Epitaxy of Polar Semiconductor Co3O4 (110): Growth, Structure, and Characterization
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.
- Author (aut): Kormondy, Kristy J.
- Author (aut): Posadas, Agham B.
- Author (aut): Slepko, Alexander
- Author (aut): Dhamdhere, Ajit
- Author (aut): Smith, David
- Author (aut): Mitchell, Khadijih N.
- Author (aut): Willett-Gies, Travis I.
- Author (aut): Zollner, Stefan
- Author (aut): Marshall, Luke G.
- Author (aut): Zhou, Jianshi
- Author (aut): Demkov, Alexander A.
- Contributor (ctb): College of Liberal Arts and Sciences