Cu2ZnSnS4 (CZTS), being related to the highly successful Cu(In,Ga)(S,Se)2, and CuInS2 materials, is a promising candidate for thin film photovoltaic devices. It has the advantage that it contains no rare or expensive elements, and therefore has cost-reduction potential for commercial systems. A two-stage process for fabrication of CZTS films is presented, which consists of sequential electrodeposition of Cu, Sn and Zn layers followed by a heat treatment in the presence of S vapour (‘sulfurisation’). Electrodeposition conditions are developed to give uniform Cu|Sn|Cu|Zn precursors of controlled morphology and composition, by the use of a rotating disc electrode system. Precursors are converted to CZTS by sulfurisation in the presence of elemental S, using a rapid thermal processing system (RTP). The sulfurisation reaction is studied by XRD and Raman spectroscopy as a function of temperature and at short time intervals, and a sequence of reactions is derived for the formation of CZTS. It is shown that the sulfurisation reaction occurs within minutes above 500°C. A model is presented for film formation when rapid heating rates are employed. The effects of sulfurisation time, background pressure and precursor composition on the morphological and structural properties of the CZTS films are investigated. Observations of grain size changes and compositional modification are made and explained in terms of the likely secondary phases present. The opto-electronic properties of the CZTS films are measured using a photoelectrochemical technique. Changes in the external quantum efficiency and band gap are studied as a function of sulfurisation parameters and precursor composition. After crystallisation of the CZTS phase during sulfurisation, the photocurrent obtained from the films continued to rise upon heating in the absence of S, which is explained by changes in acceptor concentration. Large shifts in the band gap are seen, and some proposals are made to explain the behaviour. The observations are discussed in the context of the particular compositions and sulfurisation conditions routinely used in the CZTS literature, and recommendations are made for further work.

β-W is an A15 structured phase commonly found in tungsten thin films together with the bcc structured W, and it has been found that β-W has the strongest spin Hall effect among all metal thin films. Therefore, it is promising for application in spintronics as the source of spin-polarized current that can be easily manipulated by electric field. However, the deposition conditions and the formation mechanism of β-W in thin films are not fully understood. The existing deposition conditions for β-W make use of low deposition rate, high inert gas pressure, substrate bias, or oxygen impurity to stabilize the β-W over α-W, and these parameters are unfavorable for producing β-W films with high quality at reasonable yield. In order to optimize the deposition process and gain insight into the formation mechanism of β-W, a novel technique using nitrogen impurity in the pressure range of 10-5 to 10-6 torr in the deposition chamber is introduced. This techniques allows the deposition of pure β-W thin films with only incorporation of 0.4 at% nitrogen and 3.2 at% oxygen, and β-W films as thick as 1μm have been obtained. The dependence of the volume fraction of β-W on the deposition parameters, including nitrogen pressure, substrate temperature, and deposition rate, has been investigated. The relationship can be modeled by the Langmuir-Freundlich isotherm, which indicates that the formation of β-W requires the adsorption of strongly interacting nitrogen molecules on the substrate. The dependence of β-W formation on the choice of underlayer materials has also been investigated. The β-W phase can only be obtained on the underlayer materials containing non-metallic elements. The dependence is explained by the existence of strong covalent bonds in β-W compared with that in α-W. The nickel and permalloy underlayers are the only exception to the above rule, and β-W has been successfully deposited on permalloy underlayer using very low deposition rate for spin-diffusion length measurement of β-W. The permalloy thin films usually take the (111) texture, since its (111) planes have the lowest surface energy. However, permalloy thin films deposited on β-W underlayer can achieve (002) texture using amorphous glass substrates. Therefore, the permalloy/β-W bilayer system can work as a seed layer for the formation of (002) textured films with fcc or bcc structure. The mechanism of the (002) texture formation cannot be explained by the existing models. The β-W to α-W phase transition was characterized by differential scanning calorimetry. The enthalpy of transformation is measured to be 8.3±0.4 kJ/mol, consistent with the value calculated using density functional theory. The activation energy for the β-W to α-W phase transformation kinetics is 2.2 eV, which is extremely low compared with that of lattice and grain boundary diffusion in tungsten. The low activation energy might be attributed to a diffusionless shuffle transformation process.

