NIOBIUM MICROBOLOMETERS FOR FAR-INFRARED DETECTION

Microbolometers have been fabricated using a thin niobium film as the detector element. These detectors operate at room temperature, are impedance matched to planar antennas, and are suitable for broadband use at far-infrared wavelengths. We have achieved responsivities of up to 21 V/W at a bias of 6.4 mA, and electrical noise equivalent powers (NEP) of as low as 1.1 x 10(-10) W/root Hz at 1 kHz at a bias of 3.6 mA. At this bias, the detectors are 1/f-noise limited below 1 kHz and are Johnson noise limited above 10 kHz. The 1/f noise in nV/root Hz increases approximately linearly with bias with a typical level of 0.39 I(mA)/root f(kHz). This level of 1/f noise is approximately a factor of 7 below the best reported for bismuth microbolometers.