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

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.

Theoretical Study of Monolayer and Double-Layer Waveguide Love Wave Sensors for Achieving High Sensitivity

“…Double-layer waveguide presents an effective method to improve the performance of Love wave sensors [23,24]. By adding an ultra-low-velocity layer on the SiO 2 waveguide layer, the Love wave velocity could be further decreased and more wave energy may be trapped in the waveguide layer.…”

Enhanced Sensitivity of a Love Wave-Based Methane Gas Sensor Incorporating a Cryptophane-A Thin Film

“…The sensitivity achieved from the Love wave sensing devices was 10 times higher than that of the typical Rayleigh surface acoustic wave (R-SAW) ones [ 16 ]. Another advantage of the Love wave mode for gas sensing is the temperature-compensation of the device itself by choosing proper guiding materials possessing reverse polarization of the temperature coefficient to the piezoelectric substrate [ 17 , 18 ]. Wang et al proposed a temperature-compensated Love wave device using the waveguide structure of SiO 2 /36° YX LiTaO 3 , which corresponding Love wave characteristics including dispersion relation and temperature coefficient of frequency (TCF) were investigated theoretically by solving the coupled electromechanical field equation, and the optimal waveguide structure was determined.…”

“…In this work, a temperature-compensated Love wave device for methane gas sensing was proposed, which is composed of a waveguide structure of SiO 2 /36° YX LiTaO 3 and a CrypA thin-film on top of the SiO 2 guiding layer, as shown in Figure 1 b. The 36° YX LiTaO 3 substrate offers a large piezoelectric coupling coefficient κ 2 (5.6%) and higher shear velocity (4202 m/s) over the SiO 2 guiding layer (2850 m/s), which is beneficial for reducing the acoustic attenuation and advances in mass sensitivity [ 18 ]. Also, the SiO 2 guiding layer possesses opposite polarization of the temperature of coefficient (Tcf) against the 36° YX LiTaO 3 , hence, lower Tcf of the hybrid Love wave device is expected by varying the SiO 2 thickness.…”

Love wave devices with excellent temperature stability for application in gas sensor

“…1(a). SU-8 exhibits low SH velocity, and benefits for the improvement of behavior and durability of a Love-type device when working as viscosity sensor in liquid media [1]. The theoretical model was performed to extract the optimal design parameters by solving the he coupled electromechanical field equation, and referring to the Tomar method [5].…”

“…Recently, there are great interests on Love wave devices for application in gas sensor owing to its weak longitudinal coupling attenuation, higher mass loading sensitivity and effective interdigital transducers (IDTs) protection [1]. Typical Love wave gas sensors are composed of a piezoelectric substrate with IDT pattern supporting a shear horizontal surface acoustic wave (SH SAW), a thin waveguide layer on the top of the substrate, and a sensitive layer responding to specific gases.…”