Lattice defects in SiC

This paper describes experiments for paramagnetic defects and the change of Raman spectrum by ion bombardments. Lattice disorder is reflected in Raman scattering and point defects, particularly paramagnetic defects, which are observed by ESR. Conventionally, ESR experiments have been carried out in crystals irradiated with neutrons and electrons, while ion implantations have been used for Raman scattering. To obtain the correlation, ion bombardments are applied to both of them. Two paramagnetic centers are found in crystals irradiated with neutrons and ions, and plausible models corresponding to these centers are proposed. The change of Raman Spectrum due to both acoustic and optical phonons are studied as a function of the fluence of bombarding ions. The Raman lines from the phonons at the center of the Brillouin zone are less sensitive to the amount of defects, but the lines from the phonons in the intermediate points in the zone significantly reduce their intensities even by low fluence of ion bombardments. It is concluded from experimental results that the phonons at the center of the Brilouin zone receive less influence by ion bombardments in comparison with those at the intermediate and the boundary of the zone. (Nogami, K.)