MOLECULAR-ORIENTATION OF TRIDECAFLUOROSILANE ON THE SURFACE OF OXIDIZED SILICON

The orientations of tridecafluorosilane molecules adsorbed from solution onto Si(111) surfaces (with a thin oxide), were studied in ultra-high vacuum using angle-dependent X-ray photoelectron spectroscopy, XPS(θ). When adsorbed from dilute solutions, the adsorbed layer is very thin, since these linear molecules lie flat on the surface of the Si substrate. When adsorbed from concentrated solutions, however, the adsorbed layer is thicker, since the molecules exhibit a strong preference to stand up on the surface. The data on the thicker adsorbate layer are consistent with a molecular orientation where the major axis of the molecules makes an angle with the surface consistent with sp3 hybridization of the Si-atom in the silane molecule. © 1990.