INTRINSIC JOSEPHSON-JUNCTIONS OF TL2BA2CACU2OX THIN-FILMS FOR HIGH-FREQUENCY DEVICES

We successfully observed intrinsic Josephson effects of Tl2Ba2CaCu2Ox (Tl-2212) thin films by structuring step-edges or mesas and measuring the electrical transport properties along the c-axis. For a step-edge with the height of 350 nm, a hysteretic current-voltage (I-V) curve wa s observed up to 50 K. For a 5 mu m X 5 mu m mesa structure with a hei ght of 400 nm, a hysteretic I-V curve was also observed up to 80 K. Bo th show that series connected SIS-type junctions are formed. Comparing with the critical current density (J(c)) of more than 10(6) A/cm(2) p arallel to the ab-plane, an anisotropic J(c) of 1.4 X 10(2) A/cm(2) at 4.9 K was observed. The normal resistance (R-nk) of a unit SIS juncti on was estimated to be 580 Ohm by fitting the Ambegaokar and Baratoff relation. The capacitance (C-k) of the unit SIS junction was estimated to be 3.6 X 10(-10) F/cm(2) at 77 K by the calculation of McCumber pa rameter (beta(c)). Then, the cut-off frequency (1/2 pi RnkCk) was esti mated to be 3.1 THz at 77 K as a THz detector. (C) 1997 Elsevier Scien ce B.V.