J. M. Hoffmann, B. Hauer, and T. Taubner
Applied Physics Letters 101, 193105 (2012)
Scattering-type scanning near-field optical microscopy (s-SNOM) allows for optical nanoscale imaging and provides information about topographical and chemical material properties with subwavelength resolution. In this letter, we demonstrate that the sensitivity of s-SNOM can be improved by means of infrared resonant antennas. This technique is comparable to the application of resonant nanostructures in far-field surface-enhanced infrared spectroscopy. We find that the near-field amplitude spectra of the polymer poly(ethyl methacrylate) obtained on resonant structures are increased in absolute value as well as in contrast over those obtained on non-resonant, highly reflective materials such as gold.