Approaching the Intrinsic Properties of Moir\'e Structures Using Atomic Force Microscopy Ironing

TL;DR

This paper demonstrates that atomic force microscopy ironing can significantly improve the interface quality of TMD heterostructures, enhancing moiré effects and reproducibility for studying their intrinsic properties.

Contribution

The study introduces a novel AFM ironing technique to achieve cleaner, more uniform interfaces in TMD heterostructures, improving their optical and electronic properties.

Findings

Enhanced interlayer coupling observed after ironing

Increased homogeneity of moiré patterns

Reduced disorder in TMD heterostructures

Abstract

Stacking monolayers of transition metal dichalcogenides (TMDs) has led to the discovery of a plethora of new exotic phenomena, resulting from moir\'e pattern formation. Due to the atomic thickness and high surface-to-volume ratio of heterostructures, the interfaces play a crucial role. Fluctuations in the interlayer distance affect interlayer coupling and moir\'e effects. Therefore, to access the intrinsic properties of the TMD stack, it is essential to obtain a clean and uniform interface between the layers. Here, we show that this is achieved by ironing with the tip of an atomic force microscope. This post-stacking procedure dramatically improves the homogeneity of the interfaces, which is reflected in the optical response of the interlayer exciton. We demonstrate that ironing improves the layer coupling, enhancing moir\'e effects and reducing disorder. This is crucial for the investigation of TMD heterostructure physics, which currently suffers from low reproducibility.