Low loss film bulk acoustic resonator in liquid environments
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] A film bulk acoustic resonator (FBAR) is an acoustic resonator mass sensor using the resonance of longitudinal or shears acoustic waves. There is a significant Q factor loss in liquid medium due to acoustic energy loss. This drastically affects the minimum detectable mass of the sensor. This research describes the design and fabrication of an FBAR that has low loss in liquid environments. The new design utilizes a thin vacuum gap as an acoustic energy loss isolation layer of the FBAR in the aqueous media. The sensor was characterized and the Q factor was measured to be about 153 in the air and 140 in the water. An only 9% of Q reduction in the water was observed. This thesis also describes a novel temperature sensor which has been designed and fabricated by using a liquid metal, which connects a series of parallel-plate capacitors. Linearly and stably changing capacitance with respect to the temperature variation was observed from the sensor. The capacitance changes from about 0.015pF at 0[degree sign]C to about 0.322pF at 90[degree sign]C.
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