Controlling Superconductivity in La2-xSrxCuO4+δ by Ozone and Vacuum Annealing

In this study we performed a series of ozone and vacuum annealing experiments on epitaxial La2-xSrxCuO4+delta thin films. The transition temperature after each annealing step has been measured by the mutual inductance technique. The relationship between the effective doping and the vacuum annealing time has been studied. Short-time ozone annealing at 470 degrees C oxidizes an under-doped film all the way to the overdoped regime. The subsequent vacuum annealing at 350 to 380 degrees C slowly brings the sample across the optimal doping point back to the undoped, non-superconducting state. Several ozone and vacuum annealing cycles have been done on the same sample and the effects were found to be repeatable and reversible Vacuum annealing of ozone-loaded La2-xSrxCuO4+delta (LSCO) films is a very controllable process, allowing one to tune the doping level of LSCO in small steps across the superconducting dome, which can be used for fundamental physics studies.