We have used the extreme sensitivity of electron tunneling to variations in electrode separation to construct a novel, compact displacement transducer. Electrostatic forces are used to control the separation between the tunneling electrodes, thereby eliminating the need for piezoelectric actuators. The entire structure is composed of micromachined silicon single crystals, including a folded cantilever spring and a tip. Measurements of displacement sensitivity and noise are reported. This device offers a substantial improvement over conventional technology for applications which require compact, highly sensitive transducers.
Uncooled infrared sensors are important for a number of technological and scientific measurements. We have designed, built, and tested a new uncooled infrared sensor which is made by silicon micromachining. This infrared sensor uses a tunneling displacement transducer to detect the thermal expansion of a small volume of trapped gas. Prototype devices based on this design have been operated with NEP better than 3×10−10 W/√Hz at 25 Hz, which is competitive with the best comparably sized uncooled sensors available. This article will describe the design, fabrication, and operation of all elements of this sensor.
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