Insights into Silica Bilayer Hydroxylation and Dissolution.

Hydroxylation and dissolution of well-structured silica bilayer films grown on a ruthenium single-crystal support (SiO/Ru(0001)) was studied by temperature programmed desorption and X-ray photoelectron spectroscopy (XPS). Water desorption signals from SiO/Ru(0001) hydroxylated by electron-bombardment of adsorbed ice at 100 K were found to be comparable to those of hydroxylated bulk silica samples and attributed to adsorbed molecular water and silanol groups (vicinal and terminal). Isotopic exchange between O-labeled SiO and O-labeled water suggests the occurrence of dynamic siloxane bond cleavage and re-formation during electron bombardment.

Electron stimulated hydroxylation of a metal supported silicate film.

Water adsorption on a double-layer silicate film was studied by using infrared reflection-absorption spectroscopy, thermal desorption spectroscopy and scanning tunneling microscopy. Under vacuum conditions, small amounts of silanols (Si-OH) could only be formed upon deposition of an ice-like (amorphous solid water, ASW) film and subsequent heating to room temperature. Silanol coverage is considerably enhanced by low-energy electron irradiation of an ASW pre-covered silicate film.