The Age of Graphene: A Chemical Rarity Paves the Future of Nanotechnology
Kevin Lopez, University of Southern California
Abstract
The existence of graphene was thought to be impossible at ambient temperature and
conditions. However, it was discovered by exfoliating graphite, the same material found in the
lead of pencils, with tape. Since its discovery, a scientific “gold rush” has pushed many scientists
around the world to solve problems with mass production and to find useful applications for this
material. The outcome of the work of these “frontier pioneers” will reshape the future of our
everyday lives. Also, we are expecting to see some of its applications within the spans of years.
This is outstanding for a material once thought to be nonexistent.
Introduction
honeycombs.
This
arrangement
makes
Graphene is a form of carbon, which
graphene a strong material. Also, its planar
is the same element that forms diamond and
geometry means that it can be used as a thin
graphite. Graphene consists of a network of
coating some materials.
interconnected
hexagonal
rings,
which
Years ago, graphene was thought to
should look like the pattern found in
be thermodynamically unstable at room
temperature, because the difference of
temperature across the thin lattice could
cause it to tear its bonds [2], [3], [4]. As
consequence, it remained an “academic
material” for discussion among scientists
about its theoretical properties. In 2004,
Figure 1-Graphene consists of a lattice of hexagonal rings
attached to each other into a "honeycomb" design [1]
Andre Geim and Konstantin Novoselov
isolated fragments of graphene using nothing
reduces the stress; this effect ultimately
more than a graphite crystal and tape [5].
provide strength to graphene.
Since then, scientists have been able to study
its properties in detail. Current research is
finding practical applications as an efficient
electrical
conductor,
a
substrate
for
transistors, an ingredient in future strong
composite materials, and many more uses
Figure 3-The six p-orbitals are perpendicular to the place of
the ring. The electrons in these delocalize by fusing with the
orbitals in neighboring carbons [8].
The
[6].
Fundamental Principles
electrical
conductivity
in
graphene is caused by the arrangement its
electrons. Electronic orbitals are an effect of
the wave-like properties of the electron. At
atomic scales, electrons tend to behave more
like probabilistic waves rather than solid
particles. As the electron “orbits” the
nucleus, its position cannot be determined, so
it is more useful to describe it as a probability
Figure 2-In graphene each carbon atom (A) is bonded with
three neighboring carbons (B). The angle of 120° provides
optimal separation and stabilizes graphene’s structure [7]
Graphene’s strength can be explained
by the geometry of its lattice. Since angles
between the carbon-carbon bonds is 120°
(Figure 2), the three neighboring carbons are
as far as possible from each other; this
wave. Computing the wave function of the
electron gives rise to a probabilistic map that
show regions were the electron is most likely
to be found, these regions of the space around
the atom are called electronic orbitals.
Figure 3 shows a single ring of the graphene,
which is called a benzene ring. It has six p-
orbitals, which are perpendicular to the plane
Graphene offers a better conductivity than
of the ring. Because the electron-wave in the
most metals [5]; therefore, future devices
orbitals are in phase or “harmony”, these
employing graphene wiring would run cooler
delocalize or combine, meaning that these
and would be more energy efficient than their
electrons can flow freely around the ring [9].
counterparts using copper wiring.
Since graphene consists of multiple benzene
Another
field
where
graphene’s
rings combined, all of its electrons are able to
electrical conductivity is praised is in the
move
manufacturing
across
the
material
with
little
of
photovoltaic
cells.
resistance. You might be able to think of
Graphene, being relatively inexpensive and
graphene as a highway for electrons.
abundant,
Current and Potential Implementations
Graphene’s
appropriately
substitute
current photovoltaic technology by replacing
electrical
the charge-carrying silicon layer and the grid
conductivity can be exploited to improve
of silver wires that serve as electrodes. By
electronics.
experience
eliminating these two expensive components,
electrical resistance, they give off part of their
the cost of manufacturing can be brought
energy as heat. This is why some electronic
down significantly [10]. However, the
devices feel warm after continuous use.
experimental graphene-electrode cells had
When
high
can
electrons
Figure 2-Illustration of the TiO2-G-Si structure (left) and cross-sectional electron microscope image showing the
graphene and titanium dioxide layers in a solar cell [10].
lower
efficiency
compared
the
based transistor manufacturing technology
traditional manufacturing methods remains a
has reached the 22 nanometers node. As
major drawback. This year, a team of
comparison,
researchers from the Peking University [10],
nanometers wide. As transistors get smaller,
the National Center for Nanoscience and
the silicon crystal might not be stable enough
Technology, and the Tsinghua University
to form structures, meaning that silicon
found that by adding an antireflective layer of
transistors made at the atomic level might
titanium dioxide on top of the graphene layer
eventually degrade. On the other hand,
(Figure 4) it is possible to increase the
graphene is stable enough to be able to form
photovoltaic efficiency from 8.6% to 14.6%
structures at atomic scales. Graphene might
[10]. This light-to-electricity efficiency rate
replace
is perfect for commercial use; however,
manufacturing as we begin to work at atomic
graphene’s
scales [5].
durability
in
with
the
outdoor
a
silicon
DNA
as
molecule
substrate
in
is
2
chip
environment remains to be improved on.
