Features of Hydrothermal Growth of Hierarchical Co3O4 Coatings on Al2O3 Substrates

The formation of a hierarchical cobalt(II, III) oxide coating on the surface of a polycrystalline Al 2 O 3 substrate under hydrothermal conditions was studied. Features of the microstructure of the obtained coatings were investigated by scanning electron microscopy; these coatings were shown to consist of Co 3 O 4 nanosheets arranged perpendicular to the surface of the substrate with a blossoming flower-like structure. The production of the coating of the desired composition without crystalline impurities was confirmed by IR spectroscopy, X-ray powder diffraction analysis, and energy dispersive spectroscopy elemental analysis. The roughness of the formed Co 3 O 4 film was estimated by atomic force microscopy. The local electrophysical characteristics of the produced oxide coating (work function of film surface, capacitance, and surface distribution maps of surface potential and capacitance contrast) were studied by scanning capacitance microscopy and Kelvin probe force microscopy. A local analysis of the current–voltage characteristics of the studied samples was made.