Raman spectra of 6H-SiC crystals including stacking faults have been examined for the c face using backscattering geometry. The intensity of the transverse optical phonon band at 796 cm−1, which corresponds to the phonon mode at the Γ point in 3C-SiC, is sensitive to the stacking faults. We found that the intensity of this band depends on the stacking fault density. This is explained based on the bond polarizability model. The spatial distribution of the stacking faults is studied by Raman image measurement.
The new superconductors discovered after MgB 2 are discussed. Two serious claims have been made so far. The first claim concerns a graphite-sulfur composite undergoing a transition at 35 K. Since the magnetic transition clearly has the characteristics of a superconducting shielding effect, it would be worthwhile to investigate the possibility of increasing the sample volume responsible for this transition. However, there is no zero-resistance transition and the authors suggest that the superconductivity could be due to a surface effect. Carbon in this sample has the same structure as boron in MgB 2 . The second claim is more modest, but it is really a superconduting transition at 1 K. The sample is a single crystal of Cd 2 Re 2 O 7 . The Re cations could be in a mixed valence state, but the charges do not seem to localize by lowering the temperature. The importance of these results is the discovery of a new oxide structure such as the pyrochlore, which can host a superconducting state.
Effects of H irradiation on purifying Cu films and improving their surface roughness as well as size and orientation of Cu grains in the films have been examined using a newly developed plasma CVD reactor equipped with an H atom source, in which Cu(hfac)2 is supplied as the source material. The H irradiation is effective in purifying the Cu films, increasing the grain size, and reducing the surface roughness, while it has no effect on the grain orientation. The decrease in dissociation degree of material gas leads to reduction of the surface reaction probability of Cu- containing radicals, which is important to realize conformal deposition in fine trenches. Using the control of dissociation degree of material gas independent of H irradiation, we have demonstrated conformal deposition of smooth Cu films in the trench using the developed plasma CVD reactor.
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