Revealing Interfaces of Two-Dimensional Lateral Heterostructures by Second Harmonic Generation

TL;DR

This paper demonstrates that second harmonic generation microscopy can effectively reveal atomically sharp interfaces in two-dimensional lateral heterostructures, providing a new optical method for nanoscale interface characterization.

Contribution

The study introduces SHG microscopy as a novel, sensitive technique to visualize and analyze interfaces in 2D heterostructures, highlighting its ability to detect phase differences and nanometric features.

Findings

Enhanced SHG intensity at heterojunctions due to coherent superposition.

Constructive interference reveals phase differences from material susceptibilities.

SHG microscopy can unveil nanometric features in layered heterostructures.

Abstract

The interface between two different semiconductors is crucial in determining the electronic properties at the heterojunction, therefore novel techniques that can probe these regions are of particular interest. Recently it has been shown that heterojunctions of two-dimensional transition metal dichalcogenides have sharp and epitaxial interfaces that can be used to the next generation of flexible and on chip optoelectronic devices. Here, we show that second harmonic generation (SHG) can be used as an optical tool to reveal these atomically sharp interfaces in different lateral heterostructures. We observed an enhancement of the SH intensity at the heterojunctions, and showed that is due to a coherent superposition of the SH emission from each material. This constructive interference pattern reveals a phase difference arising from the distinct second-order susceptibilities of both materials at the interface. Our results demonstrate that SHG microscopy is a sensitive characterization technique to unveil nanometric features in layered materials and their heterostructures.