Investigation of the CTGS single crystals potential for high temperature SAW devices

SAW resonators were patterned on CTGS wafers with different orientations at different propagation angles. Ir was used as a metal without additional adhesion layers. Resonator responses were acquired with a network analyzer. Resonance frequencies of the responses were measured and processed to obtain temperature behavior. For the cut with Euler angles (0, 90°, 0) almost linear behavior was observed with TCF close to -35 ppm/°C. The turnover point of the fitted parabolic curve gradually changed with propagation angle ψ (0, 90°, ψ) from negative temperatures up to about +550°C at (0, 90°, 90°). This also means that this material gives orientations (close to (0, 90°, 40°)) with the turnover point near the room temperature. Surrounding orientations should probably be same useful (the turnover point change is about 0.5°C with ψ angle change by 1´ for these orientations). The coefficient at the quadratic term (with Ir metal) has a low value of about -30 ppb/°C². This value is several times lower than that of most langasite cuts and is close to that of ST-quartz. The material seems to be chemically stable at high temperatures. CTGS shows great potential and useful properties for devices operating in a wide temperature range. Similar to ST-quartz, CTGS can serve for temperature compensated resonators and filters at room temperature. It can also work in devices operating at temperatures up to several hundred degrees C.