Graphene
a material for the future
by Olav Thorsen
What is graphene?
What is graphene?
• Simply put, it is a thin layer of pure carbon
What is graphene?
• Simply put, it is a thin layer of pure carbon
• It has a hexagonal atomic arrangement
What is graphene?
• It is a 2‐dimensional crystalline allotrope of
carbon
• All the C‐C bonds are sp2 oriented
• It is the basic building block for other
compounds like graphite, charcoal, carbon
nanotubes and fullerenes
• It has many great qualities: little weight, high strength, great electric and thermal conductivity, 2‐dimensionality
Discovery of graphene
• The graphite structure were figured out in 1916
• Graphene were theoretic development by P.R.Wallace in 1947 for understanding electric
properties of 3‐dimensional graphite
• In 1948 the first TEM pictures of thin layers of
graphite were published
Simple development of graphene
• In the 1970s graphene were grown on top of other materials, but this epitaxial graphene
got a lot of charge from its host
• In 2004 graphene got extracted from bulk graphite by micromechanical clevage and deposited on a thin layer of silicon, a process that gives almost charge neutral graphene due to backtrack through the layer of silicon
Oshima, C. and Nagashima, A. (1997). "Ultra‐thin epitaxial films of graphite and hexagonal boron nitride on solid surfaces". J. Phys.: Condens. Matter 9: 1.
Physical attributes
• Self repairing in contact with carbon
• It is only one atom thick, this gives 1 square
meter the weight of 0.77 milligrams, roughly
1/1000th of a paper
• With a tensile strength measured to about 130 gigapascals it is the strongest known compound
today, 100‐300 times stronger than steel
• It has also great elastic properties, though this
requires a very pure and perfect material to be really considerate
http://www.graphenea.com
Chemical attributes
• It is the most chemical active form of carbon
due to all atoms being placed on two surfaces
in flat sp2‐bonds
• It reacts with oxygen at about 260 degree
Celcius, it burns at 350 degrees
• Its good reactivity makes it easy to modify the
compound using oxygen‐ and nitrogen‐ groups
Denis, P. A.; Iribarne F. (2013). "Comparative Study of Defect Reactivity in Graphene". Journal of Physical Chemistry C 117 (37)
Electrical attributes
• It is a zero‐overlap semimetal, 2 holes and 2 electrons
can be charge carriers
• It has 4 outer electrons, but are bonded to 3 other
carbon atoms in 2 dimensions. This gives 1 free pi‐
electron pr atom that moves freely above and along
the surface.
• By either p‐ or n‐type doping graphene easily conducts
better than copper at room temperature
• Its electron mobility is in the range of
15 000 – 200 000 cm2 V‐1 s‐1 . Typical mobility for silicon
is 1400 cm2 V‐1 s‐1 http://www.graphenea.com
http://en.wikipedia.org/wiki/Electron_mobility
Optical attributes
• Graphene has unique optical abilities
• A single layer absorbs 2.3 % of white light, this
is cumulative with number of layers
• It also readily reaches saturable adsorption
• This speciality makes it very usable with mode locking fibre‐lasers and with other types of
ultrafast photonics. • Its optical response can be tuned electrically
http://en.wikipedia.org/wiki/Graphene
http://en.wikipedia.org/wiki/Saturable_absorption
Thermal attributes
• Its thermal conductivity is better than both
diamond and graphite
• It is phonon dominated
• Graphene has 3 different acoustic phonon modes that gives a linear dispersion relation along the
plane and quadratic dispersion relation out of the
plane, that means that thermal conductivity is dominated out of the plane at low temperatures
but vica versa at high
Mingo N., Broido, D.A. (2005). "Carbon Nanotube Ballistic Thermal Conductance and Its Limits". Physical Review Letters 95 (9): 096105
Other attributes
• Massive electrons
• Spin transport
• Anomalous quantum Hall effect
http://en.wikipedia.org/wiki/Graphene
Areas of interest and use
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Field Effect Transistors
Biodevices
Potential supercapacitor
Piezoelectric controller
Transparent conducting electrodes (touchscreens, organic photovoltaics, liquid crystal display etc..)
Solar cells!!
Increased PCR DNA production
Quantum dots
Thermal interface
Ultrafiltration
Composite materials
Production today
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Mechanical exfoliation, splitting of graphite
Epitaxial growth, mainly on SiC
Reduction of graphite oxide
Metal‐carbon‐melting
Sonication (f.ex. Interface trapping)
http://en.wikipedia.org/wiki/Graphene
THE END