Excited States at Interfaces of a Metal-Supported Ultrathin Oxide Film

TL;DR

This study uses resonant Auger spectroscopy to investigate the unoccupied electronic states at the interface of ultrathin MgO films on Ag(001), revealing metal-induced gap states, the oxide band gap, and a surface core exciton.

Contribution

It provides a novel layer-resolved analysis of unoccupied electronic states at metal-supported ultrathin oxide interfaces using resonant Auger spectroscopy.

Findings

Identification of metal-induced gap states at the interface

Measurement of the oxide band gap

Observation of a surface core exciton involving an image-potential state

Abstract

We report layer-resolved measurements of the \textit{unoccupied} electronic structure of ultrathin MgO films grown on Ag(001). The metal-induced gap states at the metal/oxide interface, the oxide band gap as well as a surface core exciton involving an image-potential state of the vacuum are revealed through resonant Auger spectroscopy of the Mg $KL_{23}L_{23}$ Auger transition. Our results demonstrate how to obtain new insights on \textit{empty} states at interfaces of metal-supported ultrathin oxide films.