,& . __ ’ __ l!I!il ELSEVIER Physica C 282-287 (1997) 2433-2434 PHYSICA E Intrinsic Josephson junctions of TlaBaKaCuzOs thin fiis S.L. Yan”, L. Fang*, M.S. Si”, J. Wang’, J.M. Haob, and Q.X. Song* * Department of Electronics, Nankai University, Tianjin 30007 1, China b Tianjin Electronic Materials Research Institute, P.O. Box 55, Tianjin 300192, China The intrinsic Josephson junction is prepared by epitaxial growth of TlzBa2CaCuzOs(T1-2212) thin film on LaA103 substrate surface which is at small slanting angle to LaAlO3(001) plane, and then by manufacturing thin film microbridge in proper direction. From the hysteretic I-V characteristics and the temperature dependence of the critical currents, the intrinsic Josephson junctions exhibit SIS junction behaviour. 1. INTRODU~ION 3. MEASUREMENT AND RESULTS Josephson junctions are the base of application and research on superconducting electronics. Many types of Josephson junctions of high-r0 superconducting thin films have been investigata such as bi-crystal junctions, bi-epitaxial junctions, and substrate-step junctions. All of these Josephson junctions are based on the grain boundaries of the high-T, materials. We report here the fabrication and properties of intrinsic Josephson junctions of epitaxial Tl-2212 thin films on LaAla substrates. 2. DEVICE FABRICATION The structure of the thin films on LaAlC& substrates were determined by x-ray diffmction (XRD) 8-28 scans and rocking curves. Figure 1 shows a rocking curve of Tl-2212(00m at 26=56.52”. In the scan range from 3’=’ to 30” there is only one peak at 6.99”, which means that the Tl- 2212 thin film grows in perfect or&r, and the Cu-0 planes are parallel each other and at a slant angle of 21.27” to the substrate surface, which is just the slant angle of the LaAl@ (001) plane to the substrate surface. Moreover, the results of asymmetric 8-28 scan proved that the thin film was pure Tl-22 12 phase. The intrinsic Josephson junctions are made by epitaxial growth of Tl-2212 thin films on LaAlC& substrates, and then manufacturing thin film microbridges. The substrate surface is at a small slanting angle a to LaA103(O01) plane. Tl-2212 superconducting thin films were epitaxially growth on LaAK& substrates by dc magnetron sputtering and post-annealing process [l] in order to keep the Cu-0 plane of the Tl-2212 film at a small slanting angle a to the substrate surface. The thin film microbridge was fabricated by standard photolithography and wet chemical etching. The direction of the microbridge was consistent with the slanting direction of the LaAl~(OO1) plane to the substrate surface. Thus, each pair of adjacent Cu-0 layers in the microbridge acts as an intrinsic Josephson junction. A microbridge is a Josephson device which consists of a series array of intrinsic Josephson junctions. 5ox10'~ r I 4.0x104 / II TL2212(COls) 3.0x104 28 = 56.52’ lncidellt angle ( o ) Figure 1: XRD rocking curve of Tl-2212(00m. The standard four-probe method was used to measure the I-V characteristics of the thin film microbridges. From the I-V curves we can also get the critical currents and the resistivities of the microbridges at different temperatures. For the Tl- 092 l-4534/97/$17.00 8 Elsevier Science B.V All rights reserved. PI1 SO92 l-4534(97)01 283-5