Re-distribution of oxygen at the interface between γ-Al2O3 and TiN

Interface of TiN electrode with gamma-Al2O3 layers was studied using near edge X-ray absorption fine structure, conventional X-ray photoelectron spectroscopy and photoelectron spectroscopy with high energies. Despite the atomic-layer deposited Al2O3 being converted into thermodynamically-stable polycrystalline cubic gamma-phase by high-temperature (1000 or 1100 degrees C) anneal, our results reveal formation of a thin TiNxOy (approximate to 1-nm thick) interlayer at the interface between gamma-Al2O3 film and TiN electrode due to oxygen scavenging from gamma-Al2O3 film. Formation of the TiO2 was not observed at this interface. As environmental effect, a strong oxidation resulting in formation of a TiO2(1.4 nm)/TiNxOy(0.9 nm) overlayers on the top of the TiN electrode is traced. Development of O-deficiency of gamma-Al2O3 is observed and related to the polarization anisotropy due to the preferential orientation of spin states involved in the X-ray absorption in the plane parallel to the surface. Investigation of the TiN electrode reveals the predominantly "stretched" octahedra in its structure with the preferential orientation relative the interface with gamma-Al2O3. This anisotropy can be correlated with approximate to 200 meV electron barrier height increase at the O-deficient TiN/gamma-Al2O3 interface as compared to the TiN/gamma-Al2O3 barrier formed under abundant oxidant supply condition as revealed by internal photoemission of electrons from TiN into the oxide.