SIMS of thin films grown by pulsed laser deposition on isotopically labeled substrates

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 18O enriched single crystalline substrates. By annealing for 100 h at 1100 °C in an 18O2 enriched atmosphere 18O concentrations of ~ 81% and ~ 63% were reached in the YSZ, and STO substrates, respectively. The film depositions were performed at different substrate temperatures up to 750 °C and different oxygen background pressures in a range from 1.5 × 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 18O 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 °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.