Dissertations / Theses on the topic 'Thin film, epitaxial'
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Jones, A. P. C. "Electroluminescence in epitaxial thin film ZnS and ZnSe." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6783/.
Borovikov, Valery. "Multi-scale simulations of thin-film metal epitaxial growth /." Connect to full text in OhioLINK ETD Center, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1216928358.
Wang, Chao-Hsiung. "The growth of thin film epitaxial oxide-metal heterostructures." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368667.
Borovikov, Valery V. "Multi-scale Simulations of Thin-Film Metal Epitaxial Growth." University of Toledo / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1216928358.
Schoofs, Frank. "Defect-induced magnetism and transport phenomena in epitaxial oxides." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/243639.
Cao, Jing. "Growth, characterization and measurement of epitaxial Sr2RuO4 thin films." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/274542.
Yan, Li. "Two phase magnetoelectric epitaxial composite thin films." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/30130.
Ph. D.
Nutariya, Jeerapat. "Epitaxial thin film growth of Pt assisted by underpotential deposition phenomena." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.616569.
Kadhim, N. J. "Morphological imperfections associated with molecular beam epitaxial growth of GaAs layers." Thesis, University of Hertfordshire, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377702.
Amiri-Hezaveh, A. "Photelectron spectroscopy of ultra-thin epitaxial f.c.c. magnetic films of iron and cobalt." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233668.
Liu, Qiang. "Optimization of Epitaxial Ferroelectric Pb(Zr0.52,Ti0.48)O3 Thin-Film Capacitor Properties." Thesis, Ecully, Ecole centrale de Lyon, 2014. http://www.theses.fr/2014ECDL0049/document.
With the intensive use of modern microelectronic devices in numerous areas, there is an increasing demand for non-volatile memories. FeRAM (ferroelectric random access memory) is one of the most potential next-generation memories for its ultra-low power consumption and high read/write rate. Among various ferroelectrics, PZT (Pb(Zr1-x,Tix)O3) exhibits high remnant polarization and low coercive field, which make it a promising candidate for FeRAM.In this dissertation, PZT(52/48) layers of various thicknesses (from 33 nm to 200 nm) have been epitaxially grown on SrTiO3 substrate, with a SrRuO3 interlayer as bottom electrode, using two deposition methods for comparison: sol-gel and sputtering. Three different conductive materials (SrRuO3, Pt and ITO) have been deposited as top electrode. The objective was a detailed study of the electrical and ferroelectric properties of these MFM (metal-ferroelectric-metal) capacitors, with a particular investigation of the influence of elaboration conditions and electrode material on leakage currents and domain switching dynamics.Sputtered and sol-gel-derived PZT capacitors showed similar properties: Above a minimum workable thickness of about 100 nm for a 100 × 100 μm2 PZT capacitor, they showed low leakage current, high maximum relative permittivity (600 - 1300) and high remnant polarization (30 - 40 μC/cm2). The dominant leakage current mechanisms were identified by fitting the results, showing different contributions as a function of electric field. PFM (piezoresponse force microscopy) characterizations confirmed the existence of ferroelectric domains of opposite directions. Coercive field was found to be highly dependent on work frequency. Besides, imprint properties were found to be dependent on top electrode, annealing procedure and bottom electrode thickness
Wang, Feng. "Surface/interface modification and characterization of C-face epitaxial graphene." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53855.
Clarke, A. "A wavevector imaging photoelectron spectrometer, with application to a magnetic overlayer system." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233729.
Kryukov, Yevgen A. "Island nucleation and growth in epitaxial, amorphous, and nanoparticle thin-films." University of Toledo / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1309450447.
McClure, Adam Marc. "Epitaxial thin film deposition of magnetostrictive materials and its effect on magnetic anisotropy." Diss., Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/mcclure/McClureA0512.pdf.
Guangnan, Zhou. "Impact of doping on epitaxial Ge thin film quality and Si-Ge interdiffusion." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62996.
Applied Science, Faculty of
Materials Engineering, Department of
Graduate
Lmouchter, Mohamed. "Epitaxial Growth and Characterization for Thin Films of Colossal Magnetoresistive Layered Manganates." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/61311.
0048
新制・課程博士
博士(工学)
甲第14050号
工博第2962号
新制||工||1439(附属図書館)
26329
UT51-2008-F442
京都大学大学院工学研究科電子物性工学専攻
(主査)教授 鈴木 実, 教授 髙岡 義寛, 教授 藤田 静雄
学位規則第4条第1項該当
Cherkassky, Alexander (Alexander Peter) 1963. "Metrology of thin silicon expitaxial films : determination of epitaxial film thickness by Fourier-transform infra-red spectrometry." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/17405.
Li, Xuebin. "Epitaxial graphene films on SiC : growth, characterization, and devices /." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24670.
Committee Chair: de Heer, Walter; Committee Member: Chou, Mei-Yin; Committee Member: First, Phillip; Committee Member: Meindl, James; Committee Member: Orlando, Thomas
Rioult, Maxime. "Hematite-based epitaxial thin films as photoanodes for solar water splitting." Palaiseau, Ecole polytechnique, 2015. https://theses.hal.science/tel-01220396/document.
