Crystalline and electronic structure of epitaxial γ-Al2O3 films

Epitaxial γ-Al2O3 films were fabricated on SrTiO3 (1 0 0) substrates using pulsed laser deposition (PLD) technique. The high quality of epitaxial growth γ-Al2O3 films was confirmed by X-ray diffraction (XRD). Atomic force microscopy (AFM) images indicated the smooth surfaces and the step-flow growth of the films. In order to illuminate the electronic properties and the local structure of the epitaxial γ-Al2O3, we experimentally measured the X-ray absorption near-edge structure (XANES) spectrum at the O K-edge and compared the spectrum with the theoretical simulations by using various structure models. Our results based on XANES spectrum analysis indicated that the structure of the epitaxial γ-Al2O3 film was a defective spinel with Al vacancies, which prefer to be located at the octahedral sites.