1. 1
Table 1 – The table shows a list of functionalities that can be added to a
graphene lattice, to modify its properties.
Deposition and Analysis of Graphene Thin Films
Andy Skippins
Systems and Process Engineering Centre
College of Engineering
Swansea University
Swansea UK
711472@swan.ac.uk
I. ABSTRACT
Graphene is considered to be the wonder-material of the 21st
century. The study set out to investigate how graphene can be
produced and implemented, using current technologies and
processes. Three alternative deposition techniques to the harsh
and expensive chemical vapour deposition (CVD) technique
were investigated, including drop-cast, Langmuir Schaefer and
scattered graphene nano-platelets.The films will be analysed,
using a Scanning Electron Microscope (SEM) and a Surface
Enhanced Ellipsometric Cross-polarised microscope (SEEC).
Further studies were performed, using DigitalSurf
MountainsMap surface analysis software.
Each of the processes had their advantages and
disadvantages. However, the drop-cast technique produced the
highest quality, and thinnest film. The film quality was almost
comparable with CVD graphene, which is much more expensive,
and limited by its harsh processing temperature. The Langmuir
Schaefer method did not provide more control over film
thickness, although polymer (TPQPOH) and salt (NaCl) crystals
formed on the surface, potentially compromising its properties.
The scattered GNPs formed the poorest quality film/layer, with
heavy agglomeration on some parts of the substrate, and
nothing on others.
II. INTRODUCTION
Despite possessing a variety of superior properties,
graphene has yet to be exploited on a significant scale. Since
its discovery, by Novoselov and Geim [1], more than a
decade ago, a considerable amount of research has been
performed, providing not only theoretical research papers,
but patents with practical applications to industry. Currently,
the most popular technique for synthesis or deposition of
graphene is chemical vapour deposition (CVD). This
requires the substrate to be heated to 1000ºC, under ultra-
high vacuum (usually in the order of 10µPa) [2]. This is a
very harsh and expensive process, thus complicating the
manufacture, and impeding the development and
commercialisation of graphene’s many applications.
Currently, most graphene is used for research, so quality
takes priority over cost. Conversely, any commercial
applications will need to compete with products already
available on the market, and will be subject to very rigid
cost restrictions. Most substrates, including polymers,
organic materials, or any kind of complex structure would
deform well before reaching the temperature required for
CVD. It has therefore been established that the material is in
desperate need of a cheaper, gentler deposition technique.
The purpose of the investigation is to explore alternative
deposition techniques, such as basic scattering, drop-casting
and the Langmuir-Schaefer. The report will also discuss the
wide range of applications for graphene, and their suggested
deposition techniques. Graphene has many possible
applications in different industries, has the most potetntial
for impact, when used in supercapacitors, biosensors (due to
its high surface area) and integrated circuits (for its
electronic properties).
A. Functionalities
Graphene will interact with these molecules differently,
sometimes temporarily, sometimes permanently. Specific
applications will be discussed later on in the paper. In order
to modify the properties of graphene, for instance make it
more stable, or interact/behave in a specific way, graphene
must be functionalized with atoms or molecules, including
oxygen, nitrogen and hydrogen. This often happens during
the fabrication process, with the corresponding
atoms/molecules present in the chamber/ solution.
In general, smaller structures, such as nano-ribbons or
nano-platelets will only exhibit these additional molecules
on the edge of the surface, where there are unsatisfied
(dangling) bonds. Larger surfaces would have more space,
inside from the edge, for molecules to attach.
Oxygen [3] Nitrogen
Carboxyl - COOH, Nx
Hydroxyl - COH NO2
Ketone - C=O NH3 - Amonia
Ether - C2O N=H
Sulfur [4] C ≡N
Boron NOx
Bio-molecules O=C-NH2
Antibodies Silver
Smell receptors Fluorine

2. 2
B. Statistics
According to national as well as global statistics [5],
graphene is rapidly becoming more and more prominent, as
technological knowledge and manufacturing processes
develop.
Research has been funded by corporations and academic
institutions alike. In the UK, the Universities are leading
the way, in terms of patent applications. The top 3
applicants are universities, with a total of 25 between them.
As of 2014, there are 13,355 patent families (inventions)
relating to graphene. This is evidence of the many practical
uses for graphene that just need final developments before
commercialisation. If predictions that graphene will follow
the path of other revolutionary materials, such as carbon
fibre, silicon, polyethylene, etc. are correct, then it will
reach the consumer markets very soon.
