The Unique Edge Reconstructions and Related Edgeless Properties of Mono- and Few-Layered α-Phase Puckered 2D Materials

The edge reconstruction of two-dimensional (2D) materials is significant for the stability, properties, and applications. Significant progress has been made in understanding the edge reconstruction of 2D materials. Herein, an overview of the latest theoretical and experimental advances on edge reconstruction of α-phase phosphorene nanoribbon and IV–VI group binary compounds MX (M = Ge, Sn; X = S, Se), focusing on the mechanism, stability, physical, and chemical properties of the edge reconstructions is provided. The status, challenges, and contradictions in experiments and theory are addressed and the progress in edge reconstruction of α-phase puckered 2D materials as well as the effects of edge reconstruction on physicochemical properties are systematically introduced. A novel tube-like edge reconstruction is suggested to be universal for α-phase puckered monolayers. While ZZ(U) edge can be another important reconstruction in bilayer. Beyond the review, the edge structures of phosphorene have odd–even layered oscillations are also proposed. The edge terminations can affect the exfoliation mechanism and electronic, transport properties. Interesting, unique U-edge, which has been verified by experiment, exhibits nearly edgeless electronic and thermal transport, which is beneficial for ultrafast microelectronics.