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

Abstract

To improve the temperature compensation of LiTaO 3 -based devices, room-temperature bonding of LiTaO 3 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/LiTaO 3 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 LiTaO 3 is lower than that (3.3 nm) on the surface of Si. Due to the adsorption energy between Mo and Si and LiTaO 3 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-LiTaO 3 chemical bonds with activated Si and LiTaO 3 substrates, respectively. The existence of adsorption energy and chemical bonds ensured that the bonded LiTaO 3 /Si sample has a strong bonding strength (14 MPa).