Optical second-harmonic investigations of the isothermal desorption of SiO from Si(100) and Si(111) surfaces

By: M. B. Raschke, P. Bratu, and U. Höfer

Surface Science 410, 351 (1998)

The isothermal desorption of SiO from the Si(100) and Si(111) surfaces was investigated by means of optical second-harmonic generation (SHG). Due to the high adsorbate sensitivity of this method, desorption rates could be measured over a wide range from 10−1 to 10−6 M L s−1. From their temperature dependence between 780 and 1000 K, activation energies of EA =3.4 +/- 0.2 eV and EA =4.0 +/- 0.3 eV and pre-exponential factors of n0 =1016 +/- 1 s−1 and n0 =1020 +/- 1 s−1 for SiO desorption were obtained for Si(100) and Si(111), respectively. In the case of the Si(100) surface, a pronounced decrease of the first-order rate constants was observed upon increasing the initial coverage from 0.02 to 0.6 M L. The results are interpreted in terms of coverage-dependent oxygen-binding configurations, which influence the stability of the oxide layer.