Oxygen in-diffusion at room temperature in epitaxial La_0.7Ca_0.3MnO_3−δthin films

Abstract

Single-crystalline La0.7Ca0.3MnO3−δ thin-films, 20 nm thick, were grown coherently on lattice well-matched (LaAlO3)0.3(Sr2AlTaO6)0.7(0 0 1) substrates by pulsed-laser deposition, and the control, diffusion and stability of oxygen in the films were carefully investigated. Using x-ray reciprocal space maps and magnetic measurements, we show clearly that the out-of-plane lattice parameter and Curie temperature of the films can change simultaneously with the oxygen content, while the in-plane lattice coherency is maintained consistently at the same time. Remarkably, contrary to those with oxygen deficiencies created during the in situ deposition at lower oxygen pressures, the ex situ vacuum-annealed films show fast oxygen in-diffusion even at room temperature and in ambient atmosphere. The results strongly suggest that the control of oxygen content via the in situ deposition process is more favourable for manganite films.