Synchrotron radiation photoemission and photostimulated desorption of deuterated methanol on Si(111)7x7 and Si(100)2x1

Deuterated methanol adsorption on Si(111)7 X 7 and Si(100)2 X 1 surfaces has been investigated, at room temperature, by synchrotron radiation photoemission and photostimulated desorption. Photoemission experiments as a function of methanol coverage show that deuterated methanol adsorption is dissociative on both surfaces and occurs via sigma(O-D) bond breakage and sigma(Si-O) bond formation. Site selectivity is displayed by the methoxy species on Si(111)7 X 7 surface, since the S-2 surface state related to the rest atoms is quickly quenched upon low coverage adsorption. The S-1 surface state is quenched only subsequently at much higher coverages. The photostimulated desorption pattern is similar for the two surfaces and strongly depends on the investigated energy range. D+ is always the most abundant ion produced, but higher mass fragments are present too in the energy range including the C 1s threshold, where multiple desorption processes are possibly taking place.