Structural variability in La0.5Sr0.5TiO3±δ thin films

La0.5Sr0.5TiO3 +/-delta films were grown by pulsed laser deposition and characterized using aberration-corrected scanning transmission electron microscopy. Single-phase films with low resistivity and a near Ti3+ valence state were stabilized by a large concentration of oxygen vacancies under reducing conductions. In contrast, single-phase films transformed into superlattices upon exposure to an oxygen rich environment through the formation of stacking faults and cation vacancies in order to reach the stable Ti4+ valence state. The resistivity of the superlattices exceeded that of single phase films by two orders of magnitude, indicating that the observed structural order had a significant effect on the overall film properties. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3672217]