BaySr1 − yTiO3 buffer layers for strain tuning of infinite-layer Sr1 − xLaxCuO2 thin films

Abstract

We report on the precise tuning of lattice strain in an infinite-layer electron-doped high temperature superconductor Sr1−xLaxCuO2 (SLCO; aSLCO=0.3949nm for x=0.1), which is a perovskite-related oxide, using perovskite BaTiO3–SrTiO3 (BSTO; BaySr1−yTiO3) buffer layers. The BSTO buffer layers formed on (001) (La0.18Sr0.82)(Al0.59Ta0.41)O3 substrates by magnetron sputtering were fully relaxed with high crystalline quality due to high oxygen partial pressure deposition and post annealing at 950°C. The lattice constants of the BSTO buffer layers could be controlled in the range of 0.3926–0.3973nm by changing the Ba content (y=0.2–0.7). These BSTO buffer layers allow coherent growth of SLCO thin films, and a clear dependence of the superconducting transition temperature on the lattice strain was observed. The fabrication of these BSTO/superconductor heterostructures may provide novel devices composed of functional perovskite thin films, in addition to a general approach for the precise control of lattice strain in functional perovskite thin films.