Higher Order Acoustic Rayleigh Modes for Sensor Applications
AMERASIA TECHNOLOGY INC WESTLAKE VILLAGE CA
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The objective of this project was to establish the theoretical foundations for applying higher order Rayleigh and interface modes to resonators for high stability sensors. Theoretical studies of the characteristics of Rayleigh waves in single and multi-layer structures were carried out for ST-cut Quartz substrates. Specified materials for this study were MgO, Y2O3, AlN, SiOx, Al2O3, and TiO2. Velocity dispersion and coupling to bulk modes were predicted and confirmed by comparison with experimental results for sputtered films. Stoneley interfacial waves were investigated as possible candidates for resonator structures because of their inherently stable and low cost geometry without any type of hermetic enclosure or package. A successful search technique was developed which accurately predicts the existence of Stoneley waves in general anisotropic and piezoelectric materials. Using this technique, Stoneley waves were for the first time predicted in single crystal quartz. Several useful orientations where Stoneley waves are well bound and piezoelectrically active were found to exist.