Small area Y-Ba-Cu-O thin films for applications in hot-electron bolometers

We are investigating the use of very thin, small area YBa2Cu3O7-x (YBCO) fi lms on Si substrates for application in hot-electron bolometers. Hot-electr on bolometers produced from high-T-C materials will be favored over their l ow-temperature counterparts in applications of radio astronomy and atmosphe ric physics where the higher operating temperatures provide distinct advant ages. Devices on Si can help advance this technology for bolometric space a pplications, where a substrate is needed with good thermal conductance and excellent IR performance, Based on our experience with YBCO bolometers and YBCO film growth on Si, we have begun a study of sub-micrometer scale devic es. Our typical YBCO films grown on Si by pulsed laser deposition have crit ical temperatures of 86 K and critical currents of 1-3 x10(6) A/cm(2) at 77 K for YBCO microbridges 45 nm thick, We have made 1-2 mum wide microbridge s from YBCO films of 25 nm to 45 nm thick. These microbridges show reduced critical temperatures of 71 K to 81 K, respectively, related to the process ing sequence that produces the microbridges.