電源管理集成電路被廣泛應用於便攜式電子應用。在同一芯片需要不同的電源電壓水平。由於芯片尺寸，工作速度和所需功耗的要求，低壓差穩壓器（LDO）在快遞瞬態響應，低噪聲，以及高精度的電子產品中具有廣泛的應用。 / LDO的負載瞬間變化取決於功率金氧半場效電晶體的大小、偏置電流和誤差放大器的增益。檢測輸出電壓，並使用大電容和電阻通過電容耦合，增加偏置電流是一個簡單的方法來改善負載瞬間變化。然而，電阻電容佔據較大的芯片面積。 / 權衡功耗和芯片尺寸，本論文中提出用數字檢測電路取代用於瞬態耦合的大電容和電阻。所提出的電路是讓功率金氧半場效電晶體的栅極電容電流增加充電或放電，以提高LDO的負載瞬間響應速度。產生這種電流通過檢測內部的變化，並產生一個電壓脈衝控制迴轉電流，然後通過使用一組數字電路去改變充電或放電的電量。 / 擬議的設計已在UMC0.18微米 CMOS制程技術實現。LDO的輸入電壓為0.9伏至1.3伏和穩壓0.7伏。最大輸出電流為50豪安。經過測量，負載瞬間變化得到改善。負載瞬間的響應時間可以從75微秒（傳統）減少到75納秒。 / Power-management IC is widely used in portable electronic applications. Different supply voltage levels are required in the same chip. Due to the size, speed and power requirements, low-dropout regulator (LDO) is generally adopted for applications which need fast transient response, low noise and high accuracy. / Transient response of a LDO is limited by the size of power MOSFET, biasing current and gain of error amplifier. Detecting the output voltage and using large RC components for capacitive coupling to increase the biasing current is a straightforward method to improve the transient response. However, this requires a large chip size for the RC components. / By considering power consumption and size, digital detection circuit is proposed to replace the large capacitors and resistors used for transient coupling. The proposed circuit is to increase the charging or discharging current to the gate of the power MOSFET to increase the transient speed of LDO. This current is generated by detecting the internal changes and generating a voltage pulse to control the slewing current by using a set of digital circuit. / The proposed design has been realized in UMC 0.18μm CMOS technology. The input voltage of the LDO is 0.9 to 1.3V and the regulated voltage is 0.7V. The maximum output current is 50mA. From the measurement, the transient response is improved. The response time due to load transient changes can be reduced from 75s (conventional) to 75ns. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Kwong, Ka Yee. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstracts also in Chinese. / Abstract / Acknowledgments / Table of Content / List of Figures / List of Tables / Chapter Chapter 1 --- LDO regulator research background / Introduction / Chapter Section 1.1 --- Generic LDO regulator structure / Chapter Section 1.2 --- Principle of LDO regulator operation / Chapter Section 1.3 --- Specifications / Chapter References / Chapter Chapter 2 --- Review of state-of-the-art transient-improvement techniques for LDO regulators / Introduction / Chapter Section 2.1 --- Slew rate improvement at power transistor gate / Chapter Section 2.2 --- Frequency compensation / Chapter Section 2.3 --- Short summary / References / Chapter Chapter 3 --- A proposed output-capacitorless LDO regulator with digital voltage spike detection / Chapter Introduction / Chapter Section 3.1 --- LDO regulator core structure / Chapter Section 3.2 --- Digital switches based LDO regulator / Chapter Section 3.3 --- LDO regulator with proposed digital voltage spike detection circuit / Chapter Section 3.4 --- Simulation result / Chapter Section 3.5 --- Short summary / References / Chapter Chapter 4 --- Measurement results / Introduction / Chapter Chapter 5 --- Conclusion and Future Work

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1977. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING. / Includes bibliographical references. / by Robert Philip Gilmore. / M.S.

