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High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum

High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum. Jens Steidtner Fritz Haber Institute, Physical Chemistry Department. Outline. Lateral resolution of aSNOM aSNOM - Optical configurations Focusing with a parabolic mirror Experimental setup

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High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum

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  1. High-resolution microscope for tip-enhanced optical processes in ultrahigh vacuum Jens Steidtner Fritz Haber Institute, Physical Chemistry Department

  2. Outline • Lateral resolution of aSNOM • aSNOM - Optical configurations • Focusing with a parabolic mirror • Experimental setup • Experimental results • Outlook 2

  3. Overcoming the diffraction limit Rayleigh`s criterion: (a) SNOM with a metal-coated tapered fiber tip (b) Apertureless SNOM with a metallic probe 3

  4. Lateral resolution of aSNOM 4

  5. TERS - Optical configurations Bottom-illumination1 Side-illumination2 Top-illumination3 [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 5

  6. Focusing with a parabolic mirror Linear polarization Radial polarization Si phonon band at 520 cm-1 6

  7. Schematic of the optical setup 7

  8. Optical platform 8

  9. Vacuum system 9

  10. Raman imaging the focus Linear polarization Radial polarization 10

  11. TERS of BCB adsorbates BCB monolayer on Au(111) Brillant cresyl blue • ~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

  12. Photobleaching in UHV / O2 12

  13. TERS of BCB molecules 13

  14. Single molecule aSNOM Lateral resolution of ~15 nm 14

  15. aSNOM of BCB adsorbates 15

  16. Outlook • Implementation of a combined AFM/STM scanner • Application of silver tips • Investigation of catalytic reactions on single crystals and oxide supported metal clusters 16

  17. Acknowledgement • Dr. Bruno Pettinger • Workshops of the Fritz Haber Institute • Danish Micro Engineering • Fritz Haber Institute of the MPS 17

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