Evolution of structure, morphology, and reactivity of hydrogenated amorphous silicon film surfaces grown by molecular-dynamics simulation

The relationship between the structure, H coverage, morphology, and reactivity of plasma deposited hydrogenated amorphous silicon (a-Si:H) film surfaces was investigated using molecular-dynamics simulations. Surfaces of a-Si:H films grown with SiH₃ as the sole deposition precursor are found to be remarkably smooth due to a valley-rilling mechanism where mobile precursors, such as SiH₃ and Si₂H₆, diffuse and react with dangling bonds in the valleys on the surface. Surface valleys are reactive due to the increased concentration of dangling bonds and decreased H coverage in these regions. The previously speculated physisorbed configuration, where SiH₃ is weakly bound to the surface through a H atom, is highly unlikely to be the mobile precursor state.