Sensitivity enhanced temperature sensor: One-port 2D surface phononic crystal resonator based on AlN/Sapphire

According to the structure of a one-port surface acoustic wave (SAW) resonator, a one-port surface phononic crystal (SPC) resonator is designed. Both one-port SAW resonator and oneport SPC resonator are fabricated on AlN/Sapphire. Frequency responses and quality factors are studied. The one-port SAW resonator has a fundamental resonance mode at 693.07 MHz. Unlike the one-port SAW resonator, the one-port SPC resonator has two distinct resonance modes at 680.28 MHz and 698.91 MHz, respectively. From the simulation results by finite element method (FEM), these two resonance modes may come from the two cavities of the one-port SPC resonator. Frequency-versus-temperature behaviors of these two resonators are investigated. The results show that the frequencies of resonance modes of these two resonators are decreased linearly with the increased temperature. A new kind of temperature sensor is proposed by using frequency difference between these two resonance modes of the one-port SPC resonator. The eventual temperature coefficient of frequency (TCF) value of the temperature sensor is -99.30 ppm degrees C-1 which is twice more than that of the one-port SAW resonator. All results prove that temperature sensitivity is enhanced by using two mode characters of one-port SPC resonator based on AlN/Sapphire.