Layer-by-layer epitaxial growth of polar FeO(111) thin films on MgO(111)

TL;DR

This study demonstrates the successful layer-by-layer epitaxial growth of polar FeO(111) thin films on MgO(111) substrates, revealing their structural, chemical, and magnetic properties through various characterization techniques.

Contribution

It introduces a method for stabilizing thick polar FeO(111) films via molecular beam epitaxy and provides detailed analysis of their structural and magnetic properties.

Findings

FeO(111) films up to 16 ML thick were stabilized.

Structural and chemical properties confirmed by LEED, AES, and CEMS.

Magnetic ordering observed at low temperatures.

Abstract

We report on the structural properties of epitaxial FeO layers grown by molecular beam epitaxy on MgO(111). The successful stabilization of polar FeO films as thick as 16 monolayers (ML), obtained by deposition and subsequent oxidation of single Fe layers, is presented. FeO/MgO(111) thin films were chemically and structurally characterized using low-energy electron diffraction, Auger electron spectroscopy and conversion electron Mossbauer spectroscopy (CEMS). Detailed in situ CEMS measurements as a function of the film thickness demonstrated a size-effect-induced evolution of the hyperfine parameters, with the thickest film exhibiting the bulk-wustite hyperfine pattern. Ex situ CEMS investigation confirmed the magnetic ordering of the wustite thin film phase at liquid nitrogen temperature.