MODIFICATIONS OF ALPHA-AL2O3(0001) SURFACES INDUCED BY THERMAL TREATMENTS OR ION-BOMBARDMENT

Monocrystalline alpha-Al2O3(0001) surfaces exhibit various crystallographic structures, depending on the heat treatment they undergo. These different thermally induced surface reconstructions, observed by means of low-energy electron diffraction, correspond to distinct surface compositions, whereas ion bombardment destroys any surface crystallinity but leaves surface stoichiometry unchanged. Whatever the treatment, the band gap is modified, due to changes in the aluminium coordination number and site geometry. These structural modifications were investigated combining X-ray photoelectron and low-energy electron loss spectroscopies.