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Graphene – Optical Properties

Graphene – Optical Properties. for monolayers. Lawrence Berkeley Lab. Manchester Group. Physics 141A Spring 2013. Michael Tsang UC Berkeley. Graphene is a single layer of carbon packed in hexagonal (honeycomb) lattice the first truly 2D material. What is Graphene. Physics 141A

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Graphene – Optical Properties

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  1. Graphene – Optical Properties for monolayers Lawrence Berkeley Lab Manchester Group Physics 141A Spring 2013 Michael Tsang UC Berkeley

  2. Graphene is • a single layer of carbon packed in hexagonal (honeycomb) lattice • the first truly 2D material What is Graphene Physics 141A Spring 2013 Michael Tsang UC Berkeley

  3. Graphene is • a single layer of carbon packed in hexagonal (honeycomb) lattice • the first truly 2D material What is Graphene MoS2 . Physics 141A Spring 2013 Michael Tsang UC Berkeley

  4. Graphenehas • CovalentBonding • sp2hybridization • Remarkably high quality 0.142nm ACloserLookatGraphene Physics 141A Spring 2013 Michael Tsang UC Berkeley

  5. Carbon Nanotubes, known since 1993 • Buckeyballs C60, known since 1996 • Graphite, known since … a long time Familiar Carbon Structures Physics 141A Spring 2013 Michael Tsang UC Berkeley

  6. Konstantin Novoselov Andre Geim Nobel Prize in Physics (2010) Isolated large sheets in order to identify and characterize graphene and verify 2D properties Physics 141A Spring 2013 Michael Tsang UC Berkeley

  7. 1. “You put scotch tape on graphite or mica and peel the top layer. There are flakes of graphite that come off your tape. 2. “Then you fold the tape in half and stick it to the flakes on top and split again. And you repeat this procedure 10 or 20 times. Each time, the flakes split into thinner and thinner flakes.” 3. “At the end you’re left with very thin flakes attached to your tape. You dissolve the tape and everything goes into solution” Methods: MicromechanicalCleavage Physics 141A Spring 2013

  8. The Optical Properties of Graphene Physics 141A Spring 2013 Michael Tsang UC Berkeley

  9. Takepreparedmacroscopicmembranesofgraphene • Shine light through the membrane • Detector measures light intensity OpticalMeasurements Physics 141A Spring 2013 Michael Tsang UC Berkeley

  10. Ideal Dirac Fermions? • ? OpticalMeasurements Physics 141A Spring 2013 Michael Tsang UC Berkeley

  11. “Dirac Fermions” refers to electrons that race through the graphene structure • Relativistic Quantum Mechanics becomes important • Dirac Equation Dirac Fermions? Richard Feynman, a founding father of quantum electrodynamics Physics 141A Spring 2013 Michael Tsang UC Berkeley

  12. The universal conductivity implies that observable, optical transmittance is also universal • It was argued that conductivity for Dirac fermions is a universal constant, G Understanding origins of πα Physics 141A Spring 2013 Michael Tsang UC Berkeley

  13. Optical Properties in Berkeley Physics Ultrafast Nano-Optics Group • Changing the optical reflection of graphene from electrical gating • Optical determination of graphene electronic structure Prof Wang welcomes interested undergraduates and graduates into his lab Professor Feng Wang (left) Physics 141A Spring 2013 Michael Tsang UC Berkeley

  14. Other Properties of Graphene • Density of: 0.77 mg/m2 • Breaking Strength: 42 N/m • Conductivity: 0.96x106Ω-1cm-1( > copper) • Thermal Conductivity: 10x greater than copper According to the Nobel Prize paper, a hammock of graphene could hold a cat (4kg) while weighing the same as one of its whiskers! Physics 141A Spring 2013 Michael Tsang UC Berkeley

  15. Recap Graphene: • 2D, honeycomb lattice of carbons • Pure, remarkable strength, conductivity • “Mechanical Cleavage” • πα = 2.3% Light Absorption • First material observed with Dirac Fermions Physics 141A Spring 2013 Michael Tsang UC Berkeley

  16. Only 193 US Patents!

  17. Whenever a new material is characterized, entire systems can change Take home message, Physics 141A Spring 2013 Michael Tsang UC Berkeley

  18. http://www.condmat.physics.manchester.ac.uk/pdf/mesoscopic/publications/graphene/Science_2008fsc.pdfhttp://www.condmat.physics.manchester.ac.uk/pdf/mesoscopic/publications/graphene/Science_2008fsc.pdf • http://archive.sciencewatch.com/inter/aut/2008/08-aug/08augSWGeim/ • http://newscenter.lbl.gov/feature-stories/2010/10/15/the-noise-about-graphene/ • http://www.nobelprize.org/nobel_prizes/physics/laureates/2010/advanced-physicsprize2010.pdf • http://blogs.ls.berkeley.edu/fengwang/research/graphene/ • http://news.softpedia.com/news/Graphene-Can-Cool-Electronics-with-Great-Efficiency-263614.shtml • http://www.scientificamerican.com/article.cfm?id=carbon-wonderland References Physics 141A Spring 2013 Michael Tsang UC Berkeley

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