Lo Kwok Wing. / Thesis submitted in: November 2003. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 95-98). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.ii / Table of Contents --- p.iii / List of Figures --- p.iv / List of Tables --- p.v / Chapter iii. --- Table of Contents / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Magnetic CoPt and FePt Alloys --- p.1 / Chapter 1.1.2 --- Crystal Structures --- p.2 / Chapter 1.1.3 --- Magnetic Properties --- p.5 / Chapter 1.2 --- Magnetic Nanocomposite Films --- p.6 / Chapter 1.2.1 --- Ferromagnetic CoPt & FePt Alloy Nanoparticles --- p.7 / Chapter 1.3 --- Preparation Methods of CoPt & FePt Nanocomposite Films --- p.8 / Chapter 1.4 --- Aim and Motivation of this Research Project --- p.9 / Chapter Chapter 2 --- Sample Preparation and Characterization Techniques --- p.11 / Chapter 2.1 --- Sample Preparation --- p.11 / Chapter 2.1.1 --- Metal Vapor Vacuum Arc (MEVVA) Implantation System --- p.11 / Chapter 2.1.2 --- Preparation Procedures --- p.13 / Chapter 2.2 --- Characterization Techniques --- p.18 / Chapter 2.2.1 --- Rutherford Backscattering Spectroscopy (RBS) --- p.18 / Chapter 2.2.2 --- X-ray Diffractometry (XRD) --- p.20 / Chapter 2.2.3 --- Atomic Force Microscopy (AFM) --- p.23 / Chapter 2.2.4 --- Vibrating Sample Magnetometry (VSM) --- p.24 / Chapter Chapter 3 --- Characterization of Co and CoPt Implanted Samples --- p.28 / Chapter 3.1 --- Composition of Implanted Samples --- p.28 / Chapter 3.2 --- Phase Evolution and Crystal Structures --- p.34 / Chapter 3.2.1 --- Phase Evolution with Annealing Temperature --- p.35 / Chapter 3.2.2 --- Grain Size of Implanted Samples --- p.37 / Chapter 3.3 --- Magnetic Properties --- p.37 / Chapter 3.3.1 --- Dependence of Hc on Film Compositions --- p.39 / Chapter 3.3.2 --- Dependence of Hc on annealing Temperature --- p.42 / Chapter Chapter 4 --- Characterization of Fe and FePt Implanted Samples --- p.44 / Chapter 4.1 --- Overview --- p.44 / Chapter 4.2 --- Low Dose Implanted Samples --- p.44 / Chapter 4.2.1 --- RBS --- p.44 / Chapter 4.2.2 --- Phase Formation and Crystal Structures --- p.48 / Chapter 4.2.2-1 --- Phase Evolution with Annealing Temperature --- p.49 / Chapter 4.2.3 --- Grain Size of Implanted Samples --- p.51 / Chapter 4.2.4 --- AFM Results --- p.53 / Chapter 4.2.5 --- Magnetic Properties --- p.55 / Chapter 4.2.5-1 --- M-H Characteristics --- p.55 / Chapter 4.2.5-2 --- Coercivity Against Annealing Temperature --- p.55 / Chapter 4.3 --- High Dose Implanted Samples --- p.61 / Chapter 4.3.1 --- RBS --- p.62 / Chapter 4.3.2 --- Phase Formation and Crystal Structures --- p.66 / Chapter 4.3.2-1 --- Phase Evolution with Annealing Temperature --- p.67 / Chapter 4.3.2-2 --- Grain Size of Implanted Samples --- p.70 / Chapter 4.3.3 --- Magnetic Properties --- p.72 / Chapter 4.3.3-1 --- M-H Characteristics --- p.73 / Chapter 4.3.3-2 --- Coercivity Against Annealing Temperature --- p.74 / Chapter 4.3.3-3 --- Low Temperature Measurements --- p.79 / Chapter 4.3.3-4 --- Coercivity against annealing time --- p.79 / Chapter 4.3.4 --- Microstructure --- p.84 / Conclusion --- p.88 / Appendices --- p.90 / Bibliolography --- p.95 / Publications --- p.98

