Chemical imaging on the nanoscale-top-illumination tip-enhanced Raman spectroscopy

A top illumination system for tip-enhanced Raman spectroscopy (TERS) in a gap-mode configuration is presented here, which allows chemical analysis of sample surfaces with a lateral resolution beyond the optical diffraction limit and optical detection of very small amounts of analyte molecules (down to single molecule sensitivity). The technique combines the high resolution of an STM with label-free, chemical-rich information of Raman spectra at ambient pressure. In this system, using a special geometry with illumination and detection perpendicular to the sample surface, a lateral resolution of