Synthesis of graphene on gold

Article abstract of DOI:10.1063/1.3584006

Here we report chemical vapor deposition of graphene on gold surface at ambient pressure. We studied effects of the growth temperature, pressure, and cooling process on the grown graphene layers. The Raman spectroscopy of the samples reveals the essential

Full text of DOI:10.1063/1.3584006

Synthesis of graphene on gold
Tuba Oznuluer, Ercag Pince, Emre O. Polat, Osman Balci, Omer Salihoglu, and Coskun Kocabas
Citation: Applied Physics Letters 98, 183101 (2011); doi: 10.1063/1.3584006
View online: http://dx.doi.org/10.1063/1.3584006
View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/98/18?ver=pdfcov
Published by the AIP Publishing
Articles you may be interested in
Substrate dielectric effects on graphene field effect transistors
J. Appl. Phys. 115, 194507 (2014); 10.1063/1.4879236
Effects of Ga ion-beam irradiation on monolayer graphene
Appl. Phys. Lett. 103, 073501 (2013); 10.1063/1.4818458
Passivating chemical vapor deposited graphene with metal oxides for transfer and transistor fabrication
processes
Appl. Phys. Lett. 102, 143505 (2013); 10.1063/1.4801927
Graphene based field effect transistor for the detection of ammonia
J. Appl. Phys. 112, 064304 (2012); 10.1063/1.4752272
Transfer-free fabrication of graphene transistors
J. Vac. Sci. Technol. B 30, 03D114 (2012); 10.1116/1.4711128
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.49.57.18 On: Thu, 11 Dec 2014 18:58:54

APPLIED PHYSICS LETTERS 98, 183101 ͑2011͒
Synthesis of graphene on gold
Tuba Oznuluer,1 Ercag Pince,2 Emre O. Polat,2 Osman Balci,2 Omer Salihoglu,2 and
Coskun Kocabas2,a͒
1Department of Chemistry, Ataturk University, 25240 Erzurum, Turkey
2Department of Physics, Advanced Research Laboratories, Bilkent University, 06800 Ankara, Turkey
͑Received 27 January 2011; accepted 9 March 2011; published online 2 May 2011͒
Here we report chemical vapor deposition of graphene on gold surface at ambient pressure. We
studied effects of the growth temperature, pressure, and cooling process on the grown graphene
layers. The Raman spectroscopy of the samples reveals the essential properties of the graphene
grown on gold surface. In order to characterize the electrical properties of the grown graphene
layers, we have transferred them on insulating substrates and fabricated field effect transistors.
Owing to distinctive properties of gold, the ability to grow graphene layers on gold surface could
open new applications of graphene in electrochemistry and spectroscopy. © 2011 American Institute
of Physics. ͓doi:10.1063/1.3584006͔
Graphene, the two-dimensional ͑2D͒ crystal of sp2 hy-
bridized carbon, provides unique electronic1 and mechanical
properties.2 Recent progress on synthesis of graphene on
large area substrates3 fosters new applications of the 2D
crystal. High speed electronics4 and macroelectronics5 are
two examples of these emerging applications. Catalytic de-
composition of hydrocarbons on transition metals provides a
more promising method for large area growth of high quality
graphene layers. Various methods such as chemical vapor
deposition ͑CVD͒,3 surface segregation,6 solid carbon
source,7 and ion implantation8 have been used to synthesis of
graphene layers on metal surfaces. Nickel9 and copper10 are
the most commonly used metal substrates for the growth.
Other metals such as ruthenium, iridium, platinum, palla-
dium, and cobalt have also been used as a substrate for CVD
of graphene.10–13 Ability to grow graphene on different met-
als provides opportunities for new applications and more in-
side to understand the growth mechanism. In this Letter we
show a method to directly grow graphene layers on gold
surface in various forms such as thin films, foils and wires.
Formation of graphene on metal surfaces has been
