Cleaning graphene: comparing heat treatments in air and in vacuum

TL;DR

This paper compares heat treatments in air and vacuum for cleaning graphene, finding pre-situ cleaning with radiative or laser heating effectively removes contamination without damaging the material.

Contribution

It provides a comparative analysis of annealing methods in different environments, highlighting the effectiveness of pre-situ cleaning techniques for graphene.

Findings

Pre-situ cleaning effectively removes contamination.

Ex situ treatments are less reliable for atomically clean surfaces.

Pre-situ methods cause minimal damage to graphene structure.

Abstract

Surface impurities and contamination often seriously degrade the properties of two-dimensional materials such as graphene. To remove contamination, thermal annealing is commonly used. We present a comparative analysis of annealing treatments in air and in vacuum, both ex situ and "pre-situ", where an ultra-high vacuum treatment chamber is directly connected to an aberration-corrected scanning transmission electron microscope. While ex situ treatments do remove contamination, it is challenging to obtain atomically clean surfaces after ambient transfer. However, pre-situ cleaning with radiative or laser heating appears reliable and well suited to clean graphene without undue damage to its structure.