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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 - PowerPoint PPT Presentation
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Graphene – Optical Properties
Michael TsangUC Berkeley
Physics 141ASpring 2013
Lawrence Berkeley LabManchester Group
for monolayers
Graphene is a single layer of carbon packed in
hexagonal (honeycomb) lattice the first truly 2D material
What is Graphene
Physics 141ASpring 2013
Michael TsangUC Berkeley
Graphene is a single layer of carbon packed in
hexagonal (honeycomb) lattice the first truly 2D material
What is Graphene
Physics 141ASpring 2013
MoS2 .
Michael TsangUC Berkeley
Graphene has Covalent Bonding sp2 hybridization Remarkably high quality
A Closer Look at Graphene
Physics 141ASpring 2013
0.142 nm
Michael TsangUC Berkeley
Familiar Carbon Structures Carbon Nanotubes, known since 1993 Buckeyballs C60, known since 1996 Graphite, known since … a long time
Physics 141ASpring 2013
Michael TsangUC Berkeley
Konstantin Novoselov Andre Geim
Nobel Prize in Physics (2010)
Physics 141ASpring 2013
Isolated large sheets in order to identify and characterize graphene and verify 2D properties
Michael TsangUC Berkeley
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: Micromechanical Cleavage
Physics 141ASpring 2013
The Optical Properties of Graphene
Physics 141ASpring 2013
Michael TsangUC Berkeley
Physics 141ASpring 2013
Optical Measurements Take prepared
macroscopic membranes of graphene
Shine light through the membrane
Detector measures light intensity
Michael TsangUC Berkeley
Physics 141ASpring 2013
Optical Measurements
Ideal Dirac Fermions?
?
Michael TsangUC Berkeley
Physics 141ASpring 2013
Dirac Fermions? “Dirac Fermions”
refers to electrons that race through the graphene structure
Relativistic Quantum Mechanics becomes important Dirac Equation
Richard Feynman, a founding father of quantum electrodynamics Michael Tsang
UC Berkeley
Physics 141ASpring 2013
Understanding origins of πα
The universal conductivity implies that observable, optical transmittance is also universal
It was argued that conductivity for Dirac fermions is a universal constant, G
Michael TsangUC Berkeley
Physics 141ASpring 2013
Ultrafast Nano-Optics Group
Changing the optical reflection of graphene from electrical gating
Optical determination of graphene electronic structure
Optical Properties in Berkeley Physics
Professor Feng Wang (left)
Prof Wang welcomes interested undergraduates and graduates into his lab
Michael TsangUC Berkeley
Other Properties of Graphene
Density of: 0.77 mg/m2
Breaking Strength: 42 N/m Conductivity: 0.96x106 Ω-1cm-1 ( > copper) Thermal Conductivity: 10x greater than
copper
Physics 141ASpring 2013
According to the Nobel Prize paper, a hammock of graphene could hold a cat (4kg) while weighing the same as one of its whiskers!
Michael TsangUC Berkeley
Physics 141ASpring 2013
RecapGraphene:
2D, honeycomb lattice of carbons Pure, remarkable strength, conductivity “Mechanical Cleavage” πα = 2.3% Light Absorption First material observed with Dirac Fermions
Michael TsangUC Berkeley
Only 193 US Patents!
Whenever a new material is characterized, entire systems can change
Take home message,
Physics 141ASpring 2013
Michael TsangUC Berkeley
http://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 141ASpring 2013
Michael TsangUC Berkeley