Ultraclean suspended graphene by radiolysis of adsorbed water

TL;DR

This paper presents a simple, robust method using radiolysis of adsorbed water in a transmission electron microscope to achieve ultraclean suspended graphene by removing surface contaminants, enabling better study of its intrinsic properties.

Contribution

The study introduces a novel, easy-to-implement cleaning technique for 2D materials that effectively removes organic contaminants without sacrificial processes.

Findings

Electron energy loss spectra show unprecedented fine-structure features.

Radicals from water radiolysis remove organic contaminants.

Method is adaptable to other materials and experimental setups.

Abstract

Access to intrinsic properties of a 2D material is challenging due to the absence of a bulk that would dominate over surface contamination, and this lack of bulk also precludes effective conventional cleaning methods that are almost always sacrificial. Suspended graphene and carbon contaminants represent the most salient challenge. This work has achieved ultraclean graphene, attested by electron energy loss (EEL) spectra unprecedentedly exhibiting fine-structure features expected from bonding and band structure. In the cleaning process in a transmission electron microscope, radicals generated by radiolysis of intentionally adsorbed water remove organic contaminants, which would otherwise be feedstock of the notorious electron irradiation induced carbon deposition. This method can be readily adapted to other experimental settings and other materials, to enable previously inhibited undertakings that rely on the intrinsic properties or ultimate thinness of 2D materials. Importantly, the method is surprisingly simple and robust, easily implementable with common lab equipment.