Preparation and Properties of Sr0.9La0.1CuO2 Thin Films Grown on BaySr1-yTiO3 Layers

Epitaxial thin films of electron-doped infinite-layer (IL) cuprate superconductor Sr_1-xLa_xCuO ₂ (SLCO, ) were grown by dc magnetron sputtering, and their structural and electrical properties were investigated systematically by changing the reduction annealing period under vacuum to remove excess apical-oxygen and the SLCO film thickness. Thin films of Ba_ySr_1-yTiO₃ with , 0.55, and 0.7, prepared on (001) (La_0.18Sr_0.82)(Al_0.59 Ta_0.41)O₃ (LSAT) substrates, were used as epitaxial buffer layers to induce different types of strain in SLCO. For the tensile strained SLCO films on Ba_0.55Sr_0.45TiO₃ and on Ba_0.7Sr_0.3TiO₃ layers, short time (several minutes) reduction annealing was found to be effective for the removal of excess apical-oxygen and the appearance of superconductivity, whereas the reduction annealing was less effective for the compressively strained SLCO films on Ba _0.4Sr_0.6TiO₃ layers. Moreover, strong thickness dependences of superconducting properties have been observed for tensile strained layers. Based on these results, the strain and reduction effects of the SLCO film properties are discussed.