Yu, Xiaojiang. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Abstracts in English and Chinese. / ABSTRACT (ENGLISH) --- p.I / ABSTRACT (CHINESE) --- p.III / ACKNOWLEDGEMENTS --- p.IV / TABLE OF CONTENTS --- p.V / Chapter 1. --- Overview of organic thin-film transistors (OTFTs) --- p.1 / Chapter 1.1 --- Introduction to OTFTs --- p.1 / Chapter 1.2 --- Basic mechanism of OTFTs --- p.4 / Chapter 1.3 --- Applications of OTFTs --- p.6 / Chapter 1.3.1 --- Driving of circuits for electronic papers and LCD --- p.6 / Chapter 1.3.2 --- Light-emitting OTFTs --- p.8 / Chapter 1.3.3 --- Sensing --- p.9 / Chapter 1.4 --- Several key issues --- p.9 / Chapter 1.4.1 --- Mobilities of OTFTs --- p.9 / Chapter 1.4.2 --- Performance of bottom-contact OTFTs --- p.10 / Chapter 1.4.3 --- Stability of OTFTs --- p.11 / Chapter 1.4.4 --- Performance of n-type organic semiconductors --- p.13 / Chapter 1.5 --- Why to study metallophthalocyanine-based OTFTs --- p.14 / Chapter 1.6 --- Objective of this thesis --- p.17 / References --- p.17 / Chapter 2. --- Experimental details for fabrication and characterization of OTFTs --- p.22 / Chapter 2.1 --- Purification of organic semiconductors --- p.22 / Chapter 2.2 --- Preparation of the gate dielectrics for OTFTs --- p.24 / Chapter 2.3 --- Deposition of organic thin films and gold source/drain electrodes --- p.26 / Chapter 2.4 --- Process flow for the fabrication of OTFTs --- p.27 / Chapter 2.5 --- Mobility measurement for the organic thin films --- p.28 / Chapter 2.6 --- Characterization of organic thin films --- p.31 / References --- p.31 / Chapter 3. --- Optimizing the growth of VOPc thin films for high-mobility OTFTs --- p.33 / Chapter 3.1 --- Experimental --- p.33 / Chapter 3.2 --- Results and discussion --- p.34 / Chapter 3.2.1 --- Growth of VOPc thin films on Si02 dielectric --- p.34 / Chapter 3.2.2 --- Growth of VOPc thin films on Ta205 and Al203/Si02 dielectrics --- p.41 / Chapter 3.4 --- Conclusion --- p.44 / References --- p.45 / Chapter 4. --- CuPc/CoPc and VOPc/CoPc p-type/p-type heterostructure OTFTs --- p.46 / Chapter 4.1 --- CuPc/CoPc OTFTs in sandwich configuration --- p.47 / Chapter 4.1.1 --- Experimental --- p.47 / Chapter 4.1.2 --- Results and discussion --- p.48 / Chapter 4.1.3 --- Conclusion --- p.57 / Chapter 4.2 --- VOPc/CoPc OTFTs --- p.57 / Chapter 4.2.1 --- Experimental --- p.57 / Chapter 4.2.2 --- Results and discussion --- p.58 / Chapter 4.2.3 --- Conclusion --- p.63 / References --- p.64 / Chapter 5. --- VOPc/F16CuPc p-type/n-type heterostructure OTFTs --- p.66 / Chapter 5.1 --- Unipolar VOPc/F16CuPc OTFTs --- p.67 / Chapter 5.1.1 --- Experimental --- p.67 / Chapter 5.1.2 --- Results and discussion --- p.69 / Chapter 5.1.3 --- Conclusion --- p.73 / Chapter 5.2 --- VOPc/F16CuPc heterostructure for bottom-contact OTFTs --- p.74 / Chapter 5.2.1 --- Experimental --- p.74 / Chapter 5.2.2 --- Results and discussion --- p.74 / Chapter 5.2.3 --- Conclusion --- p.77 / References --- p.77 / Chapter 6. --- Summary and future work --- p.80 / Summary --- p.80 / Future work --- p.81 / References --- p.83 / Appendix A: Capacitance-voltage (C-V) fitting for ITO/organic junction/AI devices --- p.85 / Appendix B: Can electric-filed influence the growth of organic thin films? --- p.89 / Appendix C: Micro-Raman study on organic thin films --- p.93 / Appendix D: Publications which contributed to this thesis --- p.97

No description available.

