FEM Simulation of a High-Performance 128°Y-X LiNbO₃/SiO₂/Si Functional Substrate for Surface Acoustic Wave Gyroscopes

To obtain a high-performance surface acoustic wave (SAW) gyroscope substrate, the propagation characteristics and gyroscopic effect of Rayleigh waves in a 128°Y-X LiNbO₃/SiO₂/Si (LNOI) functional substrate were investigated with a three-dimensional finite element method. The influence of LNOI structural parameters on Rayleigh wave characteristics, including the phase velocity (v_p), electromechanical coupling coefficient (K²) and temperature coefficient of frequency (TCF), were analyzed. The results demonstrate that the SiO₂ layer compensates for the negative TCF of 128°Y-X LiNbO₃ and enhances the K² of the LNOI substrate. The Rayleigh wave velocity change of the LNOI substrate after rotations in different directions was studied. The gyroscope gain factor (η) represents the strength of the gyroscopic effect in the differential traveling wave SAW gyroscope and is defined. The η_y and η_z of the LNOI substrate with different structural parameters were investigated. Finally, an LNOI substrate with an h_LN/λ of 0.2 and an h_SiO2/λ of 0.05 was obtained by balancing the characteristic parameters, with a K² of 3.96%, TCF of -18.75 ppm/°C and η_y of 0.26. The LNOI substrate has a better gyroscopic effect and temperature stability than the 128°Y-X LiNbO₃ crystal. The LNOI substrate meets device miniaturization and integration needs.