Origin of multiple peaks in the light emission spectra of a Au(111) surface induced by the scanning tunneling microscope

Abstract

We have measured the light emission spectra of a clean Au(111) surface induced by the scanning tunneling microscope (STM). The STM tip was made of pure Au wire. When the tip apex had a truncated shape (in the scanning electron microscope image), multiple peaks were observed whose energies and number depend on the tip shape. These peaks arise from the resonant modes of the localized surface plasmons whose energies are determined by the apex size.