Light at work at nanoscale: Tip-Enhanced Raman Spectroscopy

Abstract

Controlling light at the nanoscale, the fascinating goal of nanophononics, allows to mold the flow of light in previously unknown ways, providing access to the study of the interaction of single molecules with confined optical fields. One of the most powerful spectroscopic approach to nanoscale is Tip-Enhanced Raman Spectroscopy (TERS). TERS combines the fingerprint character of Raman spectroscopy with the high spatial resolution of scanning probe microscopies (SPM), by taking advantage of plasmonic nanostructures placed at the apex of a SPM probe. Thanks to the excitation of Localized Surface Plasmon Resonances (LSPR), such system behaves as a nano-antenna, able to explore surfaces with nanometric spatial resolution and sensitivity up to single molecule level. Herein, we report on the fabrication and characterization of newly conceived nano-antennas. In particular, we illustrate a top-down approach for TERS tip fabrication, based on the solid-state dewetting of metal-sputtered Atomic-Force Microscopy probes. Such approach produces AFM-TERS tips, exhibiting high reproducibility and efficiency.