EUROPEAN COMMISSION

Graphene Workshop Brussels, March 21-22, 2011

REPORT ON WORKSHOP

Rapporteur

Dr Livio Baldi NUMONYX

Edited by

Dr Marcin L. Sadowski DG Research

Directorate-General for Research

Industrial Technologies

Value-Added Materials Unit

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INDEX

EXECUTIVE SUMMARY··································································3

REPORT·······························································································4

1. Material···································································· 4

2. Preparation······························································ 5

3. Potential Applications ·············································· 5

4. International research funding ································ 7

5. Industrial interest ····················································· 7

6. Some considerations··············································· 8

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EXECUTIVE SUMMARY

Graphene is a new material, based on common carbon, that presents surprising

electrical, optical and mechanical properties, due to its two-dimensional structure. Its

discovery gave a Nobel Prize in 2010 to two European scientists. The number of

publications and patents on graphene has been sharply increasing, and significant

R&D investments are being made in Europe, USA and especially Asia.

The potential applications of graphene range from ICT (electrodes for flat panel

displays, touch screens, RF devices, MEMS, photo-electronic sensors, flexible

electronics, CMOS replacement) to aeronautics (light carbon-based composites),

electrical cars (batteries, super-capacitors, and lightweight alloys), energy (solar

cells) and medical (DNA analysis and sensors). Interest has been shown by leading

European industries in the field of mobile communications and car manufacturing. A

few start-ups have been already generated to provide basic materials for research.

While basic research is still needed in the field of fundamental properties and of

material production and control, for some possible applications projects targeting

industrial innovation can already start, in order to gain future competitive

advantages.

There is in Europe a strong competence on the field and a very active research

community, involving 4 Nobel Prize laureates, which could be at the base of a

coordinate research effort to maintain the European leadership on this field and

exploit it in some critical industrial applications.

A FET flagship initiative is currently under discussion. It could coordinate all the

required research efforts and help to focus research and development activity

towards industrial applications in ICT and economic growth. It was recommended to

the Commission not to focus only on ICT. Support to research and innovation cannot

miss some of the most critical applications, and it should be granted to initiatives in

other fields, such as materials and energy. The participants would particularly

welcome coordinated initiatives by DG RTD and DG INFSO in the Commission as

well as involving the EU Member States.

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REPORT

1. Material

Graphene is essentially carbon in the form of mono-layers of hexagonal benzene

rings. Arranged in multiple layers, it forms the well known graphite.

Several important properties mentioned by presenters:

• Electrical: very high intrinsic electron mobility, zero-gap semimetal, linear

dispersion curve make it an excellent conductor for electricity and heat. The

band-gap can be induced in several ways: width limitation (nano-ribbons),

applied electrical fields to bi-layers, functionalisation (saturation with hydrogen

gives a 2.6 eV band-gap).

• Mechanical: high tensile stress, good resistance to fracture, high flexibility,

impermeability to gas even in mono-layers.

• Optical: absorption coefficient (2.3%), flat over the spectrum.

• Magnetic: not fully investigated. Excellent spin propagation length (in principle

more efficient than CNTs).

Moreover its possibility to act as a 2-D electron gas opens the way to interesting

quantum effects (quantum Hall effect).

In addition the material can be functionalised by combining it with hydrogen (which

gives graphane, an insulator), as well as with fluorine or oxygen.

Very high production of papers. Patents are taking up. 2 Nobel laureates in Europe

in 2010 on the topic.

The research on graphene is also reaching out to a much wider range of compounds

with regular bi-dimensional crystalline structure, such as Molybdenite, Boron Nitride,

and Chalcogenides. Notably monolayers of such materials were reported in the

pioneering PNAS publication of the 2010 Nobel Prize winners, so an ever wider

research community and range of applications are at hand.

