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

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Markus B. Raschke, Peter Bratu, and Ulruch Höfer
Surface Science 410, 351 (1998).
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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 ML s^–1. From their temperature dependence between 780 and 1000 K, activation energies of E_A=3.4±0.2 eV and E_A=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 ML. The results are interpreted in terms of coverage-dependent oxygen-binding configurations, which influence the stability of the oxide layer.