Cleaning Interfaces in Layered Materials Heterostructures

TL;DR

This paper presents a novel cleaning process to remove blisters and contaminants from layered material heterostructures, significantly improving interface quality and electronic mobility, enabling scalable fabrication of high-performance layered material devices.

Contribution

The authors develop a new method to clean layered heterostructures, achieving large, high-mobility regions and demonstrating applicability across different materials and contamination scenarios.

Findings

Achieved blister-free graphene/hBN regions of ~5000 μm² with high mobility.

Restored high mobility in contaminated graphene after cleaning.

Successfully cleaned heterostructures based on MoS₂, demonstrating broad applicability.

Abstract

Heterostructures formed by stacking layered materials require atomically clean interfaces. However, contaminants are usually trapped between the layers, aggregating into blisters. We report a process to remove such blisters, resulting in clean interfaces. We fabricate blister-free regions of graphene encapsulated in hexagonal boron nitride of$\sim$5000$\mu $m$^{2}$, limited only by the size of the exfoliated flakes. These have mobilities up to$\sim$180000cm$^2$V$^{-1}$s$^{-1}$ at room temperature, and$\sim$1.8$\times$10$^6$cm$^2$V$^{-1}$s$^{-1}$ at 9K. We further demonstrate the effectiveness of our approach by cleaning heterostructures assembled using graphene intentionally exposed to polymers and solvents. After cleaning, these samples reach similar high mobilities. We also showcase the general applicability of our approach to layered materials by cleaning blisters in other heterostructures based on MoS$_{2}$. This demonstrates that exposure of graphene to processing-related contaminants is compatible with the realization of high mobility samples, paving the way to the development of fab-based processes for the integration of layered materials in (opto)-electronic devices.