EFN512M / EFN010FMolecular Spectroscopy and Reaction Dynamics

Group II – 1st PresentationScanning Tunneling MicroscopeJingming Long, Nanna Rut Jónsdóttir, Kári Sveinbjörnsson & Guðfinnur Baldur Skæringsson

Demonstration date: 16.09.10Presentation date: 05.10.10

ContentsPrincipals of the STM

Graphite

Graphene

Summary

Principals of the STM• Developed in 1982• Based on the tunneling effect

and the electrical conductance between two electrodes.

• The electron travels through a potential barrier.

• Low current (10 pA – 1nA)• Requires ultra-high vacuum

Principals of the STM• Movement controled with a Piezo-

material like BaTiO3.• Very sensitive to vibrations.• Different images of the same surface

due to a changing electron statesor or modifications of the tip.

• Pros: No sample damage, atomic resolution.

• Cons: Limited to conductors/semi-conductors, a difficult process to perfom.

Graphite

• An allotrope of carbon.• One of the most studied materials

with STM.

• The anomalous contrast (Moiré pattern) of the picture suggest a misoriented lower layer of graphite.

STM Images

Graphene• A stable 2D crystal, consisting of

carbon.• Good thermal and electrical

conductivity.• 200x stronger than steel.• Applications include us in:

– Single Molecule Gas Detection– Nanoribbons– Transistors– Ultracapacitors – Biodevices

STM• Graphene layer with different

supports.

STM

Graphene Layer

Summary• STM based on e- tunneling

through gap between two electrodes.

• Graphite used as calibration.

• Moiré effect suggest unparallel layers.

• Graphene stable 2D crystal where every C is seen.

References• Anomalous superperiodicity in scanning tunneling microscope

images of graphite. M. Kuwabara, D. R. Clarke, and D.A. Smith. Appl. Phys. Lett., Vol. 56, No. 24, 11 June 1990.

• On the STM imaging contrast of graphite : towards a true atomic resolution. F. Atamny et al. Phys. Chem. Chem. Phys., 1999, 1, 4113-4118.

• High-resolution scanning tunneling microscopy imaging of mesoscopic graphene sheets on an insulating surface. Elena Stolyarova, Kwang Taeg Rim, Sunmin Ryu, Janina Maultzsch, Philip Kim, Louis E. Brus, Tony F. Heinz, Mark S. Hybertsen, and George W. Flynn. PNAS, May 29, 2007, vol. 104, no. 22, 9209-9212.

• The rise of graphene. A.K. Geim and K. S. Novoselov. Nature Materials | VOL 6 | MARCH 2007.

References• Electron states of mono- and bilayer graphene on SiC

probed by scanning-tunneling microscopy. P. Mallet, F. Varchon, C. Naud, L. Magaud, C. Berger,and J.-Y. Veuillen. Physical Review B 76, 041403(R) (2007).

• Scanning tunneling microscopy of graphene on Ru(0001). S. Marchini, S. Günther, and J. Wintterlin*. Physical Review B 76, 075429 (2007).

• Lee, C. et al. (2008). "Measurement of the Elastic Properties and Intrinsic Strength of Monolayer Graphene". Science 321 (5887)

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