Linear bolometer array using a high TCR VOx-Au film

ABSTRACT We present a design for a low-noise bol ometer linear array based on the temp erature-dependent conductivity of a VO x -Au film. Typical thin film bolometers must compromise between low resistivity to limit Johnson noise and high temperature coefficient of resistivity (TCR) to maximize responsivity. Our vanadium oxide is alloyed with a small concentration of gold by co-sputtering, which gives very low resistivity and very high TCR simultaneously. The film is fabricated on an air bridge device having high thermal conductivity and small thermal time constant optimized for 30 to 60 Hz frame rates. The linear array functions as a low-power profile sensor with a modulated bias. For 1 V bias, we predict responsivity exceeding 1200 V/W. Johnson noise dominates with pred icted NEP values as low as 1.0 x 10 -11 W/Hz 1/2 . Preliminary device testing shows film resistivity below 2.5 -cm with TCR exceeding -2.0%. Preliminary measurements of NEP and D* are reported. Keywords: MEMS, bolometer, vanadium oxide, TCR