Mechanical cleaning of graphene using in situ electron microscopy

Peter Schweizer,Erdmann Spiecker,Daniela Dasler,Christian Dolle,Frank Hauke,Andreas Hirsch,Gonzalo Abellán

doi:10.1038/s41467-020-15255-3

Abstract

Avoiding and removing surface contamination is a crucial task when handling specimens in any scientific experiment. This is especially true for two-dimensional materials such as graphene, which are extraordinarily affected by contamination due to their large surface area. While many efforts have been made to reduce and remove contamination from such surfaces, the issue is far from resolved. Here we report on an in situ mechanical cleaning method that enables the site-specific removal of contamination from both sides of two dimensional membranes down to atomic-scale cleanliness. Further, mechanisms of re-contamination are discussed, finding surface-diffusion to be the major factor for contamination in electron microscopy. Finally the targeted, electron-beam assisted synthesis of a nanocrystalline graphene layer by supplying a precursor molecule to cleaned areas is demonstrated.

Highlights

Avoiding and removing surface contamination is a crucial task when handling specimens in any scientific experiment
We introduce a site-specific mechanical cleaning approach combined with in situ electron microscopy
We find that in electron microscopy surface diffusion is the major factor for recontamination

Summary

Introduction

Avoiding and removing surface contamination is a crucial task when handling specimens in any scientific experiment. We report on an in situ mechanical cleaning method that enables the site-specific removal of contamination from both sides of two dimensional membranes down to atomic-scale cleanliness. While a plethora of cleaning methods have been developed for graphene in recent years, so far none was able to demonstrate a site-specific, fully cleaned surface down to the atomic scale. Techniques such as heating[8], plasma treatment[9], laser cleaning[10], chemical activation[11], and current-driven cleaning[12] have been tried out and tested. We use the cleaning technique in combination with the obtained knowledge about recontamination mechanisms to synthesize nanocrystalline monolayer graphene in situ in transmission electron microscopy (TEM)

Methods

Results

Conclusion