Epitaxy of polar semiconductor Co3O4 (110): Growth, structure, and characterization
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 Co3O4/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.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Jun 28, 2014
- Source ID
- 10.1063/1.4885048
Entities
People
- Agham Posadas
- Ajit Dhamdhere
- Alexander A Demkov
- Alexander Slepko
- David J Smith
- Jianshi Zhou
- Khadijih N. Mitchell
- Kristy J Kormondy
- Luke G. Marshall
- Stefan Zollner
- Travis I. Willett-gies
Organizations
- Air Force Office of Scientific Research
- Arizona State University
- National Science Foundation
- New Mexico State University
- University of Texas at Austin