Three novel donor-acceptor systems have been characterised through their spectroscopic properties, magnetic susceptibility, conductivity and second harmonic generation. The magnetic properties of (H2DPE)xx+(DPE)^ x(TCNQ)gX and (H2DPA)xx+(DPA) 1 x(TCNQ)gX' where DPE = 1,2-di(4-pyridyl)ethylene, DPA = 1,2-di(4-pyridyl)ethane, TCNQ = tetracyanoquinodimethane and H2 signifies proton diquaternisation, have been found to depend upon the stoichiometry: For x > \ the magnetic susceptibility decreases with increasing x whereas for x ~ \ it is anomolously large, being ferromagnetically enhanced above the Curie Law value. A possible model involving spin dilution is proposed and its predictions are compared with the experimental results. Langmuir-Blodgett (LB) films of the long-chained analogues of the materials, (C^g)2DPE (TCNQ) 2 and (Cig^DPE^TCNQ)^" where (C16) 2 = bis(hexadecyl) were deposited and characterised. The conductivities of the LB films of the mixed valence system were found to be ~ 1000 times greater than those of the system lacking TCNQ^ molecules. Multiple layer LB films of trans-4-[4- (dimethylamino)styryl]-1- octadecylpyridinium iodide and trans-4-[4-(dimethylamino)styryl]-1- octadecylquinolinium iodide interleaved with 4,4'-dioctadecyl-3,5,3',5' -tetramethyldipyrrylmethene hydrobromide were deposited. The materials form an interlocking bilayer structure which renders their LB films exceptionally well-organised. The films’ second harmonic generation was investigated and one film was found to give the largest second harmonic signal yet seen from an LB structure.

