Kong, Yu Chau = La₂/₃Ca₁/₃MnO₃/Y₂O₃和La₂/₃Ca₁/₃MnO₃/Gd₂O多層薄膜及其三文治結構的傳導特性之研究 / 江如秋. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstract also in Chinese. / Kong, Yu Chau = La₂/₃Ca₁/₃MnO₃/Y₂O₃ he La₂/₃Ca₁/₃MnO₃/Gd₂O duo ceng bo mo ji qi san wen zhi jie gou de chuan dao te xing zhi yan jiu / Jiang Ruqiu. / Abstract --- p.i / 論文摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.x / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction to Magnetoresistance --- p.1 / Chapter 1.1.1 --- Anisotropic magnetoresistance (AMR) --- p.3 / Chapter 1.1.2 --- Giant magnetoresistance (GMR) --- p.3 / Chapter 1.1.3 --- Colossal magnetoresistance (CMR) --- p.5 / Chapter 1.1.4 --- Tunneling magnetoresistance (TMR) --- p.7 / Chapter 1.2 --- Possible origins of CMR in doped manganite --- p.8 / Chapter 1.2.1 --- Double exchange mechanism --- p.10 / Chapter 1.2.2 --- Jahn-Teller (JT) distortion --- p.14 / Chapter 1.2.3 --- Tolerance factor --- p.16 / Chapter 1.2.4 --- Charge Ordering and percolation theory --- p.18 / Chapter 1.3 --- Motivation --- p.21 / Chapter 1.4 --- Literature Review --- p.23 / Chapter 1.4.1 --- Multilayers --- p.23 / Chapter 1.4.2 --- Junction --- p.25 / Chapter 1.5 --- Scope of this thesis --- p.26 / References --- p.27 / Chapter Chapter 2 --- Instrumentation / Chapter 2.1 --- Thin film deposition --- p.30 / Chapter 2.1.1 --- Facing target sputtering (FTS) --- p.31 / Chapter 2.1.2 --- Vacuum system --- p.33 / Chapter 2.2 --- Oxygen annealing --- p.35 / Chapter 2.3 --- Characterization --- p.35 / Chapter 2.3.1 --- Alpha step profilometer --- p.35 / Chapter 2.3.2 --- X-ray diffraction (XRD) --- p.36 / Chapter 2.3.3 --- Transport measurement --- p.39 / Reference --- p.41 / Chapter Chapter 3 --- Epitaxial growth of La2/3Ca1/3MnO3 and rare earth oxide single layer thin films / Chapter 3.1 --- Introduction --- p.42 / Chapter 3.2 --- Preparation of sputtering targets of rare earth metal and La2/3Ca1/3MnO3 --- p.42 / Chapter 3.3 --- Epitaxial growth of LCMO and Re2O3 thin film --- p.44 / Chapter 3.3.1 --- Substrate materials --- p.44 / Chapter 3.3.2 --- Deposition conditions --- p.45 / Chapter 3.3.3 --- Deposition procedures --- p.48 / Chapter 3.4 --- Characterization of single layer thin films --- p.49 / Chapter 3.5 --- Discussion --- p.52 / References --- p.53 / Chapter Chapter 4 --- LCMO/Y2O3 and LCM0/Gd203 multilayers / Chapter 4.1 --- Sample preparation --- p.54 / Chapter 4.2 --- As-deposited multilayers --- p.56 / Chapter 4.2.1 --- Structural Characterization --- p.56 / Chapter 4.2.2 --- Transport properties --- p.62 / Chapter 4.3 --- Oxygen annealing --- p.67 / Chapter 4.3.1 --- Introduction --- p.67 / Chapter 4.3.2 --- Post-annealing condition --- p.68 / Chapter 4.4 --- Oxygen post-annealed multilayers --- p.69 / Chapter 4.4.1 --- Structural Characterization --- p.69 / Chapter 4.4.2 --- Transport properties --- p.76 / Chapter 4.5 --- Discussion --- p.85 / References --- p.86 / Chapter Chapter 5 --- LCMO/Y2O3/LCMO trilayer sandwiches / Chapter 5.1 --- Introduction --- p.88 / Chapter 5.2 --- Sample preparation --- p.89 / Chapter 5.3 --- Current-Voltage (I-V) measurement --- p.90 / References --- p.92 / Chapter Chapter 6 --- Conclusion / Chapter 6.1 --- Summary --- p.93 / Chapter 6.2 --- Further work --- p.94

