A SERS Hotspot at 5nm Resolution

Roughened metallic surfaces have been known since the 1970ies to enhance Raman spectra of minute amounts of deposited substances. It was soon established that so-called hotspots can give rise to many orders of magnitude of signal increase - even to the point of allowing to record spectra from single molecules. Interestingly for nano-optics, such hotspots represent also one of the rare instances of ultra-confined localized optical fields, that it, ideal test objects for establishing spatial resolution. Here, the measured spatial extent of tha sharpest rise in signal is used to estimate an imaging resolution of at least 5 nm. Possibly convolution effects due to finite probe size deteriorate this figure.

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