Kwo Young

High quality epitaxial YBCO(F) films directly deposited on sapphire

Abstract High-quality epitaxial YBa 2 Cu 3 O 7−δ (F) films were grown directly on r-plane (1 1 02) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The microwave surface resistance measured by a con-focal resonator configuration is 56 mΩ at 94.1 GHz at 77 K which is the best reported value for a YBCO film on sapphire. The improved film quality is attributed to the fluorine which is transported from the target to the growing surface of the film where it acts as an etching and/or catalytic agent to preferentially remove defects and second phase impurities and to promote better in-plane epitaxy.

Epitaxial YBCO(F) films directly deposited on sapphire and its microwave properties

Abstract High quality epitaxial YBa 2 Cu 3 O 7-δ (F) films were grown directly on r -plane (1102) sapphire by a pulsed laser deposition technique using a multiphase fluorinated target. X-ray diffraction data showed that the film is highly c -axis oriented and in-plane aligned. The c -axis and in-plane mosaic spread are 1.1° and 2.4°, respectively. The film has a Tc(R=) of 89K with a transition width less than 0.25K. The microwave surface resistance R s measured by a con-focal resonator configuration is 56mΩ at 94.1 GHz at 77K which is the best reported value for a YBCO film on sapphire. The magnetization critical current density is as high as 3x10 7 A/cm 2 at 5K and 2x10 6 A/cm 2 at 77K. A bandpass filter which is centered at 8.1 GHz is fabricated. A very low insertion loss (