Using hydrogen as an energy carrier for solar energy storage and/or fuel alternative to oil is very appealing, especially as it can be cleanly produced by solar water splitting. In this process, electron-hole pairs, generated in illuminated semiconductors dipped in an aqueous solution, realize the water oxidoreduction reactions (oxygen production at the photoanode and hydrogen production at the photocathode). Transition metal oxides, in particular hematite (α-Fe2O3) which features a quasi ideal band-gap for this application, are the most promising photoanodes materials. Hematite thin films were deposited on single crystals by oxygen plasma assisted molecular beam epitaxy. These model samples along with the use of high-end techniques, in particular using synchrotron radiation, make possible the identification of the relevant parameters affecting the photoelectrochemical properties. I firstly focused on the impact of the crystallographic structure, the stoichiometry and the surface morphology. Then the effects of doping with titanium were investigated, demonstrating the existence of an optimal doping level and an increase of the charges diffusion length inducing a high photocurrent gain. In addition, I studied the electronic structure and the surface recombinations dynamics of TiO2 - Ti-doped hematite heterojunctions, revealing a diffuse interface. Lastly, the internal electric field created by a ferroelectric thin film of BaTiO3/Nb:SrTiO3 was considered in order to enhance the performances of photoanodes. A first step toward the comprehension of the link between ferroelectric polarization and photocurrent was achieved through the evidence of an internal electric field favourable for the separation of charges
Zhang, Qianzhe. "Microstructural control of epitaxial α-quartz films." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/670104.
Epitaxial films of piezoelectric α-quartz could enable the fabrication of sensors with unprecedented sensitivity for prospective applications in electronics, biology and medicine. However, a prerequisite is harnessing the crystallization of epitaxial α-quartz, tailoring suitable film microstructures for nanostructuration. In my PhD work, we bring new insights into the crystallization of epitaxial α-quartz films on Silicon(100) from the thermal devitrification of nanoporous silica and the control the film microstructures: We show that by increasing the quantity of devitrifying agent (Sr) it is possible to switch from an α-quartz microstructure consisting of porous flat film to one dominated by larger and fully dense α-quartz crystals. The mechanism of Sr-assisted devitrification was also investigated simultaneously. Then, we found that film thickness, annealing temperature, relative humidity and the nature of surfactant also play an important role in the control of the microstructure and homogeneity of the films. By increasing its, thickness it is possible to switch from a partly crystalline and porous film to fully a crystalline and dominated by dense crystals one. Annealing temperature can impact the crystallization process very deeply for it can change the dynamics and reactivity of Sr within the silica film. High relative humidity cooperates with a suitable surfactant to create perforations on the films via a water-induced phase separation phenomenon. This perforation can also influence the film crystallinity by altering the distribution of Sr inside film. All these studies on the one hand give us a better understanding of the mechanism of Sr-assisted devitrification and on the other hand can show us a versatile microstructural control of the epitaxial α-quartz film. Besides, via a multilayer deposition method, we have extended the maximum thickness of the α-quartz films from a few hundreds of nm into the µm range. Moreover, in my thesis, we report unprecedented large-scale fabrications of ordered arrays of piezoelectric epitaxial α-quartz nanostructures on silicon(100) substrates by the combination of three cost-effective lithographic techniques: (i) laser transfer lithography, (ii) soft nanoimprint lithography on Sr-doped SiO2 sol-gel thin films and (iii) self-assembled SrCO3 nanoparticles reactive nanomasks. Epitaxial α-quartz nanopillars with different diameters (down to 50 nm) and heights (up to 2000 nm) were obtained for the first time. This part of my PhD work demonstrates the control over the shape, micro- and nano-patterning of α-quartz thin films while preserving its crystallinity, texture and piezoelectricity, which opens the opportunity to fabricate new high frequency resonators and high sensitivity sensors relevant in different fields of application.
Nana, Sandjo Albert [Verfasser]. "Solutions for fourth-order parabolic equation modeling epitaxial thin film growth / Albert Nana Sandjo." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2012. http://d-nb.info/1025882253/34.
Ebels, Ursula. "Scanning Kerr microscopy of magnetic domains in epitaxial Fe/GaAs(001) thin film systems." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389827.
Mares, Jeremy. "EPITAXIAL GROWTH, CHARACTERIZATION AND APPLICATION OF NOVEL WIDE BANDGAP OXIDE SEMICONDUCTORS." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3002.
Ph.D.
Optics and Photonics
Optics and Photonics
Optics PhD
Doucette, Luke D. "Use of an Epitaxial BaFz Buffer Layer on Silicon to Control W03 Thin Film Growth." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/DoucetteLD2002.pdf.
Sunkari, Swapna Geetha. "IMPROVED ESTIMATION OF EPITAXIAL THIN FILM THICKNESS AND DOPING USING FOURIER TRANSFORM INFRARED REFLECTION SPECTROSCOPY." MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11092004-171719/.
Souri, Maryam. "ELECTRONIC AND OPTICAL PROPERTIES OF METASTABLE EPITAXIAL THIN FILMS OF LAYERED IRIDATES." UKnowledge, 2018. https://uknowledge.uky.edu/physastron_etds/60.
