Comparison of Pure-LFE and Pseudo-LFE Mode on LiNbO_3 Acoustic Wave Sensors

摘要

Lateral field excitation (LFE) acoustic wave devices, which employ two electrodes on the same surface of a piezoelectric substrate, have been found sensitive to liquid electrical property changes. Previous studies have shown that when working in liquid, (yxl)-58° LiNbO_3 LFE devices work on pure-LFE mode (the observed bulk acoustic wave is excited by the lateral field) and (yxl)21.82° LiNbO_3 LFE devices work on pseudo-LFE mode (the observed bulk acoustic wave is not excited by the lateral field but the thickness field with the liquid acting as an virtual electrode). In this work, LiNbO_3 LFE devices on both modes are designed and their sensitivity to liquid electrical property (conductivity, permittivity) changes were investigated and compared. The results showed that the pseudo-LFE mode devices have superior sensitivities to liquid electrical property changes compared to pure-LFE mode devices.