Phosphorus-doped Si0.8Ge0.2 thin films were deposited on the Si3N4/SiO2/Si substrate by the RF sputtering. Thermal annealing was carried out to crystallize as-deposited, amorphous-like SiGe thin films. With increasing annealing temperature and time, the crystallization of the SiGe thin films progressed, resulting in a high carrier mobility and a large absolute value of Seebeck coefficient. The SiGe thin film deposited on the Si3N4/SiO2/Si substrate and then annealed at 850°C for 5 h at an argon flow rate of 150 cc/min showed a Seebeck coefficient of -198 µV/K, a Hall mobility of 10.54 cm2/Vs, a carrier concentration of 1.1×1018 cm-3 at 100°C. The thermoelectric hydrogen sensor with the SiGe thin film annealed at 850°C for 5 h showed a voltage signal of 5.81 mV, a catalyst activity of 16.17°C and a response time, corresponding to 90% voltage signal of 50 s for 3% H2 in air. The sensor operating at 100°C detected hydrogen in air at concentrations from 0.01 to 3%, and showed a good linearity between voltage signal and gas concentration.
Abstraet.A spin-probe electron spin resonance (ESR) study was made on the alcoholic solution flowing through a quartz column packed with MCM-4I to clarify the dynamics of the liquid molecules in the nanochannel. The ESR spectra of a few hydrophobic spin probes showed that they undergo rotational diffusion preferentially along the longest molecular axis, indicating that the nanochannel is effectively narrowed further for these radicals by the influence of the solvent. Since almost identical ESR spectra were observed for the static samples, which were prepared in vacuo by introducing the solutions into the quartz tube with the MCM-41 powder and sealing off, the solution in the above-mentioned experiment should really flow through the nanochannel of MCM-41. Although a laminar flow is expected from the classical theory, the calculated flow rate is almost zero. In addition, the duration for the spin-probe mo[ecules to flow through the column was basically not dependent on their affinity to the silica surface. To explain all these phenomena, we propose a model that the liquid molecules flow collective[y by slipping on the surface of the nanochannel.
The structure and properties of Na-Si-0-N oxynitride glasses have been studied by molecular dynamics calculations using a pair potential of the Busing approximation of the Born-Mayer-Huggins type. Nitrogen atoms bonded to one, two, and three silicon atoms coexist in the glass structure. The mean of the number of silicon atoms bonded to a nitrogen atom ranges from 2.4 to 2.1, decreasing with increasing Na,O content from 15 to 30 mol%. It has been assumed that nitrogen atoms bonded to two or fewer silicon atoms are formed when nitrogen atoms substitute for nonbridging atoms. The bond angle LSi-N-Si exhibits a bimodal distribution around 105-135" and 140-170", roughly corresponding to the nitrogen atoms bonded to three and two silicon atoms, respectively. The dependences of the density, the bulk thermal expansion, and the bulk modulus on the nitrogen content are consistent with those observed in real systems.
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