Optical and thermal performance advantages for silicon substrates in YBCO bolometer devices

The authors review recent progress they have made in the fabrication of epitaxial YBCO thin-film bolometers (photothermal infrared detectors) on Si wafers. Infrared (IR) transmission of the Si substrates, yttria-stabilized zirconia (YSZ) buffer layers on Si, and YBCO/YSZ/Si has ben measured from the near to the far IR at low temperatures. Si is shown to be much superior to other available choices of substrate for epitaxial-YBCO film bolometers. It is also shown, by various wafer fabrications, that the high strength and thermal conductivity of Si can be exploited to considerably reduce the device thermal-equilibration time, when irradiated with weak IR pulses, and concomitantly increase the device sensitivity. Further, the authors have fabricated monolithic quad arrays of bolometers, and found excellent element-to-element uniformity in their transitions and in their function as detectors for Fourier-transform IR spectroscopy. They have also fabricated an epitaxial YBCO-film bolometer on a submicron-thick window in a Si wafer. The rise and fall times (10-90%) were less than 500 mu s, under chopped IR illumination.<>