Substrates for zero temperature coefficient Love wave sensors

Microacoustic Love wave delay lines show high sensitivity to perturbations such as mass depositions on the wave-guide surface. Furthermore, because of their shear polarization, Love waves are ideally suited for liquid sensing applications. Using a Love wave delay line as feedback element in an oscillator allows the realization of viscosity sensors, and, using a chemical interface, chemical sensors, where the output signal is the oscillation frequency. To achieve a high effective sensitivity, the cross-sensitivity to temperature has to be kept low. We outline the proper choice of a material and especially focus on the influence of crystal cut and the major device design parameters (mass sensitivity and coupling coefficient) on the temperature coefficient of the sensor.