PROJECT TITLE :
Capacitive-Piezoelectric Transducers for High- Micromechanical AlN Resonators
A capacitive-piezoelectric (also known as, capacitive-piezo) transducer that mixes the strengths of capacitive and piezoelectric mechanisms to attain a combination of electromechanical coupling and Q beyond otherwise attainable by either mechanism separately, has allowed demonstration of a 1.2-GHz contour-mode aluminum nitride (AlN) ring resonator with Q > 300zero on par with the best measured d31-transduced AlN-only piezoelectric resonators past one GHz, and a fifty-MHz disk array with a good higher Q > 12 00zero. Here, the key innovation is to separate the piezoelectric resonator from its metal electrodes by tiny gaps to eliminate metal material and metal-to-piezoelectric interface losses thought to limit thin-film piezoelectric resonator Q, while additionally maintaining high electrical field strength to preserve a strong piezoelectric result. While Q increases, electromechanical coupling decreases, but the keff2 · Q product can still increase overall. A lot of importantly, use of the capacitive-piezo transducer allows a designer to trade electromechanical coupling for Q, providing a very helpful method to tailor Q and coupling for narrowband radio frequency (RF) channel-selecting filters for that Q trumps coupling. This capacitive-piezo transducer concept will not need dc-bias voltages and allows for a lot of thicker electrodes that reduce series resistance while not mass loading the resonant structure. The latter is very vital as resonators and their supports still scale toward even higher frequencies. [2013-0395].
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