Is graphene on copper doped?

Alexander J Marsden,Giovanni Costantini,Paolo Moras,Pavel Dudin,Maria‐Carmen Asensio,Ian Maskery,Polina M Sheverdyaeva,Neil R Wilson,José Avila,Gavin R Bell,Thomas W White,Alexei Barinov

doi:10.1002/pssr.201307224

Abstract

AbstractAngle‐resolved photoemission spectroscopy (ARPES) and X‐ray photoemission spectroscopy have been used to characterise epitaxially ordered graphene grown on copper foil by low‐pressure chemical vapour deposition. A short vacuum anneal to 200 °C allows observation of ordered low energy electron diffraction patterns. High quality Dirac cones are measured in ARPES with the Dirac point at the Fermi level (undoped graphene). Annealing above 300 °C produces n‐type doping in the graphene with up to 350 meV shift in Fermi level, and opens a band gap of around 100 meV.magnified imageDirac cone dispersion for graphene on Cu foil after vacuum anneals (left: 200 °C, undoped; right: 500 °C, n‐doped). Centre: low energy electron diffraction from graphene on Cu foil after 200 °C anneal. Data from Antares (SOLEIL).(© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Highlights

Graphene research continues at a frantic pace and is increasingly focused on material grown by chemical vapour deposition (CVD) on low-cost metal foils, a process readily scalable to industrial production [1, 2]
A recent angle resolved photoemission spectroscopy (ARPES) study [4] found that graphene grown in Ultra-high vacuum (UHV) on Cu(111) and Cu(100) single crystals is n-doped (Fermi energy EF = 300 meV above the Dirac crossing) and has an induced band-gap EG = 250 meV, with both values affected by air exposure, while a recent microARPES experiment found undoped graphene on Cu foil [8]
3 Results Spotty low energy electron diffraction (LEED) patterns could be observed from G-Cu samples even before any thermal treatment in UHV

Summary

Introduction

Graphene research continues at a frantic pace and is increasingly focused on material grown by chemical vapour deposition (CVD) on low-cost metal foils, a process readily scalable to industrial production [1, 2]. Ultra-high vacuum (UHV) surface-specific techniques such as angle resolved photoemission spectroscopy (ARPES) are ideally suited to the study of 2D materials and have been applied to graphene on single crystal surfaces [3,4,5]. A recent ARPES study [4] found that graphene grown in UHV on Cu(111) and Cu(100) single crystals is n-doped (Fermi energy EF = 300 meV above the Dirac crossing) and has an induced band-gap EG = 250 meV, with both values affected by air exposure, while a recent microARPES experiment found undoped graphene on Cu foil [8]. We use ARPES on three different SR beamlines to clarify the doping and band gap of CVD-grown graphene on copper foil (G-Cu). Experimental details and beamline information are given in the Supporting Information (online at: www.pss-rapid.com)

Results

Discussion

Conclusions