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Chemical imaging with a Raman atomic-force microscope

ABSTRACT: By integrating an atomic force microscope incorporating a metallized tip with a Raman spectrometer, it is possible to extract chemical information via optical spectroscopy well below the conventional diffraction limit of the incident radiation. The Raman atomicforce microscope utilizes the surface-enhanced Raman signal due to the tip-sample interaction to localize the spectral information. Metallic nanoparticles on the tip provide massive field enhancements to amplify the usually weak Raman signal. The resulting highly localized signal provides chemical information via the Raman spectrum at an unprecedented scale. Side illumination allows for the analysis of opaque samples.