Continued improvement of large area, in situ sputter deposition of superconducting YBCO thin films

Abstract

The deposition of thin films of superconducting YBa/sub 2/Cu/sub 3/O/sub 7-x/ onto substrates of up to 3-in diameter by an integrated off-axis sputtering is reported. The substrate is located above the center of an 8-in-diameter YBCO planar target, and, in conjunction with a negative ion shield, negative ion effects are avoided. A large radiant heater provides backside, noncontact heating of the bare substrates. YBCO films have been grown on polished 1-cm/sup 2/ MgO and LaAlO/sub 3/ substrates with T/sub c/>or=90 K, J/sub c/>or=2.5*10/sup 6/ A/cm/sup 2/ at 77 K, and microwave surface resistance R/sub S/<0.4 m Omega at 77 K and 10 GHz. The films have a very smooth surface morphology. Uniformity data for LaAlO/sub 3/ substrates are less than +or-5% in R/sub s/. Thickness uniformity results for 3-in substrates indicate less than 10% variation. The growth of epitaxial insulating films for use with YBCO films and application of the YBCO films in microwave devices are briefly discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>