engleski

Transmission electron microscopy studies of nanostructured TiO2 films on different substrates

A chemical vapour deposition (CVD) synthetic route to nanocrystalline titanium dioxide has been carefully investigated on different substrates. CVD was performed at low temperatures of 320 0C onto KCl crystal, Al foil, KBr pellet and freshly sliced mica. Films of approximately 1 mm thickness were obtained from 1M solution of TiCl4 in dichloromethane (Aldrich). Influence of the substrate to the crystallographic orientation and morphology of the films, regarding the substrate was studied by analytical electron microscopy techniques including bright-field (BF), dark-field (DF), selected area electron diffraction (SAED), high-resolution transmission electron microscopy (HRTEM) and energy dispersive spectroscopy (EDS). Investigations were carried out by using a JEOL JEM 2010 200 kV and a Morgagni FP 5005 microscope. Bright-field (BF) images of TiO2 samples prepared on different substrates obtained by Morgagni microscope have shown a large number of grains which are differently oriented regarding incoming electron beam and indicated different morphology of each sample. The difference in morphology regarding different substrate was confirmed by JEOL microscope. The average grain sizes were determined from DF images of HRTEM. Table I is showing that different substrates influenced average grain sizes of nanostructured films. The average grain sizes are increasing as the substrate changed from KCl to Al to KBr and finally to mica. The nano-grains in TiO2 films deposited onto KCl crystal, KBr pellet and freshly sliced mica are of irregular shape, while they are spherical in the film deposited onto Al foil.

titanium dioxide; aaverage grain size; chemical vapour deposition; transmission electron microscopy; rietveld refinement

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