Sebastian Thomas, Michael Krüger, Michael Förster, Markus Schenk, Peter Hommelhoff
We present a new method of measuring optical near-fields with a resolution of ~1 nm based on rescattering of photoemitted electrons. With this method, we precisely measure the field enhancement factor for tungsten and gold nanotips, for the former as a function of tip radius. The agreement with Maxwell simulations is very good. Further simulations yield a field enhancement map for all materials, which shows that optical near-fields at nanotips are governed by a geometric effect under most conditions, while plasmon resonances play only a minor role. Last, we consider the implications of our results on quantum mechanical effects near the surface of nanostructures and discuss features of quantum plasmonics.
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http://arxiv.org/abs/1209.5195
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