Edge Nonlinear Optics on a MoS ₂ Atomic Monolayer

TLDR

Stable atom‑thick materials enable a new generation of thin‑film technologies, yet real monolayers are polycrystalline mosaics whose grain boundaries influence transport and optical properties. The authors demonstrate a simple microscopy technique that uses the nonlinear optical response of MoS₂ to probe and characterize atomically thin layers. The technique should prove useful for characterizing and optimizing atomically thin membranes. Yin et al.

Abstract

Optics On the Edge The ability to isolate stable materials just one atom thick has provided the impetus for a new generation of thin films technologies. Often, the materials are conceptually imaged in the form of an artist's impression as single continuous layers—a single crystal sheet of atoms. Scanning probe and transmission electron microscopies reveal the reality, however, where the material resembles a patchwork quilt with polycrystals of different orientation and size separated by grain boundaries forming a mosaic. These structures play an influential role in determining the transport and optical properties of the membrane. Yin et al. (p. 488 ; see the Perspective by Neshev and Kivshar ) demonstrate a simple microscopy technique based on the nonlinear optical response of the materials to probe and characterize atomically thin layers of MoS 2 . The technique should prove useful during the characterization and optimization of atomically thin membranes.