Properties of shear-horizontal surface acoustic waves in different layered quartz-SiO2 structures

Acoustic wave devices based on waveguide modes with shear-horizontal polarisation in Y-rotated quartz plates are very promising for sensor application. Up to now, several systems have been reported based on standard ST-quartz. Those devices lack temperature stability, which is essential for field application. However, appropriate combinations of crystal cut angle and SiO2 overlay thickness should provide temperature compensation. Thus, different systems based on Y-rotated quartz plates with cut angles between 30 and 42.75 degrees have been investigated. First- and second-order temperature coefficients of frequency change have been calculated and measured. Moreover, properties are compiled that are relevant for the device design, i.e. acoustoelectric coupling coefficients, effective dielectric constants, and phase as well as group velocities. In summary, device configurations could be identified that combine temperature stability comparable to that of surface skimming bulk waves in the AT-cut, a suitable coupling coefficient, and high gravimetric sensitivity.