No description available.

Thesis (MS) -- Oregon State University, 2006. / Printout. Includes bibliographical references (leaf 46). Also available on the World Wide Web.

D.Ing. (Electrical & Electronic Engineering ) / In recent years, bipolar transistors have become available with large current ratings (300A-1DODA). The purpose 01 this study is to analyse the modelling 01 these devices, with a view to applying the results to detailed power electronic circuit design (for example base drive and snubber circuits). In contrast to the many curve-filling approaches existing in this field, a model which correctly represents the physical mechanisms is desirable, in order to characterise the device behaviour with a minimum number of parameters. Existing modelling techniques, which have mostly been developed for low current devices, are examined in detail to determine their validity for high current 8JTs. Alter a survey of the literature, the assumptions contained in the lundamental first order theory are investigated, together with the most important second order ellecls. This is followed by a detailed experimental investigation, to establish the dominant mechanisms for both de and dynamic operation. The behaviour 01 large power devices is dominated by conductivity modulation 01 the lightly doped collector region. This means that the Gummel-Poon model, which is based on ellects in the base is not the most appropriate for high current modelling. II also found that the the simple charge control equation can give accurate results for dynamic modelling. The dynamic saturation region 01 operation is described by a simple model, based on the quantity 01 stored charge. This is an improvement on the currently used Gummel-Poon models. The findings are all incorporated into a new model, which is included in a version of the SPICE network simulation program and then tested experimentally. The importance 01 the reverse conduction mode 01 operation is discussed and some techniques for modelling this region are presented, together with some experimental results. II is shown conclusively that the developed device based approach, models the behaviour of the devices adequately for converter design purposes, over a wide range of operating conditions.

