Dft teoria

An Introduction to Graphene and  the 2010 Nobel Physics Prize
(for senior secondary school students) HUI Pak Ming Department of Physics Chinese University of Hong Kong

23 June 2011

2010 Nobel Physics Prize

Konstantin Novoselov Andre Geim (Born 1958 and educated in Russia,  (Born 1974 in Russia, educated in the  Dutch, University of Manchester UK) Netherlands, Russian & British, University of Manchester UK)

"for groundbreaking experiments regarding the two‐ dimensional material graphene"
http://nobelprize.org/nobel_prizes/physics/laureates/2010/press.html

So, what is graphene?

Take-home message 1 – It is all about carbon! Graphene is a single layer of carbon atoms forming a honeycomb lattice.

Graphene – The perfect atomic lattice
[Picture taken from Nobel PrizeAnnouncement (public information)]

A single sheet of carbon atoms forming a honeycomb lattice!

Questions… • How to fabricate graphene? • Old Physics? • New implications to physics? • Why is it important? • Properties? [Thinnest, strongest, transparent, nice/tunable semiconductor, good thermal conductor, etc.] • Nice properties for future applications?

All is about carbon!
Diamond is aform of carbon 3D structure

http://image.wistatutor.com/content/p‐block‐elements/diamond‐structure.gif

www.diamondvues.com/84%20Carat%20Diamond.jpg

Graphite – layers of graphene

“Lead pen” (pencil) has nothing to do with lead!

http://www.benbest.com/cryonics/graphite.gif

http://mrsec.wisc.edu/Edetc/nanoquest/carbon/images/pencil.jpg

The problem over many years is: How topeel a layer of graphene off graphite?

History of Graphite – a “not‐too‐old” material
Discovery of graphite deposit: ~ 16th century (England)
Grey Knotts: England

e hite or Grap

mine was discovered in the 16th century and in those early days was used only for marking sheep. • It was called “Plumbago” (lead ore) . Scheele (1779, Swedish) showed that plumbago is CARBON, not lead • Werner(1789, German) called it GRAPHITE (Greek meaning “to write”) • 17th Century: Casting moulds for cannon and musket balls • 18th Century: Pencil industry

• The

Applications: Steel industry, refractory crucibles, electrodes, lubricant, brake linings, …

Modern graphite mine

Applications: Steel industry, refractory crucibles, electrodes, lubricant, brake linings, …
World Production ofgraphite US: 1,110 Kt/yr China: 800 Kt/yr India: 130 Kt/yr US (Synthetic): 198 Kt/yr
After Philip Kim

Applications based on Graphitic Carbon

Steel company: coke

Rubber/plastic: carbon black

Graphite refractory

Graphite electrode Pencil: graphite+clay

Graphitic Composite Materials: Carbon Fiber
Weigh ~ ¼ of aluminum Strength ~ 10 times of steel Electrical conductor Thermalconductor

More than 50% of carbon composite

Graphene – the mother of all graphites

http://www.nano‐enhanced‐wholesale‐technologies.com/images/structure‐graphene.gif

"Graphene: Exploring Carbon Flatland," A. K. Geim and A. H. MacDonald, Physics Today, August 2007, p. 35

Simple Physics of Carbon Atoms
6th element in periodic table => 1 nucleus + 6 electrons Quantum Physics (Schroedinger,Heisenberg and Dirac, Nobel Physics Prize 1932 & 1933) tells us how the 6 electrons behave under the influence of the carbon nucleus

C

Carbon

1s2   2s22px12py1

2 electrons in 1s atomic orbital (full) 2 electrons in 2s atomic orbital (full) 1 electron in 2px atomic orbital (not full) 1 electron in 2py atomic orbital (not full) 0 electron in 2pz atomic orbital (empty, not full) QuantumPhysics (3 compulsory + 1 elective) courses are a major part of our physics 4-year curriculum!

1s has very low energy, but 2s and 2p orbitals are very close in energy • 2s and 2p are very close in energy • 2s, 2px, 2py, 2pz together can hold 8 electrons • there are only 4 electrons in a carbon atom • Take-home message 2 – the 4 electrons in 2s, 2px, 2py, 2pz are responsible for bonding...