Equilibrium and nonequilibrium hydrogen coverages on vicinal Si(001) surfaces: Diffusion barriers and bonding energies
|Reviews and Highlights||Quantum Science||Molecular and Soft-matter||Ultrafast Nano-optics and Nanophotonics||Mineralogy and Geochemistry|
The surface kinetics of hydrogen adsorbed on Vicinal Si(001) surfaces, misoriented towards the  direction, is investigated by means of optical second-harmonic generation. Following the selective saturation of the double-height DB steps by exposing the surface to a well-defined dose of molecular hydrogen, the transition from this nonequilibrium to an equilibrium hydrogen distribution is monitored in the temperature range between 580 and 730 K. A thermally activated diffusion process with a barrier of 1.7±0.15 eV associated with the step depletion is observed. From measurements of the equilibrium hydrogen coverage the steps are found to be energetically favored with a H2-chemisorption energy difference of ~0.2 eV between step and terrace sites.