C-axis parallel oriented ZnO film SH-SAW sensor for electrical conductivity measurement in liquid

A shear horizontal type surface acoustic wave (SH-SAW) device can be a sensor operating in liquid, because SH-SAW propagates at liquid/solid interface without energy leakage to liquid. This device can detect changes in conductivity and viscosity of liquid. c-axis parallel oriented ZnO film can be one of the best candidates for the SH-SAW liquid sensor on various substrates. Theoretical investigation of K² value in IDT / ZnO (0°, 90°, Ψ) film / silica glass substrate structure showed that maximum value of K² = 3.4 % was found at Ψ = 55° with H / λ = 0.21. In this study, we fabricated these structures and evaluated K² values. Finally, the electrical conductivity of liquid was detected as the velocity change.