Quenching of optical second harmonic generation at the Si(001) surface by hydrogen adsorption

Abstract

A detailed study of the surface second harmonic generation (SHG) efficiency at $\mathrm{Si}(001)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ is presented. We have measured the SHG efficiency as a function of hydrogen coverage, relative to that of the clean surface, at a fundamental wavelength of 1064 nm, for substrate temperatures between 200 and 600 K, and for different polarization directions of both the fundamental and second harmonic light beams. The dependence of hydrogen-induced SHG quenching on H coverage is explained with a statistical mechanical model that has previously been invoked to describe the kinetics and dynamics of ${\mathrm{H}}_{2}$ adsorption/desorption. The model predicts an increase in the SHG intensity upon rearranging randomly adsorbed H atoms by thermal annealing, which was confirmed experimentally. An empirical parametrization of the SHG efficiency curves is presented which may be used as a practical calibration to determine hydrogen coverage on Si(001) as a function of SHG signal and temperature.