Microscopic Observation of Degradation of LaNiO₃Ultrathin Films Caused by Air Exposure

Sample degradation of LaNiO₃ ultrathin films on SrTiO₃ (001) substrate caused by air exposure is examined by means of crystal truncation rod (CTR) scattering method. Although the film is conductive right after the sample deposition, long term storage makes it insulating. CTR measurements were performed on three- and four-unit cell-thick samples just after the sample deposition and after six months of storage in air. The results show that the storage induced a signicant increase in the lattice spacing along the surface normal direction with keeping in-plane periodicity. Such a structural change can be caused by escaping oxygen atoms by the thermal uctuation. [DOI: 10.1380/ejssnt.2016.14]