MODELING THE INTERACTION OF HYDROGEN WITH SILICON SURFACES

We have investigated the prospects for developing model potentials for use in classical simulation of structural and dynamical properties of Si surfaces interacting with hydrogen. The point of view adopted requ ires that only short-range two-atom and three-atom interactions appear , and that these component functions should be fully transferable betw een small-molecule gas phase species (e.g. SiH and H-2) and Si surface s with arbitrary extent of hydrogenation. Using the silicon Stillinger -Webrr potential as a starring point and guide, a moderately successfu l set of such interaction functions was derived by non-linear paramete r optimization. This set displays proper bonding geometries and valenc e saturation when applied to several hydride species of intermediate m olecular weight (e.g. Si4H10 and Si10H16), and to dimerized Si(100) in various stages of hydrogenation. Molecular dynamics simulations show relatively large sticking probabilities for impinging H atoms at low i ncident energies, whereas H-2, at comparable energies experiences only non-sticking collisions, both roughly in agreement with experiment. S ome shortcomings of the derived model have been identified, including deficient surface diffusion kinetics; however, possible improvement st rategies have been identified. (C) 1998 Published by Elsevier Science B.V.