle/V02/Ti02 thin films displayed three useful properties photocatalysis, photo-induced super-hydrophilicity and thermochromism.

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Ross, Caroline Anne. "Electromigration in thin metal films." Thesis, University of Cambridge, 1989. https://www.repository.cam.ac.uk/handle/1810/250938.

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Morasch, Kevin R. "Nanoindentation induced thin film fracture." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Spring2005/k%5Fmorasch%5F042605.pdf.

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Sánchez, Rodríguez Daniel. "Obtaining advanced oxide thin films at low temperatures by chemical methods. Thermal analysis of thin films." Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/328723.

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L'objectiu d'aquest treball és analitzar mètodes químics de baix cost com a ruta per a sintetitzar òxids avançats a baixa temperatura. En particular, hem explorat l'SHS per a la síntesi d'un òxid catalitzador fent servir pólvores de ciano complexes heteronuclears. També hem explorat el transport de calor per a sintetitzar capes via VCS concloent que les capes primes rarament experimentaran una combustió. Per això hem analitzat la condició necessària per que tingui lloc una combustió volumètrica en una mostra sòlida que reacciona sense intercanvi de gasos amb el seu entorn. Per fer-ho, hem ampliat el criteri de Frank-Kaminetskii per a sistemes d'escalfament continu i per a reactors cilíndrics. Per la part experimental em fet servir tècniques l'anàlisi tèrmica (TA). Hem desenvolupat un mètode per a mesurar la conductivitat tèrmica en pólvores per DSC. Finalment, hem desenvolupat dos criteris per a comprovar la fiabilitat en la mesura de la temperatura als experiments de TA.
The aim of this work is to analyse chemical methods as a route to synthesise advanced oxides at low cost and low temperatures. In particular, we have explored the combustion synthesis of a catalytic perovskite-type oxide from heteronuclear cyano complex powders. We have also explored heat transfer to synthesise films via VCS and concluded that thin films will hardly experience combustion. In particular, we have analysed the conditions needed for a thermal explosion to occur in a solid sample reacting without any gas exchange with its surroundings. For that purpose, we have extended the Frank-Kamenetskii relationship to continuous heating systems and to cylindrical reactors. The experimental component of this work is based on thermal analysis methods (TA). We have developed a new method to measure thermal conductivity of powders by DSC. Finally, we have developed two analytical relationships to check the reliability of the sample temperature in TA experiments.

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ZANONI, RAYMOND. "BRILLOUIN SPECTROSCOPY OF LANGMUIR-BLODGETT FILMS (THIN FILMS, ELASTIC CONSTANTS)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183852.

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The goal of this dissertation has been to develop techniques in order to use Brillouin spectroscopy as a tool for studying the elastic properties of thin films on a scale of ≃100 Å. In order to develop that capability we have built a tandem multi-pass Fabry-Perot interferometer, and that interferometer was used to study the elastic properties of Langmuir-Blodgett films. These films were chosen because they can be deposited one molecular layer at a time. As a result of these investigations we have measured the density and elastic constants of the Langmuir-Blodgett film cadmium arachidate. Samples of cadmium arachidate were prepared on molybdenum and BK-7 glass substrates. Data were accumulated for a range of thicknesses and for different scattering geometries. These data will be used to argue that guided acoustic waves were observed in a highly anisotropic film. The observed guided acoustic waves will be identified as a Rayleigh wave and a tight band of Sezawa modes. No Love modes were detected in these experiments; however, evidence for reorientational modes typical of anisotropic liquids was detected. The dispersion of the Rayleigh wave as a function of thickness together with thick film scattering data were used to estimate the elastic constants in cadmium arachidate. In particular the shear elastic constant c₄₄ was found to be a small value: c₄₄ < 4.0x10⁸ N/m². The remaining elastic constants were estimated, assuming hexagonal film symmetry, to be c₆₆ < 4.5x10⁹ N/m², C₁₁ ≃ 1.1x10¹⁰ N/m², c₃₃ ≃ 2.1x10¹⁰ N/m², c₁₃ ≃ 1.0x10¹⁰ N/m², and c₁₂ > 3.x10¹⁰ N/m². It is interesting to note that the acoustical behavior of cadmium arachidate is quite similar to the smectic phase liquid crystals (c₄₄ = 0).