Hong, Yuanjia. "Magnetic and Transport Properties of Oxide Thin Films." ScholarWorks@UNO, 2007. http://scholarworks.uno.edu/td/615.
Asano, H., N. Koduka, K. Imaeda, M. Sugiyama, and M. Matsui. "Magnetic and junction properties of half-metallic double-perovskite thin films." IEEE, 2005. http://hdl.handle.net/2237/6775.
Plonka, Rafael. "Impact of the interface on the paraelectric-to-ferroelectric phase transition in epitaxial BaSrTiO_tn3 thin film capacitors." Jülich Forschungszentrum, Zentralbibliothek, 2007. http://d-nb.info/1000127257/34.
Hu, Xiao. "Ultra-thin oxide films." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:d7373376-84f1-459e-bffb-f16ce43f02b7.
Liu, Yanqing. "Thermal engineering in an epitaxial nanostructured germanium semiconductor." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY082/document.
This PhD project is an exhaustive study on the characterization of the thermal properties of a new type semiconducting materials based on germanium. It is a germanium matrix containing nano-inclusions with the objective of creating a perfect "electron crystal - phonon glass" material. The materials are thin films of an epitaxial germanium matrix embedded with Ge:Mn nano-inclusions, grown on a Germanium-on-insulator (GOI) substrate in CEA/INAC in Grenoble. From TEM images of the thin films it has been demonstrated that both the matrix and inclusions are monocrystalline, and the nano-inclusions have generally a spherical form with a diameter distribution ranging from 5 to 50 nm. Depending on the growth parameters in molecular beam epitaxy, i.e. the Mn concentration and the annealing temperature, the geometries, mean diameters and diameter distributions of nano-inclusions in Ge:Mn can be varied. With these unique structural features, these Ge:Mn thin films are one of the most interesting models for the study of the influence of nano-inclusions on thermal transport in a crystalline matrix.The characterization of the thermal properties of the material have been done using two advanced techniques: the 3-omega method in Institut Néel, and the Scanning Thermal Microscopy (SThM) in CETHIL (Centre d'Energétique et de Thermique de Lyon) in Lyon. A highly sensitive differential 3-omega measurement setup has been developed in the work, which permits precise (error~12%) measurements of electrical conductive thin films having low thermal conductivities. Dramatically reduced thermal conductivities have been revealed for Ge:Mn thin films containing different Mn% and having different inclusion geometries at room temperature, compared to crystalline bulk Ge. A minimum value of 3.3 Wm-1K-1 was found for Ge:Mn thin film containing 10% Mn, beating the “alloy limit” of thermal conductivity set by SiGe alloys at room temperature (6-12 Wm-1K-1). The measurement results of SThM confirmed the low thermal conductivities for all Ge:Mn/GOI samples at room temperature. Numerical simulations using different models have been performed to try to interpret the experimental results and to understand the mechanisms of the influence of the nano-inclusions on the phonon transport in semiconductor materials
Zapata, Correa James Arturo. "Epitaxial Thin Film Growth and Study of Charge and Mass Transport Properties of Mixed Ionic Electronic Conducting GdBaCo2O5+δ (GBCO)." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/368559.
Research on new oxide materials with both high mixed ionic and electronic conductivity (MIEC) is of great importance in order to achieve optimum performance in a wide range of devices that have considerable potential for clean, low carbon, electrochemical energy conversion. In the case of solid oxide fuel cells (SOFCs), in order to reduce the working temperature to the intermediate range (500-750ºC), more active cathode materials are needed. Previous studies have highlighted the great potential of GdBaCo2O5+δ (GBCO), as a cathode in SOFC, with a high reported electronic conductivity above the metal-insulator transition temperature, outstanding oxygen transport properties and enhanced surface exchange, as well as excellent stability for both structural and electrochemical performance. However, to date there is an absence of information about intrinsic ionic conductivity of this GBCO compound. To enable measurement of intrinsic electronic and particularly ionic transport properties, the greatest challenge is to synthesize dense, continuous or ideally epitaxial specimens of GBCO. The aim of this work is to achieve well-defined epitaxial GBCO deposited by PLD technique in order to fundamentally investigate their intrinsic anisotropic properties for SOFC applications. This research involved PLD target synthesis and PLD deposition for these materials. The obtained films were evaluated through crystallographic, compositional, surface morphological and microstructural characterization. Finally electrical, oxygen diffusion and surface exchange properties were characterized by Electrochemical impedance and the isotopic exchange depth profile (IEDP) with secondary ion mass spectrometry (SIMS) method. After a long process of optimization, high-quality epitaxial GBCO films mainly consisting of double-perovskite regions were obtained by PLD. The nature of the ablation process from stoichiometric GBCO target generates a deviation in the composition of the films which basically consists in a Co depletion. This composition deviation induces the appearance of characteristic stacking faults with supplementary GdO planes without affecting the overall epitaxial arrangement of the films. Despite the observed changes in the film orientation from c\\ (parallel) to c⊥ (perpendicular) upon deposition temperature increase, the film electronic conductivities seem to be mainly correlated with the cation composition. So, the larger the deviation from stoichiometric ideal composition, the lower the conductivity. This effect has been mainly ascribed to the role of defects in impeding the achievement of a long-range order of the highly conducting Pmmm structure in the films. Despite the presence of defects, the conductivities in our films, which are considered very promising for their application as cathodes in intermediate temperature SOFCs, attain values as high as 800 S/cm at temperatures between 300 and 400ºC. It also demonstrates that the appropriate choice of substrate mismatch allows growing films with either pure c-axis or a-axis orientation. This has allowed exploration of the potential anisotropy in the oxygen transport and has proven that indeed the oxygen diffusion at low temperatures is almost one order of magnitude larger along the a-axis compared to the c-axis. This has been related to the arrangement of oxygen vacancies preferentially in the GdO planes forming channels along the a-axis, and therefore providing a path for oxygen migration. However, no influence of the structure anisotropy was observed in the oxygen surface exchange rates, which were of similar values regardless of the film orientation or measuring geometry.
