Electronic structure of nanoscale iron oxide particles measured by scanning tunneling and photoelectron spectroscopies

TL;DR

This study investigates the electronic structure of nanoscale iron oxide particles using STM, STS, and photoelectron spectroscopy, revealing surface-dependent variations in electronic properties under different thermal and reducing conditions.

Contribution

It provides new insights into the surface electronic structure of nano-iron oxides and how it varies with phase and environmental conditions.

Findings

Surface band gap differs from bulk material

Electronic structure varies with phase and reduction conditions

Surface effects dominate electronic excitation spectrum

Abstract

We have investigated the electronic structure of nano-sized iron oxide by scanning tunnelling microscopy (STM) and spectroscopy (STS) as well as by photoelectron spectroscopy. Nano particles were produced by thermal treatment of Ferritin molecules containing a self-assembled core of iron oxide. Depending on the thermal treatment we were able to prepare different phases of iron oxide nanoparticles resembling gamma-Fe2O3, alpha-Fe2O3, and a phase which apparently contains both gamma-Fe2O3 and alpha-Fe2O3. Changes to the electronic structure of these materials were studied under reducing conditions. We show that the surface band gap of the electronic excitation spectrum can differ from that of bulk material and is dominated by surface effects.