Band gap of amorphous and well-ordered Al2O3 on Ni3Al(100)

The vibrational and electronic properties of amorphous and well-ordered alumina formed on Ni3Al(100) were investigated using high-resolution electron energy loss spectroscopy. The structure of well-ordered alumina was analyzed by low-energy electron diffraction. The amorphous Al2O3 films are prepared by adsorption of O-2 at room temperature, while the well-ordered Al2O3 are obtained by direct oxidation of Ni3Al at 1150 K. The band gap energy is similar to3.2 and similar to4.3 eV for amorphous alumina and well-ordered alumina thin films respectively. The lowering of the band gap with respect to the bulk value of Al2O3 is associated with defect-induced states located in the band gap. (C) 2001 American Institute of Physics.