Single atom manipulation and spectroscopy using low temperature STM

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Single atom manipulation and spectroscopy using
low temperature STM
E. Zupanic R. itko H.J.P. van Midden A.
Prodan I. Muevic
Joef Stefan Institute Condensed matter physics
F5 Ljubljana, Slovenia
SLONANO2007
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STM and STS
F5
Bardeens tunneling current
(1)
(2)
(2)
simplified
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STM and STS
F5
dconst.

• Information on
• energy gap
• chemical composition
• bonding

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Why STM ???
F5

• real-space atomic resolution imaging
• electronic structure (local density of
  electronic states)
• investigate physical/chemical properties at
  atomic level
• atomic and molecular manipulation

Why manipulation ???

• construction of atomic scale structures allows
  the study of quantum phenomena
• inducing single molecule chemical reactions
  gives insight to the reaction mechanism at a
  fundamental level
• studying of molecular nanomachines
• manipulation at atomic level is fun !

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UHV LT-STM at IJS
F5

• UHV system
• Omicron RT STM-1
• homebuilt LT STM
• Omicron LEED / AES
• ion gun
• Knudsen cell
• effusion cell

UHV p lt 10-10 mbar LT T 9 K
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Manipulation techniques
F5
Interactions between molecule/atom and STM tip
dissociation
lateral manipulation
synthesis
vertical transfer
desorption
change of conformation
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Manipulation techniques
F5

• Mechanism of manipulation
• Chemical forces between the tip and the
  adsorbates
• Tunneling electrons (dissociation and synthesis
  of molecules by applied voltage pulses)
• Electric field (the potential energy of a
  molecule in an electric field will change)

Example lateral manipulation
conformational changes of molecules
Example molecule dissociation rotation
between two stable configurations
Example field assisted diffusion
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Manipulation techniques
F5
http//www.physik.fu-berlin.de/grill/manipulation
/
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Experiment
F5
Cu (111) and (112) single crystals purity 99.999
, roughness 0.05 µm
noble metal single-crystal
UHV
LEED / AES
Knudsen source effusion cell
extraction of atoms by tip crash
clean and flat
contaminated and/or rough
ion sputtering annealing
adatoms / molecules
LT - STM
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Results
F5
Clean Cu(111) surface
Cu(111), 500 x 500 nm, T9K
Cu(111), 6.3 x 6.3 nm, T9K

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Results
F5
Cu(111) CO molecules
Cu(111), 300 x 300 nm, T25K
Cu(111), 10 x 10 nm, T25K

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Results
F5
Extraction of atoms by crashing the STM tip Cu
adatoms on Cu(111)
Cu(111), 50 x 50 nm, T9K
Cu(111), 160 x 160 nm, T9K

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Results
F5
Manipulation Cu adatoms on Cu(111)
Cu(111), 31 x 31 nm, T9K
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Results
F5
Cu(111), 14 x 14 nm, T9K
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Results
F5
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Results
F5
STS Co adatoms on Cu(111)
Cu(111), 125 x 125 nm, T9K
Cu(111), 33 x 33 nm, T9K

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Results
F5
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Results
F5
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Conclusions
F5

• STM is a very powerful nanotechnological tool
• atomic scale imaging and characterization (local
  electronic structure)
• building nanostructures from single atoms /
  molecules
• We acquired the knowledge and the technology to
  perform experiments at the atomic level!

http//www.ijs.si/ijs/dept/stm/