by Zhu, Ming. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references (leaves 73). / Abstracts in English and Chinese. / ABSTRATE (ENGLISH) --- p.I / ABSTRATE (CHINESE) --- p.III / ACKNOWLEDGEMENTS --- p.V / TABLE OF CONTENTS --- p.VI / Chapter 1. --- Introduction --- p.1 / Chapter 1.1 --- Introduction to organic semiconductors --- p.1 / Chapter 1.2 --- Charge transport in organic semiconductors --- p.1 / Chapter 1.2.1 --- Polaron models --- p.2 / Chapter 1.2.2 --- Scher-Montroll model --- p.2 / Chapter 1.2.3 --- Gaussian disorder model --- p.3 / Chapter 1.3 --- Organic semiconductors in this thesis --- p.5 / Chapter 1.4 --- Several key issues --- p.6 / References --- p.7 / Chapter 2. --- Experimental Techniques --- p.9 / Chapter 2.1 --- Materials Purification --- p.9 / Chapter 2.1.1 --- Motivation --- p.9 / Chapter 2.1.2 --- Basic principle --- p.9 / Chapter 2.1.3 --- Purification setup --- p.10 / Chapter 2.1.4 --- Parameters optimization --- p.11 / Chapter 2.2 --- Sample Fabrication --- p.11 / Chapter 2.2.1 --- Substrate treatment --- p.12 / Chapter 2.2.2 --- Thermal vacuum evaporation --- p.12 / Chapter 2.2.3 --- Spin coating --- p.12 / Chapter 2.3 --- Electrical measurement techniques --- p.13 / Chapter 2.3.1 --- J-V characteristics --- p.13 / Chapter 2.3.1.1 --- Injection versus bulk limited current --- p.13 / Chapter 2.3.1.2 --- Space Charge Limited Current --- p.15 / Chapter 2.3.1.3 --- Trap controlled Space Charge Limited Current --- p.15 / Chapter 2.3.2 --- Admittance spectroscopy --- p.17 / References --- p.20 / Chapter 3. --- Steady state J-V characteristics of organic thin films in sandwiched structures --- p.22 / Chapter 3.1 --- Experimental --- p.22 / Chapter 3.2 --- Results and discussions --- p.23 / Chapter 3.2.1 --- J-V characteristics of CuPc and TPD-PS thin films --- p.23 / Chapter 3.2.2 --- J-V characteristics of CuPc thin films with different cathodes --- p.26 / Chapter 3.2.3 --- Variable temperature J-V characteristics of CuPc thin films --- p.28 / References --- p.31 / Chapter 4. --- Dynamic Properties of Organic Semiconductors Performed by Admittance Spectroscopy --- p.32 / Chapter 4.1 --- Introduction to admittance spectroscopy --- p.32 / Chapter 4.2 --- Theoretical models --- p.32 / Chapter 4.3 --- Experimental --- p.36 / Chapter 4.3.1 --- Experimental scheme --- p.36 / Chapter 4.3.2 --- Sample preparation --- p.36 / Chapter 4.4 --- Results and discussion --- p.37 / Chapter 4.4.1 --- Unpurified CuPc --- p.37 / Chapter 4.4.2 --- Purified CuPc --- p.40 / Chapter 4.5 --- Conclusion --- p.43 / References --- p.44 / Chapter 5. --- Air-induced Trap Effect in Organic Semiconductors --- p.45 / Chapter 5.1 --- Introduction to negative capacitance phenomenon --- p.45 / Chapter 5.2 --- Experimental --- p.46 / Chapter 5.3 --- Results and discussion --- p.46 / Chapter 5.3.1 --- Admittance spectroscopy with different electrodes --- p.46 / Chapter 5.3.2 --- Admittance spectroscopy with different concentrations of oxygen --- p.48 / Chapter 5.3.3 --- Admittance spectroscopy with different humidities --- p.50 / Chapter 5.4 --- Conclusion --- p.53 / References --- p.56 / Chapter 6. --- N-type Doping of Magnesium to Zinc-Phthalocyanine (ZnPc) --- p.58 / Chapter 6.1 --- Introduction --- p.58 / Chapter 6.2 --- Experimental --- p.60 / Chapter 6.3 --- Results and discussion --- p.61 / Chapter 6.4 --- Conclusion --- p.66 / References: --- p.67 / Chapter 7. --- Summary and future work --- p.68 / Summary --- p.68 / Future work --- p.69 / References: --- p.72 / Appendix --- p.73