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2. Preparation

Several preparation methods have been perfected:

• Exfoliation from graphite. It is the simplest one and gives graphene flakes up

to mm size. This technique can be industrialised (e.g. by ultrasonication in

water and other solvents) to produce large quantities of liquid dispersions of

graphene flakes (conductive inks)

• Segregation of graphene on top of a SiC wafer by thermal treatment, CVD on

metal substrate. Roll-to-roll production of large foils demonstrated on Cu

substrates. Other substrates can be nickel or sapphire. High temperature can

be decreased by use of plasma assisted CVD. Grain size in metal and

multiple nucleation sites give rise to defects, but surface topography is the

main cause. Several approached are now targeting the metal removal and

temperature reduction. This may result in an increase of defects, however the

material will still greatly outperform any polymer-based and printed electronics

solution, as well as polycrystalline or amorphous silicon based technologies.

3. Potential Applications • Transparency, flexibility, good electrical conductivity make graphene ideally

suited for displays, especially flexible ones, touch screens, electrodes for

photovoltaics. In this respect also impermeability to oxygen can be a large

advantage, e.g. for organic solar cells. Compared to ITO it shows better

conductivity, better mechanical properties and no use of critical materials.

• Flexibility and high stress resistance make it suitable for light, high resistance

carbon composites to be used in aeronautics and cars. It can be used also as

an additive to resins in flake form.

• Graphene shows high promise for high performance microelectronics

applications, especially in the THz frequency domain.

• Great promise for spintronics, which is still in its infancy.

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• Large surface area and good conductivity make it applicable as a low cost

component for high performance batteries and super-capacitors (e-car

applications).

• Flexibility combined with impermeability to oxygen makes it useful as

packaging layer. If for alimentary goods, health risks must be shown to be

neligible. It was noted that current studies show that graphene is much less

toxic than nanotubes, at the very least.

• Good thermal conductivity can make it useful for packages and LCD

backplane lighting.

• The flat absorption spectrum could make it useful for wide-band

photodetectors. The particular band-gap structure could also lead to electron

multiplication.

• Good conductivity, also in the form of flakes, makes it applicable as

conductive filler for plastic, or conductive ink.

Other mentioned applications:

• Quantum Hall effect with clear peak separation (at cryogenic temperature) for

resistance standards.

• RF MEMS for wide band tunable antennas (actively pursued by Nokia and

Renesas Mobile).

• Functionalised graphene could be used for sensors.

• Mono-molecular membranes with nanometric holes could be used for DNA

separation.

• Hydrogen storage, with the possibility of using mechanical stress to release

the gas.

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4. International research funding.

European investments are spread out at the European Union and national levels:

roughly 45 M€ in Commission programmes, 7.8M€ in Spain, 10 M€ in Germany.

Coordination programmes in France, Spain and Germany. French and Spanish

programmes with international outreach.

In FP7 6 projects running: one on semiconductor devices (almost concluded), one on

RF tunable resonators, two on super-capacitors and two on growth process (SiC

segregation and CVD). A possible FET flagship on the topic was presented and

discussed.

Strong research investments abroad: in Singapore (>60M$), Korea (300+300M$). In

USA 30M$ on carbon electronics, and 15M$/yr on related topics.

5. Industrial interest

Patent analysis shows ~1300 inventions. At the beginning mostly batteries and

displays, after the Nobel Prize strong growth also in composite materials. Good

presence of semiconductor patents.

In Europe strong interest by Nokia (tunable RF resonators, flexible phones) not only

as final user, but also as developer of novel components. Nokia made it clear that a

strong European effort is necessary to ensure the very large supply capability

envisaged once this novel technology enters in production. BASF is investing

heavily in development, patents, and partnering with European collaborators to

develop graphene-chemistry, ranging from printable inks to large scale production of

graphene ribbons and nanodots. Their aim is not just to supply graphene-based

chemicals, but also to produce devices.

Some start-ups exist, mostly concentrating on the production of graphene flakes for

research labs.

In Korea there is a strong consortium with Samsung and LF (displays) and other

players in composites.

