PHOTOINDUCED ENHANCEMENT OF THE C-AXIS CONDUCTIVITY IN OXYGEN-DEFICIENT YBA2CU3OX THIN-FILMS

High quality thin films of oxygen-depleted YBa2Cu3Ox (x approximate to 6.6) were prepared by pulsed-laser deposition on SrTiO3, substrates t hat were cut with tilt angles of 10 degrees and 20 degrees with respec t to the [001] direction, resulting in a steplike growth of the layers . The resistance showed a semiconducting behavior along the projection of the c axis to the film surface, but a metallic behavior in the per pendicular direction, indicating that the former is dominated by the c -axis resistivity and the latter by the Bb-plane resistivity of YBa2Cu 3Ox. Long-term illumination of the samples with a 100 W halogen lamp r esulted in a significant conductivity enhancement in both directions, The photoinduced change of the out-of-plane resistance vs temperature characteristics is comparable to the effect of large hydrostatic press ure, introducing structural changes similar to that of photoexcitation . (C) 1997 American Institute of Physics.