Effects of surface hydration on the deposition of silane monolayers on silica

The deposition of a silane monolayer on silica depends on the chemical reactions between the silane molecules and the hydroxyl groups on the silica surface. We have studied the effects of dehydration and rehydration of flat silica substrates on the deposition of a self-assembled monolayer of octadecytrichlorosilane by using FTIR spectroscopy and ellipsometry. The results demonstrate that monolayer coverage increases with degree of hydration of the substrate. Patches of ordered chains form on a dehydrated surface and that coverage increases with hydration. A fully hydrated surface, however, is not necessary for complete coverage of the substrate, suggesting that not every silane group is bonded to the surface.