Selective ion photodesorption from NO adsorbed on Si(111)7 X 7 following core excitation

摘要

Selective ion photodesorption from NO adsorbed on Si(111)7 X 7 has been investigated by core electron excitation. In a first step, the adsorption of nitric oxide on the clean Si(111)7 X 7 surface has been studied over the temperature range from 15 K to room temperature using ultraviolet photoemission spectroscopy, x-ray photoemission spectroscopy, and photon stimulated desorption of ions. At room temperature, NO was found to react with the surface silicon adatoms to form silicon oxynitride sites (SiN_xO_y). At low temperature and low coverag e, in addition to a permanent dissociative adsorption, a transient molecular adsorption has been observed. At low temperature and high coverage, NO was found to be condensed. In a second step, ion photodesorption induced by core electron excitation of both the adsorbate and the substrate has been studied. Quite interestingly, selective ion photodesorption was observed by core electron excitation of both dissociatively selective ion photodesorption was observed by core electron excitation of both dissociatively adsorbed NO at room temperature and condensed NO molecules at low temperature. An "ultrafast dissociation" is proposed to explain the results of condensed NO molecules at low temperature.