III. METHODS
There are several manufacturing/deposition techniques for
graphene, with a cost-quality tradeoff. Hence, the
manufacturing process would be chosen to correspond to a
specific application. For instance, it would be
deposited/transferred to a SiO2 substrate, as an integrated
circuit, because a monolayer can easily tear, without
additional support or functionality. Current fabrication
processes are not capable of producing large isolated films,
and some of the more advanced applications are
impractical. However, there are many, forms of graphene
and processes that are not only achievable, but competitive
with existing materials.
A. Manufacturing Graphene
There are a variety of different techniques for production of
graphene, with advantages and disadvantages for each.
These are:
1) Mechanical Exfoliation
In this case, by dissecting graphite, using scotch tape. The
tape was placed on a crystal of graphite, then pulled off (at
least twice), to remove impurities from the surface.
A new piece of tape was placed onto the clean surface, and
pulled off, with a layer of graphite attached. This layer was
then repeatedly halved by sticking it to a clean piece of
tape, and pealing it off, until the thickness was eventually
reduced to a single layer.
This is a relatively simple and cheap technique, and does
not require expensive equipment. However, it cannot be
implemented on a large scale production line.
2) Plasma
Two key manufacturers of GNPs (graphene nano-platelets),
Perpetuus Advanced Materials and Haydale Ltd both
operate in Ammanford, West Wales, using plasma.
In this method, graphite powder is turned inside a chamber
(like a cement mixer), containing electrodes, that point
towards the centre. As the chamber rotates, and graphite
particles drop from the upper electrode to the bottom, an
arc forms. The plasma between the suspended particles
causes the layers in the graphite to build up charge and
energy, so that they separate (Hall effect [6]). The high
electric current flowing between the particles causes them
to join together, laterally in order to reduce resistance.
3) Liquid-phase-exfoliation
Graphite particles may be dispersed in a solvent, such as
methanol, or acetone. The solvent would then be sonicated
(vibrated at high frequency), to break down the graphite
into single layers, known as graphene.
Vacuum filtration and transfer process
Using mixed cellulose membranes (pore size 220nm), thin
films with a diameter of around 40mm, were vacuum
filtered. The films were then punched into small circles,
and transposed onto glass slides, before dissolving the filter
Fig.3. Plasma process
Fig.1. – Distribution of patent families (inventions) made by the top 10
organisations in the UK [5].
Fig.2. Patent applications and granted patents by first publication date [34].
The inset shows a more detailed view.

3. 3
membrane in acetone. The electrical and optical properties
of the circular thin films were then measured. [6]
B. Deposition
Once the GNPs have formed, for instance by plasma or
liquid-phase exfoliation, they need to be deposited onto a
substrate.
a) Chemical Vapour Deposition (CVD)
The most popular method of production is CVD [2], which
is capable of producing very high quality films. However, it
uses very expensive equipment, at extreme temperature
(~1000ºC). This makes it unsuitable for many applications,
because the intense heat would destroy/damage the
substrate.
Silicon is already suitable, due to the high purity, pristine
surface quality and good temperature performance that can
be achieved. Depending on application, the substrate could
also be made from ceramics (e.g. SiO2, quartz, etc), due to
their insulating properties, or metals for conducting (e.g.
copper, gold, etc). However, organic materials among many
other complex structures would be severely damaged or
even burnt/melted. Therefore, if this technique was to be
implemented, it would have to occur at the beginning of the
production process. Once deposited, the film can actually
be wet transferred from a copper foil, onto a (polymer)
substrate. However, this is not a practical solution, likely to
be used on a large scale, as it is very difficult to align the
substrate accurately.
CVD is also too expensive for many of its applications to
reach consumer markets.
2) Experimental
The following alternatives to CVD have been investigated:
‘Scattering’, drop-casting and Langmuir Schaefer.
a) Scattering
Depositing the film of GNPs, using the ‘scattering’
technique, proved much more straightforward than
expected. The powder was scattered onto the substrate, so
that the entire surface was covered. Excess powder was
then blown away, using compressed air. This left a very
thin layer of GNPs, most of which was invisible to the
human eye.
b) Drop-Casting
This process has successfully deposited high electron
mobility polymer thin-film transistors [7], so the transition
to graphene as a new material should be straightforward.
