부산대학교 도서관

This work presents the fabrication and characterization of a sub-GHz plate-wave-based pressure sensor relying on an ultrathin (360 nm) single-crystalline LiNbO3 film. The proposed devices exhibit multiple resonant modes which are characterized and analyzed by a precise 3-D plate wave resonator model based on finite element analysis (FEA). Generally, the main resonant modes correspond to the shear-horizontal (SH) and anti-symmetric ( ${A}{)}$ Lamb waves. To overcome the high-temperature coefficient of LiNbO3 thin film, a thick layer ( $\sim 4 ~\mu \text{m}$ ) of SiO2 was used to compensate for the temperature drift of the devices; the calculated temperature coefficients of frequency (TCF) for the multiresonant modes are lower than −27 ppm/K. The frequency and return loss ( ${S}_{{11}}{)}$ shift of the plate wave devices, the pressure sensitivity, and the pressure coefficient of frequency (PCF) were experimentally evaluated and analyzed. All the resonant modes show high PCF even with relatively lower operating frequencies (< 1 GHz). Especially it has been observed that the first-order anti-symmetric ( ${A}_{{1}}{)}$ Lamb wave is ultrasusceptible to pressure changes, which presented a record high value of ~600 ppm/bar and excellent linearity over the tested 0.6–1.8-bar pressure range. The results show that the developed sensor has sufficiently high sensitivity and can be used for precise absolute pressure-sensing.