É descrito um sistema automatizado para a realização de medidas elétricas em materiais dielétricos. Um microcomputador é responsável pelo controle e programação da temperatura da amostra, aquisição dos dados experimentais e apresentação e armazenamento dos resultados. O controle de temperatura permite aquecer e resfriar amostras a taxas constantes, manter a temperatura constante, superpor a esses processos uma variação senoidal de temperatura e ainda programar aquecimentos com taxas não lineares. Por esta versatilidade, o sistema permite realizar vários tipos de medidas elétricas tais como; corrente termo estimuladas em circuito fechado e aberto, correntes de absorção e correntes piroelétricas. Mostra-se o desempenho do sistema e alguns resultados de medidas elétricas em polímeros. / We describe an automatic system for electrical measurements in dielectric samples. The system is based on an Apple-like microcomputer, responsible for controlling and programming the sample temperature, data acquisition, display and storage. The temperature control allows heating and cooling samples at fixed rates, over which a superimposed sinusoidal perturbation may be applied, and also, non linear heating rates can be generated. Because of this versatility, the system allows many types of electrical measurements, just like thermal stimulated currents, thermal stimulated discharges, absorption currents and pyroelectric currents. We show the performance of the system and some results of practical measurements in polymers.

Wang Xiaofeng = Hf基高K介电薄膜的微观结构和电子结构研究 / 王晓峰. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 62-67). / Text in English; abstracts in English and Chinese. / Wang Xiaofeng = Hf ji gao K jie dian bo mo de wei guan jie gou he dian zi jie gou yan jiu / Wang Xiaofeng. / Table of Contents --- p.iv / List of Figures --- p.vii / List of Tables --- p.x / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Background --- p.3 / Chapter 2.1 --- Ideal high-k materials --- p.3 / Chapter 2.1.1 --- Current problems with Si02 and possible solutions --- p.3 / Chapter 2.1.2 --- Requirements on the high-k gate dielectric materials --- p.6 / Chapter 2.2 --- Recent results on high-k gate dielectrics --- p.8 / Chapter 2.2.1 --- A1203 --- p.8 / Chapter 2.2.2 --- Y203 and La203 --- p.9 / Chapter 2.2.3 --- Hf02 and Zr02 --- p.10 / Chapter 2.2.4 --- Pseudo-binary Alloys --- p.10 / Chapter 3 --- Experimental and Instrumentation --- p.13 / Chapter 3.1 --- Transmission electron microscopy (TEM) --- p.13 / Chapter 3.2 --- Transmission electron diffraction (TED) --- p.15 / Chapter 3.3 --- Electron energy loss spectroscopy (EELS) --- p.16 / Chapter 4 --- Data Analysis Methodology --- p.22 / Chapter 4.1 --- Diffraction analysis --- p.22 / Chapter 4.1.1 --- Ring ratio analysis for polycrystal diffraction pattern --- p.23 / Chapter 4.1.2 --- RDF analysis for amorphous materials --- p.24 / Chapter 4.2 --- Eliminating the plural scattering in EELS --- p.29 / Chapter 4.2.1 --- Removal of plural scattering from inner-shell edges --- p.30 / Chapter 4.2.2 --- Fourier-Ratio deconvolution --- p.30 / Chapter 4.2.3 --- "Demonstration using Co L2,3 core-loss spectrum" --- p.31 / Chapter 5 --- The Temperature Effect on the Microstructure of HfO2 Films --- p.37 / Chapter 5.1 --- Experimental --- p.38 / Chapter 5.2 --- Phase identification and crystallinity analysis of the Hf02 thin films --- p.38 / Chapter 5.2.1 --- Phase and crystallinity analysis from TEDs --- p.38 / Chapter 5.2.2 --- The phase and crystallinity evolution with the growth temperature --- p.39 / Chapter 5.3 --- The local symmetry of Hf atom in the films --- p.40 / Chapter 6 --- Effect of A1 Addition on the Microstructure and Electronic Structure of HfO2 Films --- p.43 / Chapter 6.1 --- Experimental --- p.44 / Chapter 6.2 --- RDF analysis of HfAlO films --- p.45 / Chapter 6.3 --- The local symmetry of Hf atom in the HfAlO films --- p.46 / Chapter 6.4 --- Loss functions of HfAlO films --- p.48 / Chapter 7 --- Comparison of A1 and Y Addition on the Microstructure of Hf02 Films --- p.56 / Chapter 7.1 --- Experimental --- p.57 / Chapter 7.2 --- Phase identification and crystallinity analysis of the alloy thin films --- p.57 / Chapter 7.2.1 --- Phase and crystallinity analysis from TEDs --- p.57 / Chapter 7.2.2 --- The phase and crystallinity evolution with the Y and A1 incorporation --- p.58 / Chapter 7.3 --- The local symmetry of Hf atom in the alloy thin films --- p.59 / Chapter 8 --- Conclusion --- p.61 / Bibliography --- p.62

