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[[abstract]]This thesis focuses on the development of sensors for the determination of aqueous methanol concentration in direct methanol fuel cell (DMFC) applications. The crossover of methanol from anodic compartment to the cathodic compartment and its subsequent oxidation in the cathodic compartment is the main reason for the low efficiency of DMFC, which is yet to be solved in the current DMFC technology. DMFC operated at controlled low concentration methanol feed is one of the approaches to avoid the cell voltage loss due to methanol crossover. Such an operation needs the development of a suitable methanol sensor which motivates the present study. The study consists of two major parts. In the first part, literature overview of DMFC, methanol crossover problem, methods to circumvent the methanol crossover are discussed. Apart from t...
[[abstract]]There is provided a process and its system for fabricating plasma with feedback control on plasma density. This process uses a heterodyne millimeter wave interferometer as a sensor to measure the plasma density in the process container and the plasma density that is needed in the plasma fabricating process, and then provides real-time information of the measurements to a digital control device which makes numerical calculations and then drives the RF power generator to change the RF output power so as to enable the plasma density in the plasma fabricating process to be close to the expected plasma density. The conventional operation parameter method is to control air pressure, RF power, gas flow quantity, temperature and so on. However, it does not control the plasma parameter that has the most direct influence on the proce...
[[abstract]]There is provided a process and its system for fabricating plasma with feedback control on plasma density. This process uses a heterodyne millimeter wave interferometer as a sensor to measure the plasma density in the process container and the plasma density that is needed in the plasma fabricating process, and then provides real-time information of the measurements to a digital control device which makes numerical calculations and then drives the RF power generator to change the RF output power so as to enable the plasma density in the plasma fabricating process to be close to the expected plasma density. The conventional operation parameter method is to control air pressure, RF power, gas flow quantity, temperature and so on. However, it does not control the plasma parameter that has the most direct influence on the proce...
[[abstract]]Here we present a method to synthesize single-walled carbon nanotubes (SWNTs) selectively suspended on tips of silicon-based nanostructure (Si-ns) templates. The Si-ns templates vertically aligned to the substrates are fabricated via an anisotropic etch process using reactive hydrogen plasmas, in which the etch-resistive nanomasks are the nanosized particles formed by thermal annealing of multi-layered catalytic thin films. After plasma etching, the nanosized self-masks remaining at the tips of the Si-ns directly serve as the catalysts for SWNT growth by thermal chemical vapour deposition. Consequently, the synthesized SWNTs are selectively suspended on the tips of the Si-ns, as revealed by characterizations using scanning electron microscopy and resonance Raman spectroscopy. This methodology provides a simple and straightf...
[[abstract]]The effects of nitrogen composition in HfxTayN metal-gate electrodes and postmetal annealing (PMA) treatment on the electrical properties of metal-oxide-semiconductor (MOS) devices were investigated in this work. The work function of HfxTayN gate electrodes can be adjusted by incorporating various nitrogen contents. It is found that the HfxTayN metal gate with higher nitrogen content can achieve better electrical characteristics in terms of leakage current and reliability while with only a slight increase in equivalent-oxide-thickness value. The face that only slight variation on electrical characteristics of MOS device with HfxTayN gate electrodes is observed after various PMA temperatures designates the excellent thermal stability of Hf xTayN gate electrodes. The present study indicates that HfxTayN is a promising metal-g...
Comment: This manuscript was summited to the journal Carbon at Dec. 1, 2009. The revised manuscript was submitted to the journal Carbon at Mar. 24, 2010. This manuscript has been accepted by the journal Carbon at May 2, 2010.
[[abstract]]Boron nitride nanotubes (BNNTs) were selectively synthesized on patterned bilayer (Fe/Al) catalysts by the plasma-assisted chemical vapor deposition (PACVD) method. The as-grown nanotubes comprise both coaxial and cup-stacking tubular structures. Optical transitions on cup-stacking BNNTs are investigated for the first time. The observed red-shift of free excitonic luminescence was attributed to the excitonic recombination in terms of defect trapping in the tube's surface. The O2 additives during the synthetic process were found to balance the excess H radicals that in turn enhance the growth yield of BNNTs. Moreover, our elemental mapping results provide direct evidence of the metal catalytic mechanism and the influence of the as-formed Al 2O3 underlayer.
[[abstract]]In this paper, we discuss an approach to fabricating a carbon nanotubes (CNTs) gate electrode structure for cold cathode emitter applications. The field emission behavior of the structure was studied by using single vertically aligned free-standing CNTs of various lengths and gate electrodes of various sizes to determine the optimal emission structure. A single CNT electrode source with a gate electrode was fabricated by combining optical lithography, electron-beam lithography (EBL), and inductively coupled plasma chemical vapor deposition (ICP-CVD). A single mask was adopted to define the gated structure and nano sized catalyst for CNT growth. A vertically aligned CNT was then grown within the gate hole by ICP-CVD. The CNT height inside the gate could be lengthened by multiple growth processes without affecting the field e...
[[abstract]]一種矽溶膠-凝膠(sol-gel)光波導之製程,包含溶液配置、光波導光阻模組製程及光波導澆鑄燒結成形等三個步驟。該溶液配置係以水及酒精混合,再以經調整酸鹼值之醇溶液與四氧基乙矽在室溫下攪拌而成;該光波導光阻模組製程係經軟烤、曝光、顯影,並用去離子水洗淨經氮氣槍吹乾後,再硬烤完成製作;該光波導澆鑄燒結成形係經旋鍍處理、加熱燒結,去除光阻模組等步驟,以完成一矽溶膠-凝膠(sol-gel)光波導製程。
[[abstract]]The effects of nitrogen composition in HfxTayN metal-gate electrodes and postmetal annealing (PMA) treatment on the electrical properties of metal-oxide-semiconductor (MOS) devices were investigated in this work. The work function of HfxTayN gate electrodes can be adjusted by incorporating various nitrogen contents. It is found that the HfxTayN metal gate with higher nitrogen content can achieve better electrical characteristics in terms of leakage current and reliability while with only a slight increase in equivalent-oxide-thickness value. The face that only slight variation on electrical characteristics of MOS device with HfxTayN gate electrodes is observed after various PMA temperatures designates the excellent thermal stability of HfxTayN gate electrodes. The present study indicates that HfxTayN is a promising metal-ga...
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