Two-Dimensional van der Waals Ferroelectrics: Scientific and Technological Opportunities.

Recent breakthroughs in two-dimensional (2D) van der Waals ferroelectrics have been impressive, with a series of 2D ferroelectrics having been realized experimentally. The discovery of ferroelectric order in atom-thick layers not only is important for exploring the interplay between dimensionality and ferroelectric order but may also enable ultra-high-density memory, which has attracted significant interest. However, understanding of 2D ferroelectrics goes beyond simply their atomic-scale thickness. In this Perspective, I suggest possible innovations that may resolve a number of conventional issues and greatly transform the roles of ferroelectrics in nanoelectronics. The major obstacles in the commercialization of nanoelectronic devices based on current ferroelectrics involve their insulating and interfacial issues, which hinder their combination with semiconductors in nanocircuits and reduce their efficiency in data reading/writing. In comparison, the excellent semiconductor performance of many 2D ferroelectrics may enable computing-in-memory architectures or efficient ferroelectric photovoltaics. In addition, their clean van der Waals interfaces can greatly facilitate their integration into silicon chips, as well as the popularization of nondestructive data reading and indefatigable data writing. Two-dimensional ferroelectrics also give rise to new physics such as interlayer sliding ferroelectricity, Moiré ferroelectricity, switchable metallic ferroelectricity, and unconventional robust multiferroic couplings, which may provide high-speed energy-saving data writing and efficient data-reading strategies. The emerging 2D ferroelectric candidates for optimization will help resolve some current issues (e.g., weak vertical polarizations), and further exploitation of the aforementioned advantages may open a new era of nanoferroelectricity.