Graphene

1. Graphene Graphene physically acts as a 2-Dimensional material. This leads to many properties that are electrially beneficial, such as high electron moblity and lowered power usage. Graphene is currently in its infant stages and is undergoing many applications and studies. Jared Johnson & Jason Peltier April 30th

2. Introduction • What is Graphene • Discovery • Electrical Properties • Mechanical Strength • Optical Properties • Applications • Devices

3. What is Graphene • 2-dimensional, crystalline allotrope of carbon • Allotrope: property of chemical elements to exist in two or more forms • Single layer of graphite • Honeycomb (hexagonal) lattice http://upload.wikimedia.org/wikipedia/commons/thumb/9/9e/Graphen.jpg/750px-Graphen.jpg

4. Graphene vs Other Allotropes • Graphene - Top Left • Graphite - Top Right • Nanotube - Bottom Left • Fullerene - Bottom Right http://graphene.nus.edu.sg/content/graphene

5. Discovery • Studies on graphite layers for past hundred years • Graphene theory first explored by P.R. Wallce (1947) • Andre Geim & Kontantin Novoselov Nobel Peace Prize (2010) • Physics observed using TEM http://powerlisting.wikia.com/wiki/File:Graphite.jpg http://www.telegraph.co.uk/science/science-news/8043355/Nobel-Prize-for-Physics-won-by-Andre-Geim-and-Konstantin-Novoselov.html

6. Electronic Structure • First Brillouin Zone (red) • Second Brillouin Zone (yellow) • Six corners of first Brillouin zone called Dirac points (also called K points) • Electrons and holes called Dirac fermions http://www.doitpoms.ac.uk/tlplib/brillouin_zones/zone_construction.php

7. Electronic Structure • Dirac Points are the transition between the valence band and the conduction band • The six Dirac points can be divided into to two in-equivalent sets of three (K and K'), represented by the black and white dots on part (a) • The points within each set are all equivalent because they can reach each other by reciprocal lattice vectors • Part (b) shows that the dispersion relation close to the K points looks like the energy spectrum of massless Dirac particles http://ej.iop.org/images/0034-4885/75/5/056501/Full/rpp342429f06_online.jpg

8. Electrical Properties • The Fermi level can be changed by doping to create a material that is better at conducting electricity • Experimental graphene's electron mobility is 15,000 cm2/(V*s) and theoretically potential limits of 200,000 cm2/(V*s) • Graphene electrons are like photons in mobility due to lack of effective electron and hole mass • These charge carriers are able to travel sub-micrometer distances without scattering

9. Mechanical Strengths • Bond length is .142 nm long = very strong bond • Strongest material ever discovered • ultimate tensile strength of 130 gigapascals compared to 400 megapascals for structural steel • Very light at 0.77 milligrams per square metre, paper is 1000 times heavier • Single sheet of graphene can cover a whole football field while weighing under 1 gram • Also, graphene is very flexible, yet brittle (preventing structural use)

10. Optical Properties • Absorbs 2.3% white light • Optical electronics absorb <10% white light • Highly conductive • Strong and flexible http://en.wikipedia.org/wiki/File:Graphene_visible.jpg Photograph of graphene in transmitted light.

11. Other Applications • OLED Techonologies • Body Armour • Lightweight Aircraft/vehicles • Photovoltaics • Superconductor/battery • Filtration • http://www.graphenea.com/pages/graphene-uses-applications#.U1c1hFVdV8E

12. Devices http://www.tgdaily.com/general-sciences-features/61058-team-uses-graphene-film-to-distil-vodka http://www.simplifysimple.com/index.php?news&nid=15_The-new-look-of-phones http://en.wikipedia.org/wiki/OLED

13. Summary & Conclusion Graphene, a singular layer of graphite, has been discovered to have unique properties. The high mobility and ability to travel short distances without scattering makes it one of the best materials for electrical applications. Graphene's mechanical and optical properties also allow its use to go beyond electrical applications.

14. References • "Allotrope." Wikipedia. Wikimedia Foundation, 16 Apr. 2014. Web. 17 Apr. 2014. <http://en.wikipedia.org/wiki/Allotrope>. • Cooper, Daniel R. "Experimental Review of Graphene." Hindawi Publishing Corporation, 3 Nov. 2011. Web. 16 Apr. 2014. <http://www.hindawi.com/journals/isrn/2012/501686/>. • De La Fuente, Jesus. "Graphene." Graphenea. Web. 26 Apr. 2014. <http://www.graphenea.com/pages/graphene#.U1xxufldWSo>. • Geim, Andre. "Nobel Lecture." Nobel Prize, 8 Dec. 2010. Web. 18 Apr. 2014. <http://www.nobelprize.org/mediaplayer/index.php?id=1418>. • "Graphene." Wikipedia. Wikimedia Foundation, 16 Apr. 2014. Web. 17 Apr. 2014. <http://en.wikipedia.org/wiki/graphene>. • Neamen, Donald A. Semiconductor Physics and Devices: Basic Principles. New York, NY: McGraw-Hill, 2012. Print. • Roos, Michael. "Intermolecular vs Molecule–substrate Interactions." Beilstein Journal of Nanotechnology 2012.2, 365-73. Web. 15 Apr. 2014. <http://www.beilstein-journals.org/bjnano/single/articleFullText.htm?publicId=2190-4286-2-42>. • "Graphene." NUS Graphene Research Centre. National University of Singapore, n.d. Web. 28 Apr. 2014. <http://graphene.nus.edu.sg/content/graphene>.

15. Last Slide • Graphite had been studied for over a hundred years but Geim and Novoselov found how to isolate it to be graphene and some applications for its use • The reason graphene is such a beneficial material is due to its 2D like nature and short/strong bonds • It has a super high conductivity and an electron mobility of 15,000 cm2/(V*s) • It is the strongest material ever discovered, however its brittle nature cannot be used structurally (only to help reinforce) • One of the most common current uses of graphene is in OLEDs