Superconducting niobium infrared thermal detectors and circuits on back-etched substrates

The authors report on highly sensitive thermal infrared detectors, the result of combining the two technologies of superconducting low-T/sub c/ thin-film electronics and back-etched or ´micromachined´ substrates. Functioning detectors have been fabricated consisting of a thin-film niobium Josephson junction thermometer and infrared-absorbing panel, integrated together with a DC superconducting quantum interference device, (SQUID) amplifier on a single back-etched silicon substrate. A detector made with one of two fabricated back-etched geometries has a calculated thermal conductance of 1*10/sup -7/ W/K at 4.2 K. On another device, a measured value of 9* was obtained for the amplification of the thermometer responsitivity by the integrated DC SQUID. Prospects are discussed for operating similar arrays at higher and lower temperatures than 4.2 K.<>