FABRICATION OF HIGH-QUALITY YBA2CU3OY THIN-FILMS USING PULSED-LASER DEPOSITION

High quality YBa2Cu3Oy (YBCO) thin films for directly coupled DC-SQUID s were fabricated by pulsed laser deposition. Several critical paramet ers have been optimized through systematic studies. The best quality Y BCO thin films on MgO and on LaAlO3 substrates were made under the O-2 pressure of 400 similar to 500 mTorr at the substrate temperature of 780 similar to 800 degrees C and target to substrate distance of 50 si milar to 60 mm. Films showing a T-c above 91 K and J(c) above 2x10(6) A/cm(2) at 77 K were routinely obtained. Extensive AFM and x-ray diffr action studies have been conducted for morphological and structural an alyses. The directly coupled DC-SQUIDs were fabricated from the YBCO t hin films deposited on SrTiO3 bicrystals under the optimized condition s. Measurement of 2I(c) and swing voltage gives values of 420 mu A and 30 mu V at 77 K, respectively.