Yuen, Ying Kit. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 90-96). / Abstracts in English and Chinese. / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Introduction to Electron Field Emission --- p.1 / Chapter 1.2 --- Theory of Electron Field Emission --- p.4 / Chapter 1.3 --- Fowler Nordheim Model for Electron Field Emission in Metals --- p.5 / Chapter 1.4 --- Factors Affecting the Field Emission Properties --- p.7 / Chapter 1.4.1 --- Surface Morphology --- p.7 / Chapter 1.4.2 --- Electrical Inhomogeneity --- p.7 / Chapter 1.5 --- Goal of this Project --- p.9 / Chapter Chapter 2 --- Sample Preparation and Characterization Methods / Chapter 2.1 --- Sample Preparation --- p.11 / Chapter 2.1.1 --- MEVVA Ion Implantation System --- p.13 / Chapter 2.1.2 --- TRIM Simulation --- p.17 / Chapter 2.1.3 --- Implantation Conditions --- p.19 / Chapter 2.2 --- Characterization Methods --- p.21 / Chapter 2.2.1 --- AFM - Atomic Force Microscopy --- p.21 / Chapter 2.2.2 --- C-AFM ´ؤ Conducting Atomic Force Microscopy --- p.23 / Chapter 2.2.3 --- RBS - Rutherford Backscattering Spectrometry --- p.23 / Chapter 2.2.4 --- TEM - Transmission Electron Microscopy --- p.26 / Chapter 2.2.5 --- Field Emission Measurement --- p.27 / Chapter Chapter 3 --- Field Emission Properties of Co-Si02 / Chapter 3.1 --- Introduction --- p.29 / Chapter 3.2 --- RBS results --- p.30 / Chapter 3.3 --- Experimental results of as-implanted Co-SiO2 samples --- p.32 / Chapter 3.3.1 --- AFM and results --- p.32 / Chapter 3.3.2 --- Field emission properties of as-implanted Co-Si02 --- p.35 / Chapter 3.4 --- Step-like and jump-like features in the J-E plots --- p.39 / Chapter 3.5 --- Chapter Summary --- p.43 / Chapter Chapter 4 --- Field Emission Properties of Fe-SiO2 / Chapter 4.1 --- Introduction --- p.45 / Chapter 4.2 --- RBS results --- p.46 / Chapter 4.3 --- Experimental results of as-implanted Fe-SiO2 samples --- p.48 / Chapter 4.3.1 --- AFM and results --- p.48 / Chapter 4.3.2 --- Field emission properties of as-implanted Fe-SiO2 --- p.51 / Chapter 4.3.3 --- Comparison with as-implanted Co-SiO2 --- p.54 / Chapter 4.4 --- Experimental results of annealed Fe-SiO2 samples --- p.57 / Chapter 4.4.1 --- Annealing conditions --- p.57 / Chapter 4.4.2 --- AFM and C-AFM results --- p.57 / Chapter 4.4.3 --- TEM Images --- p.62 / Chapter 4.4.4 --- Field emission properties of annealed Fe-SiO2 --- p.68 / Chapter 4.5 --- Step-like and jump-like features in the J-E plots --- p.81 / Chapter 4.6 --- Field Emission Images --- p.84 / Chapter 4.7 --- Chapter Summary --- p.85 / Chapter Chapter 5 --- Conclusion & Future Plan --- p.87 / Reference --- p.90 / Appendix / Chapter A. --- Derivation of the Fowler Nordheim Equation --- p.97

