Photonic crystals in biology

Poster Session, Tuesday, June 15
Theme A1 - B702
An alternative approach to graphene and graphitic flake preparation and their morphology on Au
and SiO substrates
Merve Altay 1 , Ahme 2 2 , * 1
1 stanbul Technical University, Department of Physics, l, Turkey
2 National University of Singapore, Department of Physics, 2 Science Drive 3, 117542, Singapore
Abstract-We are working on alternative methods for graphene production based on the known methods, especially on the HOPG exfoliation
with scotch tape technique, which is a rather inefficient one. Our method involves the preparation of a solution with graphite and graphene
flakes. We place our graphitic flakes on clean Au and SiO substrates and investigate their optical properties as well as their morphological
properties using Atomic Force Microscopy (AFM) and Scanning Tunneling Microscopy (STM). We compare our samples to the morphologies
of the known graphene samples.
There is an explosive interest on the graphene research in
the past few years [1,2]. Graphene is a single layer of graphite
with exotic properties [1,2,3]. Much of the research on
graphene has been oriented in the exploration of its electronic
properties; however the structural properties of this twodimensional
model system are also of great interest [4]. Also
and efficient method for the preparation of reliable graphene
samples is required.
Graphene is generally prepared by four different methods:
Epitaxial growth by chemical vapour deposition (CVD); the
mechanical exfoliation of highly oriented pyrolytic graphite
(HOPG) using scotch tape (the most popular method);
epitaxial growth on insulating (or semiconductor) surfaces
(like SiC); and the formation of colloidal suspensions
(graphene oxide) [5].
We prepare solutions using scotch tape with graphite on
them. By means of drop casting the solution on Au on glass or
Au on mica substrates; or on SiO wafers, we investigate their
optical and morphological properties. In our studies we use
reference graphene samples on SiO prepared by means of
mechanical exfoliation technique with lithographic Au
contacts on them. We especially studied the reference samples
by STM such that we were able to get local ato mic resolution
on the graphene structures [6].
(a) (b) (c)
(a) (b) (c)
Figure 2. STM images of our reference sample.(a)STM image of Au
contact on Graphene on SiO
(size:112nmx112nm,V=50mV,I=0.5nA).(b) STM image of Graphene
(size:128nmx128nm,V=50mV, I=1nA).(c)Atomic resolution on
Graphene (size:6.09nmx6.09nm,V=50mV, I=1nA).
Our initial results on the samples we have prepared using
our graphene production recipe hints at the possible successful
graphene flakes with considerably large sizes, even visible to
the naked eye. Their optical microscopy images compare to
those of the reference samples (figure.3). We are investigating
the properties of our flakes using raman scattering, AFM and
STM measurements.
(a) (b) (c)
Figure 1. Our reference sample.(a)Microscopy image of graphene
on SiO with Au contacts, image size: 650umx650um. (b) zoom on to
the graphene, image size:65umx65 um. Graphene is35.36umx 12um.
(c)AFM image of the same graphene with Au contact (image
size:4.00umx4.00um)
We can clearly identify the graphene samples using AFM.
The typical step height of graphene samples on SiO is about
2.6nm. This indicates the existence of a rough surface
underneath (Figure 1c). We can also aim at the graphene
samples as well as the lithographic Au contacts using the STM
tip. The Au contacts and the graphene sections of the samples
are imaged and we can get atomic resolution on the graphene
under ambient conditions (Figure 2).
Figure 3. Optical microscopy images of our samples. (a)Image of
our sample casted on Au, scale bar (red):10um., image size:
60umx60um. (b)Image of another sample of ours on SiO wafer, scale
bar: 200 um. , image size: 1000 um x 1000 um. (c) Zoom on to (b)
scale bar: 50um., image size: 300 um x 300 um.
*Corresponding author: gurlu@itu.edu.tr
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[6] Ozyilmaz, B.; Jarillo-Herrero, P.; Efetov, D.; Kim, P., APL, 97,
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 407