A major trouble with this technology
Also, the current method used to coat
had been the need to introduce an energy
graphene
vapor
band gap on graphene through a scalable and
deposition, is difficult to implement over
economical method. The energy band gap is
large pieces glass.
a barrier that is responsible for turning off the
on
glass,
chemical
Landau and Peierls never imagined
transistor. A team of researchers from the
that graphene would be so unusually strong
University of Singapore [11] has used laser
and stable [3], [4]. These two qualities will
patterning to modify specific parts of the
have major implications in the future
graphene monolayer in order to create
semiconductor industry. The current silicon-
photodectectors. This study, in principle
would provide a scalable method for the
Creating solutions of small graphene
mass-production of semiconductor elements,
particles that can be sprayed over large
such as transistors and diodes, from
surfaces is an economic alternative, because
graphene.
these small particles can be created through
Scalable Manufacturing
the exfoliation of graphite crystals. [13]
The production of graphene is fairly
Conclusions
inexpensive by exfoliating a piece of graphite
Within a decade from the discovery
as Geim and Novoselov did. Anytime you
of graphene, scientific research on graphene
write with a pencil, which is made of
has come close to reaching practical uses in
graphite, you are leaving a trace of graphite
the mid-future, probably within the spans of
flakes, some of which are one-atom-thin
years.
layers of graphene. However, this method is
monolayers of graphene remains a major
able to produce just microscopic sheets [5].
obstacle for many of the implementations.
Production
of
large
continuous
An alternative method, which has
Although currently it faces some limitations,
been already discussed, is chemical vapor
graphene’s role in future electronics and
deposition. This method allows individual
energy production promises new ways these
carbon molecules to self-assemble into
devises can be integrated into buildings.
graphene on top of a copper surface at 1000
Graphene can help to strengthen composite
°C in the presence of methane and hydrogen
materials, to produce flexible solar cells, and
gas [12]. Later, the layer of graphene can be
to build smaller and faster computers and
transferred to the silicon substrate of the solar
smartphones.
panel. Obviously, this method requires a
technology, the manufacturing costs will
considerable amount of energy.
decrease as these applications move from the
As
with
any
upcoming
experimental
phase
into
streamlined
[6] Geim, Andre K., and Konstantin S.
production. However, once all the details are
Novoselov. "The rise of
solved, these applications of graphene could
graphene." Nature materials, vol. 6, no.
be part of our daily lives.
3, pp. 183-191, Mar. 2007.
References
[1] Wikipedia. “Graphene.” Internet:
[7] St. Louis Community College.
“Valence-shell electron-pair repulsion
http://en.wikipedia.org/wiki/Graphene
(VSEPR) theory.” Internet:
[date accessed: Sep. 10, 2013]
http://users.stlcc.edu/gkrishnan/MODEL
[2] L. D. Landau and E. M. Lifshitz.
Statistical Physics, Part I. Oxford:
Pergamon Press, 1980.
[3] R. E. Peierls. “Quelques proprietes
typiques des corpses solides.” Ann. I. H.
Poincare, vol. 5, pp. 177-222, 1935.
[4] Landau, L. D. Zur Theorie der
.HTM [date accessed: Sep. 10, 2013]
[8] Wikipedia. “Aromaticity.” Internet:
http://en.wikipedia.org/wiki/
Aromaticity [date accessed: Sep. 11,
2013]
[9] T. W. Graham Solomons, C. B. Fryle,
“Aromatic Compounds” in Organic
phasenumwandlungen II. Phys. Z.
Chemistry, 10th ed. New York, NY.
Sowjetunion, vol. 11, pp. 26-35, 1937.
Wiley, 2009, pp. 632-675
[5] Novoselov, Kostya S., Andre K. Geim,
[10] Shi, Enzheng, Hongbian Li, Long Yang,
S. V. Morozov, D. Jiang, Y. Zhang, S.
Luhui Zhang, Zhen Li, Peixu Li,
V. Dubonos, I. V. Grigorieva, and A. A.
Yuanyuan Shang et al. "Colloidal
Firsov. "Electric field effect in
Antireflection Coating Improves
atomically thin carbon films." Science,
Graphene–Silicon Solar Cells." Nano
vol. 306, no. 5696, pp. 666-669, Oct.
2004.
letters, vol. 13, no. 4, pp. 1776-1781,
Flexible, and Transparent Graphene
Mar. 2013.
Films by Chemical Vapor Deposition for
[11] Singh, Ram Sevak, Venkatram Nalla,
Wei Chen, Andrew Thye Shen Wee, and
Wei Ji. "Laser Patterning of Epitaxial
Organic Photovoltaics.” ACS Nano, vol.
4, no. 5, pp. 2865–2873, Apr. 2010.
[13] Liang, Yu Teng, and Mark C. Hersam.
Graphene for Schottky Junction
"Highly concentrated graphene solutions
Photodetectors." ACS Nano, vol. 5, no.
via polymer enhanced solvent
7, pp. 5969-5975, Jun. 2011.
exfoliation and iterative solvent
[12] L. Gomez De Arco, Y. Zhang, C. W.
exchange." Journal of the American
Schlenker, K. Ryu, M. E. Thompson,
Chemical Society, vol. 132, no. 50, pp.
and C. Zhou. “Continuous, Highly
17661-17663, Nov. 2010.