The Graphene was dissolved in methanol, with
concentrations of: 0.005, 0.05, and 0.5 mg/l. The solution
was then dripped (5µl) onto SEEC slides, and left to dry.
Once the methanol had evaporated, a layer of graphene was
left behind.
The solution of the best looking film (0.05mg/ml) was then
mixed with 0.01% TPQPOH (polymeric ionomer alkaline),
and drop casted onto a SEEC slide, for comparison with the
Langmuir Schaefer film.
c) Langmuir Schaefer Approach
This technique is capable of very accurately controlled
deposition of a film [8]. Required specialist Langmuir
trough (KSV Nima by Biolin Scientific), with surface
pressure gauge.
Before any deposition, the trough had to be cleaned, by
filling up with de-ionised water, then draining it and wiping
with ethanol.
A solution of 0.1 M sodium chloride (5.844g in 1L of de-
ionised water) was mixed and poured into the trough. This
formed a continuous convex meniscus around the edge.
Once a suitable concentration of graphene had been
selected, from the drop-casting experiment explained
above, the 0.05mg/ml solution was mixed with 0.025%
(v:v) and 0.01% (v:v) TPQPOH in methanol. This solution
was dripped evenly across the surface, in volumes of 400µl
and 800µl, using a syringe.
In order to find a target pressure, an isotherm experiment
was performed, for each concentration and volume. The
barriers were closed, at a rate of 15mm per minute.
Meanwhile, a paper tab hanging from a scale measured and
recorded the surface pressure.
Fig.5. - SEEC slide (a) with Langmuir Schaefer thin film (1 layer),
from 0.5mg/ml GNPs and 0.01% TPQPOH solution, (b) with drop
cast film, from 0.5mg/ml GNPs and 0.01% TPQPOH solution (c)
with drop cast film, from 0.5mg/ml GNPs (no TPQPOH) solution (d)
with drop cast film, from 0.5mg/ml GNPs (e) with drop cast film,
from 0.5mg/ml GNPs.
(b)
(a)
(e)
(d)
(c)
Fig.4. – Langmuir trough, NSV Nima, Biolin Scientific [36]

4. 4
The Langmuir Blodgett software, provided by KSV Nima,
produced a surface pressure against area (between the
barriers) graph. A target pressure was then chosen, where
the pressure was linearly proportional to area.
To deposit the film, the trough was cleaned again, and
filled up with 0.1M NaCl, before depositing the solution,
and closing the barriers to the corresponding target
pressure. The barriers stopped, when the surface pressure
reached the target pressure (of 25mN/mm in the case of
800µl 0.01% TPQPOH).
The SEEC slide was then lowered horizontally onto the
surface, and then peeled upwards, to deposit the graphene.
An alternative technique would be Langmuir Schaefer, or
better still, Langmuir Blodgett. The difference is that the
substrate is dipped vertically, instead of horizontal,
allowing for a much larger substrate. This is therefore,
more suited to larger scale production, and is more likely to
be commercialised.
3) Analyses
a) SEEC Microscope
Apparatus used: Nanolane Sarfus High Resolution Surface
Enhanced Ellipsometric Cross-polarised (SEEC)
microscope.
A light shining on the sample (see Fig.7.), is transmitted
through the film, and reflected off the surface of a special
‘SEEC slide’. The microscope then measures the amount of
cross-polarisation of the light, as it passes through the film.
This enables the calculation of the film thickness, to a very
high degree of accuracy (±3 ångströms [9]).
For each set of samples, the microscope was calibrated,
using the calibration sample. The image was rendered from
topographical data, determined by the microscope.
For this experiment, GNPs were deposited onto the SEEC
slide in order to measure the thickness of the film. The
samples were then studied using a SEEC microscope, in
cross-polarised mode, using x10 and x50 lenses.
b) Scanning Electron Microscope
A Scanning Electron Microscope (SEM) studies a sample,
by scanning it with a beam of electrons as shown in Fig.8..
Interactions between electrons and atoms on the surface of
the sample are detected by the microscope, and indicate the
height at that specific point. SEMs can capture very high
resolution images, with depth and clarity.
