YBaCuO Films by Pulsed Laser Deposition and Sputtering

Abstract

In-situ YBa₂Cu₃O₇ films of high quality (from a J_c(T, H) and T_c point of view) have been fabricated by both, pulsed laser deposition (PLD), and on-axis rf magnetron sputtering techniques on SrTiO₃ (100) and LaA10₃ (100) substrates. In the PLD method, a pulsed Nd:YAG laser with the 355 nm tripled wave length and the energy density of 8 J/cm² has been used. In the on-axis rf magnetron sputtering method, the effects of negative oxygen ion re-sputtering have been nearly eliminated by introducing a grounded metallic mask between the target and the substrate. We have been successful in producing in-situ superconducting films at relatively low pressures as well as low substrate temperatures well outside the empirical Hammond-Bormann regime. Our films show zero resistance critical temperatures as high as 91.5 K. XRD measurements and Rocking curves of a (005) peak revealed that the films are highly c-axis oriented normal to the substrate and with the FWHM of less than 0.3 degree. The critical currents in these films determined from SQUID magnetometry at 77 K is found to be more than 10⁶ A/cm² with an exponential field and temperature dependencies. Some comparisons of the properties of the superconducting films obtained by the two different techniques are also presented.