TL2BA2CA2CU3OX THIN-FILM DC-SQUIDS WITH OPERATION TEMPERATURE NEAR 100K

Tl2Ba2Ca2Cu3Ox (TBCCO) thin films with T-c greater than or equal to 11 0 K were grown on the yttrium-stabilized (100) zirconia (YSZ) substrat es by d.c. magnetron sputtering technique. The d.c.-SQUIDS made from t he TBCCO films have operated at temperatures near 100 K. The relations hip between I-c and T of the grain boundary junctions is I proportiona l to (1 - T/T-c)(n), with n approximate to 1.6. This indicates that th ey are the long bridge junctions. The SQUIDs were biased by d.c. curre nts. Meanwhile, a 25 kHz ac. flux with a peak-to-peak amplitude of phi (0) was applied through a modulation coil. The voltage across the SQUI D was amplified by a factor of about 10,000 with a cooled transformer and a preamplifier. Our investigation showed that the d.c.-SQUIDs can operate near 100 K; some of them can even operate at 105 K.