Formation of nanostructures on surface of SiC by laser radiation

Abstract

Formation of nanostructures on a surface of 6H–SiC:N, B under irradiation by the N 2 pulsed laser was found and studied. The nanostructures have a shape of a hill, and arise along the circular line around the focussed spot. We propose the following model for the explanation of the formation of nano-hills. The laser irradiation creates a liquid phase in the bulk under a thin solid state layer. The pressure of laser radiation (LR) together with the pressure of the liquid phase result in a bulging of the material on the surface. The results of experimental studies of the irradiated surface by Atomic Force Microscope (AFM) and Friction Force Microscope (FFM) allow us to conclude that the concentration of nitrogen in nano-hills is bigger compared with that of the unirradiated crystal. The increase of the nitrogen concentration in the hills can be explained by presence of the temperature gradient field. The 6H–SiC samples contain both N and B atoms with strongly different covalent radii, in the temperature gradient field atoms of N move towards the irradiated surface, while atoms of B—into the bulk of the crystal. The obtained results are explained by presence of the Thermogradient effect (TGE).