Giridhar, Nandipati. "Kinetic Monte Carlo simulations of submonolayer and multilayer epitaxial growth over extended time- and length-scales." University of Toledo / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1248923011.
Pehlivan, Ozlem. "Growth And Morphological Characterization Of Intrinsic Hydrogenated Amorphous Silicon Thin Film For A-si:h/c-si Heterojunction Solar Cells." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615488/index.pdf.
Chiodi, M. "GROWTH AND CHARACTERIZATION OF EPITAXIAL AND CLUSTER-ASSEMBLED CR-N CODOPED TIO2 FILMS WITH ENHANCED VISIBLE-LIGHT PHOTOACTIVITY." Doctoral thesis, Università degli Studi di Milano, 2010. http://hdl.handle.net/2434/163373.
Liebig, Andreas. "Amorphous, Nanocrystalline, Single Crystalline: Morphology of Magnetic Thin Films and Multilayers." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis Acta Universitatis Upsaliensis, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8355.
Camosi, Lorenzo. "Solitons magnétiques topologiques dans des couches minces epitaxiées à symétrie réduite." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAY012/document.
In this thesis I studied the relationship between the crystal symmetry, the symmetry of the magnetic interactions and topological solitons in epitaxial magnetic thin films. The case of thin films with C2v symmetry has been considered. These systems are particularly interesting for the anisotropic properties that allow stabilising magnetic solitons with different symmetries and topology. I used theoretical and experimental approaches to investigate this phenomenon:Micromagnetic approach:The relationship between the atomistic and the micromagnetic formulations of magnetic interactions was studied as a function of the crystal symmetry.This allowed to explain the presence of anisotropicinteractions and study their effect on the configurations of 1D and 2D magnetic solitons. The discussion starts from the simplest 1D soliton, the domain wall, and step-by-step new interactions and symmetries are added in order to characterize the stability conditions and the properties of 2D solitons, skyrmions and anti-skyrmions. Our method allowed to study 2D topological solitons over a wide range of parameters and build a phase diagram as a function of the Dzyaloshinskii-Moriya interaction (DMI) strength and magnetic field intensity. This allowed us to distinguish three kinds of 2D topological solitons (skyrmions, skyrmionic bubbles and supercritical skyrmions) as a function of their size and response to an external magnetic field. We show that an inversion of DMI strength along perpendicular directions allows the stabilisation of anti-skyrmions. A micromagnetic model is developed to study the configuration and energy differences between skyrmions and anti-skyrmions. This shows that the dipolar interaction breaks the circular symmetry of the antiskyrmion and makes it more stable than the skyrmion.Experimental approach:Epitaxial magnetic systems with C2v symmetry have been grown. For each system I describe the growth parameters and crystal symmetry, followed by the results of the magnetic characterisation and finally the results from the magnetic microscopy measurements.I have investigated the DMI symmetry and strength in an out-of-plane magnetised epitaxial Au/Co/W trilayer. The DMI in this system promotes a clockwise chirality of the spin modulation with a strong anisotropy in the DMI strength. This anisotropy arises from the C2v symmetry of the Co/W stack.Skyrmions in this system should have an elliptical shape. We stabilised skyrmions in continuous films and in nanopatterned structures. Their magnetic configurations have been displayed with different microscopic techniques, XMCD-PEEM and MFM, without identifying anisotropic properties.We designed the W/Co/Au-Pt (solid solution) system to increase the effect of the anisotropic interactions on the skyrmion configuration. Microscopy studies in naturally demagnetised areas show that stripe domains parallel to the in-plane easy axis are stable in this system. The configuration with a larger periodicity has been found even for thinner Co layer after demagnetisation with a magnetic field. Kerr microscopy studies of the DW dynamics allowed to evidence the origin of this magnetic configuration, which arises from a strong anisotropy in the DW motion.MFM measurements with the application of a static magnetic field have been performed in order to confine elliptical skyrmionic bubbles but the reduced sensitivity of this technique to thin magnetic systems did not allow to display and characterise them. XMCD-PEEM measurements allowed to display the internal structure of the DWs along the in-plane hard axis of the system. They show the presence of a Néel DW component. Finally I have grown and studied a W/Fe/Co/Au system where anti-skyrmions may in principle be stabilised. However, the system did not show the out-of-plane magnetisation which is fundamental for the stabilisation of skyrmions. This means that the W/Fe in-plane anisotropy dominates the Co/Au out-of-plane anisotropy
Mirjolet, Mathieu. "Transparent Conducting Oxides Based on Early Transition Metals: From Electrical and Optical Properties of Epitaxial Thin Films, to Integration in All-Oxide Photoabsorbing Heterostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673687.
