Identification of a strong contamination source for graphene in vacuum systems

TL;DR

This study reveals that common ion vacuum gauges can cause significant, reversible n-doping in graphene due to chemical species generated in vacuum systems, which can be mistaken for other effects.

Contribution

The paper uncovers a previously unknown contamination source in vacuum systems that strongly dopes graphene, highlighting the need for careful interpretation of doping effects.

Findings

Ion vacuum gauges generate chemical species that n-dope graphene.

Doping rates can exceed 10^{12} cm^{-2}/hour.

The doping effect is reversible upon air exposure.

Abstract

To minimize parasitic doping effects caused by uncontrolled material adsorption, graphene is often investigated under vacuum. Here we report an entirely unexpected phenomenon occurring in vacuum systems, namely strong n-doping of graphene due to chemical species generated by common ion high-vacuum gauges. The effect --reversible upon exposing graphene to air-- is significant, as doping rates can largely exceed 10^{12} cm^{-2}/hour, depending on pressure and the relative position of the gauge and the graphene device. It is important to be aware of the phenomenon, as its basic manifestation can be mistakenly interpreted as vacuum-induced desorption of p-dopants.