Raman imaging and electronic properties of graphene

TL;DR

This paper demonstrates how Raman imaging can identify and analyze the electronic properties of graphene, including phase coherence and conductivity, providing experimental insights into its layered structure and charge tuning.

Contribution

It introduces a method for unambiguous identification of graphene layers using Raman scattering and explores their electronic properties through transport measurements.

Findings

Raman imaging effectively distinguishes single- and multi-layer graphene.

Phase-coherence length of about 2 μm at 2 K was measured.

Conductivity and charge density tuning in graphene were demonstrated.

Abstract

Graphite is a well-studied material with known electronic and optical properties. Graphene, on the other hand, which is just one layer of carbon atoms arranged in a hexagonal lattice, has been studied theoretically for quite some time but has only recently become accessible for experiments. Here we demonstrate how single- and multi-layer graphene can be unambiguously identified using Raman scattering. Furthermore, we use a scanning Raman set-up to image few-layer graphene flakes of various heights. In transport experiments we measure weak localization and conductance fluctuations in a graphene flake of about 7 monolayer thickness. We obtain a phase-coherence length of about 2 $\mu$m at a temperature of 2 K. Furthermore we investigate the conductivity through single-layer graphene flakes and the tuning of electron and hole densities via a back gate.