DEPOSITION OF YBA2CU3O7-DELTA THIN-FILMS BY DC MAGNETRON SPUTTERING AND STUDY OF RF-SQUID EFFECT

Superconducting thin films of YBa2Cu3O7-delta (YBCO) have been deposit ed on single crystal (100) SrTiO3 and (100) MgO substrates by dc magne tron sputtering from a single composite (123) target. The films deposi ted on SrTiO3 (100) substrates show preferred orientation depending on the substrate temperature during deposition. Both a-axis as well as c -axis oriented films of YBCO have been deposited on SrTiO3 while the f ilm is always c-axis oriented on MgO. Post annealing in flowing oxygen at higher temperature helps in growth of large size grain and also im proves the electrical properties of the films. rf-SQUID have been fabr icated on these c-axis oriented films and the SQUID behaviour due to i ntergrain Josephson weaklink has been observed up to 81.7K. The spectr al density of flux noise of the rf-SQUID is almost-equal-to 3.8 x 10(- 4) PHI0/square-root Hz at 10 Hz and 77K.