Comparison of reduction agents in the synthesis of infinite-layer LaNiO2 films

• Reduction agents were compared from a viewpoint of the facility for topotactic reduction of LaNiO3 to LaNiO2 films.
• TiH2 and CaH2 yielded infinite-layer LaNiO2 with low and metallic resistivity.
• H2 released from metal hydrides plays a dominant role in the topotactic reduction.

Reduction agents, such as activated carbon, TiH2, and CaH2, were compared from a viewpoint of the facility for the topotactic reduction of LaNiO3 to LaNiO2 films. Activated carbon did not yield infinite-layer LaNiO2 whereas both of TiH2 and CaH2 yielded infinite-layer LaNiO2 with low resistivity (∼1 mΩ cm at 300 K) as well as metallic behavior down to 70 K. Thermal desorption spectroscopy indicated that H2 released from metal hydrides plays a dominant role in the topotactic reduction.