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.