T c -δ Relations in YB 2 Cu 3 O 7-δ Thin Films: Effects of Oxygen Pressure During Growth

The Tc dependence on oxygen content was measured for YBa2Cu3O7-δ films grown with a variety of techniques (solid phase epitaxy, laser ablation, off-axis sputtering, co-evaporation) at oxygen pressures p(O2) ranging from 1.0 atm to 0.1 mTorr. Dissimilar dependences resulted for each film type, with Tc either increasing or decreasing for small increments in δ from maximum oxygen occupancy. Varying systematically with p(O2) during growth, the deviations are attributed to competing effects from hole-doping lattice defects (most likely on the Y-site) on the carrier density of the CuO2 planes and basal plane oxygen capacity, respectively, giving rise to overdoping or underdoping after low temperature oxidation in 1.0 atm of oxygen.