Nanoscopic Characterization and Mechanism Analysis of LiTaO₃/Si Interfaces Prepared by Mo/Au Nanoadhesive Layers for Applications in LiTaO₃-Based Devices

To improve the temperature compensation of LiTaO3-based devices, room-temperature bonding of LiTaO3 and Si wafers was performed in atmospheric air using Mo/Au (∼21.6 nm/ ∼78.6 nm) nanoadhesive layers. TEM observations show that each of the Mo/Si, Au/Mo, Au/Au, and Mo/LiTaO3 interfaces is tightly bonded without any defects, and after surface activation, the thickness (1.6 nm) of the amorphous layer formed on the surface of LiTaO3 is lower than that (3.3 nm) on the surface of Si. Due to the adsorption energy between Mo and Si and LiTaO3 and Au, Mo as an underlayer material can enhance the adhesion between substrates and Au and form the Mo/Au film as a whole. Meanwhile, Mo can form strong Mo–Si and Mo-LiTaO3 chemical bonds with activated Si and LiTaO3 substrates, respectively. The existence of adsorption energy and chemical bonds ensured that the bonded LiTaO3/Si sample has a strong bonding strength (14 MPa).