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 s uperconducting YBCO thick films on cleaved and polished (100) MgO substrate s (10 X 10 mm). A Nd:YAG laser with the wavelength of 355 nm was used. A YB a2Cu3O7-delta film was grown at 750 degrees C in the oxygen partial pressur e of 2.7 Pa and annealed at 550 degrees C for 30 min in 6.7 X 10(4) Pa oxyg en pressure, then cooled down to room temperature. Four-point probe measure ment and X-ray diffraction (XRD) were used to reveal the properties of supe rconducting YBCO films. The transition temperatures of these films are in t he 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 lase r ablated thick films. A glancing angle XRD was adopted to examine the orie ntation change step by step by varying X-ray incident angles in a laser abl ated thick film. We have verified that the mixture of a-axis and c-axis ori entation was strongly dominated near at the top of the film in a laser abla ted thick film. A variation of the surface resistance of the films with dif ferent film thicknesses was observed. (C) 1999 Elsevier Science S.A. All ri ghts reserved.