Adsorption and Diffusion of Si Atoms on the H-Terminated Si(001) Surface: Si Migration Assisted by H Mobility

The adsorption and diffusion of Si atoms on the monohydride terminated Si(001)-(2×1) surface is investigated using first-principles total-energy calculations. We find that the Si adatom spontaneously segregates one H atom from a surface Si dimer during adsorption, and further captures the remaining H atom of the same Si dimer during surface migration, leading to the most stable adsorption geometry. The migration of the Si adatom is assisted by the mobility of H atoms, being reduced compared with that on the bare Si surface. It is suggested that the reduction of Si diffusion has disruptive effects on Si homoepitaxy.