TL-CA-BA-CU-O STEP-EDGE JOSEPHSON-JUNCTIONS

There has been considerable progress in the development of nonhysteretic Josephson junction microelectronic technologies for YBaCuO. Such a technology for Tl-Ca-Ba-Cu-O junctions would be interesting because of the higher operating temperatures and the very different grain boundary structures in the different cuprate superconductors. We have successfully made step-edge junctions with TlCaBaCuO grown on ion-milled LaAlO3. Nonhysteretic grain boundary-based junctions have been demonstrated with critical current-normal state resistance products exceeding 5 mV at 77 K, critical current densities ranging from 500 to 25 000 A/cm2, and critical current versus field profiles suggesting very uniform junctions. Yield has exceeded 70% on over 250 junctions tested and operation has been demonstrated to 100 K.