Light Emission from Ag(111) driven by Inelastic Tunneling in the Field Emission Regime

TL;DR

This study investigates light emission from Ag(111) surfaces under high bias in STM, revealing that inelastic tunneling excites surface plasmons which radiatively decay, with tip geometry influencing the emission.

Contribution

It demonstrates that surface plasmons excited by inelastic tunneling cause light emission in the field emission regime, highlighting the role of Stark-shifted image states and tip geometry.

Findings

Surface plasmons are excited by inelastic tunneling into Stark-shifted image states.

Light emission is due to radiative decay of these surface plasmons.

Tip radius affects both the tunneling spectrum and light emission patterns.

Abstract

We study the light emission from a Ag(111) surface when the bias voltage on a scanning tunneling microscope (STM) junction is ramped into the field emission regime. Above the vacuum level, scanning tunneling spectroscopy (STS) shows a series of well defined resonances associated with the image states of the surface, which are Stark shifted due to the electric field provided by the STM tip. We present photon--energy resolved measurements that unambiguously show that the mechanism for light emission is the radiative decay of surface localized plasmons excited by the electrons that tunnel inelastically into the Stark shifted image states. Our work illustrates the effect of the tip radius both in the STS spectrum and the light emission maps by repeating the experiment with different tips.