Superconducting single-phase Sr1−xLaxCuO2 thin films with improved crystallinity grown by pulsed laser deposition

Sr1−xLaxCuO2−δ (x=0.10–0.20) thin films exhibiting an oxygen-deficient 22ap×22ap×c structure (ap and c represent the cell parameters of the perovskite subcell) were epitaxially grown by means of pulsed laser deposition in low-pressure oxygen ambient. (001) KTaO3 and (001) SrTiO3 single crystals were used as substrates, with BaTiO3 as buffer layer. The Sr1−xLaxCuO2−δ films were oxidized during cooling down in order to yield the infinite-layer-type structure. By applying this method, high quality single-phase Sr1−xLaxCuO2 thin films could be obtained for 0.10⩽x⩽0.175 doping range. The films grown on BaTiO3∕KTaO3 show superconductivity for 0.15⩽x⩽0.175 with optimum doping at x=0.15, in contrast with previously reported data.