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

We are investigating the use of very thin, small area YBa₂ Cu₃O_7-x (YBCO) films on Si substrates for application in hot-electron bolometers. Hot-electron bolometers produced from high-T_c materials will be favored over their low-temperature counterparts in applications of radio astronomy and atmospheric physics where the higher operating temperatures provide distinct advantages. Devices on Si can help advance this technology for bolometric space applications, 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 devices. Our typical YBCO films grown on Si by pulsed laser deposition have critical temperatures of 86 K and critical currents of 1-3×10⁶ A/cm² at 77 K for YBCO microbridges 45 nm thick. We have made 1-2 μm wide microbridges 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 processing sequence that produces the microbridges