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The integration of lithium niobate (LiNbO3or LN) and silicon (Si) has emerged as a promising heterogeneous platform for microelectromechanical systems (MEMSs) and photonic integrated circuits (PICs). Particularly, the lithium niobate on silicon (LNOS) architecture leverages the superior piezo-optomechanical properties of LN, making it compatible with superconducting circuits and quantum systems. This opens an avenue for the development of advanced quantum sensors and processors. However, existing LN and Si bonding methods suffer from inherent limitations, such as low interfacial strength and the formation of thick, amorphous interlayers. In this work, we present an asymmetric surface activation strategy to address these challenges. By employing proton-exchange-enhanced chemical activation on the LN surface and oxygen plasma treatment on the Si side, we have achieved remarkable bonding strengths of up to 10 MPa at a moderate annealing temperature of 150 °C. Notably, the bonding mechanism in our approach differs from that in conventional diffusion-based processes. Here, the dehydration condensation of surface functional groups results in an exceptionally thin interfacial layer, less than 2 nm thick, without the presence of amorphous LN. This innovative fabrication method for LNOS demonstrates superior reliability, piezoelectric performance, thermal management capabilities, and optical transmission qualities, paving the way for cutting-edge photonic and quantum applications.

A two-dimensional (2D) ferroelectric semiconductor, which is coupled with photosensitivity and room-temperature ferroelectricity, provides the possibility of coordinated conductance modulation by both electric field and light illumination and is promising for triggering the revolution of optoelectronics for monolithic multifunctional integration. Here, we report that semiconducting Sn2P2S6crystals can be achieved in a 2D morphology using a chemical vapor transport approach with the assistant of space confinement and experimentally demonstrate the robust ferroelectricity in atomic-thin Sn2P2S6nanosheet at room temperature. The intercorrelated programming of ferroelectric order along out-of-plane (OOP) and in-plane (IP) directions enables a tunable bulk photovoltaic (BPV) effect through multidirectional electrical control. By combining the capability of anisotropic in-plane optical absorption, a highly integrated Sn2P2S6optoelectronic device vertically sandwiched with graphene electrodes yields the polarization-dependent open-circuit photovoltage with a dichroic ratio of 2.0 under 405 nm light illumination. The reintroduction of ferroelectric Sn2P2S6to the 2D asymmetric semiconductor family provides possibilities to hardware implement of the self-powered polarization-sensitive photodetection and spotlights the promising applications for next-generation photovoltaic devices.