Spectroscopy of covalently functionalized graphene.
In order to engineer a band gap into graphene, covalent bond-forming reactions can be used to change the hybridization of the graphitic atoms from sp(2) to sp(3), thereby modifying the conjugation length of the delocalized carbon lattice; similar side-wall chemistry has been shown to introduce a band gap into metallic single-walled carbon nanotubes. Here we demonstrate that the application of such covalent bond-forming chemistry modifies the periodicity of the graphene network thereby introducing a band gap (∼0.4 eV), which is observable in the angle-resolved photoelectron spectroscopy of aryl-functionalized graphene. We further show that the chemically-induced changes can be detected by Raman spectroscopy; the in-plane vibrations of the conjugated π-bonds exhibit characteristic Raman spectra and we find that the changes in D, G, and 2D-bands as a result of chemical functionalization of the graphene basal plane are quite distinct from that due to localized, physical defects in sp(2)-conjugated carbon.
Niyogi
Sandip
S
Center for Nanoscale Science and Engineering, University of California, Riverside, California 92521, USA.
Bekyarova
Elena
E
Itkis
Mikhail E
ME
Zhang
Hang
H
Shepperd
Kristin
K
Hicks
Jeremy
J
Sprinkle
Michael
M
Berger
Claire
C
Lau
Chun Ning
CN
deHeer
Walt A
WA
Conrad
Edward H
EH
Haddon
Robert C
RC