The surface kinetics of H, which was adsorbed onto vicinal (001) surfaces which were misoriented towards the [110] direction, was investigated by means of optical second-harmonic generation. Following selective saturation of the double-height steps by exposing the surface to a well-defined dose of molecular H, the transition from the non-equilibrium to an equilibrium H distribution was monitored at temperatures ranging from 580 to 730K. A thermally activated diffusion process with a barrier of 1.7eV, which was associated with step depletion, was observed. By measuring the equilibrium H coverage, the steps were found to be energetically favored; with a H2-chemisorption energy difference of about 0.2eV between step and terrace sites.

Equilibrium and non-equilibrium hydrogen coverages on vicinal Si(001) surfaces M.B.Raschke, U.Höfer: Physical Review B, 1999, 59[4], 2783-9