Optical modulation of the physical properties of materials is important for future development of optical memories and switches, optoelectronics, and smart surfaces. Incorporation of an optically bistable photochromic compound into an electronically bifunctional material is a promising strategy for a development of photoswitchable materials. Photochromic spirooxazine ligands undergo light-induced ring-opening and closure between the closed-spirooxazine (SO) and open-photomerocynanine (PMC) forms. The structural reorganization leads to accompanying changes in electronic structure which can lead to a change in the oxidation/reduction potentials and spin state of a bound metal center. Changes in the ligand field about a metal center in turn can lead to “non-classical” photoinduced magnetic (PIM) effects. The “non-classical” PIM effect is an effect that occurs through ligand-centered processes via the metal center, rather than direct excitation at the metal center. The structural change of the photochromic compounds also results in a change in the frontier orbital energies and donor-acceptor character, which may lead to optically-gated charge-transfer and energy-transfer processes. In this dissertation, the structural factors that govern thermal relaxation of spirooxazines, as optical control units, was investigated toward controlling the photostationary states of this important class of photochromes. The electronic structure of the PMC form of azahomoadamantyl-based spirooxazines was found to control the thermal coloration/decoloration rates of photochromic spirooxazines. A significant charge-separated character of the PMC form was correlated with the slow thermal coloration/decoloration rates in spirooxazines. This concept was then extended to an investigation of the effect of Lewis-acidic metal complexation. Solution study of the charge-separated character of the PMC form via metal complexation of the photochromic spirooxazines supported the correlation between the charge-separated character of the PMC form and the rate of the thermal coloration/decoloration. The studies provide a potential pathway for modulating PMC thermal relaxation rates through optimization of the structure of the spirooxazines and metal complexation. The studies were then extended to an investigation of the photomodulation of charge-transfer processes in cobalt multinuclear clusters by photoisomerization of photochromic spirooxazines. Incorporation of optically bistable phenanthroline-spirooxazine ligands into a magnetically bistable cobalt-dioxolene valence tautomeric cluster resulted in large magnetic moments in the solid and solution states. This study suggests that the redox-isomeric behavior of the cobalt dioxolenes can be coupled to isomerization of the photochromic ligand in the solution state when the π-acceptor ability of the photochromic ligands align with the direction of charge transfer of the cobalt dioxolene components. The potential of these cobalt multinuclear clusters to enhance the relaxivity of water in MRI for biological imaging was investigated. A cobalt tetranuclear cluster was prepared and found to exhibit high magnetic moments in solution at room temperature, and large relaxivities relative to commercially available gadolinium based MRI contrast agents. Lastly, the photomodulation of ionic doping of graphene organic field-effect transistors (OFETs) by photochromic spirooxazines was investigated. The electron donor or acceptor nature of the photochromic isomers modulates the direction and magnitude of ionic doping of graphene, and in turn the gate voltages of graphene OFETs, leading to optical modulation of OFET gate voltages for data processing and memory technologies. / Graduate / 2020-02-08

<div>Since the debut of graphene, many 2D materials have emerged as promising candidates for silicon alternatives to extend Moore’s Law, such as MoS₂ and phosphorene. However, some common shortcomings such as low mobility, instability and lack of massive production methods limit the exploration and applications of these materials. Here, we introduce a novel member to the 2D category – high-mobility air-stable 2D tellurium film (tellurene).</div><div><br></div><div>Tellurium (Te) is a narrow bandgap semiconductor with unique one-dimensional chiral structure. Recently, a hydrothermal synthesizing method was developed to produce large-area tellurene nanofilms with thickness ranging from tens of nanometers down to few layers. In this thesis, a thorough investigation of Te properties in 2D quantum region was first carried out by various material characterization techniques including TEM and Raman spectroscopy. Potential applications of Te-based electronics, optoelectronic and thermoelectric devices were explored, and high-performance Te FETs were achieved with record-high drive current over 1 A/mm via device scaling and contact engineering. Magneto-transport, including weak anti-localization and Shubnikov-de-Haas oscillations was studied at cryogenic temperature. Quantum Hall effect was observed for the first time in both 2D electron and hole gases with mobility of 6,000 and 3,000 cm²/Vs, and non-trivial Berry phase in Te 2D electron system was detected as the first experimental evidence of massive Weyl fermions. This work not only demonstrates the great potential of tellurene films for electronics and quantum device applications, but also expands the spectrum of topological matters into a new material species - Weyl semiconductors.</div>

Cette thèse démontre le potentiel d'utilisation du graphène pour la fabrication de transistors à effet de champ à couche mince. Celui-ci est préparé par exfoliation en phase liquide et co-déposé avec un polymère semiconducteur du type n. Cette stratégie montre que le graphène améliore le comportement ambipolaire du polymère et plus particulièrement le transport des trous ce qui renforce l'application des matériaux composites au graphène dans les circuits logiques.Par la même approche de mélange, de nouveaux nanorubans de graphène dispersés en solution, ont été utilisés pour améliorer la performance des dispositifs basés sur un polymère amorphe de type p. Ces nanorubans forment une voie de percolation pour les charges améliorant ainsi la performance des dispositifs dans l'obscurité ainsi que sous illumination. Finalement, les dispositifs photosensibles multifonctionnels ont été examinés par l'introduction de molécules photochromiques avec différents substituants au sein des films semi-conducteurs à base de polymère ou de molécules de petite taille qui ont été trouvés influer la photocommutation. / This thesis demonstrates that graphene produced by liquid-phase exfoliation can be co-deposited with a polymerie semiconductor for the fabrication of thin film field-effect transistors. The introduction of graphene to the n-type polymeric matrix enhances not only the electrical characteristics of the devices, but also the ambipolar behavior and the hole transport in particular. This provides a prospective pathway for the application of graphene composites for logic circuits.The same approach of blending was adopted to enhance the electrical characteristics of an amorphous p-type polymer semiconductor by addition of an unprecedented solution processable ultra-narrow graphene nanoribbon. GNRs form percolation pathway for the charges resulting in enhanced deviee performance in daras weil as under illumination therefore paving the way for applications in (opto)electronics.Finally, multifunctional photoresponsive devices were examined by introducing photochromic molecules exposing different substituents into small molecule or polymeric semiconductor films that were found to affect the photoswitching behavior.