by So-kuen C. Liew. / Thesis (Ph.D.)--Chinese University of Hong Kong, 1995. / Includes bibliographical references (leaves [40-45, 3rd gp.]) and index. / Abstract --- p.ii / Acknowledgments --- p.iv / Table of Contents --- p.v / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Distributed Feedback Lasers --- p.1 / Chapter 1.2 --- Computer Model --- p.6 / Chapter 1.3 --- Analyses --- p.8 / Chapter 1.4 --- Organization of Thesis --- p.11 / Chapter 2 --- Computer Model --- p.13 / Chapter 2.1 --- Comparison of Theoretical Models --- p.15 / Chapter 2.2 --- Assumptions and Approximations --- p.17 / Chapter 2.2.1 --- Longitudinal Spatial Hole Burning --- p.17 / Chapter 2.2.2 --- Spontaneous Emission --- p.18 / Chapter 2.2.3 --- Nonlinear Gain Saturation --- p.19 / Chapter 2.2.4 --- Carrier-Induced Index Change --- p.20 / Chapter 2.2.5 --- Single-mode Operation Assumption --- p.22 / Chapter 2.2.6 --- Otbers --- p.22 / Chapter 2.3 --- Theories and Approaches --- p.25 / Chapter 2.3.1 --- Coupled Wave Theory --- p.25 / Description --- p.25 / Stop-Band --- p.29 / Second-Order DFB Laser --- p.30 / DFB Designs To Improve SMSR --- p.30 / Chapter 2.3.2 --- Transfer Matrix Approach --- p.32 / Chapter 2.4 --- Above-Threshold Model --- p.34 / Chapter 2.4.1 --- Introduction --- p.34 / Chapter 2.4.2 --- Formalism --- p.36 / Facet Output Power and Optical Spectrum --- p.39 / Photon Density Distribution --- p.41 / Variance of Photon Density Distribution --- p.42 / Nearfield Distribution --- p.42 / Surface Emission --- p.43 / Power-Current Characteristics --- p.44 / Optical spectrum --- p.45 / Subthreshold Analysis --- p.47 / Linear Yield Analysis --- p.47 / Chapter 2.4.3 --- Computer Implementation --- p.48 / Flowchart --- p.48 / Subroutines --- p.52 / "Runtime, Numerical Stability" --- p.56 / Chapter 2.5 --- "Discussion,Summary and Future Work" --- p.59 / Chapter 2.5.1 --- Validation of the DFB Model --- p.59 / Chapter 2.5.2 --- Summary --- p.67 / Chapter 2.5.3 --- Topics for Future Work in Theoretical Modeling --- p.68 / Chapter 3 --- Analysis of DFBDBR Laser --- p.72 / Chapter 3.1 --- Introduction --- p.72 / Chapter 3.2 --- Subthreshold Analysis --- p.78 / Chapter 3.2.1 --- Introduction --- p.78 / Chapter 3.2.2 --- Results --- p.81 / Symmetric End-Sections --- p.81 / Asymmetric End-Sections --- p.85 / Chapter 3.3 --- Above-threshold Analysis --- p.88 / Chapter 3.3.1 --- Analysis --- p.89 / Chapter 3.3.2 --- Length Ratio --- p.92 / Chapter 3.3.3 --- Design Plot --- p.99 / Chapter 3.3.4 --- Longitudinal Spatial Hole Burning --- p.102 / Chapter 3.3.5 --- Effective Linewidth Enhancement Factor --- p.104 / Chapter 3.3.6 --- Asymmetric DFBDBR --- p.107 / Chapter 3.4 --- Conclusion --- p.109 / Chapter 4 --- Analysis of Complex-Coupled DFB --- p.110 / Chapter 4.1 --- Introduction --- p.110 / Chapter 4.2 --- Laser Structure --- p.113 / Chapter 4.2.1 --- Grating Layer --- p.114 / Chapter 4.2.2 --- Parameter Values --- p.119 / Chapter 4.3 --- Above-Threshold Analysis of CCDFB --- p.122 / Chapter 4.3.1 --- Threshold Current --- p.122 / Grating Duty Cycle = 0.36 --- p.122 / Grating Duty Cycle = 0.15 --- p.128 / Chapter 4.3.2 --- Power Efficiency --- p.131 / Grating Duty Cycle = 0.36 --- p.131 / Grating Duty Cycle = 0.15 --- p.136 / Chapter 4.3.3 --- Summary --- p.137 / Chapter 4.4 --- Yield Analysis of LCDFB and QWDFB --- p.138 / Chapter 4.4.1 --- Introduction --- p.138 / Chapter 4.4.2 --- Method --- p.140 / Chapter 4.4.3 --- Results --- p.141 / Facet Phase Angle --- p.141 / Quarterwave Phase-Shifted DFB Laser --- p.144 / Loss-Coupled DFB Laser --- p.148 / Chapter 4.5 --- Conclusion --- p.154 / Chapter 5 --- Summary and Conclusion --- p.157 / Chapter 5.1 --- Summary --- p.157 / Chapter 5.1.1 --- Summary of Major Contributions --- p.157 / Chapter 5.1.2 --- Summary of Modeling and Validation --- p.159 / Chapter 5.1.3 --- Summary of Model Applications --- p.160 / DFBDBR Laser --- p.161 / Loss-Coupled DFB Laser --- p.162 / Chapter 5.2 --- Topics for Future Studies --- p.163 / References --- p.R-l / Appendices --- p.A-l / Chapter A. --- Derivations --- p.A-l / Chapter A.1 --- Noise Power --- p.A-l / Chapter A.2 --- Product of Field Vector and Its Adjoint --- p.A-2 / Chapter A.3 --- Gain-Coupling Coefficient --- p.A-5 / Chapter B. --- Subroutines in Computer Program --- p.A-8 / Chapter B.l --- Subroutines in 'drive.f' --- p.A-8 / Chapter B.2 --- Subroutines in 'Core.f' --- p.A-9 / Chapter B.3 --- Subroutines in 'initiaLf' --- p.A-13 / Chapter B.4 --- Subroutines in ´بmisc.f' --- p.A-14 / Chapter C. --- List of Figures --- p.A-17 / Chapter D. --- List of Tables --- p.A-22 / Chapter E. --- List of Abbreviations and Acronyms --- p.A-23 / Chapter F. --- List of Symbols --- p.A-24 / Chapter G. --- List of Publications --- p.A-27 / Index --- p.I-1

