Title: Single Layer vs Bilayer Graphene: A Comparative Study of the Effects of Oxygen Plasma Treatment on Their Electronic and Optical Properties
Authors: Nourbakhsh, Amirhasan ×
Cantoro, Mirco
Klekachev, Alexander
Pourtois, Geoffrey
Vosch, Tom
Hofkens, Johan
van der Veen, Marleen H
Heyns, Marc
De Gendt, Stefan
Sels, Bert #
Issue Date: Aug-2011
Publisher: American Chemical Society
Series Title: Journal of Physical Chemistry C vol:115 issue:33 pages:16619-16624
Abstract: This contribution presents the effects of a mild O-2 plasma treatment on the structural, optical, and electrical properties of single-layer (SLG) and bilayer graphene (BLG). Unexpectedly, we observe only photoluminescence in the SLG parts of a graphene flake composed of regions of various thickness upon O-2 plasma treatment, whereas the BLG and few-layer graphene (FLG) parts remain optically unchanged. Confirmed with X-ray photoelectron spectroscopy (XPS) that O-2 plasma induces epoxide and hydroxyl-like groups in graphene, density functional theory (DFT) calculations are carried out on representative epoxidized and hydroxylated SLG and BLG models to predict density of states (DOS) and band structures. Sufficiently oxidized SLG shows a bandgap and thus loss of semiinetallic behavior, while oxidized BLG maintains its semimetallic behavior even at high oxygen density in agreement with the results of the photoluminescence spectroscopy (PL) experiments. DFT calculations confirm that the Fermi velocity in epoxidized BLG is remarkably comparable with that of pristine SLG, pointing to a similarity of electronic band structure. The similarity is also experimentally demonstrated by the electrical characterization of a plasma-treated BLG-FET. As expected from the electronegative oxygen adatoms in the graphene, epoxidized BLG presents conductive features typical of hole doping. Moreover, the electrical characteristics suggest band structures closely related to that of epoxidized graphene while deviating from that of hydroxylated graphene. Finally, upon O-2 plasma treatment of BLG, the four-component 2D peak around 2700 cm(-1) in the Raman spectrum evolves into a single Lorentzian line, very like the 2D peak of pristine SLG. Summarizing, the data in this contribution recommend that a controlled O-2 plasma treatment, which is compatible with CMOS process flow in contrast to wet chemical oxidation methods, provides an efficient and valuable technique to exploit the transport properties of the bottom layer of BLG.
ISSN: 1932-7447
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
Semiconductor Physics Section
Molecular Imaging and Photonics
Department of Materials Engineering - miscellaneous
Molecular Design and Synthesis
× corresponding author
# (joint) last author

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