Impact Of Oxygen Diffusion On Superconductivity In Yba2cu3o7-Delta Thin Films Studied By Positron Annihilation Spectroscopy

The oxygen deficiency delta in YBa2Cu3O7-delta (YBCO) plays a crucial role for affecting high-temperature superconductivity. We apply (coincident) Doppler broadening spectroscopy of the electron-positron annihilation line to study in situ the temperature dependence of the oxygen concentration and its depth profile in single crystalline YBCO film grown on SrTiO3 (STO) substrates. The oxygen diffusion during tempering is found to lead to a distinct depth dependence of delta, which is not accessible using x-ray diffraction. A steady state reached within a few minutes is defined by both, the oxygen exchange at the surface and at the interface to the STO substrate. Moreover, we reveal the depth-dependent critical temperature T-c in the as prepared and tempered YBCO film.