Molecular-dynamics studies of the growth modes and structure of amorphous silicon films via atom deposition

Abstract

The growth modes of amorphous silicon (a-Si) films via vapor-phase and low-energy molecular-beam epitaxy are investigated with use of molecular-dynamics simulations. In these simulations, realistic interatomic interaction potentials, which include two- and three-body interactions, are employed. The dependencies of the growth mechanism and structure of the grown amorphous film on the method of deposition are investigated. For deposition normal to a (111) crystalline Si substrate, a uniform a-Si film is generated. Deposition using a beam directed at 60° from the normal to the substrate results in preferential orientation of density inhomogeneities corresponding to a columnar microstructure in the film, while deposition where the impinging particles arrive at random directions to the substrate yields an a-Si film containing microvoids. The structural characteristics of the amorphous material and of the interface between the crystal and the amorphous film are analyzed.