by Ho Hing Wa. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1999. / Includes bibliographical references. / Abstracts in English and Chinese. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Table of Contents --- p.v / Chapter 1 --- Introduction / Chapter 1.1 --- Background of optical generation of millimeter-waves --- p.1 -1 / Chapter 1.2 --- Application of the two-section DFB laser on optical generation of millimeter-waves --- p.1 -4 / Chapter 1.3 --- Analysis --- p.1-4 / Chapter 1.4 --- Organization of Thesis --- p.1 -5 / References --- p.1-6 / Chapter 2 --- Techniques of Optical Generation of Millimeter-waves / Chapter 2.1 --- Direct modulation and mode-locking of lasers --- p.2-1 / Chapter 2.2 --- Beating of two optical waves --- p.2-3 / References --- p.2-11 / Chapter 3 --- Experimental Results and Discussions / Chapter 3.1 --- Device structure and experimental setup --- p.3-1 / Chapter 3.2 --- Light-Current Characteristics of the two-section laser --- p.3-3 / Chapter 3.3 --- Spectral behaviours of the two-section DFB laser --- p.3-5 / Chapter 3.3.1 --- Linewidth of the two-section DFB laser --- p.3-5 / Chapter 3.3.2 --- Wavelength tuning of the two-section DFB laser --- p.3-5 / Chapter 3.3.3 --- Biasing conditions for the dual-mode oscillations --- p.3-16 / Chapter 3.4 --- Optical generation of millimeter-waves --- p.3-17 / Chapter 3.4.1 --- Mechanism of beating --- p.3-17 / Chapter 3.4.2 --- Generation of millimeter-waves by optical beating --- p.3-20 / Chapter 3.5 --- Optical Transmission of the millimeter-waves --- p.3-22 / References --- p.3-24 / Chapter 4 --- Theory of DFB Laser / Chapter 4.1 --- Development of DFB laser --- p.4-1 / Chapter 4.2 --- Structure of DFB laser --- p.4-2 / Chapter 4.3 --- Model of one-section DFB laser --- p.4-4 / Chapter 4.4 --- Analysis of two-section DFB laser --- p.4-10 / Chapter 4.4.1 --- Introduction of transfer matrix method --- p.4-11 / Chapter 4.4.2 --- Formulation of transfer matrix --- p.4-12 / Chapter 4.4.3 --- Application of the transfer matrix --- p.4-13 / References --- p.4-17 / Chapter 5 --- Numerical Analysis of the Spectral Behaviours of the Two-Section DFB Laser / Chapter 5.1 --- Solving the Transcendental Equation --- p.5-1 / Chapter 5.2 --- Simulation of the spectral behaviour of the two-section DFB laser --- p.5-4 / Chapter 5.2.1 --- Assumptions and Approximations --- p.5-4 / Chapter 5.2.2 --- Parameters --- p.5-5 / Chapter 5.2.3 --- Computer Implementation --- p.5-6 / Chapter 5.2.4 --- Results and Discussion --- p.5-7 / References --- p.5-14 / Chapter 6 --- Conclusion / Chapter 6.1 --- Summary --- p.6-1 / Chapter 6.2 --- Future works --- p.6-2 / Appendices / Appendix A Source code for simulation of spectral behaviours of the two-section DFB laser --- p.A-1

"The objective of this project was to extend fundamentally the current kp theory by applying the Burt-Foreman formalism, rather than the conventional Luttinger-Kohn formalism, to a number of novel nanostructure geometries. The theory itself was extended in two ways. First in the application of the Burt-Foreman theory to computing the momentum matrix elements. Second in the development of a new formulation of the multiband kp Hamiltonian describing cylindrical quantum dots. A number of new and interesting results have been obtained. The computational implementation using the finite difference method of the Burt-Foreman theory for two dimensional nanostructures has confirmed that a non-uniform grid is much more efficient, as had been obtained by others in one dimensional nanostructures. In addition we have demonstrated that the multiband problem can be very effectively and efficiently solved with commercial software (FEMLAB). Two of the most important physical results obtained and discussed in the dissertation are the following. One is the first ab initio demonstration of possible electron localization in a nanowire superlattice in a barrier material, using a full numerical solution to the one band kp equation. The second is the demonstration of the exactness of the Sercel-Vahala transformation for cylindrical wurtzite nanostructures. Comparison of the subsequent calculations to experimental data on CdSe nanorods revealed the important role of the linear spin splitting term in the wurtzite valence band."

"January 1998." / Thesis (Ph.D.)--Chinese University of Hong Kong, 1998. / 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. / Abstract in Chinese.

