FEM study of NOW and NO2W adsorption system

Nitric oxide adsorption on tungsten and nitric dioxide adsorption on tungsten have been investigated by the FEM method. When NO or NO₂ adsorbs gradually on W at 300 K and at 80 K, the FEM patterns which appear at first are found to be similar to those which appear in N₂ adsorption on W. In the case of NO adsorption on W at 80 K, with further exposure, no further change of the FEM patterns is observed. However, in the cases of NO adsorption on W at 300 K, NO₂ adsorption on W at 300 K, and NO₂ adsorption on W at 80 K, further changes of the FEM patterns are observed with further exposure, and the FEM pattern which is obtained at the saturated state is found to be similar to the FEM pattern which appears at the saturated state of O₂ adsorption on W. From the above results it is suggested that NO and NO₂ dissociate on W at 300 and at 80 K.     

Temperature dependence of the linewidth of the first-order Raman spectra for MnF2 crystal

The first-order Raman spectra ofE _gandA _1g modes in MnF₂ crystal were measured at temperatures from 4.2 to 563 K, and the values of the linewidths obtained. The temperature dependence of the linewidths was analyzed by the phonon dispersion curves based on the rigid ion model, and the result showed that it was caused approximately by the cubic anharmonic term in crystal potential energy.     

Diamond-like carbon films prepared by pulsed-laser evaporation

Diamond-like carbon thin films were prepared by pulsed-laser evaporation. In this method a carbon target was irradiated by a XeCl laser with a power density of 3×10⁸ W/cm² and carbon atoms, together with a small number of ions, were produced. Deposition rates and film properties changed sensitively with substrate temperature. The films deposited at 50°C were diamond-like, having reasonable hardness, high refractive index (2.1–2.2 at 633 nm), optical transparency in the infrared, electrical resistivity of 10⁸ cm and chemical inertness (no dissolution in a HFHNO₃ solution). The band gap measured from optical absorption was 1.4 eV. Raman spectrum and infrared absorption, whose features varied with the substrate temperature, were also measured. The films were amorphous and no crystallinity was observed, as confirmed by x-ray diffraction, transmission electron diffraction and Raman spectroscopy. Hydrogen atoms were incorporated in the films with a typical H/C ratio of 0.3. The application of a negative bias to the substrate modified the deposition due to the presence of ions.