known for 40 years.13 Single crystal Ru and Pt are the earli-
est metals on which epitaxial graphene due to the segregation
of carbon impurities has been observed.13 Recent studies
have demonstrated CVD of a single layer graphene on large
number of metal substrates. Gold surface, however, has not
been used for graphene growth. Previously adsorption of
graphenelike polycyclic hydrocarbon across gold step edges
has been reported.14 We believe that the synthesis of large
area graphene on gold surface could motivate new applica-
tions especially in electrochemistry15,16 and spectroscopy.17
It is known that gold surface has no catalytic activity. Gold
nanoparticles, however, show some diameter dependent cata-
lytic activity for oxidation of carbon monoxide and
alcohols.18 It is found that the smaller particles are more
active for oxidation. Furthermore growing single-walled car-
bon nanotubes ͑SWNTs͒ and multiwalled carbon nanotubes
over gold nanoparticles also shows catalytic activity of the
gold nanoparticles. Bhaviripudi et al.19 grew SWNTs on
SiO2 substrates using Au nanoparticles. More recently Yuan
et al.20 showed the growth of well aligned SWNT using Au
particles. This catalytic activity could be due to the solubility
of carbon in gold clusters.21 The mechanism of catalytic ac-
tivity of Au particles during CVD process still remains un-
clear. We believe that the role of gold nanoparticle during the
CVD process could provide more inside to understand the
growth mechanism of graphene layers on gold surface.
Figure 1 shows the schematic representation of the steps
of the preparation of the gold foils, deposition, and transfer
process of the graphene layers on dielectric substrates. We
used 25 ␮m thick gold foils obtained by pressing high purity
gold plates ͑99.99% from Vakıf Bank͒. In order to remove
impurities and reconstruct the single crystalline surface, the
gold foils were annealed with a hydrogen flame for 20 min
before use. Owing to the fast heating and cooling rates, hy-
drogen flame annealing provides more complete crystalliza-
tion of the gold foil than the furnace annealing.22 The result
of this treatment was a polycrystalline gold surface partially
͑111͒ oriented, with a roughness lower than a few nanom-
eters. After the annealing step, the gold foil is placed in
quartz chamber and the chamber is flushed with Ar gas for 5
min. The foil is heated up to 975 °C under Ar and H2 flow
͓240 SCCM and 8 SCCM, respectively ͑SCCM denotes cu-
bic centimeter per minute at STP͔͒. Methane gas with a rate
of flow of 10 SCCM is sent to the chamber for 10 min. After
stopping the methane flow, we cooled the chamber with a
natural cooling rates around 10 C/s. We have also developed
a transfer printing method to the transfer the graphene from
the gold foil to insulating dielectric substrates. After the
deposition, an elastomeric stamp polydimethylsiloxane
͑PDMS͒ is applied on the graphene coated gold foil. The
gold layer is etched by diluted gold etchant ͑type TFA,
Transene Co. Inc.͒. After complete etching of the gold foil,
the graphene layer on PDMS is applied on a 100 nm SiO2
coated silicon wafers. Peeling the PDMS releases the
graphene on the dielectric surface.
After the growth, we inspect the grown graphene layers
using optical microscope and scanning electron microscope.
Figure 2͑a͒ shows scanning electron micrograph of the
graphene on gold foils, respectively. The inset in Fig. 2͑a͒
shows the optical micrograph of the graphene on the gold
a͒
Author to whom correspondence should be addressed. Electronic mail:
ckocabas@fen.bilkent.edu.tr.
0003-6951/2011/98͑18͒/183101/3/$30.00
98, 183101-1
© 2011 American Institute of Physics
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.49.57.18 On: Thu, 11 Dec 2014 18:58:54