Los óxidos conductores transparentes (TCO) son esenciales en dispositivos tecnológicos. Su capacidad para combinar alta conductividad eléctrica y transparencia óptica a la luz visible los hace particularmente útiles en una gran variedad de dispositivos: pantallas, células solares, ventanas inteligentes, etc. El óxido de indio y estaño (ITO) es hasta ahora el TCO más extendido. Un gran inconveniente del ITO es su alto coste ya que el indio, su componente principal, es un material escaso. Por otro lado, algunos óxidos metálicos intrínsecos de metales de transición también son transparentes. En estos materiales, la banda (3,4)d es estrecha y parcialmente llena. Es la responsable de la alta densidad de portadores libres y su masa efectiva grande hace que la luz no se refleje en el visible y que el borde de reflexión (frecuencia de plasma) esté en la región del IR cercano. En esta tesis, hemos explorado las propiedades de las películas delgadas de óxidos metálicos (SrVO3 (SVO; 3d1) y SrNbO3 (SNO; 4d1)) crecidas por deposición de láser pulsado (PLD). Dado que la calidad epitaxial es fundamental para obtener buenas propiedades funcionales, el primer paso consistió en optimizar los parámetros de crecimiento de las películas SVO/SNO. Las películas deben crecerse en ultra alto vacío (UHV) para estabilizar el estado de oxidación 4+ de V/Nb y usar temperaturas de depósito altas (700-800°C) para permitir la movilidad de las especies sobre el sustrato. Sin embargo, la ablación en UHV y la expansión de la pluma del PLD, muy enérgica, provocan la creación de defectos puntuales en las películas. Hemos resuelto este problema utilizando un gas inerte durante el crecimiento, que controla la expansión de la pluma. Finalmente, hemos estudiado el impacto de la deformación epitaxial en la conductividad eléctrica y la transparencia óptica. Se obtuvieron películas con una conductividad mayor que ITO y una transparencia similar. Por otra parte, la observación de que la frecuencia de plasma en estos materiales esté en el IR cercano, se atribute comúnmente a un aumento de la masa efectiva de los electrones debido a las correlaciones e-e dentro de la banda estrecha 3d. Tras un análisis sistemático de los datos de transporte de SVO llegamos a la conclusión de que la teoría del líquido de Fermi no puede explicar el aumento de la masa efectiva de los portadores. En cambio, hemos sugerido que el acoplamiento electrón-fonón y el carácter 2D de la superficie de Fermi juegan un papel importante. Además, hemos demostrado que la imagen clásica de banda rígida, de un electrón libre que evoluciona en una banda 3d-t2g es solo una aproximación, como lo demuestra la hibridación observada de los orbitales V-3d y O-2p. Hemos observado también que la tensión epitaxial, afecta a la hibridación, el orden orbital y últimamente a la resistividad de las capas. Hemos podido observar y explicar que a la frecuencia de plasma se excitan, en las condiciones de iluminación adecuadas, pasmones de volumen. Una observación y descripción poco frecuentes y que, en esencia, están relacionadas con la componente π de la polarización de la luz y el gradiente de carga en la superficie del material. Finalmente, hemos probado la idoneidad de SVO como electrodo en heteroestructuras fotoabsorbentes “todo-óxido”. Hemos observado la respuesta fotovoltaica, usando capas epitaxiales de LaFeO3 como absorbente y hemos puesto de relieve el papel de la función de trabajo del electrodo en el rendimiento del dispositivo. Como perspectiva, hemos demostrado que los electrodos transparentes SVO y SNO, al tener funciones de trabajo distintas, podrán permitir ajustar y optimizar los dispositivos. Este trabajo aporta un nuevo conocimiento fundamental de las propiedades de óxidos y demuestra su versatilidad en componentes fotovoltaicos.