In recent years, sintering of powdered materials in microwaves has emerged as a manufacturing technique with many potential advantages over conventional sintering methods, including the possibility of faster processing and finer microstructure, along with the potential for vast energy savings. However, the technique remains on the level of laboratory studies and is underutilized in industry, mostly due to the difficulty of controlling the process: the intrinsically nonuniform temperature pattern that results from microwave heating routinely induces nonuniform mechanical deformation. Mathematical models and computer simulations can help to clarify the factors that influence this process and aid experimentalists in the design of efficient processing equipment. Although a number of modelling techniques have been reported to this end, they appear to inadequately represent the entire chain of related physical phenomena, which involves interaction of the electromagnetic field with the material, heat transfer, and mechanical deformation, each of which is coupled with both of the others, and all of which occur on different time scales. In this work, we present an original comprehensive mathematical formulation that accounts for the chain of physical processes comprising microwave sintering in one- and two-dimensional scenarios. We develop models for simulating the coupled electromagnetic, thermal, and mechanical phenomena at their appropriate time and spatial scales, and in addition, we account for the temperature and density dependence of the full set of thermal and dielectric properties of the material undergoing sintering. The electromagnetic and temperature fields are approximated using finite difference methods, and the mechanical problem is solved using the Master Sintering Curve representation of the density kinetics, which gives a way of accounting for the effect of microscale transport on the macroscopic property of relative density. For constant-rate sintering trials, we use the exponential integral to compute the work of sintering, which reduces computation time. The presented algorithms are all implemented and shown in MATLAB and Python. Simulation of density and temperature evolution of the sintered sample shows processing times and shrinkage rates comparable to experimental results. This work lays a theoretical and computational foundation for modelling the general three-dimensional problem and computer-aided design of efficient sintering processes.

Based on the combined surface and volume RWG (Rao-Wilton-Glisson) basis functions, a simulator of a patch antenna on a finite dielectric substrate using the Method of Moments (MoM) has been implemented in Matlab. The metal surface is divided into planar triangular elements whereas the (inhomogeneous) dielectric volume is divided into tetrahedral elements. The structure under study is comprised of a typical patch antenna consisting of a single patch above a finite ground plane, and a probe feed. The performance of the solver is studied for different mesh configurations. The results obtained are tested by comparison with the commercial ANSOFT HFSS v8.5 and WIPL-D simulators. The former uses a large number of finite elements (up to 30,000) and adaptive mesh refinement, thus providing the reliable data for comparison. Behavior of the most sensitive characteristic ¡V antenna input impedance ¡V is tested, close to the first resonant frequency. The error in the resonant frequency is estimated at different values of the relative dielectric constant ƒÕr, which ranges from 1 to 20. The reported results show reasonable agreement. However, the solver needs to be further improved.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 1970. / Includes bibliographical references (leaves 327-332). / by John David Ramshaw. / Ph.D.

Wang, Ranshi = 透明电解质/氧化锌异质结热稳定性的研究 / 王然石. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2007. / Includes bibliographical references (leaves 130-134). / Abstracts in English and Chinese. / Wang, Ranshi = Tou ming dian jie zhi/yang hua xin yi zhi jie re wen ding xing de yan jiu / Wang Ranshi. / Chapter I. --- Abstract / Chapter II. --- Acknowledgement / Chapter III. --- Table of contents / Chapter IV. --- List of figures / Chapter V. --- List of tables / Chapter 1 --- Introduction / Chapter 1.1 --- Motivations / Chapter 1.2 --- Outline of thesis / Chapter 2 --- Experimental Conditions and Techniques Used / Chapter 2.1 --- Sample preparation / Chapter 2.1.1 --- Radio frequency magnetic sputtering / Chapter 2.1.2 --- ITO glass / Chapter 2.1.3 --- Thermal evaporation / Chapter 2.1.4 --- Thermal annealing / Chapter 2.2 --- Optical characterization of ZnO / Chapter 2.2.1 --- Photoluminescence (PL) measurement / Chapter 2.2.2 --- SEM and cathodoluminescence spectroscopy / Chapter 2.3 --- Time-of-FIight Secondary Ion Mass Spectroscopy (TOF-SIMS ) / Chapter 2.4 --- Electrical measurements / Chapter 3 --- Calibrations / Chapter 3.1 --- Sample Thickness / Chapter 3.2 --- Calibrations of cathodeluminescence measurements / Chapter 3.2.1 --- Probe current and specimen current / Chapter 3.2.2 --- Sample uniformity in CL measurement / Chapter 3.2.3 --- Mirror position / Chapter 3.2.4 --- Non-linear relation between CL emission and current / Chapter 3.2.5 --- CL band-edge emission stability / Chapter 3.2.6 --- Effect of magnification / Chapter 3.2.7 --- Effect of electron beam shift / Chapter 3.2.8 --- Conclusions / Chapter 3.3 --- C-V measurement / Chapter 4 --- Experimental Results and Data Analysis / Chapter 4.1 --- Optical properties / Chapter 4.1.1 --- Luminescence of ZnO / Chapter 4.1.2 --- Light emitting thermal stability of A10x (MgO) capped ZnO film / Chapter 4.1.2.1 --- Emission degradations in annealing treatment by PL / Chapter 4.1.2.2 --- Evidence about the interface degradation / Chapter 4.1.2.3 --- CL studies of the emission from sample surface / Chapter 4.2 --- Secondary Ion Mass Spectroscopy (SIMS) studies of AIOx-capped ZnO / Chapter 4.2.1 --- Data processing / Chapter 4.2.2 --- Diffusion width / Chapter 4.3 --- Simulation of Zn out diffusion to the dielectric layer / Chapter 4.3.1 --- Structure and assumptions / Chapter 4.3.2 --- Calculations of diffusion by Fick's Law / Chapter 4.3.3 --- Simulation of PL reduction from diffusion / Chapter 4.3.4 --- Short-time PL / Chapter 4.4 --- Simulation of defects generation in emission reduction process / Chapter 4.4.1 --- Some calculations of continuity equation / Chapter 4.4.2 --- First order equation for defect generation / Chapter 4.5 --- Electrical measurements / Chapter 4.5.1 --- Theory of C-V measurement for MOS structure / Chapter 4.5.1.1 --- MOS Structure / Chapter 4.5.1.2 --- Discussions about surface charge and energy level in C-V experiments of MOS / Chapter 4.5.1.3 --- Useful formulations / Chapter 4.5.2 --- Experimental results of C-V and parameter extraction / Chapter 4.5.2.1 --- Effect of series resistance correction / Chapter 4.5.2.2 --- Effect of thermal annealing to C-V curves on dielectric/ZnO/ITO / Chapter 4.5.2.3 --- Doping concentration (ND) / Chapter 4.5.2.4 --- Discussion about the fixed and mobile charge / Chapter 4.5.3 --- Simulation of C-V relation in dielectric/ZnO / Chapter 4.5.4 --- Current-voltage (I-V) measurements / Chapter 4.5.5 --- Conductance-voltage measurements (G-V) and interface trap density / Chapter 4.5.6 --- DLTS measurements for extracting interface trap density / Chapter 5 --- Discussions and Conclusion / Chapter 5.1 --- Mechanism / Chapter 5.2 --- Conclusions / Chapter 5.3 --- Future plan / Chapter 6 --- References