For this experiment, GNPs were scattered onto a silicon
substrate, to analyse the particles at a molecular level. The
substrate was mounted onto the frame, and placed inside
the machine, before setting up the microscope. Once the
vacuum (11.2k) had been established and the lens focused
on the sample, the microscope captured a number of images
of the graphene.
IV. RESULTS AND DISCUSSION
A. Analysis of GNPs
The films have been studied using SEM and SEEC
microscopy, at the micro and macro scales, respectively.
1) Deposition
a) Scattering
The scattering deposition technique was somewhat
unsuccessful, because of the agglomeration of GNPs.
Heavy agglomeration can be observed from Fig.9.(a) The
quality of the film was poor, and would better be classified
as a layer of GNPs, rather than a film.
Fig.7. Schematic of SEEC microscope operation [9]
Fig.6. Schematic of Langmuir Schaefer and Langmuir Blodgett
Deposition [35]
Fig.8. Schematic of Scanning Electron Microscope operation [40]

5. 5
b) Drop-Cast
Once the methanol had evaporated off the SEEC slides, a
residual film was left on the surface, with a slightly
different colour to the original slide. Nevertheless, the film
was much smoother, and more homogenous than that
produced by the scattering technique. Dispersing graphene
in a solvent also provides more control over the film
thickness, by changing the concentration of graphene
(mg/ml).
c) Langmuir-Schaefer
Many of the isotherm experiments with just GNPs proved
unsuccessful. The surface pressure did not adequately, with
respect to area. This was unexpected, as in previous
experiments with TPQPOH and Nafion, a steady and
substantial pressure build up may be observed. This
suggested that despite being hydrophobic, the GNPs did not
seem to float on the surface, of the water. However, adding
a small amount of TPQPOH to the solution provided the
platelets with additional buoyancy, making them float on
the surface.
2) SEEC Microscope
Heavy agglomeration was observed in the scattered GNP
layer; this technique produced a non-homogenous layer.
Fig.9.(a) shows that the particles are not dispersed on the
surface, rather they have clumped together. This made it
very difficult for the microscope to focus on the entire
sample, particularly with the x50 lens. The most likely
cause for the agglomeration of the particles on the surface
is due to the very basic deposition method.
In the drop-cast sample from the higher concentration
solution had some agglomeration of GNPs, and less in the
lower concentration.
It can be seen from Fig.9.(d), that salt (NaCl) and polymer
(TPQPOH) crystals formed on the surface of the Langmuir
Schaefer film. These may compromise the performance of
the film.
3) Electron Microscope
A sample of scattered GNPs was studied, using an SEM. It
was observed that the platelets had agglomerated together,
so that parts of the silicon substrate were bare, and parts
were speckled.
4) MountainsMap
Further studies of the films were performed, using
DigitalSurf MountainsMap surface analysis software.
Images from the SEM were converted to surfaces, using the
colours to determine thickness. However, the SEEC images
were converted more accurately, using the topographical
data, as a pre-determined thickness.
It was observed that the average film thickness for the
drop-cast sample (from 5µl) was 12.2nm, and the Langmuir
Schaefer film was 18.3 with just 1 layer. This was an
unexpected result, because the LS technique was designed
to provide better control of film thickness.
Fig.9. – (a)Scattered GNPs. (b)Drop-cast film from 0.5mg/ml
solution of GNPs. Inset: non-homogenous region. (c)Drop-
cast film from 0.05mg/ml (best) soln. (d)Langmuir Schaefer
film of GNPs with TPQPOH.
(a)
(d)(c)
(b)
Fig.12. Drop-cast GNP film with TPHPOH, rendered in
DigitalSurf MountainsMap surface analysis software.
Fig.11. – SEM image of agglomerated GNPs by scattering-
Platelets are relatively large; 1-4µm in diameter, and up to
100nm thick.
-5
0
5
10
15
20
25
30
80100120140160180200
SurfacePressure(mN/m)
Surface Area (cm2)
Graphene (0.05mg/ml)
Graphene (0.005mg/ml)
Graphene (0.05mg/ml) + TPQPOH
Fig.10. Isotherm data for 800µl of various Graphene solutions dripped
onto Langmuir Trough.

6. 6
B. Defects
A defect is an irregularity in the lattice structure. These
could come from any of the fabrication processes, or even
the atmosphere or radiation [10]. This is fundamentally a
limiting factor for graphene, and its performance [11].
