Effects of AlN Coating Layer on High Temperature Characteristics of Langasite SAW Sensors

Lin Shu; Bin Peng; Yilin Cui; Dongdong Gong; Zhengbing Yang; Xingzhao Liu; Wanli Zhang

doi:10.3390/s16091436

Effects of AlN Coating Layer on High Temperature Characteristics of Langasite SAW Sensors

Sensors (Basel). 2016 Sep 6;16(9):1436. doi: 10.3390/s16091436.

Authors

Lin Shu¹, Bin Peng², Yilin Cui³, Dongdong Gong⁴, Zhengbing Yang⁵, Xingzhao Liu⁶, Wanli Zhang⁷

Affiliations

¹ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. s89s89s@126.com.
² State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. bpeng@uestc.edu.cn.
³ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. g3ingmtg@gmail.com.
⁴ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. 15196609270@163.com.
⁵ China Gas Turbine Establishment, Jiangyou 621703, China. zbyang668@163.com.
⁶ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. xzliu@uestc.edu.cn.
⁷ State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China. wlzhang@uestc.edu.cn.

Abstract

High temperature characteristics of langasite surface acoustic wave (SAW) devices coated with an AlN thin film have been investigated in this work. The AlN films were deposited on the prepared SAW devices by mid-frequency magnetron sputtering. The SAW devices coated with AlN films were measured from room temperature to 600 °C. The results show that the SAW devices can work up to 600 °C. The AlN coating layer can protect and improve the performance of the SAW devices at high temperature. The SAW velocity increases with increasing AlN coating layer thickness. The temperature coefficients of frequency (TCF) of the prepared SAW devices decrease with increasing thickness of AlN coating layers, while the electromechanical coupling coefficient (K²) of the SAW devices increases with increasing AlN film thickness. The K² of the SAW devices increases by about 20% from room temperature to 600 °C. The results suggest that AlN coating layer can not only protect the SAW devices from environmental contamination, but also improve the K² of the SAW devices.

Keywords: AlN coating layer; high temperature; langasite; temperature coefficient of frequency.