Synchrotron Radiation Photoemission and Photostimulated Desorption of Deuterated Methanol

Deuterated methanol adsorption on Si(111)7 × 7 and Si(100)2 × 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 σO-D bond breakage and σSi-O bond formation. Site selectivity is displayed by the methoxy species on Si(111)7 × 7 surface, since the S2 surface state related to the rest atoms is quickly quenched upon low coverage adsorption. The S1 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 Is threshold, where multiple desorption processes are possibly taking place.