Oxygen diffusion in LaInO3 films grown by molecular beam epitaxy

Abstract

Oxygen tracer diffusion experiments were used to characterize oxygen transport, and thus oxygen-vacancy behavior, in thin films of the perovskite-type oxide LaInO3, grown by molecular beam epitaxy (MBE) on DyScO3 substrates. 18O2/16O2 exchange anneals were performed at temperatures 620≤T/K≤920 at an oxygen activity of aO2=0.200, and also at varying oxygen activities of 0.018≤aO2≤0.500 at T=873 K; isotope penetration profiles in the films were measured subsequently by time-of-flight secondary ion mass spectrometry (ToF-SIMS) depth profiling. Complementary molecular dynamics simulations of oxygen tracer diffusion in undoped LaInO3, with three different sets of interatomic potentials, were also carried out as a function of temperature. From the analysis of both experimental and computational tracer diffusion data, we concluded that the oxygen vacancies present in the LaInO3 films form in order to charge compensate acceptor-type point defects (most probably, lanthanum vacancies introduced in the MBE growth process). ToF-SIMS profiles also yielded evidence of faster cation (Dy and Sc) diffusion (but not of faster anion diffusion) along dislocations in the LaInO3 thin films at T=1173 K, behavior consistent with positive dislocation cores surrounded by negative space-charge tubes.