Shinku

Pb₅CrO₈ thin films have been deposited by means of an electron beam evaporation technique on glass substrates. The thin film fabrication conditions were studied using X-ray diffraction and TEM as a function of substrate temperature (Ts) and annealing temperature (Ta). It was found that the substrate temperature contributed to film crystallinity, and the annealing proces enhanced film orientation. The optimum conditions of Ts and Ta were 300°C and 350°C, respectively. The optical bandgap energy of the thin film, derived from the transmittance and reflectance spectra, was 2.22 eV. A Pb₅CrO₈ thin film device with Au interdigital electrodes was photosensitive in the visible region. The ratio of photocurrent to darkcurrent was about 160 and the photocurrent increased linearly with the light intensity in the log log-plot. The result suggests that Pb₅CrO₈ may be a new photoconductive material.

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Irradiation of a small spot on the wall of a vacuum chamber with a high power laser pulse causes laser-induced thermal desorption (LITD) of gases which produces a pressure pulse. We measured the peak height and the rate of decay of the pressure pulse of each component gas desorbed at various stages of the degassing process of a vacuum chamber made of stainless steel, A Q-switched YAG laser with a maximum output energy of about 22 mJ/pulse was used for the irradiation. The laser irradiation experiment was started after pumping the chamber for 650 h at room temperature. Subsequent measurements were carried out at room temperature after degassing the chamber for various duration at 100°C, 150°C and 250°C. The sticking probability of gas molecules on the chamber wall can be obtained from the difference between experimental and calculated values of time constants of the decay of pressure pulses. The sticking probability of water molecules increased markedly after degassing the chamber at 250°C.

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