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

Interface of TiN electrode with γ-AlO 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 AlO being converted into thermodynamically-stable polycrystalline cubic γ-phase by high-temperature (1000 or 1100 °C) anneal, our results reveal formation of a thin TiNO (≈1-nm thick) interlayer at the interface between γ-AlO film and TiN electrode due to oxygen scavenging from γ-AlO film. Formation of the TiO was not observed at this interface. As environmental effect, a strong oxidation resulting in formation of a TiO(1.4 nm)/TiNO(0.9 nm) overlayers on the top of the TiN electrode is traced. Development of O-deficiency of γ-AlO 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 γ-AlO. This anisotropy can be correlated with ≈200 meV electron barrier height increase at the O-deficient TiN/γ-AlO interface as compared to the TiN/γ-AlO barrier formed under abundant oxidant supply condition as revealed by internal photoemission of electrons from TiN into the oxide.