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

Abstract

An infinite-layer-structure epitaxial thin film of LaNiO2 was prepared by low-temperature reduction with CaH2 from a LaNiO3 epitaxial thin film grown on a SrTiO3(100) substrate. The oxygen content changed reversibly from the perovskite LaNiO3 to the infinite-layer LaNiO2 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.