Wang Juan = 納米金顆粒與氧化鋁複合物薄膜光學吸收譜中的尺寸和濃度效應 / 王娟. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references (leaves 55-58). / Text in English; abstracts in English and Chinese. / Wang Juan = Na mi jin ke li yu yang hua lv fu he wu bo mo guang xue xi shou pu zhong de chi cun he nong du xiao ying / Wang Juan. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgment --- p.iii / Table of contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.ix / Chapter CHAPTER 1: --- Introduction --- p.1 / Chapter CHAPTER 2: --- Background --- p.3 / Chapter 2.1 --- Optical response of metal-particle/matrix composite system in an electronic field --- p.3 / Chapter 2.1.1 --- The concept of plasmon and the dielectric function of metal particle --- p.3 / Chapter 2.1.2 --- The concept of surface plasmon resonance --- p.4 / Chapter 2.2 --- The theories describing the optical absorption properties of metal particle/matrix composite system --- p.5 / Chapter 2.2.1 --- The Mie theory --- p.5 / Chapter 2.2.2 --- The Maxwell-Garnett (M.G.) effective medium theory --- p.6 / Chapter 2.3 --- Previous experimental works in the field --- p.7 / Chapter CHAPTER 3: --- Experimental and instrumentation --- p.8 / Chapter 3.1 --- Fabrication of the Au-nanoparticle /A12O3-matrix composite thin films --- p.11 / Chapter 3.1.1 --- Sputtering techniques and radio-frequency magnetron sputtering --- p.11 / Chapter 3.1.2 --- Experimental set up and the deposition process --- p.13 / Chapter 3.2 --- The chemical and structural characterizations of the films --- p.14 / Chapter 3.2.1 --- X-ray Photoelectron Spectroscopy (XPS) --- p.14 / Chapter 3.2.2 --- X-ray Diffraction (XRD) --- p.15 / Chapter 3.2.3 --- Transmission Electron Microscopy (TEM) --- p.17 / Chapter 3.3 --- The optical absorption measurement: UV spectrometer --- p.21 / Chapter CHAPTER 4: --- Results and discussions --- p.23 / Chapter 4.1 --- General description of the as-prepared samples --- p.23 / Chapter 4.1.1 --- Chemical composition of the films --- p.23 / Chapter 4.1.2 --- General microstructure of the films and the relationship between the deposition parameters --- p.25 / Chapter 4.2 --- The optical absorption: relationship between the SPR absorption and the microstructure --- p.27 / Chapter 4.2.1 --- The shifting of the surface plasmon resonance --- p.27 / Chapter 4.2.1.1 --- The size effect on the SPR frequency shifting --- p.27 / Chapter 4.2.1.2 --- The concentration effect on the SPR frequency shifting --- p.42 / Chapter 4.2.2 --- The broadening of the surface plasmon resonance: size dependence of the relaxation time of free electrons --- p.51 / Chapter CHAPTER 5: --- Conclusions --- p.53 / Appendix --- p.54 / Reference --- p.55

Zhao Kun. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese. / Zhao Kun.

