Influence of metallization on phase velocity and thermal sensitivity of Surface Acoustic Wave devices

Most of Surface Acoustic Wave devices exhibit a very small sensitivity to t hermal effects. However, even on intrinsically compensated crystal cuts, th e deposition of metal strips at the surface (transducers or reflectors) ind uces important changes in the thermoelastic properties of the device. A the oretical approach based on the Sinha-Tiersten perturbation method is propos ed to model the influence of metallization on SAW properties on (ST, X) Qua rtz, namely the temperature stability of the phase velocity of Rayleigh wav es. Since this perturbation method only gives access to the first order Tem perature Coefficient of Frequency (TCF), it is combined with a conventional calculation of the second order TCF to predict the evolution of the turnov er temperature. The proposed calculation also requires temperature derivati ves of the elastic constants of the metal which can be calculated for diffe rent materials. Finally, theoretical results are compared to experimental d ata measured on SAW devices on (ST, X) Quartz using Aluminum gratings.