The optical near-field interaction between probing tip and sample is determined by the dielectric properties of the specimen. The dielectric properties of materials are determined by e.g. chemical composition or crystal structure, leading to a characteristic near-field spectral signature for infrared-active materials which allows to identify the materials. The topography image (top, gray) shows an approximately 1µm large Silicon Carbide (SiC) island in an extended Au film. The amplitude images reveal a wavelength-dependent optical near-field signal of SiC where SiC appears much brighter than Au at 929cm^-1 and much darker than Au at 978cm^-1. The near-field spectral signature (bottom) of SiC exhibits in the mid-infrared spectral regime a 20-fold enhanced amplitude signal of SiC compared to Au.

Application-Spectroscopic-indentification-of-materials-1