Zhang, Weihua; Cui, Xudong; Martin, Oliver J. F.:

Local field enhancement of an infinite conical metal tip illuminated by a focused beam

In: Journal of Raman spectroscopy : JRS ; an international journal for original work in all aspects of Raman Spectroscopy, including higher order processes and also Brillouin- and Rayleigh scattering, Jg. 40 (2009) ; Nr. 10, S. 1338–1342
ISSN: 0377-0486
Zeitschriftenaufsatz / Fach: Elektrotechnik
We present a systematic numerical investigation of conical metal tips which are commonly used in tip-enhanced Raman spectroscopy (TERS). Different from previous studies, we focus on how the tip length and the illumination condition influence the local field enhancement at the tip apex, and provide a useful reference for real experiments. In particular, we show that the type of illumination has a dramatic influence on the field enhancement: a localized illumination spot – as used in experiments – producing a very different response than a plane wave illumination – as usually used in previous models. Also,the effect of the different geometrical parameters, such as the sharpness of the tip apex and the cone angle, provides guidance to optimize the tip design. Finally, we investigate the influence of the substrate and compare numerical data with results deduced froma simplifiedmodel, finding good agreement. This brings newinsights into the enhancementmechanismof TERS.
Copyright!c 2009 JohnWiley & Sons, Ltd.