TRANSPORT-PROPERTIES OF TL2BA2CACU2O8 WEAK LINKS ON LAALO3 BICRYSTAL SUBSTRATES

Josephson junctions and de superconducting quantum interference device s (SQUIDs) have been fabricated in ex situ epitaxial Tl2Ba2CaCu2O8 fil ms on bicrystal LaAlO3 substrates with symmetric 32 degrees [001] tilt grain boundaries. The critical temperature T-c, of the junctions was in the range 105-107 K and the critical current densities at 77 K vari ed between 3X10(2) and 3X10(4) A/cm(2), two or three orders of magnitu de less than those of the film. The I-V curves are described by a resi stively shunted junction model. Close to T-c, the temperature dependen ce of the critical current was described by (1 - T/T-c)(2). The flux n oise spectra S-Phi(f) of de SQUIDs were measured in the locked-loop re gime with constant current bias at temperatures up to 94 K. The white noise level was 50 mu Phi(0)/root Hz at 77 K. The crossover frequency to 1/f noise was low, about 5 Hz, and the flux noise level at 1 Hz was 440 mu Phi(0)/root Hz. (C) 1996 American Institute of Physics.