Adsorption and diffusion of Si adatom on hydrogenated Si(100) surfaces

We present first-principles total-energy calculations which provide a detailed picture of adsorption and diffusion of a Si adatom on hydrogenated Si(100) surfaces. We find that the adatom spontaneously substitutes for the H atom upon adsorption. We also find that the pathways and barriers of the adatom diffusion are sensitive to H coverage. Calculated results are consistent with H-induced variation in morphology of overlayers observed in epitaxial growth.