Observation of carbon-facilitated phase transformation of titanium dioxide forming mixed-phase titania by confocal Raman microscopy



Confocal Raman microscopy, a relatively new and advanced technique, is found to be suitable for imaging the chemical morphology below the submicrometer scale. It has been employed to probe the phase transformation of carbon-containing titania (TiO2) nanopowder and titania thin film subjected to laser annealing. The observation of phase transformation from the anatase phase to the rutile phase at high laser power annealing is attributed to carbon inclusion inside or on the surface of titania. Upon annealing, carbon could react with the oxygen of titania and create oxygen vacancies favoring the transformation from the anatase to the rutile phase. This study provides evidence for the carbon-assisted phase transformation for creating carbon-containing mixed-phase titanium dioxide by laser annealing. We explicitly focus on the presence of carbon in the phase transformation of TiO2 using confocal Raman microscopy. In all of the investigated samples, mixed anatase/rutile phases with carbon specifically was found at the rutile site. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) studies have been performed in addition to Raman mapping to verify the mixed-phase titania formation. Copyright © 2010 John Wiley & Sons, Ltd.