Les Transistors Organiques Electrochimiques (OECT) sont largement utilisés comme les capteurs dans de nombreux appareils bioélectroniques. Bien qu’ils aient été largement étudiés au cours de ces dernières années, il n'y a pas encore de compréhension fondamentale et univoque principe de fonctionnement d'un OECT, notamment en ce qui concerne le mécanisme du dé-dopage.Cette thèse est consacrée à la modélisation des Transistors Organiques Electrochimiques. Tout d'abord, un modèle d'état stationnaire numérique a été établi. Ce modèle utilisant les équations de Poisson-Boltzmann, Nernst-Planck et Nernst, nous permet de décrire finement le processus du dé-dopage dans la couche de PEDOT: PSS ainsi que, la distribution des ions et trous dans le capteur. Il a été prouvé expérimentalement que le modèle numérique dit de « neutralité global » est valable pour expliciter le fonctionnement global du capteur, mais aussi, l'origine et le résultat du processus du dé-dopage. La transition d’un modèle totalement numérique à un modèle analytique a été réalisée en ajustant la fonction analytique logistique paramétrique de Boltzmann au profil de conductivité calculé numériquement.Nous avons pu ainsi extraire, la fonction analytique de la dépendance du courant de drain en Fonction du potentiel local. Cette fonction ajuster sur un profil de courant de drain mesuré expérimentalement en fonction du potentiel appliqué permet d'obtenir la conductivité maximale d'une couche de PEDOT: PSS entièrement dopée. La conductivité maximale était dépendante non seulement du matériau, mais aussi de la taille du canal. Il est possible d'extraire, en utilisant la valeur de conductivité maximale et un modèle de semi-conducteur conventionnel, les autres paramètres pour la description complète d’OECT: densité intrinsèque de charge, densité de trous initiaux, concentration initiale de PSS- et capacité volumétrique de la couche polymère conductrice. Le fait d'avoir un outil permettant d'extraire et de caractériser facilement tous les OECT permet non seulement d'augmenter le niveau de description de compréhension du transistor, mais surtout de mieux maitriser la corrélation entre paramètres internes et externes.Finalement, l’approche que nous avons réalisée, couplant modélisation analytique et numérique, nous a permis de proposer une description complète du fonctionnement physique d’un OECT. En outre nous avons pu valider expérimentalement la pertinence de nos modèles en les comparants avec les caractéristiques obtenues via des mesures réelles. / Organic Electrochemical Transistors are widely used as transducers for sensors in bioelectronics devices. Although these devices have been extensively studied in the last years, there is a lack of fundamental understanding of their working mechanism, especially concerning the de-doping mechanism.This thesis is dedicated to Organic Electrochemical Transistors modelling. First of all, a numerical steady state model was established. This model allows implementing the Poisson-Boltzmann, Nernst-Planck and Nernst equations to describe the de-doping process in the conductive PEDOT:PSS layer, and ions and holes distribution in the device. Two numerical models were proposed. In the first, Local Neutrality model, the assumption of electrolyte ions trapping in PEDOT:PSS layer was taken into consideration, thus the local neutrality was preserved. In the second model the ions were allowed to move freely under applied electric field inside conductive polymer layer, thus only global electroneutrality was kept. It was experimentally proven that the Global Neutrality numerical model is valid to explain the global physics of the device, the origin and the result of the de-doping process. The transition from totally numerical model to analytical model was performed by fitting the parametric analytical Boltzmann logistic function to numerically calculated conductivity profiles. As a result, an analytical equation for the Drain current dependence on applied voltage was derived. By fitting this equation to experimentally measured Drain current- applied voltage profiles, we could obtain the maximum conductivity of a fully doped PEDOT:PSS layer. The maximum conductivity is shown to be dependent not only on the material, but also on device channel size. Using the maximum conductivity value together with the Conventional Semiconductor model it is possible to extract the other parameters for the full description of the OECT: intrinsic charge carrier density, initial holes density, initial PSS- concentration and conductive polymer layer volumetric capacitance. Having a tool to make easy parameters extraction and characterization of any OECT, permits not only to increase the level of device description, but most importantly to highlight the correlation between external and internal device parameters.Finally it is shown how to make the whole description of the real OECT device, all the models were validated by fitting the modeled and experimentally measured data profiles.As a result, not only the purely theoretical model was presented in this thesis to describe the device physics, but also the prominent step was made on simple real device characterization.

A physics-based insulated gate bipolar transistor (IGBT) model has been successfully implemented into a widely available circuit simulation package, IG-Spice. Based on the semiconductor physics, the model accurately predicts the nonlinear junction capacitance variations, recombinations, and conductivity modulation of the power device. The procedure to incorporate the model into IG-Spice and various methods to ensure convergence are described. The IG-Spice IGBT model is presented, including all the physical effects which have been shown to be important in describing the device. Effectiveness of the model is shown by comparing the measured data for single device used in inductive load, and by comparing the static and dynamic current sharing of paralleled IGBTs. The simulated results are verified with experimental results. Accuracy is determined by the accuracy of the required parameters extracted. / Master of Science

No description available.

published_or_final_version / Electrical Engineering / Master / Master of Science in Engineering

Atomically thin Molybdenum disulfide, MoS2, a star member of the group VI transition metal dichalcogenide(TMDC) family has been attracting rising interests for its potential applications in emerging electronics and optoelectronics. Bulk MoS2is a semiconductor with an indirect gap located between the top of valence band at Γ points and the bottom of conduction band in mid of K and Γ points in its Brillouin zone. Atomically thin MoS2 films including monolayers and multilayers, being chemically inert, present a class of intrinsic 2D semiconductors which are widely regarded as a platform for ultimate electronics. As yet tremendous efforts focus on the optical properties and electric transport study. In this thesis, we report the experimental study of photocurrent measurements on MoS2thin films. The sample preparation, device fabrication, optical and electric characterizations are introduced. The experiments have been carried out on a field effect transistor (FET) structured MoS2 device. The photocurrent spectroscopy reveals the interband excitonic transitions at spin-split bands around K valleys. The results demonstrate that MoS2has potential applications in optoelectronics. / published_or_final_version / Physics / Master / Master of Philosophy