关键词: lateral-field-excitation, LiNbO₃, piezoelectric coupling factor, acoustic wave phase velocity

Abstract: LiNbO$_{3}$ has been found attractive for lateral field excitation (LFE) applications due to its high piezoelectric coupling. In this paper, bulk acoustic wave propagation properties for LiNbO$_{3}$ single crystal excited by a lateral electric field have been investigated using the extended Christoffel--Bechmann method. It is found that the LFE piezoelectric coupling factor for $c$ mode reaches its maximum value of 95.46{\%} when $\psi  = 0^\circ$ for both (yxl)-58$^\circ$ and (yxwl)$\pm 60^\circ/58^\circ$ LiNbO$_{3}$. The acoustic wave phase velocity of $c$ mode TSM (thickness shear mode) changes from 3456 m/s to 3983 m/s as a function of $\psi$. Here $\psi$ represents the angle between the lateral electric field and the crystallographic $X$-axis in the substrate major surface. A 5 MHz LFE device of (yxl)-58$^\circ$ LiNbO$_{3}$ with $\psi=0^\circ$ was designed and tested in air. A major resonance peak was observed with the motional resistance as low as 17 ${\rm \Omega}$ and the $Q$-factor value up to 10353. The test result is well in agreement with the theoretical analysis, and suggests that the LFE LiNbO$_{3}$ device can be a good platform for high performance resonator or sensor applications.

Key words: lateral-field-excitation, LiNbO₃, piezoelectric coupling factor, acoustic wave phase velocity