by Yueng Hiu Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaf 56). / Text in English; abstracts in English and Chinese. / by Yueng Hiu Wa. / Acknowledgements --- p.i / Abstract --- p.ii / 論文摘要 --- p.iii / Table of contents --- p.iv / List of Figures --- p.v / List of Tables --- p.vi / Chapter Chapter I --- Introduction / Chapter 1.1 --- Development of magnetoresistance materials --- p.1 / Chapter 1.1.1 --- Magnetoresistance (MR) --- p.1 / Chapter 1.1.2 --- Giant magnetoresistance (GMR) --- p.1 / Chapter 1.1.3 --- Colossal magnetoresistance (CMR) in rare-earth manganites ..… --- p.4 / Chapter 1.2 --- Our research motivation --- p.5 / Chapter 1.2.1 --- Scope of this thesis --- p.7 / Chapter Chapter II --- Instrumentation / Chapter 2.1 --- Vacuum annealing system --- p.8 / Chapter 2.2 --- X-ray diffraction (XRD) --- p.11 / Chapter 2.3 --- Rutherford backscattering spectroscopy --- p.13 / Chapter Chapter III --- Oxygen diffusion / Chapter 3.1 --- Introduction --- p.15 / Chapter 3.2 --- Theory --- p.16 / Chapter 3.3 --- Experimental --- p.21 / Chapter 3.4 --- Result and discussion --- p.24 / Chapter Chapter IV --- Vacuum annealing effect in La0.67Ca0.33Mn03 thin films / Chapter 4.1 --- Introduction --- p.31 / Chapter 4.2 --- Principles of resonant RBS and ion channeling --- p.32 / Chapter 4.2.1 --- Resonant RBS and its application / Chapter 4.2.2 --- Ion channeling and its application / Chapter 4.3 --- Experimental --- p.39 / Chapter 4.4 --- Data analysis and discussion --- p.48 / Chapter 4.5 --- Conclusion --- p.50 / Chapter Chapter V --- Conclusion

by Li Ho. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Li Ho. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vi / List of Tables --- p.viii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Magnetoresistance --- p.1 / Chapter 1.1.1 --- Giant magnetoresistance (GMR) --- p.3 / Chapter 1.1.2 --- Colossal magnetoresistance (CMR) in perovskite manganites --- p.5 / Chapter 1.1.2.1 --- Perovskite-type structure --- p.5 / Chapter 1.1.2.2 --- Metal-insulator transition --- p.7 / Chapter 1.1.2.3 --- Possible origin of CMR --- p.11 / Chapter 1.2 --- Low field magnetoresistance in CMR materials --- p.12 / Chapter 1.2.1 --- Single crystal and polycrystalline perovskite manganites --- p.12 / Chapter 1.2.2 --- Manganite trilayer junctions --- p.13 / Chapter 1.2.3 --- Possible mechanism of low field MR --- p.15 / Chapter 1.3 --- Our motivation --- p.15 / Chapter 1.3.1 --- Brief review of several manganite multilayer systems --- p.16 / Chapter 1.3.2 --- Scope of this thesis work --- p.18 / Reference --- p.19 / Chapter Chapter 2 --- Preparation and characterization of manganite thin films / Chapter 2.1 --- Thin film deposition --- p.22 / Chapter 2.1.1 --- Facing-target sputtering (FTS) --- p.22 / Chapter 2.1.2 --- Vacuum system --- p.25 / Chapter 2.2 --- Fabrication and characterization of PCMO and LCMO targets --- p.27 / Chapter 2.3 --- Epitaxial growth of LCMO thin films --- p.31 / Chapter 2.3.1 --- Substrate materials --- p.31 / Chapter 2.3.2 --- Deposition conditions --- p.32 / Chapter 2.3.3 --- Deposition procedure --- p.33 / Chapter 2.3.4 --- Results and discussions --- p.34 / Chapter 2.3.4.1 --- Morphology --- p.35 / Chapter 2.3.4.2 --- Structure --- p.39 / Chapter 2.3.4.3 --- Transport properties --- p.42 / Chapter 2.3.4.4 --- Conclusion --- p.48 / Chapter 2.4 --- Epitaxial growth of PCMO thin films --- p.49 / References --- p.51 / Chapter Chapter 3 --- LCMO/PCMO multilayer / Chapter 3.1 --- Sample preparation --- p.53 / Chapter 3.2 --- Results and discussion --- p.53 / Chapter 3.2.1 --- Structure characterization --- p.55 / Chapter 3.2.2 --- Transport properties --- p.59 / Chapter 3.2.3 --- Low-field magnetoresistance --- p.55 / Chapter 3.2.4 --- Magnetization --- p.73 / Chapter 3.3 --- Conclusion --- p.76 / References --- p.77 / Chapter Chapter 4 --- Conclusions --- p.78