Magnetic field effects (MFE) on electrochemical systems have been of interest to researchers for the past 60 years. MFEs on mass transport, such as magnetohydrodynamics and magnetic field gradients effects are reported, but MFEs on electron transfer kinetics have been rarely investigated. Magnetic modification of electrodes enhances electron transfer kinetics under conditions of high concentrations and low physical diffusion conditions, as shown by Leddy and coworkers. Magnetic microparticles embedded in an ion exchange polymer (e.g., Nafion) applied to electrode surfaces. Rates of electron transfer reactions to diffusing redox probes and to adsorbates are markedly enhanced. This work reports MFEs on hydrogen evolution on illuminated p-Si; MFEs on hydrogen evolution on noncatalytic electrodes; a model for MFEs on homogeneous self-exchange reactions; and a convolution based voltammetric method for film modified electrodes. First, a MFE on the photoelectrochemical hydrogen evolution reaction (HER) at p-Si semiconductors is demonstrated. The HER is an adsorbate reaction. Magnetic modification reduces the energetic cost of the HER by 400 - 500 mV as compared to Nafion modified electrodes and by 1200 mV as compared to unmodified p-Si. Magnetically modified p-Si achieves 6.2 % energy conversion efficiency. Second, from HER on noncatalytic electrodes, the MFE on photoelectrochemical cells arises from improved heterogeneous electron transfer kinetics. On glassy carbon electrodes, magnetic modification improves heterogeneous electron transfer rate constant, k₀,for HER 80,000 fold. Third, self exchange reaction rates are investigated under magnetic modification for various temperatures, outersphere redox probes, and magnetic particles. Arrhenius analyses of the rate constants collected from the experiments show a 30 - 40 % decrease in activation energy at magnetically modified electrodes. A kinetic model is established based on transition state theory. The model includes pre-polarization and electron nuclear spin polarization steps and characterizes a majority of the experimental results. Lastly, a convolution technique for modified with uniform films electrodes is developed and coded in Matlab (mathematical software) for simple and straightforward analysis of Nafion modified electrodes.

Control of solid state ordering in conjugated small molecules is paramount to the continued development and implementation of organic materials in electronic devices. However, there exists no reliable method on which to predicatively determine how a change to the molecular structure will impact the solid-state packing. As such, the molecule must be synthesized before its solid-state packing can be definitively evaluated. However, once the packing structure of a material is known there exist both qualitative structure- function relationships derived from the literature, as well as quantitative computational methods that can be employed to suggest if a material will perform well in a given device. This type of bottom-up strategy is used in Chapter 2 to design and synthesize a high performance material for organic field effect transistors. A core molecule is synthesized, and through rigorous optimization of pendant and solubilizing groups a material with exceptional solid-state packing is developed and its performance in an organic field effect transistor is discussed. Chapter 3 discusses the use of conjugated organic molecules in conjunction with inorganic materials to develop hybrid organic/inorganic materials. A scalable synthesis is developed so derivatives can be rapidly synthesized and their properties evaluated. Two classes of materials are developed and synthesized: tetracene-based ligands for quantum dots and diammonium-substituted anthracene and tetracene derivatives for 2D-perovskites. Initial results for both classes of materials are presented. Chapter 4 discusses the topochemical photopolymerization of heptacene [4+4] dimers. Multiple derivatives were synthesized in order to give the ideal alignment of molecules in the crystal, followed by irradiation of crystals to give crystal templated polymerization. In Chapter 5, triarylmethane derivatives are synthesized and their performance as radiochromic sensors is evaluated. Chapter 6 involves the development of a robust synthetic scheme toward a difficult to attain π- extended regioisomer of pyrene. Photophysical characterization reveals that the direction of π-extension from the pyrene core has a profound effect on electron delocalization.

