Role of oxygen pressure during deposition on the microwave properties of YBCO films

Abstract

We have studied the effect of oxygen pressure (PO,) during pulsed laser deposition on the properties of YBCO films, with particular attention to the low power microwave surface resistance R-s. Above a threshold oxygen pressure the properties of the films are nearly independent of PO2 during deposition and are typical of high quality YBCO films. The films made below this threshold pressure have increased disorder which produces a reduced T-c and an expanded c-axis lattice parameter. However, these films also have significantly reduced low temperature R-s, which is likely a direct result of the increased scattering in these films. Preliminary Raman measurements show no increase in the Y-Ba cation disorder in these low PO2 films, so that a different disorder mechanism must be present.