Jiann-Ruey Chen

The Preparation and High Photon-Sensing Properties of Fluorinated Tin Dioxide Nanowires

The photon-sensing abilities of SnO 2 nanowires have been investigated before and after surface fluorination by microwave plasma-enhanced chemical vapor deposition. The electrical conductance and photon-sensing abilities of SnO 2 nanowires were remarkably improved by an effective doping of fluorine into the surface of the nanowires. These results demonstrated that the fluorinated SnO 2 nanowires have potential applications as UV photodetectors with high photon-sensing properties.

Application of diamond coating to tool steels

Abstract Various attempts were made to grow diamond film on SKD 61 for tribological applications in the laboratory. One of the promising ways in which to achieve this end is to interpose an intermediate layer which is compatible with both diamond film and the substrate of SKD 61. Some refractory metals were found to be satisfactory for this particular purpose. Molybdenum, for instance, was first deposited on SKD 61 by an electron beam evaporator at ambient temperature. Such molybdenum-deposited SKD 61 was first dry etched in hydrogen plasma to remove possible oxides and contaminations. Then diamond film was allowed to grow at a temperature of ∼ 500°C without much disturbance of the mechanical strength of the tool. This combination of diamond/molybednum/SKD 61 provided two interfaces leading to satisfactory adhesion strengths and an overall mechanical integrity. Carbides were often observed at the interface, but no oxide was detected. Multilayers of Mo and Ni as well as a single layer of TiN on SKD 61 were also explored in this research and they were proved to be effective in retarding the mutual alloying effect between carbonaceous materials and ferrous alloys.

Preparation of Pt / SnO2 Core–Shell Nanowires with Enhanced Ethanol Gas- and Photon-Sensing Properties

Pt/SnO 2 core-shell nanowires were prepared by a process that involves thermal evaporation of SnO 2 nanowires and subsequent atomic layer deposition of Pt, and their gas- and photon-sensing properties were investigated systematically. Transmission electron microscopy analysis showed that the Pt shell with a thickness of 8.8 nm is composed of numerous Pt nanoparticles with average diameters of ∼5.3 nm. The Pt/SnO 2 core-shell nanowires with high electrical conductance exhibit remarkably enhanced ethanol gas- and photon-sensing properties due to the surface functionalization resulting from the effective Pt catalyst and the formation of hetero-nanostructures fabricated by the SnO 2 core and Pt shell.

Investigations of the biological corrosion of condenser tubes by scanning auger microprobe techniques

Abstract A duration test was conducted at the inlet bay of Hsin-Da Power Plant in Taiwan to study the roles of macro-organisms and micro-organisms in facilitating or inhibiting the microbiologically influenced corrosion (MIC) of metal alloys in seawater. A significant amount of fouling organisms was grown on the attachment plate submerged in the field for 56 and 92 days. Copper toxicity resulted in little fouling but slight corrosion still occurred on the copper plate. Titanium was found to be 100% fouled by the fouling organisms. Stainless steel plate was found to have the worst MIC corrosion among the tested samples. After mechanically peeling off the polychaeta and barnacle organisms, samples were analyzed by the scanning Auger microprobe (SAM). SAM results indicate that sodium, oxygen and sulfur accumulated on the MIC regions of the sample surfaces covered by the fouling organisms, and chlorine and nitrogen were distributed in the regions compensating for the local distributions of sodium, oxygen and sulfur. It was proposed that the development of a thick macro-fouling mass will cause the anaerobic zones to develop on the metal surface, wherein the MIC processes are accelerated.

Diffusion barrier study on TaSix and TaSixNy

Abstract TaSi x and TaSi x N y films as diffusion barriers between aluminium and a silicon substrate have been investigated in this work. The grain sizes of the films were measured from transmission electron micrographs. The chemical binding was examined by X-ray photoelectron spectroscopy. Then various sintering conditions were applied on Al/barrier/ n + -p-Si diodes while the specific contact resistance and the diode reverse leakage current density were measured to study the stability of the TaSi x and TaSi x N y films as diffusion barriers. Results show that the TaSi x N y film can act as a better diffusion barrier than the TaSi x film, even though the TaSi x N y film shows a slightly higher resistivity (170 μΩ cm) than the TaSi x film (68 μΩ cm). The Al/TaSi x N y /n + -p-Si diode remained stable after sintering at 530°C for 30 min, while the TaSi x film of the same thickness can no longer act as an effective barrier if the sintering temperature is higher than 475°C. The enhanced barrier property of the TaSi x N y film is caused by the additional existence of Si-N and Ta-N bondings.

