INSITU GROWTH OF EPITAXIAL YBA2CU3O7 THIN-FILMS BY ON-AXIS UNBALANCED DC MAGNETRON SPUTTERING

In-situ superconducting YBa2Cu3O7 thin films are grown epitaxially onto MgO(100) substrates by on-axis d.c. magnetron sputtering. The magnetron uses an unbalanced magnetic field configuration to circumvent resputtering effects, and high quality thin films are realized with excellent reproducibility. A stoichiometric target is sputtered in an Ar-O2 mixture (Ar-to-O2 ratio of 15 to 1) and films are deposited onto the heated substrates placed 40 mm directly in front of the target. We report on the growth and properties of films prepared as a function of sputtering pressure p(t) = 1 - 100 Pa, and as a function of the heater temperature T(s) = 600-860-degrees-C. c axis epitaxy is obtained over a wide range of deposition conditions (T(s) greater-than-or-equal-to 700-degrees-C; p(t) greater-than-or-equal-to 30 Pa). Typical films have excellent crystalline quality, a transition temperature T(c) = 85-90 K, a critical current density J(c)77 K greater-than-or-equal-to 10(6) A cm-2 and a resistance ratio R300 K/R100 K = 2.0-3.1.