Hydrogen desorption kinetics from H-Si(111) surfaces studied by optical sum frequency generation and second harmonic generation.

摘要

We have studied hydrogen desorption from a flat H-Si (111)1 × 1 surface at 711K by observing sum frequency generation (SFG) and second harmonic generation (SHG) spectra. Flat H-Si (111) surfaces were prepared by dosing hydrogen molecules in an ultra-high vacuum chamber with a base pressure of 10?8 Pa. Combining the SFG and SHG methods, the desorption order has been clarified over the whole hydrogen coverage range from 1 monolayer (ML) to 0ML. The hydrogen desorption was assigned as second order in the high coverage range of 1ML–0.18ML by using SFG spectroscopy and as first order in the coverage range of 0.18ML–0.0ML by using SHG spectroscopy.