Thermal desorption of ultrathin silicon oxide layers on Si(111)

The mechanism of oxide desorption from the surface of Si(111) is studied. Oxide layers formed by different chemical treatments were thermally removed in a UHV chamber and the removal process was probed by Auger electron spectroscopy. Results show that the oxide formed by HCl desorbs very fast and the desorption rate is initially almost linear in time, while for oxides formed by HNO3 , H2 SO4and NH4 OH the rate is initially slow, becoming faster at later times. Similarity in AES spectra of different oxides indicates that the difference in the desorption rates of different oxides cannot be attributed to the difference in chemical environment. Linear increase of void coverage with the square of time (except for HCl oxide) shows that growth of voids in the oxide layer is controlled by the reaction at the perimeter of voids. The difference in the desorption behaviour of different oxides is attributed to the density of voids.

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