ALL-THIN-FILM GEAU THERMISTORS FOR PARTICLE-DETECTION

All-thin-film thermistors for thermal detection of nuclear radiation a re described. Co-evaporated Ge1-xAux films were deposited on 7.5 x 7.5 x 0.25 mm Si chips, along with highly interdigitated gold electrodes patterned using photolithography. Values of alpha = d(lnR)/d(InT) grea ter than 6 were obtainable at any desired operating temperature by var ying x. A device was tested at 0.019 K in which the 200-digit electrod e pattern used gave a sensitive GeAu region 20 mum long in the bias fi eld direction, 2000 angstrom thick and effectively 50 cm wide perpendi cular to the bias field (L/A = 2.0 cm-1). The device had alpha = 6.5, G(e/ph) = 8 x 10(-12) W/K, heat capacity between 0.7 and 4.4 x 10(-12) J/K, and optimum bias power 1.5 x 10(-11) W. Thermal pulses from 60 K eV x-rays absorbed in the substrate at T less-than-or-equal-to 0.07 K were easily detectible with this arrangement.