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Boye, Shawn Alexander. "Magnetotransport Measurements of Ni Thin Films." Doctoral thesis, Uppsala University, Department of Earth Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4653.

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This thesis presents transverse magnetoresistance (MR) and Hall resistivity measurements of nickel thin films at temperatures between 280 and 455 K and pressures up to 6 GPa. An experimental system was developed for conducting precise magnetotransport measurements using the current reversal and van der Pauw techniques in combination with a 10 T superconducting magnet. Polycrystalline Ni_0.985O_0.015 thin film samples were manufactured with preexisting point contacts allowing highly reproducible magnetotransport measurements at pressure in the diamond anvil cell (DAC).

The magnetic resistivity above the technical saturation of the magnetization was found to decrease linearly to the highest applied fields, 10 T, while the field derivative, 0.010-0.018 µΩ cm T^-1 between 280 and 316 K, increased with temperature and decreased with pressure. The decrease in the magnetoresistance is attributed to spin wave damping of electron-magnon scattering processes at high fields. The magnon mass, 535(14) meV Å² at 0 K and 0 GPa, determined from longitudinal magnetic resistivity theory is a slightly increasing function of pressure. Correlation between the zero field resistivity and the extraordinary Hall coefficient (EHC) confirmed side jump scattering as the dominant diffusion mechanism at 0 GPa, however, skew scattering was found to become increasingly important with pressure.

The effect of oxygen and pressure on the density of states (DOS) at the Fermi level was investigated through total energy band structure calculations using a periodic supercell of 64 atoms to simulate the sample chemistry. The DOS of Ni_0.985O_0.015 at the Fermi level was found to increase by 27% at 10 GPa relative to 0 GPa. However, when compared to the results for pure Ni, decreases of 60% and 23% occurred for the corresponding calculations at 0 and 10 GPa. The relative differences in the magnetic resistivity are attributed to competing effects between the DOS, average magnetic moment and magnon mass.

The technique developed for conducting magnetotransport measurements at pressure is applicable to the study of electronic diffusion in ferromagnets as well as geophysical problems such as the geodynamo.

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Warnicke, Peter. "Tailored Properties of Ferromagnetic Thin Films." Doctoral thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9403.

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Magnetic thin films and patterned nanostructures have been studied with respect to their magnetic properties using SQUID-magnetometry, magnetic force microscopy, electrical measurements, and micromagnetic calculations. Properties of vortex domain walls, trapped in Permalloy nanowires with artificial constrictions, were investigated experimentally and by numerical calculations. In particular, the geometrical extent and strength of the pinning potential were evaluated. In these wires, long-range vortex domain wall displacement induced by spin polarized alternating currents was obtained numerically at reduced threshold current densities as compared with the direct current case. Due to the asymmetry of the energy potential, the long-range displacement direction is determined by the vortex chirality. Strained FeCo/Pt superlattices with strong perpendicular anisotropy were investigated experimentally. The strain was controlled by varying the thickness of each alternating layer with monolayer precision and was found to have a dominating effect on the total anisotropy. Epitaxial films of the diluted magnetic semiconductor (Ga,Mn)As were studied with focus on how the ferromagnetic transition temperature could be controlled by post-growth annealing. The ferromagnetic transition temperature was enhanced by approximately 85% for a Mn-doping concentration of 6% under certain conditions. A method to manipulate micrometer sized magnetic particles on patterned arrays of elliptical Permalloy microstructures was studied. Controlled motion and separation of the magnetic particles were obtained using applied rotating magnetic fields. The domain structure of the elliptical elements was studied numerically.

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43

Edström, Curt. "Wet etching of optical thin films." Thesis, Tekniska Högskolan, Högskolan i Jönköping, JTH, Kemiteknik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-13988.

