Electrical Properties of Epitaxial Thin Films of Oxyhydrides ATiO3–xHx (A = Ba and Sr)

We have studied electronic properties of perovskite oxyhydrides ATiO 3– x H x (A = Ba, Sr). Epitaxial thin films of ATiO 3– x H x with various hydride compositions, up to x = 0.58 for Ba and x = 0.45 for Sr, are prepared by the low-temperature CaH 2 reduction of the corresponding oxide films deposited on (LaAlO 3 ) 0.3 (SrAl 0.5 Ta 0.5 O 3 ) 0.7 (LSAT) substrates by pulsed laser deposition. Resistivity measurements for A = Sr show a metallic phase over a wide range of H – composition, implying a substantial stabilization of H 1s orbitals that should be distributed over O 2p orbitals. On the other hand, for A = Ba, a semiconducting behavior is seen up to ∼5–8% of H – substitution. Interestingly, a similar contrasting behavior is observed in a Nb-substituted BaTiO 3 and SrTiO 3, which suggests that a local cation–off centering in lightly doped Ba films creates in-gap states in the band structure (as opposed to the Sr films), hindering the electron transport.