Spintronics reaches beyond typical charge-based information storage technologies by utilizing an addressable degree of freedom for electron manipulation, the electron spin polarization. With mounting experimental data and improved theoretical understanding of spin manipulation, spintronics has become a potential alternative to charge-based technologies. However, for a long time, spintronics was not thought to be feasible without the ability to electrostatically control spin conductance at room temperature. Only recently, graphene, a 2D honeycomb crystalline allotrope of carbon only one atom thick, was identified because of its predicted, long spin coherence length and experimentally realized electrostatic gate tunability. However, there exist several challenges with graphene spintronics implementation including weak spin-orbit coupling that provides excellent spin transfer yet prevents charge to spin current conversion, and a conductivity mismatch due to the large difference in carrier density between graphene and a ferromagnet (FM) that must be mitigated by use of a tunnel barrier contact. Additionally, the usage of graphene produced via CVD methods amenable to semiconductor industry in conjunction with graphene spin valve fabrication must be explored in order to promote implementation of graphene-based spintronics. Despite advances in the area of graphene-based spintronics, there is a lack of understanding regarding the coupling of industry-amenable techniques for both graphene synthesis and lateral spin valve fabrication. In order to make any impact on the application of graphene spintronics in industry, it is critical to demonstrate wafer-scale graphene spin devices enabled by wafer-scale graphene synthesis, which utilizes thin film, wafer-supported CVD growth methods. In this work, high-quality graphene was synthesized using a vertical cold-wall furnace and catalyst confinement on both SiO2/Si and C-plane sapphire wafers and the implementation of the as-grown graphene for fabrication of graphene-based non-local spin valves was examined. Optimized CVD graphene was demonstrated to have ID/G ≈ 0.04 and I2D/G ≈ 2.3 across a 2" diameter graphene film with excellent continuity and uniformity. Since high-quality, large-area, and continuous CVD graphene was grown, it enabled the fabrication of large device arrays with 40 individually addressable non-local spin valves exhibiting 83% yield. Using these arrays, the effects of channel width and length, ferromagnetic-tunnel barrier width, tunnel barrier thickness, and level of oxidation for Ti-based tunnel barrier contacts were elucidated. Non-local, in-plane magnetic sweeps resulted in high signal-to-noise ratios with measured ΔRNL across the as-fabricated arrays as high as 12 Ω with channel lengths up to 2 µm. In addition to in-plane magnetic field spin signal values, vertical magnetic field precession Hanle effect measurements were conducted. From this, spin transport properties were extracted including: spin polarization efficiency, coherence lifetime, and coherence distance. The evaluation of industry-amenable production methods of both high-quality graphene and lateral graphene non-local spin valves are the first steps toward promoting the feasibility of graphene as a lateral spin transport interconnect material in future spintronics applications. By addressing issues using a holistic approach, from graphene synthesis to spin transport implementation, it is possible to begin assessment of the challenges involved for graphene spintronics.

