Foxcroft Essay Competition 2016
Aiden McGuirk
The Wonders of Graphene
Just like computers in schools would have been an unfamiliar sight to most people thirty years ago, the
computers of tomorrow could have the same effect that the personal computer has had on us in the future.
Advances in modern science and key discoveries that allow us to take advantage of the simple principles we
see in a plain old pencil could revolutionise the way we live.
In the past twelve years’ carbon has emerged as a strong potential replacement for silicon in computers.
Carbon continues to amaze us with its properties and the ideas for its use, which are wide and varied, and
include; the discovery of hydrocarbons as fuels, plastics, the most expensive jewellery, medical advancements
and the latest addition to an already impressive list; super computers.
Researchers are now making a name for themselves by researching the individual honeycomb-like sheets that
slide off a graphite pencil lead and form the lines on the page. These sheets of carbon are now commonly
known as Graphene, a new allotrope of carbon. Graphene has been impressing us in recent years by boasting
some very spectacular properties. Graphene sheets are flat sheets of carbon atoms hexagonally bonded, these
sheets are known to be thinner than 10 nanometres.1
Prior to 2004 the idea of there being flat graphene layers by themselves was thought to be impossible. Then
two teams one led by Andre Geim at the University of Manchester and the other Kostya Novoselov at the
Institute for Microelectronics Technology in Chernogolovka, Russia, were able to isolate graphene and were
able to begin the study of its properties.
The remarkability that Graphene is made even more staggering when we consider the simple technique used
to discover this allotrope of carbon. The researchers glued square graphite flakes that were already just five
nanometres in thickness and with sides up to two millimetres in length to a glass plate. They then placed a
piece of adhesive tape over the graphite flake and by peeling off the tape they removed some of the graphite
layers. They then dissolved the adhesive with a propanone (CH3C(O)CH3) solvent to reveal the thinnest layers.
Silicon wafers were dipped into the propanone solution, where van der Waals forces attracted the graphene
sheets, which stuck to the wafers. Graphene was identified because the wafers they rested on were violetblue, but if the graphene was present it made the wafers look blue. This difference in colour change is what
revealed to the researchers that it was graphene that was attracted to the silicon.2
Efforts to mass produce graphene so far have not been completely successful. Therefore, making graphene
one of the most expensive materials in the world, with a sample smaller than the breadth of a hair costing
more than $1000 in April 2008. 1
The reason why the pursuit to make graphene sustainably is so great is because of its remarkable properties
and uses. Graphene is so strong that a sheet of it as thin as “Clingfilm” could support an elephant, it is tougher
1
Chemistry review/Volume 19/Number 2/November 2009
2
http://www.graphene.manchester.ac.uk/explore/the-story-of-graphene/discovery-at-manchester/
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Foxcroft Essay Competition 2016
Aiden McGuirk
than diamond, stretchy as rubber, is virtually invisible, conducts heat and electricity better than any copper
wire and weighs next to nothing.3
Graphene has a breaking strength 200 times greater than steel, this makes it the strongest material ever
tested. The reason why graphene conducts electricity is the same reason as graphite. 1 Each carbon atom is
bonded to three others. This leaves one spare electron which is liberated and free to move throughout the
sheet. 1
What is special about graphene is that its electron mobility is ten times higher than the fastest of the
semiconductors and 100 times higher than silicon. Graphene features electron mobility values between 0.3
and 1 m2V-1s-1.1
The reason why graphene’s electrons are able to move so fast is because they behave as though they have no
mass. Whereas in other materials the reason why their electron mobility is so much lower is because the mass
of the electron does affects their mobility. In graphene it is said that the electrons behave like photons. They
are considered to be as particles of light that move at a speed independent of their mass, leading to the fact
they move around 300 times faster than expected.1 This property along with the size of the sheet could lead to
graphene replacing silicon in computers; making them faster and smaller than ever before.
One of the main ways that graphene can be manufactured is a production method called Chemical Vapour
Deposition or CVD. Chemical Vapour Deposition is where gaseous reactants are deposited onto a substrate. In
CVD two gases are combined in a reaction chamber. The temperature that a substance will start to be
deposited at is the primary condition that defines the type of reaction that will occur, so it is essential that the
temperature is correct.4
Graphene can be synthesised on a polycrystalline nickel film. The nickel films are first annealed in an argon or
hydrogen atmosphere at 1173-1273K5 to increase the grain size. The films are then exposed to a hydrogen and
methane gas mixture. The methane decomposes into carbon and hydrogen. The carbon atoms dissolve into
the nickel film to form a solid solution. The reaction chamber is then cooled slowly, as the temperature
decreases carbon’s solubility in the nickel also decreases. Therefore, during the cooling, the carbon atoms
begin to diffuse out of the nickel surface to form graphene. Since nickel has a lattice structure similar to that of
the hexagonal pattern found in graphene and since they have similar lattice constants; Nickel can serve as an
excellent lattice-matched substrate for graphene growth. 6
The rate of cooling is a vital factor in determining the quality and the thickness of the graphene films. Medium
cooling rates are found to produce the highest quality graphene, because it leads to optimum carbon
segregation and a minimal amount of layers. 7 The microstructure of the nickel films are also an important
factor in the formation of the graphene film morphology.8 Graphene films grown on a nickel film are usually
3
http://www.dailymail.co.uk/sciencetech/article-2045825/Graphene-strong-sheet-clingfilm-support-elephant.html
http://www.graphenea.com/pages/cvd-graphene#.V1QGl_krLIV
5
ASM Handbook: Alloy Phase Diagrams; Massalski, T. B.; Okamoto, H.; Subramanian, P. R.; Kacprzak, L., Eds.; ASM International:
Materials Park, OH, 2002; Vol. 3.
