Graphene Oxidation: Thickness Dependent Etching and Strong Chemical Doping

TL;DR

This study investigates how oxygen interacts with graphene layers, revealing layer-dependent etching behaviors and significant chemical doping effects that alter electronic properties.

Contribution

It uncovers the layer-dependent etching kinetics and strong chemical doping effects of oxygen on graphene, highlighting differences from graphene oxide.

Findings

Etching rate varies with graphene thickness, similar to bulk graphite in three-layer samples.

Single-layer graphene exhibits faster, random etching with pit formation.

Oxygen induces a substantial hole doping, shifting the Fermi level by ~0.5 eV.

Abstract

Patterned graphene shows substantial potential for applications in future molecular-scale integrated electronics. Environmental effects are a critical issue in a single layer material where every atom is on the surface. Especially intriguing is the variety of rich chemical interactions shown by molecular oxygen with aromatic molecules. We find that O2 etching kinetics vary strongly with the number of graphene layers in the sample. Three-layer-thick samples show etching similar to bulk natural graphite. Single-layer graphene reacts faster and shows random etch pits in contrast to natural graphite where nucleation occurs at point defects. In addition, basal plane oxygen species strongly hole dope graphene, with a Fermi level shift of ~0.5 eV. These oxygen species partially desorb in an Ar gas flow, or under irradiation by far UV light, and readsorb again in an O2 atmosphere at room temperature. This strongly doped graphene is very different than graphene oxide made by mineral acid attack.