Improved current transport properties of post annealed Y1Ba2Cu3O7-x thin films using Ag doping

The influence of Ag doping on the transport properties of Y1Ba2Cu3O7-x thin films prepared by Y, BaF2, and Cu co-evaporation and optimized ex situ post annealing has been investigated. Both undoped an Ag doped films have values of T-c above 90 K, but J(c) (77 K) is highly dependent on the nominal thickness (t(nom)) of th as-deposited film. For undoped films with t(nom) less than or equal to 300 nm J(c) (77 K) (much less than 10(6) A/cm(2)) decreases monotonically with increasing film thickness. Above 300 nm J(c) (77 K) decreases rapidly to values below 5X10(5) A/cm(2).Ag doped films with t(nom) greater than or equal to 200 nm have higher J(c) (77 K) values than those of undoped films, there is a large decrease in J(c) (77 K) for Ag doped films with t(nom)greater than or equal to 300 nm. It was found that the higher values J(c) (77 K) for the Ag doped films were due to a better epitaxial growth of the YBCO compound. The low values of J(c) (77 K) for both undoped and Ag doped single layer films with t(nom)greater than or equal to 300 nm were found to be due to the absence of 1-2-4 inclusions in these films. Based on these findings high J(c) (77 K) value of 4, 1X10(6) A/cm(2). This is almost a doubling of the J(c) (77 K) value as compared to the value for the 300 nm single layer undoped film (2,2X10(6) A/cm(2)). Ag doped double layer films of 2X150 nm and 2X215 nm had comparable J(c) (77 K) values (5,8X10(6) and 5,6X10(6) A/cm(2), respectively). In comparison with the undoped 2X150 nm film J(c) (77 K) is thus further increased (by about 50%) when doping with Ag. (C) 1996 American Institute of Physics.