Growth and oxidation of ultra-thin Al films on the Re(0001) surface

The growth and oxidation of ultra-thin Al films on the Re (0001) surface are studied by X-ray photoelectron spectroscopy (XPS), low energy ion scattering (LEIS) and high resolution electron energy loss spectroscopy (HREELS). The first monolayer of Al grows in a two-dimensional fashion and almost completely covers the Re(0001) substrate at 300 K. Al films of thickness <15 Angstrom are oxidized by annealing to 970 K in 1 x 10(-4) Torr oxygen to form stoichiometric aluminium oxide films. LEIS results show that the oxide films formed at 970 K cover the substrate completely. Hexagonal LEED patterns are observed from the aluminium oxide films, consistent with ordered structures similar to those of crystalline alpha- or gamma-Al2O3. The XPS Al 2s and O 1s binding energies of the aluminium oxide films increase as a function of the film thickness; this thickness-dependent shift may be related to Schottky barrier formation at the Al2O3/Re interface.