Comparison of reduction agents in the synthesis of infinite-layer LaNiO sub(2) films

Reduction agents, such as activated carbon, TiH sub(2), and CaH sub(2), were compared from a viewpoint of the facility for the topotactic reduction of LaNiO sub(3) to LaNiO sub(2) films. Activated carbon did not yield infinite-layer LaNiO sub(2) whereas both of TiH sub(2) and CaH sub(2) yielded infinite-layer LaNiO sub(2) with low resistivity ( similar to 1 m Omega cm at 300 K) as well as metallic behavior down to 70 K. Thermal desorption spectroscopy indicated that H sub(2) released from metal hydrides plays a dominant role in the topotactic reduction.