High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum Jens Steidtner...
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High-resolution microscope for tip- enhanced optical processes in ultrahigh vacuum Jens Steidtner Fritz Haber Institute, Physical Chemistry Department
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Transcript of High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum Jens Steidtner...
High-resolution microscope for tip-enhanced optical processes in
ultrahigh vacuum
Jens SteidtnerFritz Haber Institute, Physical Chemistry Department
Outline
• Lateral resolution of aSNOM
• aSNOM - Optical configurations
• Focusing with a parabolic mirror
• Experimental setup
• Experimental results
• Outlook
2
Overcoming the diffraction limit
(a) SNOM with a metal-coated tapered fiber tip
(b) Apertureless SNOM with a metallic probe
Rayleigh`s criterion:
D
frx
22.1
3
Lateral resolution of aSNOM
3
00)(
R
dRgERE S
3
2
2
)(1
)0(
)()(
dR
r
I
rIrF
SNF
NFNF
2
122 ))(( rdRR S
6
2
2
)(1
)0(
)()(
dR
r
I
rIrF
STER
TERTER
4
TERS - Optical configurations
Bottom-illumination1 Side-illumination2 Top-illumination3
5
[1] R. Stöckle, Y. D. Suh, V. Deckert, R. Zenobi, Chem. Phys. Lett. 318, 131 (2000)
[2] B. Pettinger, G. Picardi, R. Schuster, G. Ertl, J. Electroanal. Chem. 554, 293 (2003)
[3] J. Steidtner, B. Pettinger, Rev. Sci. Instrum., in print
Focusing with a parabolic mirror
6
Linear polarization Radial polarization
Si phonon band at 520 cm-1
Schematic of the optical setup
7
Optical platform
8
Vacuum system
9
Raman imaging the focus
Linear polarization Radial polarization
10
TERS of BCB adsorbates
Brillant cresyl blue
BCB monolayer on Au(111)
• ~36000 molecules are in the focal spot• Only 90 molecules are in the tip-enhanced region• By approaching the tip the signal is raised by a factor of 3920• This equals a Raman enhancement factor of 1.6*106
11
Photobleaching in UHV / O2
12
TERS of BCB molecules
13
Lateral resolution
of ~15 nm
)()(
1)0()(
6
2
2
bgIdR
rIrI
S
14
Single molecule aSNOM
aSNOM of BCB adsorbates
15
Outlook
16
• Implementation of a combined AFM/STM scanner
• Application of silver tips
• Investigation of catalytic reactions on single crystals and oxide supported metal clusters
Acknowledgement
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• Dr. Bruno Pettinger
• Workshops of the Fritz Haber Institute
• Danish Micro Engineering
• Fritz Haber Institute of the MPS
