An investigation of the TiOx–SiO2/Mo(1 1 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.