Graphene oxidation: thickness-dependent etching and strong chemical doping

Area of Science:

• Materials Science
• Surface Chemistry
• Condensed Matter Physics

Background:

• Patterned graphene is crucial for molecular-scale electronics.
• Environmental interactions, especially with oxygen, significantly affect single-layer graphene's properties due to its high surface-area-to-volume ratio.

Purpose of the Study:

• To investigate the environmental effects of molecular oxygen on graphene.
• To understand the kinetics of oxygen etching on graphene with varying layer numbers.
• To characterize the doping effects of oxygen species on graphene.

Main Methods:

• Comparative etching studies of single-layer and three-layer graphene with molecular oxygen.
• Analysis of etch pit morphology and nucleation sites.
• Measurement of Fermi level shifts using techniques sensitive to electronic doping.
• Investigation of oxygen species adsorption/desorption dynamics.

Main Results:

• Oxygen etching rates differ significantly between single-layer graphene and thicker samples, with single-layer graphene exhibiting faster etching and random pit formation.
• Three-layer graphene etching resembles that of bulk natural graphite.
• Basal plane oxygen species induce strong p-type doping in graphene, causing a Fermi level shift of approximately 0.5 eV.
• Oxygen species can be reversibly adsorbed and desorbed, indicating a dynamic interaction.

Conclusions:

• The number of graphene layers critically influences oxygen etching kinetics and mechanisms.
• Surface oxygen species act as significant dopants for graphene, creating a distinct electronic state compared to graphene oxide.
• These findings are vital for controlling graphene's surface chemistry and electronic properties in device applications.