Comparison of Thickness Field and Lateral Field Excitation in a Single Acoustic Wave Sensor

摘要

In the present study, two different types of thickness shear modes (TSMs) excited in a single acoustic wave sensor are investigated. A 5 MHz (yxl)-16.51° LiTaO_3 device is fabricated and tested in different concentrations of NaCl and 2-propanol water solutions. Experiment results have shown that the TSM wave excited by the thickness field exhibits greater sensitivity to changes in liquid properties than by the lateral field. It is believed that the device woks in a quasi-lateral-field-excitation mode and the liquid, as a virtual electrode of the thickness-field-excitation resonant configuration, plays a critical role for the resonant characteristic changes. In contrast, the resonant characteristic of the TSM wave launched by the lateral-field-excitation is little affected by liquid property changes due to the two electrodes on the same surface of a piezoelectric substrate.