6
Eizenberg, M.; Blakely, J. M. Carbon Monolayer Phase Condensation on Ni(111). Surf. Sci. 1979, 82, 228–236.
7
Yu, Q. K.; Lian, J.; Siriponglert, S.; Li, H.; Chen, Y. P.; Pei, S. S. Graphene Segregated on Ni Surfaces and Transferred to Insulators.
Appl. Phys. Lett. 2008, 93, 113103
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Reina, A.; Jia, X.; Ho, J.; Nezich, D.; Son, H.; Bulovic, V.; Dresselhaus, M. S.; Kong, J. Large Area, Few-Layer Graphene Films on
Arbitrary Substrates by Chemical Vapor Deposition. Nano Lett. 2009, 9, 30–35
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Foxcroft Essay Competition 2016
Aiden McGuirk
monolayer with regions of multilayers. Most of the multilayer graphene formation occurs at the nickel grain
boundaries, which are defects in the polycrystalline nickel films.8 The annealing of the nickel films at these
high temperatures in a hydrogen or argon atmosphere does not only increase single-crystalline nickel grain
size, thus decreasing the number of grain boundaries, but it also eliminates certain impurities in the nickel.8
This leads to the increased quality of the graphene that is produced.
Graphene has many properties which are not only unique to it, but it also properties that are superior to
others. This has led to it being one of the most researched materials ever since its discovery, with 3000
research papers and 400 patents in 2010.3 These have included developments in the use of graphene in
supercomputers or quantum computers, solar cells, touch screens and medical sensors.
Graphene could be used to make lightweight and flexible solar cells. The Advanced Technology Institute (ATI)
at the University of Surrey have created a one-atom-thick flexible graphene sheet that can generate electricity
from the heat and light it absorbs.9 This was made possible by a manufacturing process known as
nanotexturing. The process involves building nano-sized graphene around a textured metal surface. When
deciding what pattern to texture the metal surface the research team based their design on the eyes of a
moth. This was because the eyes of a moth possess microscopic patterning that offers them the remarkable
ability to see in very low-light. It is this structure that is crucial in the absorption of light. Graphene on its own
absorbs only 2-3% of the light that falls on the sheet, this is why it is almost invisible.9 After the ATI research
team textured the surface the absorbency of the sheet increased by 90%.9 The sheet is thus the material with
the highest light absorbency in the world. These solar cells could line buildings, windows and cars to power
electrical components.
Graphene sheets could also be rolled up into carbon nanotubes. Nanotubes are so thin that 10,000 of them
would make up the width of a human hair.10 Nanotubes could radically improve medical diagnostic
techniques. This can be achieved by altering the surface of the carbon nanotubes so that some of the carbon
atoms are modified so that they are covalently bonded to a molecule that behaves like a biological receptor.
The nanotube is connected to a transistor, when the molecule is bonded to the receptor, this changes the
nanotubes conductive properties. This change is the detected by the transistor and how it affects it depends
on the disease. As many different receptors can be bonded to the nanotube many different diseases can be
tested for, including early stages of cancer. This could lead to doctors being able to discover diseases and
illnesses within patients faster. Nanotubes as medical sensors do still have its drawbacks. It is believed that
carbon nanotubes are toxic, as they can cause illnesses such as asthma on inhalation, and they are very
difficult to purify.
As our fascination in the element carbon and graphene increases; our demand for it will only increase.
Carbons mediocrity is what makes it such a spectacular element. It is the defining standard in many of our
measurements; be it our scale of relative atomic mass and it is the backbone of our existence as we ourselves
are carbon-based life forms. Carbon is pivotal in the functioning of our society; in powering our cars and
homes, down to the toys that children play with. The possible technological gain from producing graphene is
massive. There are numerous applications that graphene is being trialled in, if only a fraction of these
successful they would be of significant benefit to us all.
9
http://sciencenewsjournal.com/scientists-create-ultra-thin-graphene-sheet-that-can-power-a-house/
Chemistry Review/September 2014/Volume 24/Number 1
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