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.