CaCu3Ti4O12 (CCTO), an unusual perovskite-like material, is known for extraordinarily high (often reaching 104) and relatively frequency independent dielectric constant. Recently, it has drawn a lot of attention, because of its potential applications in microelectronics and microwave devices. / In this investigation, CCTO powders were synthesized by two routes, a conventional solid-state reaction and a wet-chemistry method. Three kinds of materials, polyvinyl alcohol (PVA, an organic binder), boric oxide (B 2O3, a well-known glass former), hafnium oxide (HfO 2, a material with high dielectric constant ∼25), were added to the pre-reacted CCTO powder and sintered into ceramics. The effects of these additives on the microstructures, or electric and dielectric properties of CCTO ceramics were investigated. In addition, CCTO thin films were also successfully prepared. The AC conductivity, impedance, and complex dielectric permittivity were used to analyze the data. These observations were well explained in terms of an internal barrier layer capacitor (IBLC) model with Maxwell-Wagner (MW) dielectric relaxation. / Yuan, Wenxiang = 高介電常數材料CaCu₃Ti₄O₁₂χχχ / 苑文香. / Adviser: S.K. Hark. / Source: Dissertation Abstracts International, Volume: 73-01, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Yuan, Wenxiang = Gao jie dian chang shu cai liao CaCu₃Ti₄O₁₂ de yan jiu / Yuan Wenxiang.

Lui Man Leung. / "May 2004." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2004. / 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.

The development and characterization of lithographically patterned dielectric superlattice systems are presented, which have enabled the first clear realization of fully developed fractal mini-gaps owing to the interplay between a quantizing magnetic field and a lithographically defined spatial superlattice potential. Following a history of lateral superlattice gating on 2-D electron gas systems, we present patterned dielectric superlattice graphene systems of unmatched quality, allowing for the characterization of Hofstadter fractal band structure under triangular and square lattice geometries. Hexagonal boron nitride, graphene heterostructures are uniquely suited to integration with patterned gating structures, due to their high mobility and thin encapsulating dielectric environment. These systems have already been utilized for the observation of Hofstadter’s fractal spectrum through the moiré superlattice effect, but such systems are limited in their tunability. The patterned dielectric superlattice allows for control of the superlattice geometry, polarity, and strength. Utilizing this control, we compare the resultant fractal spectra from both triangular and square superlattice potentials, which confer unique gap structures in agreement with their lattice symmetry. More generally, patterned dielectric superlattices can be used to generate a variety of spatially dependent scalar potentials onto van der Waals heterostructures with length scales of order 10nm, while maintaining low disorder.

Photonic properties depend on both dielectric contrast in a microscopic composite and the arrangement of the microstructural components. No theory exists for direct prediction of photonic properties, and so progress relies on numerical methods combined with insight into manufacturable composite architectures. We present a discussion of effective photonic crystal production techniques and several numerical methods to predict dispersion relations of hypothetical but fabricable structures. / Singapore-MIT Alliance (SMA)