Spectral Decomposition Of Raman Spectra Of Mixed-Phase Tio2 Thin Films On Si And Silicate Substrates

We present a method to fit Raman spectra of TiO2 thin films on silicon wafers, fused silica, and crown glass with adjustable model spectra of the different components of the substrate and the thin film. With reasonable restrictions of the fitting parameters, the method developed in this paper allows a simultaneous fit to the measured spectra. The TiO2 thin film spectrum is split into one spectrum for the amorphous phase and spectra for each crystalline phase (anatase, rutile, and brookite) being divided into first-order scattering and a phase background (including second-order scattering). Moreover, if the substrate is luminescent, the substrate spectrum is split into luminescence and Raman spectra. All decisions on parameters are made by the fitting procedure within a simultaneous fit of a series of spectral models to the observed Raman spectrum. The main strategies for preparing such models are pointed out in a way that they should be applicable to other materials. TiO2 is a promising and flexible material for photocatalytic applications with rapidly growing interest in mixed-phase TiO2 as nanostructured material or thin film. For the analysis of such films, it is important to differentiate the signals of the various phases and to distinguish between signals from the substrate and the film. This provides a means to improve the quantitative evaluation of Raman spectra.