Doping dependence of superconducting properties in pulsed-laser-deposited La2-xSrxCuO4+delta (0 <= x <= 0.30) thin films

We have studied the Sr doping dependence of the superconducting properties of thin La(2-chi)Sr(chi)Cuo(4+delta) Alms grown by pulsed laser deposition over the range of 0 less than or equal to chi less than or equal to 0.30. W e found that the strain in the films depends on the Sr doping level. In 100 0 Angstrom La2-chiSrchiCuO4+delta films grown on 1000 Angstrom SrLaA10(4) b uffer layer, the strain changes from compressive to tensile when a: increas es. For both compressive and tensile strain, Alms prepared in strongly oxid izing ozone/molecular oxygen mixture are superconducting for all Sr content with chi less than or equal to 0.25. When the films are cooled in pure mol ecular oxygen the a dependence is similar to that in the bulk, although the transition temperature depends on the strain. The results suggest that the Sr content, epitaxial strain, and oxygenation conditions are all important factors influencing the superconductivity in La2-chiSrchiCuO4+delta thin f ilms.