183101-2
Oznuluer et al.
Appl. Phys. Lett. 98, 183101 ͑2011͒
FIG. 1. ͑Color online͒ Schematic rep-
resentation of the steps of deposition
and transfer process of graphene
growth on gold film.
foil. The grain boundaries and wrinkles on the polycrystal-
line gold surface are clearly seen.
and I2D/IG peaks are given in Figs. 3͑c͒ and 3͑d͒, respec-
tively. The average width and the intensity ratio is around
40 cm−1 and 1.5, respectively. The distributions of the his-
tograms further support high percentage of single layer
graphene.
Raman spectroscopy provides clear finger prints of
graphene layers. Raman spectrum of the samples was mea-
sured using a confocal microraman system ͑Horiba Jobin
Yvon͒ in back-scattering geometry. A 532 nm diode laser is
used as an excitation source and the Raman signal is col-
lected by a cooled charge-coupled device camera. Figure
2͑b͒ and 2͑c͒ shows the Raman spectrum of the graphene as
grown on gold and after the transferring on SiO2 wafer. The
To further characterize the grown graphene layers, we
have fabricated FETs in thin film geometry. Source and drain
electrodes are fabricated on the transferred graphene layer
using a standard UV photolithography. The schematic repre-
sentation of the graphene FET is shown in Fig. 4͑a͒. The
devices are isolated from each other by O2 plasma etching of
the graphene layers between the devices. A highly doped
silicon substrate functions as a global gate electrode and 100
nm thick SiO2 forms the gate dielectric. The 2D Raman in-
tensity map of the graphene layer used for the device is
shown in Fig. 4͑b͒. Figure 4͑c͒ shows the transfer character-
istics of a device with a channel length of 8 ␮m and channel
width of 100 ␮m at a drain bias of 1 V. The Dirac point of
expected Raman peaks of D, G, D , and 2D can be seen on
Ј
the graph. The position of D, G, D , and 2D peaks are 1371,
Ј
1600, 1640, and 2743 cm−1 on gold and 1339, 1584, 1620
and 2676 cm−1 on SiO2 substrate. There is a significant red-
shift after the transfer process, likely due to release of com-
pressive strain on the graphene film. The inset in Fig. 2͑c͒
shows the zoomed 2D peak and the Lorentzian fit. The fit has
a symmetric Lorentzian shape with a width of 37 cm−1. The
shape and the width of the 2D peak is a good indication of
single layer graphene or noninteracting a few layers of
graphene. The D-band Raman signal of graphene on gold is
relatively more intense than the graphene grown on copper.
This intense D band is likely due to the large lattice mis-
match between gold and graphene. The lattice constant of
bulk graphite and hexagonally closed-packed gold surface
are 2.46 Å and 2.88 Å, respectively.
In order to find the optimum growth conditions we per-
formed Raman spectroscopy on samples grown at tempera-
tures between 850 and 1050 °C ͓see Fig. 2͑d͔͒. At low tem-
peratures around 850 °C, we do not observe a significant 2D
peak. On the other hand at very high temperatures there is a
significant D and G peaks which indicates formation of
multilayer defective graphene layers. For the samples grown
at temperatures between 850 and 1000 °C, the Raman spec-
tra look relatively the same. We have also studied the effect
of the cooling process on the grown graphene layers. How-
ever we do not observe any significant change in the Raman
spectra for cooling rates between 10 and 0.5 C/s.
Figures 3͑a͒ and 3͑b͒ shows micro-Raman mapping im-
ages of the graphene layers on SiO2. The micro-Raman map-
ping images are measured using confocal microraman sys-
tem with a spatial resolution of 300nm. Figure 3͑a͒ shows
the 2D map of the Lorentzian width of 2D peak obtained by
scanning the sample and Lorentzian curve fitting for each
point. The intensity ratio mapping images of 2D and G peaks
is shown in Fig. 3͑b͒. The histogram of the Lorentzian width
FIG. 2. ͑Color online͒ ͑a͒ Scanning electron micrograph of the graphene
coated gold foils. The inset shows the optical micrograph of the same area.
͑b͒ Raman spectra of the graphene as grown on gold surface. ͑c͒ Raman
spectra of the graphene on SiO2 substrate. The inset shows the zoomed
spectrum of the 2D peak and Lorentzian fit. The width of the Lorentzian is
around 37 cm−1. ͑d͒ Raman spectra of the graphene samples grown at a
range of temperatures between 850 and 1050 °C.
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.49.57.18 On: Thu, 11 Dec 2014 18:58:54

