石墨烯在金属表面上 Graphene on metal surfaces

U N

C O

R R

E C

T E

D

P R

O O

F

1

2

Graphene on metal surfaces

3

J.Wintterlin a,*,M.-L.Bocquet b

4a Ludwig-Maximilians-Universität München,Dept.Chemie und Biochemie and Center for Nanoscience CeNS,Butenandtstr.5-13,81377Munich,Germany 5

b

Universitéde Lyon,Laboratoire de Chimie,Ecole Normale Supérieure de Lyon,CNRS,F69007Lyon,France

68a r t i c l e i n f o 9Article history:

10Available online xxxx 11Keywords:12Review 13Graphene

14Metal surfaces 15Nickel

16Ruthenium 17Platinum 18Iridium

19

20a b s t r a c t

21The article reviews work on graphene monolayers adsorbed on metal surfaces.Graphene layers on metals 22have been prepared by surface segregation of carbon and by decomposition of hydrocarbons.The films 23are often not rotationally aligned to the metal surface.However,for a number of hexagonally close-24packed surfaces perfectly ordered epitaxial overlayers can be obtained,with domains larger than the ter-25races of the metal substrate.In most cases the well-ordered overlayers display moiréstructures with 26large periodicities,resulting from the lattice mismatch between graphene and the underlying metal.27These structures are connected with a buckling of the graphene layer indicating local variations of the 28binding to the metal.For the metal–graphene spacings values between approximately 2.1and 3.8Åwere 29found,depending on the metal.Reasons for these strong variations are not yet clear,but there are indi-30cations that the systems fall into two classes that differ qualitatively with respect to the metal/graphene 31interaction.These variations are also reflected by the electronic structure.There are metal–graphene sys-32tems in which the p band is significantly downshifted in energy compared to the free-standing graphene,

33and a band gap of order eV has opened at the K

point of the Brillouin zone.In other systems,the electronic 34structure of free-standing graphene is almost intact.The perfectness of the epitaxial moiréphases offers 35promising applications,e.g.,as templates for nanostructures.

36Ó2009Published by Elsevier B.V.

37

3839 1.Introduction

40The publication in 2004of a method to prepare free-standing 41graphene,single 2D carbon sheets with the same structure as the 42individual layers in graphite,has initiated enormous scientific 43activities [1–4].Graphene is a unique material.It is strictly 2D 44(apart from a small,long-range buckling [5]),it has a high crystal-45lographic quality,and it is stable under ambient conditions.It has a 46very special electronic structure,the p and p *bands touch in a sin-47gle point at the Fermi energy (E F )at the corner of the Brillouin 48zone,and close to this so-called Dirac point the bands display a lin-49ear dispersion.This topology of the bands gives rise to exotic elec-50tronic transport properties –the charge carriers behave like 51relativistic particles –which manifest themselves in unusual phe-52nomena such as an anomalous quantum Hall effect [6,7].The bal-53listic charge carrier transport at 300K and at high charge carrier 54concentrations makes graphene also interesting for applications 55in electronic devices [4].

56In the adsorbed form on metal surfaces graphene has been 57known for at least 40years.The formation of graphene was first 58observed during preparation of Pt and Ru single crystal surfaces 59[8–12].When during the usual preparation the samples were 60

annealed to high temperatures,carbon impurities segregated from

61the bulk to the surface.It was soon realized that one form of this 62surface carbon is graphene [11].Graphene on metal surfaces is also 63known from industrial heterogeneous catalysis,where,for reac-64tions involving hydrocarbons,the deposition of graphitic carbon 65on the catalyst surface is a major reason for deactivation [13,14].66Recent investigations have shown that these graphitic layers can 67consist of a few graphene layers only,or even of monolayers 68[15].Not surprisingly,the current boom in research on free-stand-69ing graphene has led to renewed interest in graphene adsorbed on 70metal surfaces.Exploration of these systems has meanwhile be-71come a third main field of graphene research,in addition to inves-72tigations of free-standing graphene and of epitaxial graphene on 73SiC.(The decomposition of SiC is the second major method for 74graphene preparation [16–18],apart from the mechanical exfolia-75tion from graphite.)

76In this contribution,we give an overview of results for metal–77graphene systems.The available published material on graphene 78on metals has strongly grown since two previous reviews from 791997[19,20],and currently the field is developing so rapidly that 80we cannot hope to provide much more than a snapshot.An impor-81tant issue in many of the investigations has been the question of 82how the graphene layer interacts with the metal,which,of course,83is the discriminating factor from isolated and SiC-supported graph-84ene:Is the graphene layer physisorbed –as one may expect from 85the very weak interaction between the layers in bulk graphite –86

or is it bound more strongly?And how is the electronic structure

0039-6028/$-see front matter Ó2009Published by Elsevier B.V.doi:10.1016/j.susc.2008.08.037

*Corresponding author.Tel.:+4908921807606;fax:+49089218079994.E-mail

address:wintterlin@cup.uni-muenchen.de (J.Wintterlin).Surface Science xxx (2009)xxx–xxx

Contents lists available at ScienceDirect

Surface Science

j o u r n a l ho m e p a g e

:w w w.e l s e vier.c om/locate/susc