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A surface acoustic wave (SAW) device with an aluminum nitride (AlN) composite structure of Al2O3/IDTs/AlN/Metal/Si was proposed for sensing at extreme high-temperature in this work. Optimization allowing determination of optimal design parameters for SAW devices was conducted using the typical coupling of modes (COM) model. The SAW propagation characteristics in the layered structure were investigated theoretically by employing the finite element method (FEM). Multiple acoustic-wave modes that occurred in the AlN composite structure was analyzed, and the corresponding suppression of spurious mode was proposed. The COM simulation parameters corresponding to the effective acoustic-wave mode were extracted, and the optimized parameters of the one–port SAW resonator with a high-quality factor were determined. [ABSTRACT FROM AUTHOR]

Research has shown that SAW (surface acoustic wave) devices with an LGS/Pt (langasite La3Ga5SiO14/platinum) structure are useful in high-temperature sensor applications. Extreme high temperature brings great acoustic attenuation because of the thermal radiation loss, which requires that the sensing device offer a sufficiently high quality factor (Q) and a low loss. Therefore, it is necessary to improve the performance of the quality factor as much as possible so as to better meet the application of high-temperature sensors. Based on these reasons, the main work of this paper was to extract accurate simulation parameters to optimize the Pt/LGS device and obtain Q-value device parameters. Optimization of SAW devices with LGS/Pt structure for sensing extreme high temperature was addressed by employing a typical coupling of modes (COM) model in this work. Using the short pulse method, the reflection coefficient of Pt electrodes on LGS substrate was extracted accurately by characterizing the prepared SAW device with strategic design. Other relevant parameters for COM simulation were determined by finite element analysis. To determine the optimal design parameters, the COM simulation was conducted on the SAW sensing device with a one-port resonator pattern for sensing extreme temperature, which allows for a larger Q-value and low insertion loss. Experimental results validate the theoretical simulation. In addition, the corresponding high-temperature characteristics of the prepared sensing device were investigated. [ABSTRACT FROM AUTHOR]

A new AlN film-based surface acoustic wave (SAW) device was explored for sensing strain at high temperature. AlN/metal/Si multilayer composite structure was proposed to construct the strain sensing chip, and the corresponding theoretical analysis on SAW propagation were performed by using finite element method (FEM). High-quality AlN piezoelectric thin-film was prepared by using magnetron sputtering on Si substrate, and Pt electrodes was then lithographically prepared to build the sensing chips with one-port resonator pattern operating at 607 MHz and 620 MHz. To compensate the temperature cross sensitivity and enhance the strain sensitivity, two sensing chips were positioned perpendicular on a ceramic package, then the differential frequency signal was extracted to evaluate the applied strain. A high-temperature strain testing platform was constructed to characterize the prepared strain sensor with orthometric structure, larger strain sensitivity of 0.84 ppm/ μ ε at 550 °C in the range 0 – 500 μ ε and excellent temperature stability of 0.624 ppm/°C at the temperature range of 20–600 °C were achieved successfully. [Display omitted] • High-quality AlN piezoelectric thin films and high-temperature electrodes prepared. • Orthometric dual-resonator SAW chip based on AlN/metal/Si multilayer structure proposed. • larger strain sensitivity of 0.84 ppm/ μ ε at 550 °C in the range 0 – 500 μ ε and excellent temperature stability of 0.624 ppm/°C at the temperature range of 20 – 600 °C were achieved successfully. [ABSTRACT FROM AUTHOR]

• A Y-cut 35o X quartz with perfect temperature stability was employed as the piezoelectric substrate of the sensing device patterned by one-port resonator. • Optimization towards SAW sensing device allowing larger Q-value was conducted by using COM model. • A wireless and passive SAW strain sensor with high sensitivity and excellent temperature stability was developed at operation frequency of 434MHz. A temperature-compensated surface acoustic wave (SAW) device was developed to build a wireless and passive strain sensor. Y-cut 35° X quartz with perfect temperature stability was employed as the piezoelectric substrate of the sensing device patterned by one-port resonator. Optimization by coupling of modes (COM) model towards sensing chip was conducted to determine the optimal design parameters, which offers lager Q-value. The prepared sensing device by standard photolithographic technique operating at 434MHz was characterized wirelessly. High strain sensitivity, excellent temperature stability, and high resolution were achieved in the wireless measurements. [ABSTRACT FROM AUTHOR]