TY - JOUR
T1 - Epitaxy of polar semiconductor Co3O4 (110)
T2 - Growth, structure, and characterization
AU - Kormondy, Kristy J.
AU - Posadas, Agham B.
AU - Slepko, Alexander
AU - Dhamdhere, Ajit
AU - Smith, David
AU - Mitchell, Khadijih N.
AU - Willett-Gies, Travis I.
AU - Zollner, Stefan
AU - Marshall, Luke G.
AU - Zhou, Jianshi
AU - Demkov, Alexander A.
PY - 2014/6/28
Y1 - 2014/6/28
N2 - 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.
AB - 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.
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U2 - 10.1063/1.4885048
DO - 10.1063/1.4885048
M3 - Article
AN - SCOPUS:84903831278
SN - 0021-8979
VL - 115
JO - Journal of Applied Physics
JF - Journal of Applied Physics
IS - 24
M1 - 243708
ER -