Transparent conductive oxides (TCOs) and polycrystalline silicon (poly-Si) thin-films are very promising for application in photovoltaics. It is extremely challenging to develop cheap TCOs and poly-Si films to make photovoltaic devices. The aim of this thesis is to study sputtered aluminum-doped ZnO TCO and poly-Si films by solid-phase crystallization (SPC) for application in low-cost photovoltaics. The investigated aspects have been (i) to develop and characterize sputtered aluminum-doped ZnO (ZnO:Al) films that can be used as a TCO material on crystalline silicon solar cells, (ii) to explore the potential of the developed ZnO:Al films for application in ZnO:Al/c-Si heterojunction solar cells, (iii) to make and characterize poly-Si thin-films on different kinds of glass substrates by SPC using electron-beam evaporated amorphous silicon (a-Si) [referred to as EVA poly-Si material (SPC of evaporated a-Si)], and (iv) to fabricate EVA poly-Si thin-film solar cells on glass and improve the energy conversion efficiency of these cells by post-crystallization treatments. The ZnO:Al work in this thesis is focused on the correlation between film characteristics and deposition parameters, such as rf sputter power (Prf), working gas pressure (Pw), and substrate temperature (Tsub), to get a clear picture of film properties in the optimized conditions for application in photovoltaic devices. Especially the laterally non-uniform film properties resulting from the laterally inhomogeneous erosion of the target material are investigated in detail. The influence of Prf, Pw and Tsub on the structural, electrical, optical and surface morphology properties of ZnO:Al films is discussed. It is found that the lateral variations of the parameters of ZnO:Al films prepared by rf magnetron sputtering can be reduced to acceptable levels by optimising the deposition parameters. ZnO:Al/c-Si heterojunction solar cells are fabricated and characterized to demonstrate the feasibility of the fabricated ZnO:Al films for application in heterojunction solar cells. In this application, expensive indium-tin oxide (ITO) is usually used. Under the standard AM1.5G spectrum (100 mW/cm2, 25 ??C), the best fabricated cell shows an open-circuit voltage of 411 mV, a short-circuit current density of 30.0 mA/cm2, a fill factor of 66.7 %, and a conversion efficiency of 8.2 %. This is believed to be the highest stable efficiency ever reported for this type of cell. By means of dark forward current density-voltage-temperature (J-V-T) measurements, it is shown that the dominant current transport mechanism in the ZnO:Al/c-Si solar cells, in the intermediate forward bias voltage region, is trap-assisted multistep tunneling. EVA poly-Si thin-films are prepared on four types of glass substrates (planar and textured glass, both either bare or SiN-coated) based on evaporated Si, which is a cheaper Si deposition method than the existing technologies. The textured glass is realized by the UNSW-developed AIT process (AIT = aluminium-induced texture). The investigation is concentrated on finding optimized process parameters and evaluating film crystallization quality. It is found that EVA poly-Si films have a grain size in the range 0.8-1.5 ??m, and a preferential (111) orientation. UV reflectance and Raman spectroscopy measurements reveal a high crystalline material quality, both at the air-side surface and in the bulk. EVA cells are fabricated in both substrate and superstrate configuration. Special attention is paid to improving the Voc of the solar cells. For this purpose, after the SPC process, the samples receive the two post-crystallization treatments: (i) a rapid thermal anneal (RTA), and (ii) a plasma hydrogenation. It is found that two post-crystallization treatments more than double the 1-Sun Voc of the substrate-type cells. It is demonstrated that RTA improves the structural material quality of the cells. Furthermore, a hydrogenation step is shown to significantly improve the electronic material quality of the cells. Based on the RTA???d and hydrogenated EVA poly-Si material, the first mesa-type EVA cells are fabricated in substrate configuration, by using sputtered Al-doped ZnO as the transparent front contact. The investigation is focused on addressing the correlation between the type of the substrate and cell performance. Optical, electrical and photovoltaic properties of the devices are characterized. It is found that the performance of EVA cells depends on the glass substrate topography. For cells on textured glass, the AIT texture is shown to have a beneficial effect on the optical absorption of EVA films. It is demonstrated that a SiN barrier layer on the AIT-textured glass improves significantly both the crystalline quality of the poly-Si films and the energy conversion efficiency of the resulting solar cells. For cells on planar glass, a SiN film between the planar glass and the poly-Si film has no obvious effect on the cell properties. The investigations in this thesis clearly show that EVA poly-Si films are very promising for poly-Si thin-film solar cells on glass.

TiN is used commercially as a wear resistant coating on cutting tools and as a diffusion barrier in microelectronics. TiN has gained increased interest as a material for MEMS, however there has been very little work carried out in the area of patterning and releasing TiN for use as a structural MEMS material. This thesis presents an investigation into the patterning and release of filtered arc deposited TiN thin films using surface micromachining techniques. Two novel strategies are presented for patterning TiN thin films and are achieved using excimer laser micromachining and photolithographic wet-etching. TiN was deposited onto single crystal Si and Cr and Cu sacrificial layers on Si. The use of Cr as a sacrificial layer was found to facilitate the best quality patterning of the TiN and hence the majority of the work involved using Cr sacrificial layers. TiN was deposited using partial filtration and full filtration and differences in the ability to selectively laser pattern the TiN from the Cr sacrificial layer are presented. Various analytical techniques were employed to investigate the origin of the difference in laser patterning the TiN thin films. The establishment of TiN and Cr as a novel material combination for surface micromachined MEMS was extended by etching the Cr sacrificial layer to facilitate the release of TiN stress-measurement structures. The major finding of this thesis is that filtered arc deposited TiN thin film on Cr can be used as a material combination to surface micromachine freestanding TiN structures as high quality patterning and etch selectivity can be achieved using both excimer laser micromachining and photolithographic wet-etching.

Thesis (Ph.D.)--University of Delaware, 2007. / Principal faculty advisor: Siu-Tat Chui, Dept. of Physics & Astronomy. Includes bibliographical references.

Graduation date: 2005

Graduation date: 2003

Graduation date: 1995