Microscopic analysis of carbon phases induced by femtosecond laser irradiation on single-crystal SiC

Elemental analysis of femtosecond laser-induced modified region was carried out by transmission electron microscopy and Raman spectroscopy. The relative Raman intensities of a-SiC were higher in the peripheral region of laser irradiated spot where the fine ripple was formed. On the contrary, the relative Raman intensities of a-Si were higher in the central region where the coarse ripple was formed. This result suggests that the material migration has strongly occurred in the higher fluence region. On the other hand, the mapping of carbon atoms in the topmost amorphous layer of laser induced periodic structures did not show any significant segregation. In addition, Raman spectroscopic analysis showed that the domain size of carbon was very small (< 1 nm). From these facts, it was found that the carbon atoms were uniformly distributed in the topmost amorphous layer and were randomly connected without forming any observable fine particles.