A laterally vibrating lithium niobate mems resonator array operating at 500^◦ c in air

This paper reports the high-temperature characteristics of a laterally vibrating piezoelectric lithium niobate (LiNbO₃; LN) MEMS resonator array up to 500^◦ C in air. After a high-temperature burn-in treatment, device quality factor (Q) was enhanced to 508 and the resonance shifted to a lower frequency and remained stable up to 500^◦ C. During subsequent in situ high-temperature testing, the resonant frequencies of two coupled shear horizontal (SH0) modes in the array were 87.36 MHz and 87.21 MHz at 25^◦ C and 84.56 MHz and 84.39 MHz at 500^◦ C, correspondingly, representing a −3% shift in frequency over the temperature range. Upon cooling to room temperature, the resonant frequency returned to 87.36 MHz, demonstrating the recoverability of device performance. The first-and second-order temperature coefficient of frequency (TCF) were found to be −95.27 ppm/^◦ C and 57.5 ppb/^◦ C² for resonant mode A, and −95.43 ppm/^◦ C and 55.8 ppb/^◦ C² for resonant mode B, respectively. The temperature-dependent quality factor and electromechanical coupling coefficient (k_t²) were extracted and are reported. Device Q decreased to 334 and total k_t² increased to 12.40% after high-temperature exposure. This work supports the use of piezoelectric LN as a material platform for harsh environment radio-frequency (RF) resonant sensors (e.g., temperature and infrared) incorporated with high coupling acoustic readout.