Material-specific mapping of metal/semiconductor/dielectric nanosystems at 10 nm resolution by backscattering near-field optical microscopy

We report that three main constituents of nanosystems—metals, semiconductors, and dielectrics—can be categorically distinguished by their specific optical near-field contrast at 633 nm wavelength. The decisive property is the local dielectric constant as we show by calculations based on dipolar coupling theory. Experiments with Au/Si/PS(polystyrene) nanostructures using an apertureless scattering-type near-field optical microscope yield optical images at 10 nm resolution, with clear material contrast close to predicted levels.