According to Rao [11], a variety of defects can occur in
graphene, which include adatoms, vacancies, point defects,
line defects, and edge defects. Defects can also form, due to
the absorption of ultra-violet photons, as they cause
graphene to oxidise [10].
Because graphene is a 2-D material, the occurrence of
defects has a much more significant effect on the electronic
and structural properties of the film.
1) Adatoms
A surplus or deficit of electrons in the atom’s outer shell is
the most common cause of defect. This could be due to a
contaminant molecule, donating or accepting the electron,
which would otherwise bond the carbon atoms together.
2) Impurities
Due to the extremely high surface area to volume ratio,
graphene is likely to attract impurities which would
compromise the performance of the material. Therefore, it
is crucial that it is kept in an environment free from
potential impurities. Functionalities may also be added,
which can repel additional impurities, although this is not
100% effective. Specific atoms are often added
deliberately, to enhance the properties, or simply make it
more stable.
3) Functionalities
Graphene is usually doped with other atoms/molecules,
such as oxygen, carbon or nitrogen groups, to improve the
functionality and properties of the material. These may
disrupt the lattice structure, creating a vacancy, or
donate/accept electrons, to satisfy the bond.
4) Geometry
The conductivity of a graphene sheet depends on its
orientation. For nano-platelets, the orientation would be
random, so bulk conductivity will be an average. However,
this is critical for mono-layers that rely on conduction, such
as sensors, transistors or electrodes.
Electrons flowing in the armchair direction (shown in red)
will have to travel further than the zigzag direction (yellow
arrows). Consequently, in the armchair direction, it
exhibits semiconductor properties, but metallic, in the
zigzag. Any vector between armchair and zigzag will be a
combination of each, maintaining the same aspect ratio.
C. Current Applications
1) Ink
Graphene enabled ink is derived from the drop cast method.
Perpetuus Carbon, in a joint venture with Gwent Electronic
Materials, who are operating under the name Perpetuus
Electronic Materials have developed an electrically
conductive ink, containing GNPs.
The ink has a low resistance of less than 1Ω/□, which is the
best conductivity achieved by any graphene enabled ink in
the world. [12] This ink can provide a new approach to
PCB (printed circuit board) manufacture, as it is so much
easier to apply to the circuit.
The ink can be printed via ink jet or flexographic printing,
making it much cheaper and more convenient than
traditional PCB manufacture. An additional benefit is that it
can be printed on a flexible substrate, without
compromising the performance.
Circuits like RFID (Radio Frequency Identification) tags
could potentially benefit from graphene enabled inks, due
to significantly reduced cost [13]. However, the ink does
have a higher resistivity than copper, so performance and
range would be compromised.
The ink is also becoming a popular demonstration/learning
tool, allowing children to draw circuits, and even sensors
[14].
2) Transparent Electrode
GNPs may also be added to a transparent, flexible polymer
(Polyethylene terephthalate [4]), allowing it to conduct
electricity. This enhanced polymer has the potential to
replace indium tin oxide (ITO) [12], which is very rare, and
expensive to produce. A thin film can be applied to the
surface of a solar panel or various display screens, such as
OLED, LCD, electroluminescent, electro-chromatic and
plasma.
The two key characteristics are transparency and
conductivity, are difficult to find in the same material.
However, these properties are essential for the top surface
of a solar-panel, so that electrons can be transported away
from the re-generation site, and more can be promoted to
the conduction band. Transparency is also important, to
minimise reflection of photons off the surface, when used
in a bright environment.
Fig.13. Lattice geometry.
a
z

7. 7
Transparency is also important to allow the user to view the
image on screen.
The powder-coating or scattering techniques would not be
suitable for this application, because the layer is not
transparent, and would absorb many of the photons passing
through. Drop casting would produce a much more
transparent film, however, achieving an even coating across
the surface may be difficult. Modifications to the technique
would be required, such as spin-coating, where the
substrate is rotated very quickly, allowing centrifugal force
to spread the film evenly across the surface. Langmuir
Blodgett may also be feasible.
Wuxi Graphene Film Co. Ltd [15], and Gwent Electronic
Materials [12], have proven that the technology is readily
available. At the end of 2013, Wuxi Graphene finished a
“demonstration production line, with a projected annual
output of 5million pieces of graphene touchscreen
products”.
