20.4. 2007 NOKIA MEETING 1

APS MARCH MEETING 2007APS MARCH MEETING 2007 Denver, Colorado 5.3.-9.3. 2007Denver, Colorado 5.3.-9.3. 2007

LATEST IN GRAPHENE RESEARCHLATEST IN GRAPHENE RESEARCH Mikko Paalanen

Low Temperature LaboratoryHelsinki University of Technology

20.4. 2007 NOKIA MEETING 2

APS MARCH MEETING 2007APS MARCH MEETING 2007 STATISTICSSTATISTICS

SCIENTIFIC SESSIONS Total 520 Graphene sessions 7 + a

tutorial session Carbon nanotube sessions 14

INVITED TALKS Total 720 Graphene talks 10 (6 E, 4 T) Carbon nanotube talks 11 (8 E, 3 T)

20.4. 2007 NOKIA MEETING 3

STATISTICSSTATISTICS

Contributed talks about graphene Total 66

Theory talks 37

ExperimentalElectron transport 14Mechanical properties 9Microscopy 6

29

More experiments needed, theory is advancing fast

20.4. 2007 NOKIA MEETING 4

COMPETITORS COMPETITORS ON EXPERIMENTAL SIDEON EXPERIMENTAL SIDE

Univ. of Manchester (Andrei Geim et al since 2004) Georgia Tech (Walter DeHeer et al) Colombia University (Philip Kim et al) Rutgers University (Eva Andrei et al) IBM Yorktown (Avouris et al) Cornell University (Paul McEuen et al)

20.4. 2007 NOKIA MEETING 5

THREE INTERESTING THREE INTERESTING RESULTSRESULTS

Colombia University (Philip Kim et al) IBM Yorktown (Avouris et al) Leiden University (Carlo Beenakker et al)

20.4. 2007 NOKIA MEETING 6

ENERGY BAND GAP ENGINEERING OF ENERGY BAND GAP ENGINEERING OF GRAPHENE NANORIBBONSGRAPHENE NANORIBBONS

arXiv:cond-mat/0702511arXiv:cond-mat/0702511Colombia, Philip Kim et alColombia, Philip Kim et al

20.4. 2007 NOKIA MEETING 7

Dead edge of the order of 15 nm!Dead edge of the order of 15 nm!

20.4. 2007 NOKIA MEETING 8

Energy gap scales as 1/(w – wEnergy gap scales as 1/(w – w00) ) No orientation dependenceNo orientation dependence

wwminmin = 15 nm = 15 nmEEgmax gmax = 200 meV= 200 meV

20.4. 2007 NOKIA MEETING 9

IBM, AVOURIS et alIBM, AVOURIS et alarXiv:cond-mat/0701599arXiv:cond-mat/0701599

1/f noise similar to CNT1/f noise similar to CNTDue to resistance fluctuationsDue to resistance fluctuations

wwminmin = 20 nm = 20 nmEEgmax gmax = 30 meV= 30 meV

20.4. 2007 NOKIA MEETING 10

SNS-JUNCTION IN GRAPHENESNS-JUNCTION IN GRAPHENELeiden University, Carlo BeenakkerLeiden University, Carlo Beenakker

arXiv:cond-mat/0609623arXiv:cond-mat/0609623

Supercurrent creates a transverseSupercurrent creates a transversespin and thermal currentsspin and thermal currents

Thermal current depends Thermal current depends on phase differenceon phase difference

20.4. 2007 NOKIA MEETING 11

WHY GRAPHENEWHY GRAPHENEWHY NOT CARBON NANOTUBESWHY NOT CARBON NANOTUBES

High electron mobility even at room temperature Long mean free path, electron backscattering weak Long coherence length (dephasing due to e-e collisions)

Contacts easier to make than for nanotubes Can be fabricated lithographically as large wafers (SiC) Metallic interconnects may not be needed Promise for new type of electronics

Electron wave guide electronics Terahertz detectrors .....

20.4. 2007 NOKIA MEETING 12

INTERESTING QUESTIONSINTERESTING QUESTIONS

How do electronic properties depend on substrate? Free standing sheet versus SiC Multilayered graphene Interphase states and doping

What about narrow wires and quantum dots? Rough edges seem to play a role? How to prepare smooth edges? Tuning of the gap in narrow wires?