Made available in DSpace on 2014-06-11T19:31:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-12-05Bitstream added on 2014-06-13T20:41:14Z : No. of bitstreams: 1 lima_ec_dr_ilha.pdf: 2673140 bytes, checksum: 4fe5d64f1442666680854f09eb619017 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O sistema ferroelétrico PbZr1-xTixO3 (PZT) vem sendo amplamente estudado devido às interessantes propriedades físicas para composições próximas ao Contorno de Fases Morfotrópico (CFM). A compreensão da fenomenologia de filmes ferroelétricos está atualmente sob intensa investigação, pois o fenômeno da ferroeletricidade exibe uma dependência intrínseca com relação à dimensão das amostras. O processamento de filmes é muito importante para o desenvolvimento da miniaturização de dispositivos eletrônicos com baixo consumo de energia e baixa tensão de operação. Desta forma, os métodos químicos tem tido grande evolução com respeito à obtenção de filmes com boa homogeneidade e cristalinidade. As temperaturas de pirólise e de cristalização desempenham um papel fundamental na cristalinidade dos filmes. Devido às altas temperaturas de obtenção dos filmes produzidos com os métodos químicos, a volatilidade do óxido de chumbo no sistema PZT torna-se um problema fundamental para discussão. Esta observação evidenciou a presença de uma fase indesejada intitulada pirocloro. A resposta dielétrica e ferroelétrica dos filmes obtidos com a fase pirocloro revela uma degradação destas propriedades. Para contornar o problema várias hipóteses foram testadas a fim de encontrar um meio para supressão da fase pirocloro. Desta forma, a síntese dos filmes foi empregada de forma a estudar o desempenho do excesso de óxido de chumbo em função da temperatura de pirólise para diferentes substratos. A transformação da fase pirocloro para perovskita foi reportada em função da temperatura de pirólise. Diferentes técnicas experimentais foram utilizadas neste estudo visando mapear a estrutura cristalina de longo e curto alcance ao longo da espessura dos filmes, o stress/strain residual em torno da interface... / The system ferroelectric PbZr1-xTixO3 (PZT) has been widely studied due to interesting physical properties for compositions near the Morphotropic Phase Boundary (MPB). The understanding of the phenomenology of ferroelectric films is currently under intense investigation, because the phenomenon of ferroelectricity shows an intrinsic dependence with respect to sample size. The film processing is very important for the development of miniaturization of electronic devices with low power consumption and low voltage operation. Therefore, chemical methods have had great progress with respect to obtaining films with good homogeneity and crystallinity. The pyrolysis temperature and crystallization play a key role in the crystallinity of the films. Due to high temperatures for obtaining films with chemical methods, the volatility of lead oxide in the PZT system becomes a fundamental problem for discussion. This observation revealed the presence of an unwanted entitled pyrochlore phase. The ferroelectric and dielectric response of the films obtained with the pyrochlore phase shows a degradation of these properties. To overcome this problem several hypotheses were tested in order to find a way to suppress the pyrochlore phase. Thus, the synthesis of the films was employed in order to study the performance of the excess lead oxide as a function of pyrolysis temperature for different substrates. The transformation of pyrochlore to perovskite phase was reported as a function of pyrolysis temperature. Different experimental techniques were used in this study to map the crystal structure of long and short range along the different thicknesses of the films, the stress/strain residual around the interface film/substrate, morphology, electrical properties, piezoelectric and ferroelectric films. The integrated analysis of the results aims to understand the phenomenology associated with the origins of self-polarization in ferroelectric thin films

