Free-standing amorphous Y-Ba-Cu-O detectors for uncooled IR detection and the effects of doping

Abstract

Amorphous semiconducting Y-Ba-Cu-O has shown promise as the temperature sensitive element for uncooled IR detectors as both a bolometer and pyroelectric material. Thin films can be easily fabricated by RF magnetron sputtering at room temperature from a composite target. As a bolometer, Y-Ba- Cu-O possesses a relatively high temperature coefficient of resistance of 3.5% K-1 near room temperature. As a pyroelectric detector, pyroelectric coefficients as high as 20 (mu) C/cm2-K have been measured yielding a pyroelectric figure of merit of 0.065 (cm3/J)1/2. In Y-Ba-Cu-O, the oxygen concentration has been shown to determine the hole concentration and mobility. However, the anion stoichiometry plays an equally important role in determining the electronic characteristics. In this work, we have explored the effects of substitution for Cu and the corresponding changes on the electronic properties affecting the performance as an IR detector. Further, we have fabricated micromachined 1 X 10 arrays in which utilize a self-supporting Y-Ba-Cu-O thin film geometry. In this case, the Y-Ba-Cu-O film is held above the substrate only by the electrode arms, without the need of any underlying bridge material. These detectors posses a low thermal mass and have yielded detectivities as high as 108 cm-Hz1/2/W, which extrapolates to NETDs less than 20 mK.