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

4. Lateral resolution of aSNOM 4

5. TERS - Optical configurations Bottom-illumination 1 Side-illumination 2 Top-illumination 3 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

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

7. Schematic of the optical setup 7

8. Optical platform 8

9. Vacuum system 9

10. Raman imaging the focus Linear polarizationRadial polarization 10

11. 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*10 6 11

12. Photobleaching in UHV / O 2 12

13. TERS of BCB molecules 13

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

15. aSNOM of BCB adsorbates 15

16. 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

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