SYNCHROTRON-RADIATION-INDUCED DECOMPOSITION OF THIN NATIVE OXIDE-FILMS ON SI(100)

Thin native oxide films on Si(100) have been previously shown to be decomposed by exposing the film surface to synchrotron radiation (SR) in the vacuum-ultraviolet region. In this study, photoemission and photon-stimulated desorption (PSD) experiments are performed to investigate the synchrotron-radiation-induced decomposition of a native oxide film on Si(100). For mass analysis of the PSD ions, the time-of-flight method is utilized. Si 2p core-level and valence-band photoemission spectra demonstrate that the native-oxide decomposition preferentially takes place on the thin parts of the native oxide film which are terminated with Si - OH and Si - H bonds. It is shown that the native-oxide decomposition is accompanied by desorption of H + and O+ ions. The H+ PDS ion yield decreases exponentially with increasing the exposure time of SR, whereas the O+ PSD one first increases with the exposure time, and subsequently decreases with the exposure time after the H+ PSD ion yield substantially drops. The behavior of the O+ PSD ion yield is explained in terms of the photon-induced Si - O bond breaking reaction promoted by removing surface hydrogen atoms through the H+ PSD process in which a Si - H bond and the O - H bond in a Si - OH bond are ruptured.