Edge optical scattering of two-dimensional materials

TL;DR

This paper demonstrates that edge optical scattering in 2D materials, especially for samples larger than 2 μm, provides a size- and shape-independent way to probe their intrinsic dielectric properties, verified through experiments on MoS2.

Contribution

It introduces the concept that edge optical scattering acts as a knife-edge diffraction, offering a size- and shape-independent method to study 2D materials' dielectric properties.

Findings

Edge scattering is size- and shape-independent for samples larger than 2 μm.

High-angle scattering spectra are determined by intrinsic dielectric properties.

Experimental verification on MoS2 shows clear detection of excitons.

Abstract

Rayleigh scattering has shown powerful abilities to study electron resonances of nanomaterials regardless of the specific shapes. In analogy to Rayleigh scattering, here we demonstrate that edge optical scattering from two-dimensional (2D) materials also has the similar advantage. Our result shows that, in visible spectral range, as long as the lateral size of a 2D sample is larger than 2 {\mu}m, its edge scattering is essentially a knife-edge diffraction, and the intensity distribution of the high-angle scattering in $\mathbf{k}$ space is nearly independent of the lateral size and the shape of the 2D samples. The high-angle edge scattering spectra are purely determined by the intrinsic dielectric properties of the 2D materials. As an example, we experimentally verify this feature in single-layer $MoS_{2}$, in which A and B excitons are clearly detected in the edge scattering spectra, and the scattering images in $\mathbf{k}$ space and real space are consistent with our theoretical model. This study shows that the edge scattering is a highly practical and efficient method for optical studies of various 2D materials as well as thin films with clear edges.