Correlation between the electronic and atomic structure, transport properties, and oxygen vacancies on La0.7Ca0.3MnO₃ thin films

We present a study of the role of oxygen vacancies on the atomic and electronic structure and transport properties on a 20 nm thick La0.7Ca0.3MnO3 film grown by the pulsed laser deposition method on a SrTiO3 (001) substrate. The results show that oxygen vacancies induce an atomic structure modification characterized by the movement of the La/Ca cations to the perovskite regular position, by the reduction of the MnO6 basal plane rotation, and by a cooperative tilting of the octahedra along the out-of-plane direction. The out-of-plane lattice parameter increases due to the reduction of the Mn valence upon oxygen vacancies creation. As a consequence, a shift of the Metal-to-Insulator transition to lower temperatures is found to occur. We discuss the influence of the competitive phenomena of manganese valence and Mn-O-Mn bond distortion on the transport properties of manganite thin films.