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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

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.

ContributorsKormondy, Kristy J. (Author) / Posadas, Agham B. (Author) / Slepko, Alexander (Author) / Dhamdhere, Ajit (Author) / Smith, David (Author) / Mitchell, Khadijih N. (Author) / Willett-Gies, Travis I. (Author) / Zollner, Stefan (Author) / Marshall, Luke G. (Author) / Zhou, Jianshi (Author) / Demkov, Alexander A. (Author) / College of Liberal Arts and Sciences (Contributor)
Created2014-06-28