Binding and surface diffusion of SiH3 radicals and the roughness of hydrogenated amorphous silicon

Abstract

Local density formalism pseudopotential calculations find that the growth radical SiH3 binds to the hydrogen-terminated (111)Si surface. The bound site is not the three-center Si–H–Si bridging site previously assumed. It has a direct Si–Si bond between the SiH3 and the surface Si, and the terminal hydrogen is displaced to a bond center of a lateral surface Si–Si bond. This site is more stable as the unpaired electron can delocalize over more Si–Si bonds. A bound site validates the standard model of the growth of hydrogenated amorphous silicon (a-Si:H) and microcrystalline Si, in which a mobile growth species allows surface diffusion and creates smooth surfaces.