Epitaxy of polar semiconductor Co3O4 (110): Growth, structure, and characterization

Kristy J. Kormondy, Agham B. Posadas, Alexander Slepko, Ajit Dhamdhere, David Smith, Khadijih N. Mitchell, Travis I. Willett-Gies, Stefan Zollner, Luke G. Marshall, Jianshi Zhou, Alexander A. Demkov

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

The (110) plane of Co3O4 spinel exhibits significantly higher rates of carbon monoxide conversion due to the presence of active Co3+ species at the surface. However, experimental studies of Co3O4 (110) surfaces and interfaces have been limited by the difficulties in growing high-quality films. We report thin (10-250 Å) Co3O4 films grown by molecular beam epitaxy in the polar (110) direction on MgAl2O4 substrates. Reflection high-energy electron diffraction, atomic force microscopy, x-ray diffraction, and transmission electron microscopy measurements attest to the high quality of the as-grown films. Furthermore, we investigate the electronic structure of this material by core level and valence band x-ray photoelectron spectroscopy, and first-principles density functional theory calculations. Ellipsometry reveals a direct band gap of 0.75 eV and other interband transitions at higher energies. A valence band offset of 3.2 eV is measured for the Co3O 4/MgAl2O4 heterostructure. Magnetic measurements show the signature of antiferromagnetic ordering at 49 K. FTIR ellipsometry finds three infrared-active phonons between 300 and 700 cm 1.

Original languageEnglish (US)
Article number243708
JournalJournal of Applied Physics
Volume115
Issue number24
DOIs
StatePublished - Jun 28 2014

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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