LPICM, École Polytechnique, CNRS, 91128 Palaiseau, France
HORIBA Jobin Yvon SAS, Raman Division, 231 rue de Lille, 59650 Villeneuve d'Ascq, France
In Tip-Enhanced Raman Spectroscopy (TERS) a metal (or metallized) sharp tip is used to enhance the electromagnetic field by a localized surface-plasmon excitation. Two different modes – atomic force mode (AFM) and scanning tunneling mode (STM) – together with their respective types of probe tips are used in TERS experiments. We have compared the efficiency in enhancing the Raman signal on a thin dye layer for metal-coated AFM tips as well as for electrochemically etched metal STM tips. A much higher enhancement factor and better reproducibility were found when using STM tips. The very different performance is mainly attributed to the more efficient plasmonic excitation when using bulk-metal tips and possibly to the morphological differences in the tip and apex shapes existing between the two tip types.
(Received July 19 2007)
(Accepted August 22 2007)
(Online publication October 31 2007)