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

Markus B. Raschke and Ulrich Hofer
Phys. Rev. B 59, 2783 (1999).
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The surface kinetics of hydrogen adsorbed on Vicinal  Si(001) surfaces, misoriented towards the [110] 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.