Characterization of YBCO superconducting films fabricated by pulsed laser deposition

YBa2Cu3O7-delta thick films with the thickness in the range of 1000-2000 nm including different orientations were investigated for the application of microwave devices. Pulsed laser deposition (PLD) has been used to deposit superconducting YBCO thick films on cleaved and polished (100) MgO substrates (10 X 10 mm). A Nd:YAG laser with the wavelength of 355 nm was used. A YBa2Cu3O7-delta film was grown at 750 degrees C in the oxygen partial pressure of 2.7 Pa and annealed at 550 degrees C for 30 min in 6.7 X 10(4) Pa oxygen pressure, then cooled down to room temperature. Four-point probe measurement and X-ray diffraction (XRD) were used to reveal the properties of superconducting YBCO films. The transition temperatures of these films are in the range of 86-89 K. Two types of X-ray diffraction standard theta-2 theta technique and a glancing angle technique were used to characterize the laser ablated thick films. A glancing angle XRD was adopted to examine the orientation change step by step by varying X-ray incident angles in a laser ablated thick film. We have verified that the mixture of a-axis and c-axis orientation was strongly dominated near at the top of the film in a laser ablated thick film. A variation of the surface resistance of the films with different film thicknesses was observed. (C) 1999 Elsevier Science S.A. All rights reserved.