*3.4. Crystalline Phase Identification of TiO2 Thin Films*

A typical XRD diffraction pattern of the TiO2 thin films deposited on F:SnO2 coated glass substrate is shown in Figure 5. The thin films deposited were thinner than the F:SnO2 layer (~400 nm) so breakthrough to the substrate was observed for all samples. The samples showed peaks representing a mixture of anatase, the preferred crystal phase in the [101] plane, as well as rutile, which is the more thermodynamically stable phase and was present in the [211] plane. The presence of the brookite phase was also observed in the [121], [221] and [203] planes. This mixture of phases is commonly observed in the production of TiO2 derived thin films [2,8], and it is believed that the sol-gel method described herein has resulted in the production of largely amorphous TiO2 thin films which cannot be detected by XRD. For further determination of the TiO2 phase, Raman spectroscopy was used, whereby a typical spectrum is shown in Figure 6. All samples gave strong Raman bands centred at 147, 395, 513 and 642 cm<sup>í</sup><sup>1</sup> , with a weaker band centred at 198 cm<sup>í</sup><sup>1</sup> , all of which are attributable to anatase titanium dioxide indicating that whilst there is poor long range order, anatase predominates over a short range [23].

**Figure 5.** XRD pattern for sample B (3 layers) produced with 6 × 10<sup>í</sup><sup>4</sup> mol·dm<sup>í</sup><sup>3</sup> Tween® 40 surfactant and annealed at 500 °C/ 15min. Red assigned peak denotes presence of anatase in the [101] plane. Blue peaks denote presence of brookite, and black peak denotes presence of rutile. Peaks denoted with an asterisk are from the casserite substrate. This diffraction pattern was the same for samples A, C, D and E.

**Figure 6.** Typical Raman spectrum obtained for all samples. This spectra was for sample B3 annealed at 500 °C for 15 min. Peaks match the reference spectra for TiO2 anatase [23].
