Atomic-level contact formation between LiNbO3 and Si wafers via surface-activated bonding at room temperature

Fabrication of high-quality LiNbO₃/Si interfaces is crucial for the heterogeneous wafer-level integration of single crystal LiNbO₃ and Si. Bonded LiNbO₃/Si wafers are promising for integrated photonics and RF devices owing to their unique electro-optic, nonlinear-optic, and piezoelectric properties. This study focuses on forming a directly bonded interface between LiNbO₃ and Si wafers using the surface-activated bonding (SAB) method, combined with Ar fast atom beam irradiation at room temperature, and on performing atomic-level analyses of the LiNbO₃/Si bonded interface and debonded surfaces. The surface activation process produces amorphous Li-deficient LiNbO₃ and Si layers. The SAB method enables LiNbO₃ and Si wafers to form a void-free, atomically bonded interface. Atomic-scale observations and elemental analyses of both the bonded interface and debonded surfaces suggest that the bond strength between LiNbO₃ and Si is primarily determined by the Ar irradiation-induced amorphous LiNbO₃ layer. This study lays a foundation for the future development and mechanistic understanding of SAB for fabricating heterogeneously integrated LiNbO₃ wafers, with potential applications in photonic and RF devices.