SAW-relevant material properties of langasite in the temperature range from 25 to 750 °C: New experimental results

The aim of this work is to determine the acoustical parameters of langasite up to the highest possible point of temperature. This paper presents measurements of transfer functions for delay lines on langasite at frequencies ranging from 150 MHz to 1 GHz, at temperatures from 25 to 750degC. Two cuts with Euler angles (0deg, 138.5deg, 26.6deg) and (0deg, 30.2deg, 26.6deg) have been studied. The devices were fabricated using langasite as substrate, with two different platinum (Pt) layer heights (45 nm and 75 nm), on a zirconium (Zr) adhesion layer (4 nm). A special signal processing algorithm utilizing cross-correlation was implemented in MATLAB and used for the analysis of measured data. The material parameters relevant for SAW devices, such as phase velocity, propagation loss, and electromechanical coupling coefficient, have been determined as a function of temperature.