Transparent conducting oxides (TCOs) are key elements to many technological devices. Their ability to combine high electrical conductivity and high optical transparency to visible light, make them particularly useful in a myriad of devices such as displays, solar cells, smart windows, etc. Indium tin oxide (ITO) is so far the most widespread TCO. By Sn-doping, this wide band gap In2O3 semiconductor can reach low resistivity (only about two orders of magnitude above conventional metals) while preserving its transparency. A major drawback of ITO is its high cost as indium, its main component, is a scarce material. Moreover, due to its nature of doped-semiconductor, some physical limits impose that its properties cannot be further improved. On the other hand, some intrinsic metallic oxides composed of early transition metals also turn out to be transparent. In these materials, the partially filled narrow d band is responsible for high density of free carriers with increased effective mass, thus bringing the reflection edge down to the near-IR region. In this thesis, we were interested in exploring the properties of metallic oxide thin films grown by pulsed laser deposition (PLD), namely SrVO3 (SVO; 3d1) and SrNbO3 (SNO; 4d1). As high epitaxial quality is essential to obtain good functional properties, the first step consisted in optimizing the growth parameters for single phase and flat SVO/SNO films, displaying high crystallinity, conductivity and transparency. As anticipated, films need to be grown in ultra-high vacuum (UHV) to stabilize the 4+ oxidation state of V/Nb and using a high substrate temperature (700-800°C) to allow good mobility of the species on the substrate. However, the deposition in UHV and its subsequent highly energetic PLD plasma plume lead to a high concentration of point defects. We have solved this issue by using an inert background gas. Finally, we have studied the impact of epitaxial strain on the electrical conductivity and optical transparency window. All in all, it turned out that optimal films display larger conductivity than ITO, for a similar transparency. Conventional wisdom would suggest that a low plasma frequency would be due to the electron-electron correlations within the narrow nd1 band. In a systematic analysis of SVO transport data (temperature-dependent resistivity, etc.), we have concluded that the Fermi liquid theory alone cannot account for the carrier mass enhancement. Instead, we have suggested that the 2D-like Fermi surface and the electron-phonon coupling play a major role. In addition, we have shown that the classical rigid band picture, of one free electron evolving in a 3d-t2g band is only a rough approximation, as attested by the observed hybridization of the V 3d and O 2p orbitals. Moreover, strain affects this hybridization by modifying the orbital hierarchy and covalency which could be responsible for the observed strain-dependent resistivity and effective mass. By appropriate optical measurements, we have also discussed the nature of the plasmonic excitations at plasma frequency in SNO and SVO films. Interestingly, the possibility of exciting volume plasmons in these TCOs gives a glimpse on their potential applications in the field of plasmonics. Finally, we have tested the suitability of SVO as electrode in photoabsorbing all-oxide heterostructures. In particular, we have successfully observed a photovoltaic effect in LaFeO3-based capacitors and disclosed the important role of the electrode work function on the device performances. As outlook, we have concluded that SVO and SNO, by having distinct work functions, could allow to tune any device properties. This work demonstrates the suitability and high potential of this whole new category of TCOs as electrode material in all-oxide devices. We are convinced that it opens the way to a plethora of possible devices, photovoltaic-wise or other.
Universitat Autònoma de Barcelona. Programa de Doctorat en Física
Li, Chenhui. "Application de techniques d’opto-acoustique et de calculs de premiers principes à la caractérisation des propriétés élastiques de films minces." Electronic Thesis or Diss., Paris 13, 2019. http://www.theses.fr/2019PA131091.
Elastic properties are of fundamental importance for a material. With the combination of picosecond laser ultrasonic and Brillouin light scattering techniques, we measured sound velocities in various magnetron-sputtering-deposited thin films including epitaxial binary and ternary transition metal nitrides (TaN, TiN, ZrN, Ti1-xZrxN), polycrystalline high entropy alloys or multicomponent transition metal alloys ((CoCrCuFeNi)1-x(Al,Nb)x), and their nitrogen interstitial alloys (CoCr(Cu,Mn)FeNiNx). The longitudinal and shear sound velocities (VL and VT respectively) are correlated to the effective elastic constants through ⟨C33⟩= ρV2L and ⟨C44⟩= ρV2T. On the other hand, Density functional theory (DFT) based ab-initio calculations were performed to provide single crystal elastic constants w/o considering vacancies. It was found that for the epitaxial binary and ternary nitrides, vacancies play a huge role on elastic properties especially in the case of TaN. While in the case of TiN, ZrN and Ti1-xZrxN, the influence of vacancies is smaller but still noticeable. In the case of polycrystalline multicomponent alloys and interstitial alloys, the sound velocities and effective elastic constants were found to be associated to chemical alloying (Al, Nb and N) effects, phase transitions (FCC, BCC and amorphous), textures and porosity changes. The elastic modulus agrees to nanoindentation modulus EIT. The overall agreement between our elastic property measurements and DFT calculations were reached. Besides, DFT calculations also provided valuable insights into structural properties and phase stability. Additionally, we studied structural and mechanical (including elastic) properties of a bulk CoCrCuFeNi as a reference to thin film properties. With the CoCrCuFeNi films on a flexible Kapton® substrate, we performed tensile tests and studied fracture properties of thin films, as a preliminary work to further link thin film elasticity to plasticity. Keywords: Thin film, epitaxial, polycrystalline, sound velocity, elastic constant, transition metal nitride, multicomponent alloy, interstitial alloy, point defects, microstructure, porosity, texture, Brillouin light scattering, picosecond laser ultrasonic, nanoindentation, mechanical property, flexible substrate, fracture toughness, crack and buckle, ab-initio, DFT
Mc, Grath Oran F. K. "Structural and magnetic properties of epitaxial W/Fe/W and Gd/Fe films grown by pulsed laser deposition." Université Joseph Fourier (Grenoble), 1994. http://www.theses.fr/1994GRE10209.
Zheng, Ma. "Synthesis and Characterization of ε-Fe2O3 Nanoparticles and Thin Films." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671968.
