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Microscopic study of TiO2 nanostructures formed by electrochemical method

TiO2 as the material exhibits properties that allow its use in various applications such as photocatalysts, solar cells, gas sensors, and biomedical applications. The typical organic solar cells are produced on transparent conductive layers covered with nanostructured TiO2. The surface roughness is one of the key parameters for high efficiency. In that sense the nanotube arrays offer numerous advantages. The initial Ti films were deposited by evaporation (Fig 1) or magnetron sputtering. By variation of deposition conditions, different crystal sizes, orientation and grain sizes were obtained. TiO2 nanostructures were formed by anodic oxidation on Ti substrates in ethylene glycol based electrolytes. Anodization parameters (anodization time, applied voltage, amount of added water and ammonium fluoride), were varied during preparation of TiO2 nanostructures. As-prepared TiO2 films were amorphous, while polycrystalline TiO2 anatase phase was obtained after heat treatment. The film structure and crystallinity, before and after annealing, were studied by Raman spectroscopy and grazing incidence X-ray diffraction. Scanning electron microscopy was used to determine the morphologies of prepared anodic films. The diameter, shape and density of the nanostructures were correlated with the processes parameters. The results indicate that geometric characteristics and morphology of prepared TiO2 critically depend on initial Ti crystal grains sizes as well as anodization conditions (Fig 2).

TiO2 nanotubes ; FEG-SEM ; anodization

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