Light emission from Na/Cu(111) induced by a scanning tunneling microscope

TL;DR

This study investigates light emission from a Na overlayer on Cu(111) induced by a scanning tunneling microscope, revealing bias-dependent emission mechanisms including plasmon mediation and quantum well transitions.

Contribution

It provides experimental measurements and a model explaining the bias-dependent light emission mechanisms from Na/Cu(111) surfaces under STM.

Findings

Light emission spectra depend on bias voltage.

Emission mechanisms switch from plasmon-mediated to quantum well transitions.

Model calculations agree with experimental results.

Abstract

Measurements of light emission from a scanning tunneling microscope probing a Na overlayer on the (111) surface of Cu are reported along with results of a model calculation that essentially agree with the experimental ones. The observed light emission spectra show two characteristic features depending on the bias voltage. When the bias voltage is smaller than the energy of the second quantum well state formed outside the Na overlayer the light emission is due to a plasmon-mediated process, while for larger biases light emission is mainly caused by quantum well transitions between the two levels.