Experimental results on a quartz microresonator IR sensor

The resonance frequency of a quartz bulk acoustic wave resonator is sensitive to temperature. This sensitivity has been exploited in thermometers made of single, macroscopic quartz resonators which can accurately detect temperature changes of microkelvins. It has been theoretically shown that a microresonator can be a high performance IR sensor and sensor array, combining its small thermal mass and high thermal isolation capability, the steep frequency vs. temperature characteristics of resonators made of certain cuts of quartz, and the intrinsic low noise characteristics of quartz crystal oscillators. This paper is a progress report about the measurements on prototype AC-cut microresonator IR sensors operating at a 160 MHz fundamental mode frequency. The dimensions of the microresonators were 500/spl times/500/spl times/10 /spl mu/m/sup 3/ and 600/spl times/600/spl times/10 /spl mu/m/sup 3/. A 10 nm thickness of evaporated titanium was applied to the front side of the resonators for an IR absorption coating. The sensors were measured in a vacuum chamber. A 500 K blackbody IR source irradiated the samples through a zinc selenide IR window. A detectivity D* of 8/spl times/10/sup 7/ cmHz/sup 0.5/ watt/sup -1/ was achieved.