Van der Waals Ferroelectrics: Theories, Materials and Device Applications.

In recent years, an increasing number of two-dimensional (2D) van der Waals (vdW) materials have been theory-predicted or laboratory-validated to possess in-plane (IP) and/or out-of-plane (OOP) spontaneous ferroelectric polarization. Due to their dangling-bond-free surfaces, interlayer charge coupling, robust polarization, tunable energy band structures, and compatibility with silicon-based technologies, vdW ferroelectric materials exhibit great promise in ferroelectric memories, neuromorphic computing, nanogenerators, photovoltaic devices, spintronic devices, and so on. Here, we review the very recent advances in the field of vdW ferroelectrics. Firstly, theories of ferroelectricity are briefly discussed. Then we provide a comprehensive summary of the non-stacking vdW ferroelectric materials based on their crystal structures and the emerging sliding ferroelectrics. In addition, we enumerate their potential applications in various branches/frontier fields, with a focus on artificial intelligence. Finally, we discuss the challenges and development prospects of vdW ferroelectrics. This article is protected by copyright. All rights reserved.