1) Electromagnetic Induction (EMI) sheilding
As an additive to various polymers [16], the electrical
conductivity of GNPs can protect sensitive circuits and
instruments from noise that would otherwise interfere with
signals passing through the circuit.
2) Strength Enhancing Additive
GNPs can be added to polymers, such as epoxy resin, to
improve its tensile strength, as well as toughness.
According to Kuilla [19], glass transition temperature, and
consequently tensile strength and toughness were
improved, with increasing concentrations of GNPs.
Improvements of 125% and 100% for tensile strength and
roughness were observed, respectively. The toughened
epoxy could then be used as a matrix for many composites,
with improved performance. The GNPs would be
manufactured by the plasma process. This application does
not require deposition; the GNPs are added directly to the
epoxy, before it is combined with the fibres.
3) Sensors
A graphene nanoribbon can be used to detect certain
molecules in the air, with a very high sensitivity. When a
molecule attaches to the graphene, the chemical reaction
releases or consumes an electron. Graphene is naturally p-
type, so a donor atom would decrease, and an acceptor
atom would or increase the conductivity, however, this can
be reversed in the presence of functional groups. Gases
such as ammonia (NH3) will donate an electron, and
nitrogen-dioxide (NO2) will accept an electron. On a
graphene nanoribbon, the graphene is sensitive enough, to
detect just one molecule.
These gases only interact temporarily via non-covalent
interactions with graphene, so when the concentration
drops, the molecules will detach, returning the graphene
nanoribbon to its normal state. This allows the
concentration to be continuously monitored.
In general, the surrounding device would be made in a
semiconductor fabrication facility, which would already
have a CVD chamber. The production line should be
engineered, so that any elements on the substrate, that are
sensitive to heat, are added after the CVD process.
In most cases, the key to fighting disease is early detection,
and graphene biosensors are capable of just that. A
graphene nanoribbon can be functionalised with biological
ligands enabling it to detect disease biomarkers [17].
Diseases, such as cancer, diabetes, HIV, etc can be
identified much earlier on, before the more severe
symptoms have taken effect, and caused damage. These
sensors will respond to just one molecule, and are therefore
much more sensitive, allowing diagnosis, before it is too
late. This also means that the tests can be non-invasive, i.e.
from a urine or saliva sample, and results are almost
immediate, so patients don’t have to wait days for
feedback.
When a biomarker interacts with a receptor, it transfers
electrons into or from the graphene, increasing or reducing
its conductivity [18].
The sensors are very small, so in the future, more different
diseases could be tested at once, from just one panel, by an
amateur with limited medical knowledge.
DNA can also be detected with this method, using a
matching DNA strand. This would be useful in forensics,
where only a very minute sample is available.
The concept of using organic ligands for detection has
already been proven successful in the GE Healthcare
BiacoreTM
Surface Plasmon Resonance (SPR) detector, [19]
which is capable of good sensitivity and selectivity. Using
graphene biosensors, however, is a much better alternative,
because it does not require expensive equipment; the
technology is on the device itself. Graphene also has the
advantage of being able to test for many different analytes
at once.
4) Photodetector
Although graphene is visually transparent, it interacts
strongly with photons anywhere between the microwave
and ultraviolet wavelengths. This means that graphene
photodetectors could span wavelengths of at least 5 orders
of magnitude. The enormous bandwidth would therefore,
provide an exceptional data-rate. According to Xia et al,
speeds of 10Gbit/s have been achieved [20].
5) Hydrogen Storage
Graphene, functionalised with hexagonal boron nitride
platelets can be stacked, to form very low density foam.
Hydrogen atoms experience weak interactions with the
graphene foam, so the extremely high surface area allows a
Fig.14.-Voltage-Current graph [18], comparing the sensor, when 80HdG
is present (green) and not present (red).

8. 8
large quantity of hydrogen to be stored in the container, at
lower pressure. This makes the container safer, as it is less
likely to explode, and if it does the hydrogen will take
longer to expand [21].
Hydrogen has a very high energy density, and can be used
in fuel cells, which can efficiently transfer chemical energy
to electrical, before being refilled with hydrogen.
Currently, graphene foam is produced by CVD, but it is
possible that other techniques will be developed in the
future. The foam can be placed inside the container, once it
has cooled down, so heat exposure in this process would
not be a problem.
