Physical properties of nanostructured TiO2 thin films grown by RF magnetron sputtering: Impact of substrate type

Abstract

Titanium dioxide (TiO2) thin films were successfully prepared on three different substrates (glass, quartz and silicon
(Si(100)) at room temperature with a deposition time of 90 min using RF magnetron sputtering technique. The TiO2 thin
films are then air-annealed at 400°C for one hour and the effect of the substrate type on the microstructure, morphology,
surface topography, transmittance and optical band gap of these films was investigated by X-ray diffraction (XRD), Raman
spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM) and UV-Visible (UV-Vis)
spectrophotometry. XRD analysis showed that all thin films are polycrystalline and crystallize only in the tetragonal anatase
structure of TiO2 with a preferential orientation along the (101) plane. The crystallinity, peak intensity, and crystallite growth
are found to be substrate type dependent. The observed Raman peaks confirmed the presence of anatase phase in all
samples in good agreement with XRD data. SEM and AFM images revealed that TiO2 thin films exhibit a different surface
topography, which seems to be influenced by the substrate type, as expressed in terms of average grain size and surface
roughness. Transmittance spectra put into evidence that the TiO2 thin film grown on quartz demonstrated a higher average
transmission in the visible region than that deposited on glass substrate. Moreover, the obtained values of band gap and
refractive index for TiO2 thin films deposited on glass and quartz substrates were found to be 3.615 and 3.512 eV,
and 2.248 and 2.271, respectively