Tunable optical absorption and interactions in graphene via oxygen plasma

TL;DR

This study demonstrates that mild oxygen plasma exposure can controllably modify the optical conductivity and doping levels in single-layer graphene, affecting excitonic interactions and enabling tunable optical properties without significant structural damage.

Contribution

It reveals how oxygen plasma exposure can be used to tune graphene's optical and electronic properties by modulating doping and many-body interactions in a controlled manner.

Findings

Reduction of excitonic binding energy observed

Suppression of conductivity below a threshold consistent with Pauli blocking

Control of doping levels without structural damage

Abstract

We report significant changes of optical conductivity in single layer graphene induced by mild oxygen plasma exposure, and explore the interplay between carrier doping, disorder, and many-body interactions from their signatures in the absorption spectrum. The first distinctive effect is the reduction of the excitonic binding energy that can be extracted from the renormalized saddle point resonance at 4.64 eV. Secondly, the real part of the frequency-dependent conductivity is nearly completely suppressed below an exposure-dependent threshold in the near infrared range. The clear step-like suppression follows the Pauli blocking behaviour expected for doped monolayer graphene. The nearly zero residual conductivity at frequencies below 2Ef can be interpreted as arising from the weakening of the electronic self-energy. Our data shows that mild oxygen exposure can be used to controlably dope graphene without introducing the strong physical and chemical changes that are common in other approaches to oxidized graphene, allowing a controllable manipulation of the optical properties of graphene.