Abstract
Photon-stimulated desorption (PSD) of positive ions from thick SiO2 films has been investigated by means of time-of-flight mass spectroscopy. From the untreated surface, H+, H2+, O+, OH+, H2O+, SiHx+ (x=0–3), and SiO+ were detected. Both soft x-ray irradiation and Ar+ ion bombardment reduced the H+ and O+ yields and increased the SiHx+ yield as a result of preferential removal of the oxygen-terminated sites at the outermost surface. The O+ and H+ PSD yields are correlated but the SiHx+ and H+ yields are not, indicating that most of the H+ ions originate from hydroxyl sites. Thermal treatment of the specimen at 800 °C, on the other hand, reduced the intensity of all the ion signals because of the structural change induced by condensation of H2O with the formation of surface siloxane bonds.
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