Simulation of microcrystal grain size effect in microcrystalline silicon thin film transistors

Abstract A numerical simulation to predict and analyze the characteristics of microcrystalline silicon thin film transistors is proposed. This model is derived from Poissons equation, with the consideration of the effect of microcrystal grain size. A reference microcrystal grain size is introduced and is obtained from the dependence of the energy gap on grain size. From this the density of microcrystalline silicon acceptor-like states and the mobility of microcrystalline silicon can also be deduced as functions of the grain size. The I – V characteristics of the device are obtained and are compared with experimental data from the literature. The results indicate that the proposed model conforms fairly well with the literature data.

A theoretical analysis of temperature dependence on hydrogenated amorphous silicon thin-film transistors

The temperature dependence on current-voltage characteristics of hydrogenated amorphous silicon thin-film transistors is investigated. Experiments have been performed from 304 to 404 K, while a theoretical model is proposed to explain the experimental data. In this model, the current-voltage characteristics of hydrogenated amorphous silicon thin-film transistors are derived from the Poissons equation in which the temperature dependence on the concentration of the localized charges, the concentration of electrons in the conduction band, and the field-effect mobility of the electrons is considered. This proposed model conforms very well to the experimental data.

Investigations of the growth of tungsten and tungsten silicides on SiO2 substrates by low pressure CVD method

Abstract Growth of tungsten and tungsten silicide films on SiO2 substrate through the reaction via WF6, SiH4, and/or H2 gases in a vertical type low pressure chemical vapor deposition (LPCVD) system was investigated. It was found that the metal tungsten can be selectively deposited on Si, but not on SiO2. If a very small amount of SiH4 is introduced into the reaction chamber, tungsten films can be deposited on the SiO2 substrate, and its growth rate is highly dependent on the substrate temperature. For the growth of tungsten silicides, amorphous WSix was observed in the as-deposited films on the SiO2 substrate. After short annealing, formation of W and tetragonal W5Si3 crystallites was observed. After prolonged annealing, the film finally transforms into W and WSi2 if x≲2.3, and transforms completely into WSi2 if x>2.3. The resistivity of the film drops from 1400 to 160 μΩ cm after annealing at 700°C for 30 min, and begins to increase after further annealing. The change of the film resistivity can be explained by the improvement of the crystallinity, and the transformation to W5Si3, WSi2, and W.

Effect of heat-treatment on Electrochemical Properties of Ti-Ni-Cr Based Hydrogen Storage Alloys for Ni/MH Batteries

Effect of heat-treatment on electrochemical properties of Ti-Ni-Cr based hydrogen storage alloys for Ni/MH batteries were investigated. All alloys were prepared by melting the mixture of Ti, Ni, and Cr metals in arc furnace under an argon atmosphere. At first, Ni were partially substituted by Cr to form the Ti2Ni(subscript 1-x)Cr(subscript x) alloy with x=0, 0.2, 0.4 and 0.6, and then heat-treatment was performed on the prepared Ti-Ni-Cr based alloy electrodes at 800℃ for 10 hr in vacuum furnace. The hydrogen absorption-desorption characteristics in gas-solid reactions and the electrochemical properties as metal hydride (MH) electrodes were investigated. Changes in the crystal structure and morphology after heat-treatment were identified from X-ray diffraction pattern (XRD). Results indicated that heat-treatment on the Ti-Ni-Cr based alloy electrodes could improve their hysteresis curve, but decrease the energy capacity of the alloy.

A theoretical analysis of temperature dependence on hydrogenated amorphous silicon thin-film transistors with the consideration of resistance of the a-Si:H film layer as a function of temperature

The temperature dependence on current-voltage characteristics of hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs) is investigated. Experiments have been performed from 304 to 404 K, while a theoretical model is proposed to explain the experimental data. The current-voltage characteristics of hydrogenated amorphous silicon thin-film transistors are derived from the Poissons equation, in which the temperature dependence on the concentration of the localized charges, the concentration of electrons in the conduction band, and the field-effect mobility of electrons is considered. The work is further extended by considering the resistance of the a-Si:H film layer as a function of temperature. It is shown that the results conform the experimental data to a certain degree. And with the consideration of the resistance of the a-Si:H film layer as a function of temperature, the fitting of the theoretical model to the experimental data is much improved.