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6. Some considerations

In the Workshop a lot of interesting properties and of potential applications were

presented in widely different areas, which seems to indicate a high degree of

knowledge of the material, and – afer 5 years of investigations - a lack of

fundamental limitations.

Graphene is indeed just the first of a much broader class of bi-dimensional

compounds with interesting properties. It was suggested that these compounds

could be combined with graphene to produce meta-materials with novel properties.

Common topics of investigation are:

• Reliable material characterisation, including the role of defects and

contaminants/doping, supported by ab initio calculations, to help distinguish

intrinsic properties from defect induced ones.

• Production methods, with a special attention to the size of layers, control of

properties and cost. For several applications there are competing solutions,

and cost will be a decisive success factor.

• Interaction with other materials (substrates, coatings, environment) needed for

practical use of the material.

• ESH issues: toxicology only critical if use for food packaging is considered.

Otherwise it will probably not be a severe issue.

Other topics of investigation are determined by the application area, and it could

be the most resource consuming part of a programme.

Application areas should be chosen according to:

• Scientific challenge

• Potential for economic exploitation in Europe. The latter must be considered

with care, taking into account both excellence in research and the size of the

potential market.

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Possible application sectors affected:

• Transparent conducting layers for displays: it is probably the application with

largest potential. End-users, such as Nokia, made clear that the extremely

large envisaged market does require the establishment in Europe of one or

more suppliers with production volumes compatible with their large phone

volumes. BASF is quickly closing this gap, at least for solution processed

samples.

• Touch-screens: see above. Need involvement of a large European

manufacturer that could supply Nokia.

• Batteries/super-capacitors: there is a strong strategic interest from European

car manufacturers investigating electrical cars, avoiding any dependence on

foreign suppliers for critical components.

• Light composites: good position of European manufacturers and interest of

European end-users (airbus, car manufacturers). Cost vs. competing

solutions can be the most critical issue, but also dependence on strategic

materials.

• Photovoltaics: graphene will be an excellent chance for Europe to regain the

cutting edge, provided that the Commission gives strong support and that

there are companies investing in this critical area.

• Semiconductor devices: two main areas

§ Silicon replacement for advanced CMOS. Intel has shown interest in

graphene, while among European companies ST Microelectronics is still

working on the development of options for advanced CMOS. Again, large

scale and low cost production of the material will be critical.

§ RF transistors or MEMS: could be of interest for more companies. Less

demanding for material. Millimetre wave sensors could be a large

market.

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• Medical sensors: strong pharma industry in Europe and many IC

manufacturers could be interested. The Delft group has shown that graphene

can out-perform any other material, when it comes to pore-based DNA

detection.

• Conductive ink. This was first developed in Europe and has strong backing

from BASF. It could tap in the large market for printable electronics.

Graphene undoubtedly presents a variety of interesting properties, opening the way

to its exploitation in a wide spectrum of applications. Moreover, it is the leading

example of a new class of bi-dimensional materials with peculiar properties. The

presence in Europe of a lively scientific community with top-level competence in the

field, as demonstrated by the two Nobel Prizes, justifies a focused research action. It

is important that the Flagship initiative or any other dedicated research programme in

this area, intending to insure economical growth for Europe, also foresees a smooth

transition from research to industrial exploitation. Given the strategic size of the

initiative, economic exploitation will not be due only to the already flourishing start-up

companies. The range of application topics on which the programme should be

focused needs to be greatly supported by the end users, as well as the companies

involved in manufacturing. A joint initiative with other sectors (materials, energy,

mobility) would greatly improve the reach and the benefits of this program, and this

should be complemented by other research programs. Moreover, a continuity of

research efforts is needed over a long period of time in order to bring about

exploitable results. However, given the diversity of potential applications, any

dedicated research initiative would also require focusing in order to cover the most

critical issues without spreading the resources too thin.

Image: courtesy of Chris Ewels