Este trabalho tem como objetivo principal, o estudo de técnicas de microscopia para a caracterização estrutural de semicondutores, visando o desenvolvimento das técnicas de preparação de amostras, visto que a caracterização estrutural é de suma importância para a obtenção de melhores resultados no processo de produção de filmes de semicondutores do grupo III-V. Dentre as técnicas mais utilizadas na caracterização estrutural, destacam-se as técnicas de microscopia eletrônica de varredura e de transmissão, juntamente com a microscopia de força atômica. Foram utilizadas amostras semicondutoras de InGaAs/GaAs e InAs/GaAs, crescidas pela técnica de MBE (epitaxia por feixe molecular), contendo pontos quânticos, estruturas estas ricas em detalhes. Tais amostras foram preparadas e caracterizadas em cada uma das técnicas em estudo. A microscopia de varredura e de força atômica apresentam fácil preparação. Os resultados obtidos, porém mostram que a técnica de microscopia eletrônica de varredura não oferece resolução suficiente para visualização das heteroestruturas; já a técnica de microscopia de força atômica mostra resultados excelentes da topografia dos pontos quânticos. Para a microscopia de transmissão a preparação de amostras mostra-se muito difícil e demorada, entretanto, o resultado obtido foi muito satisfatório. O processo de preparação passa por etapas de clivagem, \"dimpling\" e \"ion milling\". As imagens obtidas revelam com clareza a estrutura de pontos quântico. Com o estudo realizado, foi possível determinar as principais características de cada técnica, assim como determinar uma metodologia que pode vir a ser aplicada a outros tipos de heteroestruturas semicondutoras / This work has as main objective, the study of microscopy techniques for structural characterization of semiconductors and the development of the techniques of sample preparation, because the structural characterization is of highest importance for the obtaining of better results in the process of production of semiconductors thin films. The techniques more used in the structural characterization, are the techniques of electronic microscopy (Scanning and Transmission), together with the Atomic Force Microscopy. Samples of InGaAs/GaAs and InAs/GaAs were used, grown by the technique of MBE (Molecular Beam Epitaxy), with quantum dots, structures these rich ones in details. Such samples were prepared and characterized in each one of the techniques in study. The Scanning Microscopy and Atomic Force present easy preparation. The obtained results even so they show that the technique of Scanning Microscopy doesn\'t offer enough resolution for visualization of the heteroestructures; already the technique of Atomic Force shows excellent results of the topography of the quantum dots. For the Transmission Microscopy the preparation of samples is shown very difficult and delayed, however, the obtained result was very satisfactory. The preparation process goes by cutting stages, dimpling and ion milling. The obtained images reveal with clarity the quantum structure of points. With the accomplished study, it was possible to determine the main characteristics of each technique, as well as determining a methodology that can come to be applied to the other types of semiconductors heterostructures

Thin layer deposits of cadmium sulfide (CdS) for photovoltaic purposes can be made by cathodic deposition from a nonaqueous solution. There were numerous parameters that were controlled in this electro-deposition. Several of these parameters, including temperature, current density, reactant concentrations and impurity level doping, were studied and optimized. The mechanism of this deposition process is not fully understood, mainly due to the complex chemistry of sulfur. Part of this complexity is the presence of S(,6) and S(,7) along with the major component of S(,8) in sulfur solutions. At 90(DEGREES), these minor species constitute 2% of the total sulfur. Electrochemical studies were made on these species with gold, porous carbon and CdS single crystal electrodes. These showed that S(,6) and S(,7) are electrochemically more reactive than S(,8). Furthermore, they may be the main reacting species in CdS formation, even though they are present at such low levels. Adsorption of all species of sulfur was noted at room temperature and this adsorption may be causing excess sulfur to be incorporated into the CdS deposits. There has been an important development in the measurement of impurity levels of semiconductors called electrochemical photocapacitance spectroscopy. It can be used to analyze impurity levels in a wide variety of semiconductors by shining subband gap light on the semiconductor in a photoelectrochemical cell while measuring the capacitance on the surface. Interpretation of these spectra has previously been qualitative. A quantitative model was developed here along with a computer program utilizing this interpretation. Several types of semiconductors were analyzed by this technique, including these CdS deposits which showed impurity levels that may be due to excess sulfur. Other types of compound semiconductors can also be made by this cathodic deposition. It is hoped that the information gathered here can be used to improve these other semiconductor depositions as well as CdS.

Graduation date: 2004

As VLSI technology scales to 65nm and below, traditional communication between design and manufacturing becomes more and more inadequate. Gone are the days when designers simply pass the design GDSII file to the foundry and expect very good man¬ufacturing and parametric yield. This is largely due to the enormous challenges in the manufacturing stage as the feature size continues to shrink. Thus, the idea of DFM (Design for Manufacturing) is getting very popular. Even though there is no universally accepted definition of DFM, in my opinion, one of the major parts of DFM is to bring manufacturing information into the design stage in a way that is understood by designers. Consequently, designers can act on the information to improve both manufacturing and parametric yield. In this dissertation, I will present several attempts to reduce the gap between design and manufacturing communities: Alt-PSM aware standard cell designs, printability improve¬ment for detailed routing and the ASIC design flow with litho aware static timing analysis. Experiment results show that we can greatly improve the manufacturability of the designs and we can reduce design pessimism significantly for easier design closure.

Graduation date: 1991