Papers by Author: Shigeki Matsuo

Abstract: Femtosecond (fs) laser modification on single crystal silicon carbide (SiC) was studied from the viewpoints of electric conductivity. Fourier transform infrared (FTIR) spectroscopy was carried out on femtosecond laser modified area. The intensity decrease of reststrahlen band due to the modification was observed, and this decrease was explained by the degradation of crystallinity due to the laser irradiation. Polarization dependence of reststrahlen band was also observed on laser modified samples. Current-voltage characteristics and Hall measurements on fs-laser modified region were carried out by fabricating the metal contacts on the ion implanted areas. The specific resistance up to 5.9×10-2 m was obtained for fs-laser modified area.

Abstract: We carried out cross-sectional transmission electron microscopy (TEM) investigation of femtosecond laser-induced ripples formed on 4H-SiC single crystal surface. Here, we paid attention to the crystal structures underlying the coarse and fine ripples and the three-dimensional distribution of amorphous phase. Conventional and high-resolution TEM analyses made clear that a continuous amorphous layer approximately of 50 nm thick exist at the topmost region of both coarse and fine ripples. The result strongly suggests that the fundamental surface deformation process is common for coarse and fine ripples, even though the factors which determine their periods are different.

Abstract: Deep-ultraviolet (DUV) micro-Raman spectroscopy was applied to study the micro structures of surface defects in a 4H-SiC homoepitaxially grown film. From DUV Raman spectrum, inclusions of 3C-SiC was found in comet defects. The shape of 3C-structure in comets was investigated and it was found that 3C inclusions in comets can be classified into two types. In addition, spectrum broadening due to the coupling of nonfolded longitudinal optical phonon mode and the photo-excited carriers was also found. The formation mechanisms of 3C inclusion in comets were discussed.