An investigation of the TiOx-SiO2/Mo(1Â 1Â 2) interface

The interaction of TiOx with SiO2/Mo(1 1 2) has been studied using high-resolution electron energy loss spectroscopy, Auger electron spectroscopy, low-energy electron diffraction, and molecular adsorption. Ti at varying coverages was deposited onto a SiO2/Mo(1 1 2) surface followed by oxidation at 600 K and annealing at various temperatures. TiOx disperses and covers the SiO2 surface after oxidation and annealing below 800 K, whereas TiOx-SiO2 interfaces undergo significantly restructuring when annealed to temperatures above 1000 K. Upon annealing a TiOx-covered SiO2(monolayer)/Mo(1 1 2) surface, SiO2 diffuses to the surface and is bonded via Si-O-Ti linkages. SiO2 in this bonding configuration decomposes and desorbs more easily than from a Mo(1 1 2) surface where the binding is via Si-O-Mo linkages. On the other hand, for a TiOx-covered SiO2(multilayer)/Mo(1 1 2) surface, TiOx prefers to phase separate into three-dimensional clusters, minimizing the contact area with the SiO2 substrate. The annealing temperature is a key parameter in defining the properties of TiOx-SiO2 mixed oxide surfaces.