Temperature Effects on the Propagation Characteristics of Love Waves along Multi-Guide Layers of Sio2/Su-8 on St-90°X Quartz

Fangqian Xu,Wen Wang,Jiaoli Hou,Minghua Liu

doi:10.3390/s120607337

Abstract

Theoretical calculations have been performed on the temperature effects on the propagation characteristics of Love waves in layered structures by solving the coupled electromechanical field equations, and the optimal design parameters were extracted for temperature stability improvement. Based on the theoretical analysis, excellent temperature coefficient of frequency (Tcf) of the fabricated Love wave devices with guide layers of SU-8/SiO2 on ST-90°X quartz substrate is evaluated experimentally as only 2.16 ppm.

Highlights

There has been great interest in Love wave devices in bio or chemical sensors owing to their very low longitudinal coupling attenuation, higher mass loading sensitivity and effective interdigital transducers (IDTs) protection in harsh gas and liquid environments [1,2,3,4,5]
Typical Love wave devices are composed of a piezoelectric substrate with an IDT pattern supporting a shear horizontal surface acoustic wave (SH-SAW), and a thin waveguide layer on the top of the substrate
The Love wave velocity decreases with increases of the thickness of the guide layers, and the effect on the Love wave velocity from the SU-8 thickness was more obvious over the SiO2 guide layer

Summary

Introduction

There has been great interest in Love wave devices in bio or chemical sensors owing to their very low longitudinal coupling attenuation, higher mass loading sensitivity and effective interdigital transducers (IDTs) protection in harsh gas and liquid environments [1,2,3,4,5]. Typical Love wave devices are composed of a piezoelectric substrate with an IDT pattern supporting a shear horizontal surface acoustic wave (SH-SAW), and a thin waveguide layer on the top of the substrate. Due to the waveguide effect, the acoustic energy is trapped into the thin guide layer, resulting in larger mass loading effects from any applied perturbation. One of the conditions for Love wave formation is Sensors 2012, 12 the SH-SAW with high shear velocity propagating along the piezoelectric substrates. As the difference of the shear velocities between the substrate and guiding layer becomes larger, the conversion efficiency of acoustic energy into the Love wave is increased, resulting in higher sensitivity to applied perturbations

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Results