In situ functionalization of graphene

TL;DR

This paper presents a novel in situ method to generate, monitor, and functionalize graphene defects using Argon plasma and ammonia, achieving stable n-doping without ambient exposure.

Contribution

The study introduces an in situ approach for defect creation and functionalization of graphene, improving control and stability of chemical modifications.

Findings

Defects are generated by Argon plasma and monitored via in situ Raman spectroscopy.

Defect density decreases significantly upon air exposure.

In situ ammonia functionalization results in stable n-doping in graphene.

Abstract

While the basal plane of graphene is inert, defects in it are centers of chemical activity. An attractive application of such defects is towards controlled functionalization of graphene with foreign molecules. However, the interaction of the defects with reactive environment, such as ambient, decreases the efficiency of functionalization and makes it poorly controlled. Here, we report a novel approach to generate, monitor with time resolution, and functionalize the defects $\textit{in situ}$ without ever exposing them to the ambient. The defects are generated by an energetic Argon plasma and their properties are monitored using $\textit{in situ}$ Raman spectroscopy. We find that these defects are functional, very reactive, and strongly change their density from $\approx 1\cdot10^{13} cm^{-2}$ to $\approx 5\cdot10^{11} cm^{-2}$ upon exposure to air. We perform the proof of principle $\textit{in situ}$ functionalization by generating defects using the Argon plasma and functionalizing them $\textit{in situ}$ using Ammonia functional. The functionalization induces the n-doping with a carrier density up to $5\cdot10^{12} cm^{-2}$ in graphene and remains stable in ambient conditions.