Near-Field Manipulation in a Scanning Tunneling Microscope Junction with Plasmonic Fabry-Pérot Tips

Near-field manipulation in metallic nanocavities can provide various applications in nanoscale science and technology. In particular, gap plasmon in scanning tunneling microscope (STM) junctions is of key interest to nanoscale imaging and spectroscopy. Here we report that plasmonic properties of an STM junction can be manipulated by nanofabrication of Au tips using focused ion beam (FIB) milling. An exemplary Fabry–Perot like resonator of surface plasmons is demonstrated by producing a single groove on a smoothed tip shaft. STM-induced luminescence spectra of these tips exhibit spectral modulation originating from the interference between localized and propagating surface plasmon modes. In addition, we show that the quality factor of the plasmonic Fabry–Perot interference can be improved by optimizing the overall tip shape. Our approach paves the way for near-field imaging and spectroscopy with a high degree of accuracy.