Transcript EFN512M / EFN010F Molecular Spectroscopy and Reaction Dynamics

EFN512M / EFN010F
Molecular Spectroscopy and Reaction Dynamics
Group II – 1st Presentation
Scanning Tunneling Microscope
Jingming Long, Nanna Rut Jónsdóttir, Kári Sveinbjörnsson & Guðfinnur
Baldur Skæringsson
Demonstration date: 16.09.10
Presentation date: 05.10.10
Contents
Principals 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/semiconductors, 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)
Thank you