Epitaxial growth of single-crystal Ca1−xSrxCuO2 thin films by pulsed-laser deposition

Single-crystal thin films of Ca1−xSrxCuO2, the ‘‘infinite layer’’ parent compound for the high temperature superconductors, have been grown by pulsed-laser deposition over the composition range 0.15≤x≤1.0 utilizing a single-target codeposition growth scheme. Four-circle x-ray diffractometry reveals that these Ca1−xSrxCuO2 thin films are very high-quality single crystals of the tetragonal, infinite layer phase with extremely narrow diffraction peaks, complete in-plane crystalline alignment with the (100) SrTiO3 substrate, and virtually no impurity phases present. A systematic expansion of the c-axis lattice constant is observed as the Sr content is increased. Four-point transport measurements show that these single-crystal Ca1−xSrxCuO2 films are semiconducting, with room temperature resistivities on the order of an ohm-cm. These results demonstrate that this metastable compound can be epitaxially stabilized over a wide range of composition.