En las dos últimas décadas, el polimorfo de óxido de hierro(III) ε-Fe2O3 ha pasado de ser una rareza científica a estar en el centro de una intensa actividad investigadora por sus propiedades multiferroicas y una elevada coercividad a temperatura ambiente. Estas propiedades ponen de relieve aspectos fundamentales relacionados con la complejidad de su diagrama de fases magnético y suscitan interés por sus aplicaciones potenciales en tecnologías de la información o fotocatálisis. A pesar de este interés creciente, la síntesis y caracterización de materiales de tipo ε-(Fe1-xMx)2O3 en que el Fe3+ se sustituye por otros cationes metálicos ha sido poco estudiada. Tampoco se acaban de entender los mecanismos que controlan la estabilización de la ε-Fe2O3 en capas delgadas, muy relevantes para las aplicaciones de interés. Esta tesis pretende hacer avanzar el conocimiento en estos aspectos, concretamente explorando la síntesis y caracterización de nanopartículas ε-(Fe1-xMx)2O3 dopadas con metales de transición magnéticos (M = Cr, Mn, Co , Ru). También se ha centrado en los mecanismos de estabilización de capas epitaxiales de ε-Fe2O3, caracterizando su estructura y propiedades. La investigación en nanopartículas ha permitido profundizar en el conocimiento de las transiciones de fase del sistema ε-Fe2O3 y ha puesto de manifiesto su sensibilidad a la deformación y los campos magnéticos. Se ha visto que el Cr3 + sustituye preferencialmente el Fe3 + en los entornos octaédricos regulares del ε-(Fe1-xCrx)2O3, y que reduce de forma drástica la anisotropía magnética y la magnetización de saturación de las nanopartículas. La sustitución del Fe3 + por Cr3 + se ha podido estudiar hasta x=0.25 sin observarse la aparición de otras fases secundarias, aunque para x>0.1 se han obtenido claros indicios de cambios estructurales. La sustitución con Mn se ha estudiado hasta x=0.20 sin que tampoco en este caso se observara la aparición de fases secundarias en aumentar el contenido de Mn. Sin embargo, por encima de x>0.1 también se han observado cambios estructurales. Para bajos niveles de sustitución el Mn aumenta la anisotropía magnética aunque esta disminuya rápidamente para x>0.05, coincidiendo con un fuerte incremento de la magnetización. A diferencia de lo que ocurre con el Cr y el Mn, la sustitución con Co no puede ir más allá del 3% atómico sin que aparezcan fases secundarias. Pero incluso estos niveles tienen el efecto de aumentar a y al mismo tiempo comprimir b y c, muy probablemente como consecuencia de fenómenos magnetoelásticos relacionados con el momento orbital del Co2 +. Estos efectos magnetoelásticos parecen tener una fuerte influencia sobre la transición magnética del sistema ε-Fe2O3 a alta temperatura, en particular estabilizando las subredes magnéticas de los hierros en entornos octaédricos regulares y tetraédricos. Respecto a la sustitución con Ru, cabe decir que ha sido complicada debido a la volatilidad de este metal y que los resultados de la caracterización magnética de diferentes síntesis no han resultado reproducibles y deben mejorarse. En cuanto a capas delgadas de ε-Fe2O3, esta Tesis ha investigado el crecimiento de Sc0.2Al0.4Fe1.4O3 sobre diferentes sustratos y se ha visto que se pueden obtener capas epitaxiales de buena calidad sobre sustratos LSAT(111), STO (111), mica (001) y YSZ (001). Esto ha permitido estabilizar capas delgadas epitaxiales de ε-Fe2O3 sobre sustratos flexibles como la Mica con Sc0.2Al0.4Fe1.4O3 como capa tampón. Con la caracterización magnética de capas ε-Fe2O3 sobre Mica se ha detectado una transición magnética a baja temperatura similares a la ya conocida para nanopartículas de ε-Fe2O3, pero desconocida para capas delgadas. También se ha investigado la estabilización de ε-Fe2O3 sobre espinela Fe3O4(111) como capa tampón y sobre MgAl2O4(111). La transición a baja se ha estudiado de forma detallada con espectroscopia Raman.
