Doping and characterization of YBa2Cu3O7-delta thin films prepared by pulsed laser deposition

High-quality, smooth, optimally doped, c-axis thin films of YBa2Cu3O7-delta were grown on (001) MgO substrates by pulsed laser deposition and subseque nt oxygen annealing, They were characterized structurally by theta -2 theta and four-axis x-ray diffraction and, electrically, by a self-inductance me asurement, Through subsequent annealing in reduced pressure oxygen environm ents, underdoped films were produced and again characterized using the same techniques. The doping is reversible and reproducible. A monotonic decreas e of T-c and an increase of the c-axis length were found with a decrease of the oxygen partial pressure during the annealing. From these data correspo nding values of delta were determined. The width of the rocking curve of th e (005) peak was found to be substantially unchanged, at 0.28-0.29 degrees, between the optimally doped and the underdoped films. The relative peak in tensities showed a systematic variation with delta in agreement with model calculations by Ye and Nakamura. The grain alignment is exclusively along t he MgO high symmetry axes throughout the film. Resistance-temperature chara cteristics allowed the pseudogap onset temperature, T*, to be determined as a function of doping.