Epitaxial thin films of ATiO3-xHx (A= Ba, Sr, Ca) with metallic conductivity

Year: 2012 DOI: 10.1021/ja302465c

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Takeshi Yajima, Atsushi Kitada, Yoji Kobayashi, Tatsunori Sakaguchi, Guillaume Bouilly, Shigeru Kasahara, Takahito Terashima, Mikio Takano, Hiroshi Kageyama.   Journal of the American Chemical Society, 2012, 134, 8782-8785.


Epitaxial thin films of titanium perovskite oxyhydride ATiO3−xHx (A = Ba, Sr, Ca) were prepared by CaH2 reduction of epitaxial ATiO3 thin films deposited on a (LaAlO3)0.3(SrAl0.5Ta0.5O3)0.7 substrate. Secondary ion mass spectroscopy detected a substantial amount and uniform distribution of hydride within the film. SrTiO3/ LSAT thin film hydridized at 530 °C for 1 day had hydride concentration of 4.0 × 1021 atoms/cm3 (i.e., SrTiO2.75H0.25). The electric resistivity of all the ATiO3−xHx films exhibited metallic (positive) temperature dependence, as opposed to negative as in BaTiO3−xHx powder, revealing that ATiO3−xHx are intrinsically metallic, with high conductivity of 102−104 S/cm. Treatment with D2 gas results in hydride/deuteride exchange of the films; these films should be valuable in further studies on hydride diffusion kinetics. Combined with the materials’ inherent high electronic conductivity, new mixed electron/hydride ion conductors may also be possible.