MICROSTRUCTURAL CHANGES IN TLBA2CACU2O7-DELTA THIN-FILMS AFTER REDUCING ANNEALS WHICH ENHANCE CRITICAL-CURRENT DENSITY

Microstructural changes in TlBa2CaCu2O7-partial derivative (Tl-1212) e pitaxial thin films resulting from low oxygen partial pressure furnace anneals at 600 degrees C are studied using high resolution transmissi on electron microscopy (TEM), These postgrowth anneals have been shown to significantly raise the superconducting transition temperature fro m 70 to 90 K, and greatly improve the magnetic flux pinning and the cr itical current density, Changes occur in both the microstructure and t he morphology of the films that correlate with changes in J(c). Plan v iew TEM and high-resolution cross-sectional TEM analysis of the films before and after anneals demonstrates changes in the lattice fringe im age, overall contrast modulation, and nanometer-scale discontinuities.