Incidence of multilayers in chemically exfoliated graphene

TL;DR

This paper introduces a Raman spectroscopy method combined with vapor-phase potassium intercalation to accurately determine the distribution of layer numbers in chemically exfoliated graphene, revealing a significant presence of single-layer and few-layer flakes.

Contribution

The study presents a novel Raman spectroscopy technique with vapor-phase intercalation for precise layer number distribution analysis in chemically exfoliated graphene.

Findings

Identified a lightly doped stage with coexistence of doped and undoped Raman modes.

Determined an upper limit of five layers for flakes, with significant single-layer content.

AFM measurements confirmed the distribution of layer numbers.

Abstract

An efficient route to synthesize macroscopic amounts of graphene is highly desired and a bulk characterization of such samples, in terms of the number of layers, is equally important. We present a Raman spectroscopy-based method to determine the distribution of the number of graphene layers in chemically exfoliated graphene. We utilize a controlled vapor-phase potassium intercalation technique and identify a lightly doped stage, where the Raman modes of undoped and doped few-layer graphene flakes coexist. The spectra can be unambiguously distinguished from alkali doped graphite, and a modeling with the distribution of the layers yields an upper limit of flake thickness of five layers with a significant single-layer graphene content. Complementary statistical AFM measurements on individual few-layer graphene flakes find a consistent distribution of the layer numbers.