183101-3
Oznuluer et al.
Appl. Phys. Lett. 98, 183101 ͑2011͒
FIG. 3. ͑Color online͒ The micro-Raman mapping images of ͑a͒ the Lorent-
zian width of the 2D peak and ͑b͒ intensity ratio ͑I2D /IG͒ of 2D and G peaks
of the graphene on SiO2 layer. The Lorentzian widths are obtained by fitting
the spectrum for each point. The scale bars are 5 ␮m. Histogram of ͑c͒ the
Lorentzian width of the 2D peak and ͑d͒ the intensity ratio ͑I2D /IG͒.
the device is around Ϫ20 V which is likely because of the
trapped charges on the dielectric layer or unintentional dop-
ing during the fabrication process. The on-off ratio of the
device is around 2. The calculated field effect mobility of the
device is around 20 cm2/V s. The output characteristics are
given in Fig. 4͑d͒. The modulation of the channel conductiv-
ity is clearly seen from the graph.
The Raman spectra together with the transport measure-
ments provide solid evidence that gold surface can be used
as a substrate for graphene. Graphene growth on metal sub-
strates shows different growth mechanism depending on the
solubility of carbon in the metal. Two different growth
mechanisms have been proposed for nickel and copper sub-
strate. Very recently, using sequentially introduced isotopic
carbon, Li et al.23 demonstrated that the growth mechanism
on nickel is based on diffusion and precipitation, however,
the growth mechanism on copper is based on surface adsorp-
tion. Maximum solubility values of carbon in nickel, copper,
and gold are 2.7%, 0.04%, and 0.06%, respectively.24 The
solubility in gold is slightly more than copper and much less
than nickel. Based on these solubility values and the ob-
served minor effect of cooling rates, we speculate that the
growth mechanism of graphene on gold surface could be
similar with copper.
In summary we have reported the synthesis of graphene
layers on gold surface using CVD technique. The Raman
spectra of the samples reveal the essential feature of the
graphene grown on gold. The back-gated FETs that use the
transferred graphene layers as an effective semiconductor are
fabricated and characterized. Further surface characterization
experiments are needed to understand the growth mechanism
and the nature of the interaction between the gold and
graphene. We believe that, gold surface coated with graphene
layer could provide a unique configuration for various new
applications ranging from surface plasmon resonance sensors
to electrochemical analysis.
FIG. 4. ͑Color online͒ ͑a͒ Schematic representation of the back-gated
graphene FETs. ͑b͒ Raman intensity map of 2D peak from the graphene
layer bridging the source and drain electrodes. ͑c͒ Transfer and ͑d͒ output
characteristics the transistor with a channel width of 100 ␮m and a channel
length of 8 ␮m.
1K. S. Novoselov, A. K. Geim, S. V. Morozov, D. Jiang, Y. Zhang, S. V.
Dubonos, I. V. Grigorieva, and A. A. Firsov, Science 306, 666 ͑2004͒.
2A. H. Castro Neto, F. Guinea, N. M. R. Peres, K. S. Novoselov, and A. K.
Geim, Rev. Mod. Phys. 81, 109 ͑2009͒.
3X. S. Li, W. W. Cai, J. H. An, S. Kim, J. Nah, D. X. Yang, R. Piner, A.
Velamakanni, I. Jung, E. Tutuc, S. K. Banerjee, L. Colombo, and R. S.
Ruoff, Science 324, 1312 ͑2009͒.
4Y. M. Lin, C. Dimitrakopoulos, K. A. Jenkins, D. B. Farmer, H. Y. Chiu,
A. Grill, and P. Avouris, Science 327, 662 ͑2010͒.
5J. A. Rogers, Nat. Nanotechnol. 3, 254 ͑2008͒.
6N. Liu, L. Fu, B. Dai, K. Yan, X. Liu, R. Zhao, Y. Zhang, and Z. Liu,
Nano Lett. 11, 297 ͑2011͒.
7Z. Sun, Z. Yan, J. Yao, E. Beitler, Y. Zhu, and J. M. Tour, Nature ͑London͒
468, 549 ͑2010͒.
8S. Garaj, W. Hubbard, and J. A. Golovchenko, Appl. Phys. Lett. 97,
183103 ͑2010͒.
9A. Reina, X. Jia, J. Ho, D. Nezich, H. Son, V. Bulovic, M. S. Dresselhaus,
and J. Kong, Nano Lett. 9, 30 ͑2009͒.
10L. Gao, J. R. Guest, and N. P. Guisinger, Nano Lett. 10, 3512 ͑2010͒.
11J. Coraux, A. T. N’Diaye, M. Engler, C. Busse, D. Wall, N. Buckanie, F.
Heringdorf, R. van Gastei, B. Poelsema, and T. Michely, New J. Phys. 11,
039801 ͑2009͒.
12E. Sutter, P. Albrecht, and P. Sutter, Appl. Phys. Lett. 95, 133109 ͑2009͒.
13J. Wintterlin and M. L. Bocquet, Surf. Sci. 603, 1841 ͑2009͒.
14M. Treier, P. Ruffieux, R. Schillinger, T. Greber, K. Mullen, and R. Fasel,
Surf. Sci. 602, L84 ͑2008͒.
15C. S. Shan, H. F. Yang, J. F. Song, D. X. Han, A. Ivaska, and L. Niu, Anal.
Chem. 81, 2378 ͑2009͒.
16Y. Y. Shao, J. Wang, H. Wu, J. Liu, I. A. Aksay, and Y. H. Lin, Elec-
troanalysis 22, 1027 ͑2010͒.
17L. Wu, H. S. Chu, W. S. Koh, and E. P. Li, Opt. Express 18, 14395 ͑2010͒.
18H. Kanzow and A. Ding, Phys. Rev. B 60, 11180 ͑1999͒.
19S. Bhaviripudi, E. Mile, S. A. Steiner, A. T. Zare, M. S. Dresselhaus, A.
M. Belcher, and J. Kong, J. Am. Chem. Soc. 129, 1516 ͑2007͒.
20D. N. Yuan, L. Ding, H. B. Chu, Y. Y. Feng, T. P. McNicholas, and J. Liu,
Nano Lett. 8, 2576 ͑2008͒.
21N. Yoshihara, H. Ago, and M. Tsuji, Jpn. J. Appl. Phys. 47, 1944 ͑2008͒.
22V. L. De Los Santos, D. Lee, J. Seo, F. L. Leon, D. A. Bustamante, S.
Suzuki, Y. Majima, T. Mitrelias, A. Ionescu, and C. H. W. Barnes, Surf.
Sci. 603, 2978 ͑2009͒.
This work was supported by the Scientific and Techno-
logical Research Council of Turkey ͑TUBITAK͒ Grant No.
109T259 and Marie Curie International Reintegration Grant
͑IRG͒ Grant No. 256458.
23X. Li, W. Cai, L. Colombo, and R. S. Ruoff, Nano Lett. 9, 4268 ͑2009͒.
24H. Okamoto and T. Massalski, J. Phase Equilibria 5, 378 ͑1984͒.
This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to IP:
130.49.57.18 On: Thu, 11 Dec 2014 18:58:54