6) Contaminant Removal
Graphene is capable of removing some metals, including
radioactive nuclides from water [22], in particular,
radioactive isotopes of actinides (such as uranium,
plutonium and americium) [23] and lanthanides (‘rare
earths’ such as europium).
This would be very useful, in the clean-up after a nuclear
disaster, as the nuclides are very harmful to the
environment, for decades afterwards. Radionuclides are
also released in fracking and mining operations.
Again, graphene foam, produced by CVD would be used,
then removed from the substrate; i.e. no limitations due to
temperature exposure.
D. Future Applications
There is a lot of potential for development of graphene
applications that are in earlier stages of development
1) Integrated Circuits
A potential application for the film made by drop-casting or
Langmuir Schaefer (or similar) could be transistors.
Typically, transistors are made from silicon, which is in
many ways very suitable for integrated circuits. According
to Moore’s law, [24] “the number of transistors on an
affordable CPU will double every two years”. This
statement has been true for the past four and a half decades,
but the rate has begun to saturate. At around 14nm for
FinFETs [25] the gate length has reached its practical
minimum, due to a number of factors. Smaller devices have
been made, but their performance is inferior.
In order to continue improving the performance of
processors, new technologies and materials will require
development.
According to Murali [26], Graphene has an electron
mobility of µ=10,000cm/Vs, 10 times higher than that of
Si. This is caused by the conservation of pseudo-spin, i.e.
backscattering is forbidden. Therefore, it is effectively a
quantum well, and scattering is reduced to two dimensions.
This increases the switching rate for the device, and
consequently, the processor speed.
Using graphene nanoribbons for the channel, as well as
(carbon nanotubes) for inter-connects, between devices, the
chip performance and functionality can be significantly
improved.
Although not yet in mass production, Lin et al. [27], have
demonstrated the concept of an analogue fully integrated
circuit in the form of an RF mixer (radio-frequency
transmitter). The performance of this prototype was
degraded, due to the harsh fabrication process. Further
developments of the process allowed the production of a
more sophisticated IC, capable of sending a text message.
Thus, graphene has the potential to tackle some of the
issues faced by the semiconductor industry.
Due to its zero band-gap and high production cost (for the
quality required), transistors are not a currently viable
application for graphene.
2) Energy Storage
a) Li-ion batteries
Lithium-ion batteries already use graphite anodes, so the
transition to graphene should be relatively straightforward.
According to Zhao, et al [28], the capacity, as well as
charging rate, have both been improved by a factor of 10,
using graphene anodes instead of graphite (conventional
material). This is due to the extremely high surface area,
provided by graphene, which the ions can interact with.
Millions of holes (ϕ10-20nm) were punched into each layer
of graphene, to allow more direct access to the layers
below.
At Rice University, [21] hydrogen enriched graphene oxide
has been proven to be an effective anode in lithium-ion
batteries The addition of boron atoms helps the lithium-ions
to ‘stick’ to the graphene, allowing energy to be stored
more efficiently.
b) Supercapacitors
Graphene also has potential applications for
supercapacitors, which are made from cheaper materials
and can charge/discharge quicker and more efficiently. A
supercapacitor is essentially, two conductive plates,
separated by a dielectric. Between the plates are
electrolytes, suspended in (graphene) foam. As the charge
across the plates builds up, the electrolytes move to the
negative plate, allowing the supercapacitor to store energy.
Supercapacitors also have the benefit of high cycle
stability, which means they can last much longer than
batteries. The porous coating, which is usually activated
carbon that supports the electrolytes, may easily be
replaced by graphene.
The energy capacity of the supercapacitors is proportional
to the area of the conductor-dielectric interface [29]. This
can be optimised by using graphene, as it has much more
surface area per unit weight (1520m2
/g) [30] than any other
material.
Although the current method of producing this kind of
graphene is CVD, it is possible to scribe the graphene oxide
layer into a suitable graphene film, using a standard
LightScribe DVD optical drive [32].
It has been estimated that using graphene technology, a
storage capacity of 550F/g is achievable, compared with a
standard 1 Farad capacitor weighing around 2kg.
Supercapacitors are already being used in the automotive
industry, to recapture energy, while breaking, so that it can
be re-used.
3) Filtering Membrane
A graphene membrane can act as an excellent filter,
preventing any molecules from passing through. This
includes helium, which is known for its ability to pass
through the smallest pores in a material.
