Preparation and Properties of Sr<sub>0.9</sub>La<sub>0.1</sub>CuO<sub>2</sub> Thin Films Grown on Ba<sub>y</sub>Sr<sub>1-y</sub>TiO<sub>3</sub> Layers

Abstract

Epitaxial thin films of electron-doped infinite-layer (IL) cuprate superconductor Sr 1-x La x CuO 2 (SLCO, x = 0.1) 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 y Sr 1-y TiO 3 with y = 0.4, 0.55, and 0.7, prepared on (001) (La 0.18 Sr 0.82 )(Al 0.59 Ta 0.41 )O 3 (LSAT) substrates, were used as epitaxial buffer layers to induce different types of strain in SLCO. For the tensile strained SLCO films on Ba 0.55 Sr 0.45 TiO 3 and on Ba 0.7 Sr 0.3 TiO 3 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 0.4 Sr 0.6 TiO 3 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.