Laser processing of high T/sub c/ superconducting films

The discovery of high-temperature superconductivity with T/sub c/>90 K in the Y-Ba-Cu-O system has revived interest in thin-film superconducting devices. By now the preparation of bulk superconducting oxide samples, using conventional ceramic techniques (grinding, firing, and pelletizing), has been well established and reproduced by many groups. On the other hand, preparing thin films has turned out to be relatively more difficult, although a number of groups are beginning to report success. The approaches have primarily been electron-beam evaporation and sputter deposition. Multiple sources as well as single sources have been utilized, and there are problems with both approaches. The authors have avoided these problems by depositing RE-Ba-Cu-O (where RE = Y or Gd or Eu) thin films using pulsed excimer laser deposition from a bulk target. After annealing, these films show superconductivity with onsets as high as 93 K and zero resistivity at 86 K on (100) SrTiO/sub 3/ substrates. Pellets (1 cm in diameter, 2 mm thick) with composition Y/sub 1/Ba/sub 2/Cu/sub 3/O/sub 7-x/ were prepared in the usual way and mounted in a vacuum system with a base pressure of 5 X 10/sup -7/ Torr