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Evaluation of the wet etching properties of several different thin film oxidesgrown by physical vapour deposition was performed in this work. MgO, Al2O3,SiO2, TiO2, HfO2 ZrO2 and Y2O3 were coated on two types of substrates; Si andborosilicate glass and etching tests were performed in different etchingsolutions. MgF2 thin films have also been evaluated. Important aspects of the choice of the thin films was taken into account in orderto match to good optical properties such as refractive index (n), extinction coefficient (k) and optical thickness (TP) as well as good chemical properties in the wet etching process. A description is made of the physics of optical filters and how a combination of different oxides stacked onto each other can create interference filters. A description of the manufacturing process of the thin films where physical vapour deposition (PVD) was used is presented. Thermal shift of the optical spectra caused by porous coatings was investigated and analyses of the thin films by ellipsometry, surface profilometry and transmission spectrophotometry have been performed. The wet etching properties were evaluated by monitoring the transmission insituon transparent borosilicate glass substrates. A method of how to measure the wet etching rate for different thin films is described. A computer software was used to calculate the Pourbaix diagrams in order to understand the chemical behaviour of the etching solutions. The pH can have a significant impact on the etching behaviour. In case of TiO2, it can be dissolved in an alkaline solution of H2O2. The catalytically process behind this is evaluated. Etching rate for both Y2O3 andSiO2 were matched by adjusting the etchant concentration as a case example. The group IVB oxides are difficult to etch. The catalytic etching of TiO2 with peroxide is slow but detectable. Al2O3, Y2O3 and MgO are reasonably easy to etch but have too low refractive indices to be useful in multilayer optical filters. The In-situ etching instrument was found to be very useful for measuring etching rates.
Utvärdering av våtkemiska egenskaper för flera olika oxidtunnfilmer utfördes idetta arbete på tunnfilmer av MgO, Al2O3, SiO2, TiO2, HfO2 ZrO2 and Y2O3 vakuumdeponerade på både kiselwafers och borosilikatglas. Etstester gjordes med ett flertal etslösningar. Även MgF2-tunnfilmer utvärderades. Både optiska och kemiska egenskaper togs i beaktande vid utvärderingen av tunnfilmerna. De optiska lagar som gäller för tunnfilmer redovisas, bl a hur kombinationer av olika oxider kan skapa interferrensfilter. En beskrivning av tillverkningsprocessen varvid PVD användes presenteras. Termiskt skift av det optiska transmissionsspektrat orsakat av porositet undersöktes. Analyser av tunnfilmerna med ellipsometri, profilometri och transmissions spektroskopi utfördes. Våtetsningsegenskaperna utvärderades genom att mäta in-situ vid etsprocessen på transparenta borosilikatglassubstrat. Metoden för att mäta etshastigheten för olika oxider är beskriven. Datorberäkningar av pourbaixdiagram användes för att skapa en förståelse av de kemiska egenskaperna för etslösningarna. Etsegenskaperna påverkas till stordel av lösningens pH. TiO2 kan etsas i basisk lösning av peroxid. Denna process utvärderades, likaså utvärderades etshasigheten för Y2O3 och SiO2 för att erhålla matchande par avoxider som en fallstudie. Grupp IVB oxiderna är mycket svåra att etsa. Katalytisk etsning av TiO2 med peroxid är detekterbar men långsam. Al2O3, Y2O3 och MgO är förhållandevis enkla att etsa men har för låga brytningsindex för att var praktiskt använbara i optiska multilagerfilter. In-situ etsinstrumentet befanns vara ett utmärkt verktyg för att mäta etshastigheten för tunnfilmer.

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44

Scharnberg, Michael [Verfasser]. "Functional organic thin films / Michael Scharnberg." Kiel : Universitätsbibliothek Kiel, 2008. http://d-nb.info/1019629851/34.

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45

Little, Scott Allen. "Equilibrium microstructure of epitaxial thin films." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27652.

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46

Mariani, Federica. "PEDOT:PSS thin films: Applications in Bioelectronics." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/11915/.

