Preparation of mixed Al₂O₃/SiO₂ thin films supported on Mo(100)

Deposition of metallic Al onto a SiO₂ thin film, supported on a Mo(100) substrate, at 100 K, followed by annealing to 1200 K, leads to the formation of a homogeneous Al₂O₃/SiO₂ film. In the temperature regime from 100 to 800 K, Al is completely oxidized and metallic Si is formed. The important step for the formation of Si-O-Al bonds is the concerted diffusion of aluminum oxide into the bulk of the SiO₂ film with the concomitant desorption of volatile silicon monoxide as a result of the solid state reaction of Si and SiO₂ in the temperature range from 800 to 1200 K. XPS core level shifts indicate that the electronic structure of these films is very similar to that of bulk aluminosilicates.