Dissociative adsorption of silane on the Si(100)-(2x1) surface

Density functional theory calculations have been used to explore the mechanism of dissociative adsorption of silane (SiH4) on the Si(100)-(2 X 1) surface. Two reaction paths are described that produce silyl (SiH3) and hydrogen atom fragments adsorbed on the dimer dangling bonds. The energy barrier on the lowest energy path is 12-14 kcal/mol (depending on the details of the theoretical method used), while the barrier on the other path is about 17 kcal/mol. The initial step in both mechanisms is abstraction of a hydrogen atom from silane by an electron-deficient surface atom. It is also possible for the surface to react by forming a bond between the more electron-rich surface atom and the silane Si atom. This latter reaction path has a prohibitively high barrier (39 kcal/mol), and it leads to different products (adsorbed SiH2 and elimination of H-2) . These results are discussed in the context of Si film growth kinetics, ultrahigh vacuum studies of silane adsorption and other theoretical studies of silicon surface chemistry. (C) 1999 American Institute of Physics. [S0021-9606(99)70905-0].