Orientador: Eudes Borges de Araújo / Banca: José de los Santos Guerra / Banca: Keizo Yukimitu / Banca: Antonio Sergio Bezerra Sombra / Banca: José Antonio Eiras / Resumo: O sistema ferroelétrico PbZr1-xTixO3 (PZT) vem sendo amplamente estudado devido às interessantes propriedades físicas para composições próximas ao Contorno de Fases Morfotrópico (CFM). A compreensão da fenomenologia de filmes ferroelétricos está atualmente sob intensa investigação, pois o fenômeno da ferroeletricidade exibe uma dependência intrínseca com relação à dimensão das amostras. O processamento de filmes é muito importante para o desenvolvimento da miniaturização de dispositivos eletrônicos com baixo consumo de energia e baixa tensão de operação. Desta forma, os métodos químicos tem tido grande evolução com respeito à obtenção de filmes com boa homogeneidade e cristalinidade. As temperaturas de pirólise e de cristalização desempenham um papel fundamental na cristalinidade dos filmes. Devido às altas temperaturas de obtenção dos filmes produzidos com os métodos químicos, a volatilidade do óxido de chumbo no sistema PZT torna-se um problema fundamental para discussão. Esta observação evidenciou a presença de uma fase indesejada intitulada pirocloro. A resposta dielétrica e ferroelétrica dos filmes obtidos com a fase pirocloro revela uma degradação destas propriedades. Para contornar o problema várias hipóteses foram testadas a fim de encontrar um meio para supressão da fase pirocloro. Desta forma, a síntese dos filmes foi empregada de forma a estudar o desempenho do excesso de óxido de chumbo em função da temperatura de pirólise para diferentes substratos. A transformação da fase pirocloro para perovskita foi reportada em função da temperatura de pirólise. Diferentes técnicas experimentais foram utilizadas neste estudo visando mapear a estrutura cristalina de longo e curto alcance ao longo da espessura dos filmes, o stress/strain residual em torno da interface... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The system ferroelectric PbZr1-xTixO3 (PZT) has been widely studied due to interesting physical properties for compositions near the Morphotropic Phase Boundary (MPB). The understanding of the phenomenology of ferroelectric films is currently under intense investigation, because the phenomenon of ferroelectricity shows an intrinsic dependence with respect to sample size. The film processing is very important for the development of miniaturization of electronic devices with low power consumption and low voltage operation. Therefore, chemical methods have had great progress with respect to obtaining films with good homogeneity and crystallinity. The pyrolysis temperature and crystallization play a key role in the crystallinity of the films. Due to high temperatures for obtaining films with chemical methods, the volatility of lead oxide in the PZT system becomes a fundamental problem for discussion. This observation revealed the presence of an unwanted entitled pyrochlore phase. The ferroelectric and dielectric response of the films obtained with the pyrochlore phase shows a degradation of these properties. To overcome this problem several hypotheses were tested in order to find a way to suppress the pyrochlore phase. Thus, the synthesis of the films was employed in order to study the performance of the excess lead oxide as a function of pyrolysis temperature for different substrates. The transformation of pyrochlore to perovskite phase was reported as a function of pyrolysis temperature. Different experimental techniques were used in this study to map the crystal structure of long and short range along the different thicknesses of the films, the stress/strain residual around the interface film/substrate, morphology, electrical properties, piezoelectric and ferroelectric films. The integrated analysis of the results aims to understand the phenomenology associated with the origins of self-polarization in ferroelectric thin films / Doutor

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