New Superconducting Sr₂CuO_4-δ Thin Films Prepared by Molecular Beam Epitaxy

Abstract

We report the synthesis of new superconducting Sr 2 CuO 4-δ thin films ( T c onset ∼75 K) using molecular beam epitaxy (MBE). This superconductor has a tetragonal structure with an in-plane lattice constant a 0 ∼3.79 Å and a c -axis lattice constant c 0 ∼13.55 Å. This c -axis lattice constant is significantly larger than previously reported for this system. Strong oxidation using ozone gas at a low temperature of around 350°C is essential to the realization of phase conversion from the orthorhombic insulating phase (Sr 2 CuO 3 ) to the tetragonal superconducting phase (Sr 2 CuO 4-δ ).