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

Abstract

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 °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.

Comparative Study of Three SAW Configurations for Temperature Sensing

“…| 𝑓=𝑓 0 (19) The calculated k 2 for the delay line configuration is 0.492% at the center frequency f0=444.8 MHz.…”

“…The piezoelectric constants of AlN are; e15=-0.48 C/m 2 , e13=-0.58 C/m 2 , and e33=1.55 C/m 2 , and its relative dielectric permittivity constants are 11=22=9 and 33=11. Silicon constituting the substrate is also considered as an anisotropic material (Mono crystal) with c11=166 GPa, c12=64 GPa and c44=80 GPa, its density is 2330 kg/m 3 [18,19]. The electrical losses in metallic regions (originating from the Joule effect) are neglected.…”

“…The relative change in the resonance frequency due to temperature change can be expressed as a function of the two relative changes in acoustic velocity and the distance d, as expressed in (6) [19]:…”

Modelling and Validation of a Guided Acoustic Wave Temperature Monitoring System

“…This can be extended to B [15], C [16,17], or phased-array [18] scans to build an image of damage in an area by moving the transducers around and carrying out multiple measurements. Surface acoustic waves (SAWs) are also used for structural health monitoring applications, commonly based on the use of interdigital transducers (IDTs) operated as either delay lines or resonators, which can operate in harsh environments and can be interrogated wirelessly [19,20]. These types of sensor generally propagate SAWs within their own structure, rather than through the material on which they are deposited.…”

Thermally Tunable Surface Acoustic Wave Cavities

“…The growing interest in this periodic structures is connected to their peculiar properties, such as anomalous dispersion (negative refraction) [5], occurrence of band-gaps [6], efficient wave-guiding [7] and near zero group velocity [8]. Very recently, they were also used to enhance sensing capabilities [9].…”