Silicon based integrated circuit (IC) technology is approaching its physical limits. For sub 10nm technology nodes, the carbon nanotube (CNT) based field effect transistor has emerged as a promising device because of its excellent electronic properties. One of the major challenges faced by the CNT technology is the unwanted growth of metallic tubes. At present, there is no known CNT fabrication technology which allows the fabrication of 100% semiconducting CNTs. The presence of metallic tubes creates a short between the drain and source terminals of the transistor and has a detrimental impact on the delay, static power and yield of CNT based gates. This thesis will address the challenge of designing robust carbon nanotube based circuits in the presence of metallic tubes. For a small percentage of metallic tubes, circuit level solutions are proposed to increase the functional yield of CNT based gates in the presence of metallic tubes. Accurate analytical models with less than a 3% inaccuracy rate are developed to estimate the yield of CNT based circuit for a different percentage of metallic tubes and different drive strengths of logic gates. Moreover, a design methodology is developed for yield-aware carbon nanotube based circuits in the presence of metallic tubes using different CNFET transistor configurations. Architecture based on regular logic bricks with underlying hybrid CNFET configurations are developed which gives better trade-offs in terms of performance, power, and functional yield. In the case when the percentage of metallic tubes is large, the proposed circuit level techniques are not sufficient. Extra processing techniques must be applied to remove the metallic tubes. The tube removal techniques have trade-offs, as the removal process is not perfect and removes semiconducting tubes in addition to removing unwanted metallic tubes. As a result, stochastic removal of tubes from the drive and fanout gate(s) results in large variation in the performance of CNFET based gates and in the worst case open circuit gates. A Monte Carlo simulation engine is developed to estimate the impact of the removal of tubes on the performance and power of CNFET based logic gates. For a quick estimation of functional yield of logic gates, accurate analytical models are developed to estimate the functional yield of logic gates when a fraction of the tubes are removed. An efficient tube level redundancy (TLR) is proposed, resulting in a high functional yield of carbon nanotube based circuits with minimal overheads in terms of area and power when large fraction of tubes are removed. Furthermore, for applications where parallelism can be utilized we propose to increase the functional yield of the CNFET based circuits by increasing the logic depth of gates.

This thesis describes the development and demonstration of a new technique for the fabrication of well-defined quantum dots in a bulk silicon substrate, for potential applications such as quantum computation in coupled quantum dots. Hall characterisation was performed on double-gated mesaMetal-Oxide- Semiconductor Field-Effect Transistors (MOSFETs) on a silicon-on-insulator (SOI) substrate, for the purpose of silicon quantum dots in etched nanowires on SOI. Carrier density and mobility results are presented, demonstrating top- and backgate control over the two inversion layers created at the upper and lower surfaces of the superficial silicon mesa. A new technique is developed enabling effective depletion gating of quantum dots in a bulk silicon substrate. A lower layer of aluminium gates is defined using electron beam lithography; the surface of these gates is oxidised using a plasma oxidation technique; and a further layer of aluminium gates is deposited. The lower gates form tunable tunnel barriers in the narrow inversion layer channel created by the upper MOSFET gate. The two layers of gates are electrically isolated by the localised layer of aluminium oxide. Low-temperature transport spectroscopy has been performed in both the many electron (∼100 electrons) and the few electron (∼10 electrons) regimes.Excited states in the bias spectroscopy provide evidence of quantum confinement. Preliminary temperature and magnetic field dependence data are presented. These results demonstrate that depletion gates are an effective technique for defining quantum dots in silicon. Furthermore, the demonstration of the first silicon radio-frequency single electron transistor is reported. The island is again defined by electrostatically tunable tunnel barriers in a narrow channel field effect transistor. Charge sensitivities of better than 10μe/√Hz are demonstrated at MHz bandwidth. These results establish that silicon may be used to fabricate fast, sensitive electrometers.

"August 2003" Bibliography: leaves 108-117. 1. Ruthenium-106 ophthalmic applicators -- 2. General principle of thermoluminescent dosimeter -- 3. Study of basic characteristics of CaSO4:Dy TLD -- 4. Measurements of COB and CCA type ruthenium-106 ophthalmic applicator dose distributions -- 5. Determination of the dose rate distribution using a MOSFET detector -- 6. Summary and conclusion. In this project, small CaSO4:Dy TLDs and a semiconductor MOSFET dosimeter were used for the determination of on-axis depth dose-rate distributions of 15-mm and 20-mm ruthenium-106 applicators in acrylic eye phantoms. The TLDs were also used to determine off-axis dose distributions.