First-Order Shear Horizontal Mode Resonators Design of High $\boldsymbol{k}_{\mathbf{t}}^{2}$ Based on LiNbO3 Thin Film

In this work, high performance first-order shear horizontal (SH1) resonators with three electrode configurations based on Lithium niobate (LiNbO
3
) thin film have been designed. The optimal Euler angle of LiNbO
3
and device structure are analyzed by numerical calculation and finite element analysis (FEA). A high electromechanical coupling factor
$(\boldsymbol{K}^{2})$
is achieved by applying double IDT electrode configuration and an electromechanical coupling coefficient
$(\boldsymbol{k}_{\mathbf{t}}^{2})$
as high as 32.8% is achieved by optimizing normalized LiNbO
3
thickness, electrode coverage and normalized IDT thickness. The obtained SH1 resonators have a large
$\boldsymbol{k}_{\mathbf{t}}{}^{2}$
while meeting the frequency requirement of new fifth-generation (5G) communication, which solves the disadvantage of low phase velocity of fundamental mode shear horizontal (SHO) wave based on LiNbO
3
thin film. This result demonstrates a first step towards introducing LiNbO
3
thin film based on SH1 as an alternation to SH0 mode and other traditional piezoelectric materials for 5G communication.