Graphene: facts and perspectives - O.V. Lounasmaa Laboratory
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Graphene project meeting Graphene nanoribbons Romain Danneau [email protected] Nano Group Low Temperature Laboratory Helsinki University of Technology LTL 20 th of April 2007
Transcript of Graphene: facts and perspectives - O.V. Lounasmaa Laboratory
Graphene project meeting
Graphene nanoribbons Romain Danneau
Nano GroupLow Temperature Laboratory
Helsinki University of Technology
LTL20th of April 2007
LTL
Graphene: definition Band structure: semi-metal Nano-ribbons: can be semiconducting Two kind of samples: exfoliation and epitaxial Nano-ribbons: first experiments Future and perspective
Outline
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Graphene: definition
Atomic orbitals sp2
0DFullerene
1DNanotube
3DGraphite
2D Graphene
For a review: A.K. Geim and K.S. Novoselov, Nature Mat. 6. 183 (2007).
Graphene is a 2D allotropeof carbon
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Graphene: a semi-metal
A.K. Geim and K.S. Novoselov, Nature Mat. 6. 183 (2007).
Linear dispersion around the Dirac point: carrier act like massless relativistic particles
Two sublattices: notion of chiralityNew physics!!
Anomalous QHE (even at room temperature)Applications in microelectronics: great potential
(high mobility, high current density, high thermal conductivity, large MFP)But no gap... no real on-off transistor
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Graphene nano-ribbons: metallic or semiconductor
armchair edgesSC
zigzag edgesSC or M
K. Nakada et al., Phys. Rev. B 54, 17954 (1996).
Y.-W. Son et al., Phys. Rev. Lett 97, 216803 (2006).
Graphene nano-circuit: gap controled either by the orientation or the width of the ribbon
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Graphene: two type of samples (so far…)
Mechanical exfoliation (using tape for example) of highly orientated
pyrolytic graphite (HOPG) bulk.
H.B. Heersche, PhD thesis, TU Delft, 2006.
A.K. Geim and K.S. Novoselov, Nature Mat. 6. 183 (2007).
Grown by graphitization processin commercial SiC wafers.
C. Berger et al., Science 312, 1191 (2006).
Work supportedBy Intel inc.
P. Mallet et al., cond-mat/0702406
Single layer possiblebut no transport measurements
published so far
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Already some results on nano-ribbons…
M.Y. Han et al., Phys. Rev. Lett. (in press), cond-mat/0702511.
Si-SiO2 substrateCr-Au contact
contact resistance ~1 kΩDifferent widths
and different relative orientations
Columbia University (P. Kim group)
IBM New York (P. Avouris group)
Patterned by e-beamOxigen plasma etch
Z. Chen et al., cond-mat/0701599.
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Graphene nano-ribbons: a semiconductor
M.Y. Han et al., Phys. Rev. Lett. (in press), cond-mat/0702511.
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Graphene nano-ribbons: a semiconductor
M.Y. Han et al., Phys. Rev. Lett. (in press), cond-mat/0702511.
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A- Introductioni-
Also Qdots!
A.K. Geim and K.S. Novoselov, Nature Mat. 6. 183 (2007).
CB is observed and the system can be pinch-off even at room temperature
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Projects:Nano-circuits in the ballistic regime using nano-ribbons ribbons and metallic side-gatesQdots, Josephson junctions, SET, RF-SET…Working with both HOPG and epitaxial graphene
Conclusion and perspectives
Conclusions:Graphene can become a semiconductorOn-off transistors are possible
Thank you!
