Lateral heterostructures of two-dimensional materials by electron-beam induced stitching

TL;DR

This paper introduces a new electron-beam stitching method to create stable, nearly atomically sharp lateral heterostructures of graphene and MoS2 with molecular carbon nanomembranes, enabling transfer and freestanding applications.

Contribution

The study presents a novel electron-beam induced stitching technique to synthesize stable 2D heterostructures with sharp interfaces, advancing fabrication methods for 2D material heterostructures.

Findings

Heterostructures have nearly atomically sharp boundaries.

The structures exhibit high mechanical stability and transferability.

The method enables fabrication of freestanding 2D heterostructures.

Abstract

We present a novel methodology to synthesize two-dimensional (2D) lateral heterostructures of graphene and MoS2 sheets with molecular carbon nanomembranes (CNMs), which is based on electron beam induced stitching. Monolayers of graphene and MoS2 were grown by chemical vapor deposition (CVD) on copper and SiO2 substrates, respectively, transferred onto gold/mica substrates and patterned by electron beam lithography or photolithography. Self-assembled monolayers (SAMs) of aromatic thiols were grown on the gold film in the areas where the 2D materials were not present. An irradiation with a low energy electron beam was employed to convert the SAMs into CNMs and simultaneously stitching the CNM edges to the edges of graphene and MoS2, therewith forming a heterogeneous but continuous film composed of two different materials. The formed lateral heterostructures possess a high mechanical stability, enabling their transfer from the gold substrate onto target substrates and even the preparation as freestanding sheets. We characterized the individual steps of this synthesis and the structure of the final heterostructures by complementary analytical techniques including optical microscopy, Raman spectroscopy, atomic force microscopy (AFM), helium ion microscopy (HIM), X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM) and find that they possess nearly atomically sharp boundaries.