Turn-over Temperature in Lateral-Field-Excited Thin-Film Lithium Tantalate Contour-Mode Resonators

SummaryIn the present work, the possibility of designing thin-film lithium tantalate bulk resonators that exhibit a turn-over temperature in their frequency-temperature characteristic is explored. The simulation results suggest that contour-mode resonators carefully aligned to a specific crystalline orientations on an X-cut LiTaO
3
(LT) film exhibit a turn-over temperature. The exact location of the turn-over temperature could be adjusted by rotation within the X-cut. Preliminary experimental results measured from resonators fabricated on a 1.8um LT film bonded to a Si substrate confirm the existence of the predicted turn-over temperature. A zero-temperature coefficient of frequency (TCF) has been observed at 100 °C in resonators rotated 40 degrees with respect to -Y-axis in X plate of LT.