In the course of the last two decades, the ferric oxide polymorph ε-Fe2O3 has transitioned from being a scientific rarity to attracting increasing attention for its multiferroic character and huge coercive field at room temperature. Such uncommon properties bring out fundamental aspects related to its complex magnetic phase diagram and also make ε-Fe2O3 appealing for applications in information technologies or photocatalysis. In spite of this rising interest, the synthesis and characterization of ε-(Fe1-xMx)2O3 in which Fe3+ is substituted by other metallic cations remains largely unexplored. Moreover, the mechanisms governing the stabilization of ε-Fe2O3 in form of thin films, the form preferred for most applications, are still poorly understood. This Thesis aims at advancing knowledge in this particular area by exploring the synthesis and characterization of ε-(Fe1-xMx)2O3 nanoparticles substituted with magnetic transition metals (M= Cr, Mn, Co, Ru). It also focuses on the stabilization mechanisms of ε-Fe2O3 epitaxial thin films and the characterization of their structural and magnetic properties. The research on nanoparticles has brought new insights on the high and low temperature phase transitions of pure ε-Fe2O3, revealing its sensitivity to magnetic fields and strain state. It has been found that Cr3+ preferentially substitutes Fe3+ in the regular octahedral environment of ε-(Fe1-xCrx)2O3, drastically reducing the magnetic anisotropy and saturation magnetization of the nanoparticles. The Fe3+ replacement by Cr3+ was studied up x=0.25 without the appearance of other secondary phases but strong evidence of structural evolution was observed for x>0.10. The Mn substitution was studied up to x=0.20 and did not induce the appearance of additional secondary phases but above x=0.10 a structural change was also observed. In connection with this, low Mn substitution has the effect of enhancing the magnetic anisotropy which rapidly falls for x>0.05 while the magnetization is strongly increased. In contrast to Cr and Mn, the Co substitution was found to be limited to 3 at. % with secondary phases appearing above this limit. Even such small substitutions resulted in significant changes of the lattice parameters with the effect of stretching a and compressing b and c, most likely as a consequence of magnetoelastic effects related to the unquenched orbital moment of Co2+. The latter seems to strongly influence the high temperature magnetic transition of ε-Fe2O3 by magnetically stabilizing the regular octahedral and tetrahedral sublattices of Fe3+. The Ru substitution was challenging due to the volatility of this metal and the magnetic characterization of the nanoparticles presented reproducibility issues among different batches, indicating that experimental improvements are still needed. Regarding the research on ε-Fe2O3 thin films, the Thesis has investigated the growth of Sc0.2Al0.4Fe1.4O3 on different substrates finding that it yields high-quality epitaxial films on LSAT (111), STO (111), Fluorophlogopite Mica (001) and YSZ (001) substrates. This has allowed us to stabilize epitaxial ε-Fe2O3 films on flexible Mica substrates using Sc0.2Al0.4Fe1.4O3 films as a buffer layer. The magnetic characterization of the ε-Fe2O3 films on Mica revealed the existence of a low temperature magnetic transition which reminds that of ε-Fe2O3 nanoparticles, but which had not been previously reported in films. The stabilization of epitaxial ε-Fe2O3 films on Fe3O4 (111) spinel buffer layers or directly on MgAl2O4 (111) (MAO(111)) substrates was also investigated and it was found that impurities are prone to appear when Fe3O4 (111) layers are used. The low temperature magnetic transition was also found on the ε-Fe2O3 films directly grown on MAO(111) and was studied by Raman spectroscopy.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials
Meyer, Tricia Lynn. "Structure, magnetism and transport properties of CaxSr1-xMn0.5Ru0.5O3 bulk and thin film materials." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1386001173.
Choi, Suk. "Growth and characterization of III-nitride materials for high efficiency optoelectronic devices by metalorganic chemical vapor deposition." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45823.
Plonka, Rafael [Verfasser]. "Impact of the interface on the paraelectric-to-ferroelectric phase transition in epitaxial BaSrTiO_tn3 thin film capacitors / Rafael Plonka. [Forschungszentrum Jülich in der Helmholtz-Gemeinschaft, Institut für Festkörperforschung (IFF), Elektronische Materialien (IFF-6)]." Jülich : Forschungszentrum, Zentralbibliothek, 2007. http://d-nb.info/1000127257/34.
Chancerel, François. "Croissance, report, soulèvement (epitaxial lift-off) et fabrication de cellules solaires InGaAs permettant le recyclage du substrat d'InP pour le photovoltaïque concentré (CPV)." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEC031/document.
This PhD thesis deals with the implementation of the epitaxial lift-off (ELO) process from an InP substrate allowing the detachment of active layers and the substrate recycling. The final target is to realize multi-junction solar cells in an economically competitive way for concentrated photovoltaic. The ELO process consists in the under-etching of a sacrificial layer inserted between the substrate and the active layers. It is well known and mastered on a GaAs substrate with the use of a sacrificial layer of AlAs with a thickness of about 5 nm. Such a layer is not usable on an InP substrate due to the high lattice mismatch between AlAs and InP. In order to adapt the ELO process to an InP substrate, this work aimed to develop a specific sacrificial layer based on an AlAs/InAlAs superlattice. Thus, it is possible to circumvent problems related to the lattice mismatch and to the strained layer growth. After optimization of growth conditions of this superlattice, using this type of sacrificial layer, we achieve a sufficient thickness and therefore a sufficient under-etching rate in order to meet the requirements of the ELO process. Then, the transfer and lift-off of thin crystalline film based InGaAs solar cells have been developed. This kind of solar cells showed performances similar to those obtained with a standard epitaxial growth on an InP substrate, or even better under concentration due to optical confinement effects. Finally, the recycling of the InP substrate carried out by a process using only two wet chemical cleaning steps made it possible to produce InP surfaces of sufficient quality to achieve a promising second epitaxial growth
Huang, Kuo Hsiong. "Epitaxial growth of sputtered thin films." Thesis, University of Cambridge, 1991. https://www.repository.cam.ac.uk/handle/1810/251508.
Little, Scott Allen. "Equilibrium microstructure of epitaxial thin films." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/27652.
Thelander, Erik. "Epitaxial Ge-Sb-Te Thin Films by Pulsed Laser Deposition." Doctoral thesis, Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-164106.
Cherkassky, Alexander (Alexander Peter) 1963. "Metrology of very thin silicon epitaxial films." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/46178.
Includes bibliographical references (p. 135-139).
by Alexander Cherkassky.
Sc.D.