Deposition of thin films over large areas with a simple sputtering technique for microwave applications

A simple sputtering technique is presented for the fabrication of (YBCO) films over large areas. The magnetron sputtering source combines operation in an unbalanced magnetic field configuration and use of large YBCO targets. YBCO films were deposited on substrates with sizes up to . The films are characterized by x-ray diffraction, pole figures, ac susceptibility, transport properties and thickness uniformity. The results show that these films are of good quality with perfect c -axis orientation, epitaxial growth, critical temperature of , critical current density of at 77 K and thickness uniformity better than 5% over an substrate. A two-pole bandpass filter with centre frequency of 13 GHz and 3 dB fractional bandwith of about 15% was designed to test the microwave performance of these films. A YBCO filter exhibits at 77 K an insertion loss of more than 5 dB lower than an equivalent Au filter on substrate at the same temperature.