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

Abstract

Articles you may be interested inMagnetic and structural properties of BiFeO3 thin films grown epitaxially on SrTiO3/Si substrates J. Appl. Phys. 113, 17D919 (2013) The (110) plane of Co 3 O 4 spinel exhibits significantly higher rates of carbon monoxide conversion due to the presence of active Co 3þ species at the surface. However, experimental studies of Co 3 O 4 (110) surfaces and interfaces have been limited by the difficulties in growing high-quality films. We report thin (10-250 Å ) Co 3 O 4 films grown by molecular beam epitaxy in the polar (110) direction on MgAl 2 O 4 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 Co 3 O 4 /MgAl 2 O 4 heterostructure. Magnetic measurements show the signature of antiferromagnetic ordering at 49 K. FTIR ellipsometry finds three infrared-active phonons between 300 and 700 cm À1

Comparative study of optical and magneto‐optical properties of normal, disordered, and inverse spinel‐type oxides

“…Similar electronic structure and electronic transitions have also been found in other transitions metal oxides such as , , , . Optical investigations of CCO and ZCO have revealed a strong dependence of the electronic structure on the growth method and conditions in relation to the structural properties . A smaller lattice constant, narrower spectral features with lower transition energies of the CCO film grown by molecular beam epitaxy (MBE), Ref.…”

Quasi-two-dimensional electron gas at the epitaxial alumina/SrTiO3 interface: Control of oxygen vacancies

“…3(b)), as described elsewhere. 35 As the two methods returned the same value, there is no band bending present. 40,41 Furthermore, the binding energy of the Al 2p core level (76 eV) and the shape of the alumina valence band indicate no sign of any Al suboxide.…”

“…More details of the experimental system can be found elsewhere. 35,36 All substrates were outgassed in the MBE chamber at 700 for 30 min under ultra-high vacuum (UHV) prior to alumina deposition. The substrate temperature was measured by a thermocouple (calibrated by pyrometer measurement of a silicon substrate) in close proximity to the substrate heater.…”

Electronic and optical properties of NbO2

“…Details are described elsewhere. 67 The resulting dielectric function for a 36.8 nm-thick film with a surface roughness of 0.6 nm (determined by atomic force microscopy) is shown in Fig. 7(c).…”