In-situ fabrication of Y-Ba-Cu-oxide thin films by pulsed laser deposition

The authors report the in situ deposition of laser-ablated YBa/sub 2/Cu/sub 3/O/sub 7- delta / films on MgO substrates, using the third and second harmonics of an Nd-YAG laser. The conditions needed during postdeposition oxygenation to produce the best films were investigated. Highly oriented samples were made using the third harmonic (wavelength lambda =355 nm) on <100> MgO and have a transition temperature T/sub c/ of 85 K and a critical current density J/sub c/ of 1.5*10/sup 5/ A/cm/sup 2/ at 77 K, which rises to 9*10/sup 6/ A/cm/sup 2/ at 4.2 K. Films made with the second harmonic on MgO are, as expected, markedly poorer in quality. Highly oriented films have also been made on <110> and <100> SrTiO/sub 3/ with lambda =355 nm. Deposition on SrTiO/sub 3/ has yielded lower T/sub c/'s, probably due to poor-quality substrates. Anisotropic resistivity in films on <110> SrTiO/sub 3/ has been observed, with superconducting transitions in both directions.