In particular, this property would be useful, in the
distillation process, allowing water to evaporate off,

9. 9
condensing the target substance (e.g. ethanol) back into the
container.
E. Health and Safety Concerns
As with any new material, there are concerns about the
health and safety implications of graphene.
For example, Carbon nanotubes (CNT) breakdown into
particles that can enter organic cells, damaging DNA.
CNTs have been classified as hazardous carcinogens,
capable of causing cancer [31].
Thankfully, graphene does not behave in the same way; it
can (usually) be broken down, and does not affect
biological processes. However, all nanomaterials should be
treated with caution [31].
V. CONCLUSIONS
It has been confirmed that graphene has a tremendous
amount of potential, with many different applications
across various industries. Some of which may take longer
to materialise, due to complications in graphene synthesis.
The transition from laboratory testing to commercial
manufacturing has proven challenging for many products
and companies working on the material. However, there are
simpler, (easier, cheaper, etc.) methods for deposition,
which are also less damaging to the substrate. Although the
films produced in the experiments were of poorer quality
than CVD (chemical vapour deposition), they are still in
very early stages of development. It is more than likely that
further developments will make these techniques capable of
surface qualities comparable with CVD films.
It was concluded that drop-casting was the overall most
effective alternative to chemical vapour deposition.
However, each of the deposition techniques, have
advantages and disadvantages, so their selection will
depend on the specific application.
1) Scattering deposition
The scattering technique is the most basic, and
consequently the cheapest, easiest, quickest, etc. However,
the film quality is poor, and would be unsuitable for most
applications.
2) Drop-Cast deposition
Drop-casting produces a much more homogenous film
(Fig.9.(b) and (c) compared with (a)), and is more
straightforward than Langmuir Schaefer. The solution can
be mixed with other chemicals, to modify the properties of
the film. The thickness of the film can also be controlled,
by changing the concentration of the solution. Both the
drop-cast, and Langmuir Schaefer processes could use
graphene dispersions, produced directly from liquid-phase
exfoliation of graphite. This would omit a large process
from manufacturing, thus reducing the cost.
3) Langmuir-Schaefer deposition
The additive used to make the GNPs float could affect the
material properties, (e.g. conductivity), thus making it
unsuitable for some applications.
The Langmuir Schaefer technique enabled more control of
the film thickness, by choosing the number of dips/layers.
Therefore, a thin film was expected on the 1 layer LS
sample. However, the average film thickness was 18.2nm;
4nm thicker than the drop-cast samples. This is most likely
due to the complexity of the experiment. There were many
variables, which have yet to be optimised, so perhaps
further developments will enable the synthesis of a thinner,
better quality film.
B. Future Recommendations
Suppose that the subphase (NaCl solution in the
experiment) can be developed, that will evaporate, leaving
no residue. This could permit the synthesis of pristine
graphene, on a much wider range of substrates, with any
number of layers.
Further developments should be made on the additive used
to float the GNPs on the surface of the Langmuir trough.
For instance, perhaps a new functionality, added during the
manufacturing of the GNPs, that forms a gap in the
graphene-water interface. Although the TPQPOH was
effective in this task, it is by no means the most effective
solution; incorporating it into the manufacturing process
could potentially help.
If the scatter technique was chosen for a manufacturing
process, it would have to be modified, for scalability, and to
ensure an even coating of the GNPs. Potentially, it could be
applied by electrostatic powder coating [32]. The particles
and substrate would be charged, with opposite polarity,
causing the particles to repel eachother (ensuring even
density), but attach to the substrate. Charging the substrate
would require it to be somewhat conductive. This technique
is widely used to produce a very robust layer, protecting the
material underneath.
Drop casting is already capable of depositing a good quality
film, without limitations of substrate material or cost, so
there is little room for improvement. Nevertheless, there are
some additives that could improve the film characteristics,
and these should be explored, in order to optimise
performance for a more specific application.
Further analysis of the films should also be performed, to
verify the results of the experiments. These would include
Raman spectroscopy, which is a better indication of film
quality.
Although the films were compared with CVD samples
found online [4], they should be studied using the same
apparatus, and the same techniques, to ensure a fair
comparison.
VI. ACKNOWLEDGEMENTS
Dr Paolo Bertoncello & Dr Thierry Maffeis, Swansea
University
Dr Afshin Tarat & Dylan Walters, Perpetuus Advanced
Materials

10. 10
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