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Owing to their capability of merging the properties of metals and conventional polymers, Conducting Polymers (CPs) are a unique class of carbon-based materials capable of conducting electrical current. A conjugated backbone is the hallmark of CPs, which can readily undergo reversible doping to different extents, thus achieving a wide range of electrical conductivities, while maintaining mechanical flexibility, transparency and high thermal stability. Thanks to these inherent versatility and attracting properties, from their discovery CPs have experienced incessant widespread in a great plethora of research fields, ranging from energy storage to healthcare, also encouraging the spring and growth of new scientific areas with highly innovative content. Nowadays, Bioelectronics stands out as one of the most promising research fields, dealing with the mutual interplay between biology and electronics. Among CPs, the polyelectrolyte complex poly (3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS), especially in the form of thin films, has been emphasized as ideal platform for bioelectronic applications. Indeed, in the last two decades PEDOT:PSS has played a key role in the sensing of bioanalytes and living cells interfacing and monitoring. In the present work, development and characterization of two kinds of PEDOT:PSS-based devices for applications in Bioelectronics are discussed in detail. In particular, a low-cost amperometric sensor for the selective detection of Dopamine in a ternary mixture was optimized, taking advantage of the electrocatalytic and antifouling properties that render PEDOT:PSS thin films appealing tools for electrochemical sensing of bioanalytes. Moreover, the potentialities of this material to interact with live cells were explored through the fabrication of a microfluidic trapping device for electrical monitoring of 3D spheroids using an impedance-based approach.

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Longchamp, Jean-Nicolas. "Thin films on icosahedral AIPdMn quasicrystal /." Berlin : Logos Verlag, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17423.

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Rehse, Nicolaus. "Nanostructure formation in thin polymer films." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972521976.

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Henry, Christine L., and christine henry@alumni anu edu au. "Bubbles, Thin Films and Ion Specificity." The Australian National University. Department of Applied Mathematics, Research School of Physical Sciences and Engineering, 2009. http://thesis.anu.edu.au./public/adt-ANU20091117.073007.

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Bubbles in water are stabilised against coalescence by the addition of salt. The white froth in seawater but not in freshwater is an example of salt-stabilised bubbles. A range of experiments have been carried out to investigate this simple phenomenon, which is not yet understood.¶ The process of thin film drainage between two colliding bubbles relates to surface science fields including hydrodynamic flow, surface forces, and interfacial rheology. Bubble coalescence inhibition also stands alongside the better known Hofmeister series as an intriguing example of ion specificity: While some electrolytes inhibit coalescence at around 0.1M, others show no effect. The coalescence inhibition of any single electrolyte depends on the combination of cation and anion present, rather than on any single ion.¶ The surfactant-free inhibition of bubble coalescence has been studied in several systems for the first time, including aqueous mixed electrolyte solutions; solutions of biologically relevant non-electrolytes urea and sugars; and electrolyte solutions in nonaqueous solvents methanol, formamide, propylene carbonate and dimethylsulfoxide. Complementary experimental approaches include studies of terminal rise velocities of single bubbles showing that the gas-solution interface is mobile; and measurement of thin film drainage in inhibiting and non-inhibiting electrolyte solution, using the microinterferometric thin film balance technique.¶ The consolidation of these experimental approaches shows that inhibiting electrolytes act on the non-equilibrium dynamic processes of thin film drainage and rupture between bubble surfaces and not via a change in surface forces, or by ion effects on solvent structure. In addition, inhibition is driven by osmotic effects related to solute concentration gradients, and ion charge is not important.¶ A new model is presented for electrolyte inhibition of bubble coalescence via changes to surface rheology. It is suggested that thin film stabilisation over a lifetime of seconds, is caused by damping of transient deformations of film surfaces on a sub-millisecond timescale. This reduction in surface deformability retards film drainage and delays film rupture. It is proposed that inhibiting electrolyte solutions show a dilational surface viscosity, which in turn is driven by interfacial concentration gradients. Inhibiting electrolytes have two ions that accumulate at the surface or two ions that are surface excluded, while non-inhibiting electrolytes have more evenly distributed interfacial solute. Bubble coalescence is for the first time linked through this ion surface partitioning, to the ion specificity observed at biological interfaces and the wider realm of Hofmeister effects.¶

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Dalnoki-Veress, Kari. "Confinement effects on thin polymer films." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0011/NQ33298.pdf.

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Dissertations / Theses on the topic 'Photoresponses in thin films'

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