The oxygen diffusion kinetics in a strontium titanate (STO)-yttria stabilized zirconia (YSZ) heterostructure were investigated by secondary ion mass spectrometry (SIMS) depth profiling of pulsed laser deposited thin films grown on O-18 enriched single crystalline substrates. By annealing for 100 h at 1100 degrees C in an O-18(2) enriched atmosphere O-18 concentrations of similar to 81% and similar to 63% were reached in the YSZ, and STO substrates, respectively. The film depositions were performed at different substrate temperatures up to 750 degrees C and different oxygen background pressures in a range from 1.5 x 10(-5) mbar to 0.1 mbar to observe differences in the diffusion of the oxygen ions from the substrate into the films. Flat profiles of O-18 were obtained for the YSZ thin films implying a very fast diffusion that determines the isotope distribution during the deposition. For the STO films pronounced concentration profiles were obtained at 650 degrees C allowing estimations of the diffusion constant. Elemental mapping of the YSZ films revealed pinholes of micron size which are hardly detectable by other techniques. (C) 2013 Elsevier B.V. All rights reserved.