Reversible changes of epitaxial thin films from perovskite LaNiO3 to infinite-layer structure LaNiO2

Abstract

An infinite-layer-structure epitaxial thin film of ${\text{LaNiO}}_2$ was prepared by low-temperature reduction with ${\text{CaH}}_2$ from a ${\text{LaNiO}}_3$ epitaxial thin film grown on a ${\text{SrTiO}}_3\left(100\right)$ substrate. The oxygen content changed reversibly from the perovskite ${\text{LaNiO}}_3$ to the infinite-layer ${\text{LaNiO}}_2$ without losing the structural framework and the topotactic relationship. Consequently, the oxidation state of Ni ions in the film changed from trivalent to divalent to monovalent.