Ab initio study of silane and disilane adsorption on Si(100)-(2x1) surface

Silane (SiH$_{4})$ and disilane (Si$_{2}$H$_{6})$ are common precursors for the growth of Si and SiO$_{2 }$thin films for microelectronic and photovoltaic devices. The adsorption of silane and disilane on Si(100)-(2x1) surface, which are important steps in the growth of Si films in atomic layer epitaxy (ALE), were investigated using density functional theory calculations. The silane molecule dissociates on the Si surface at the intra-dimer site with barrier energy of 0.22 eV. We investigate both Si-Si bond cleavage and Si-H bond cleavage mechanisms for adsorption of Si$_{2}$H$_{6}$ on Si (100) surface. A Si-H bond cleavage mechanism was found to be more favored than Si-Si bond cleavage mechanism due to the lower barrier energy of 0.04 eV. The lower barrier energy for Si$_{2}$H$_{6}$ dissociation than that of SiH$_{4}$ agrees well with the experimental results showing that Si$_{2}$H$_{6}$ has higher sticking coefficient than SiH$_{4 }$on Si surface at 300K. The vibration frequencies of Si$_{2}$H$_{5}$, SiH$_{3}$, SiH$_{2}$, SiH resulting from dissociation of silane and disilane were calculated and compared with experimental results available. The simulation results will facilitate the controlled ALE for atomically precise manufacturing applications.