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Huang, Xiaobo. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 108-111). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

Cette thèse a exploré comment, en mélangeant des matériaux avec des propriétés électriques différentes, il est possible de fabriquer des transistors avec des performances accrues. Des transistors organiques à effet de champ basés sur un oligothiophène (DH4T) ont été fabriqués et optimisés jusqu’à ce que les mobilités mesurées fussent supérieures à celles observées dans des films évaporés. Ces résultats ont été obtenus par le contrôle précis des interfaces et de la vitesse d’évaporation. Des polymères de type p ont été mélangés à des polymères de type n. Chaque solution obtenue a été utilisée pour la fabrication de transistors ambipolaires. Les transistors ont été caractérisés et il a été possible de fabriquer des transistors avec des mobilités équilibrées pour chaque paire de polymères. Des transistors à effet de champ basés sur un mélange de P3HT et d’une molécule photochromique (DAE-Me) ont été fabriqués. Le courant a été mesuré pendant et entre les irradiations et il a été démontré qu’une mémoire non-volatile à multiple niveaux peut être fabriquée / This thesis explored how, by blending of materials with different electrical characteristics, it is possible to fabricate transistors with new or improved performances. First, organic field-effect transistors based on a single oligothiophene, DH4T, were fabricated and optimized until the measured mobility was superior to that observed in vacuum deposited films. This was achieved through careful tuning of the interfaces using self-assembled monolayers and by strong control of the solvent- evaporation rate. P-type polymers were blended with an n-type polymer. Each resulting solution was used for the fabrication of ambipolar field-effect transistors. These devices were characterized and it was found that for each pair of p- and n-type polymers, a transistor with balanced mobilities and high Ion/Ioff could be fabricated. Finally field-effect transistors based on a blend of P3HT and a photoswitchable diarylethene (DAE-Me) were fabricated. The current was measured during and between irradiations and it was demonstrated that a non-volatile multilevel memory could be fabricated.

The nonlinear behaviour of the base emitter junction in HBTs is investigated. Nonlinearities cause troublesome distortion and intermodulation of signals and raise the bit error rate. They are therefore a key issue in microwave communication systems. Hewlett-Packard's Microwave Design System (MDS) software package has been used to simulate these phenomena. The simulation results are verified by an analytical method called nonlinear current method which is a derivative of the Volterra series approach. With the aid of this method new analytical expressions are derived that provide insight into the subtleties of nonlinear phenomena. These expressions are evaluated by the program MAPLE and subsequently compared with the MDS results. Two different models for the B-E junction are juxtaposed. The derived equations reveal the identity and correspondence between the two models. Finally, this thesis also addresses harmonic balance simulation which is the type of simulation MDS employs to simulate nonlinear circuits.

No description available.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.