Radio Frequency Magnetron Sputtering Growth of Titanium Dioxide Thin Films: Effects of Substrate Temperature on Microstructural and Optical Properties

Abstract

Titanium dioxide thin films were deposited by radio frequency sputtering on glass substrates at different substrate temperatures. Hence, we first optimized the preparation conditions and parameters which offer better control and reproducibility of film fabrication. Then, we investigate the structural, morphological and optical properties of the prepared titanium dioxide thin films. To do so, we used several characterization techniques: X-ray diffraction, Raman spectroscopy, scanning electron microscopy, atomic force microscopy and ultraviolet-visible spectroscopy. Interesting results were obtained, e.g. X-ray diffraction analysis shows that the films crystallize only in the anatase tetragonal structure with a preferential orientation along the (101) plane. The intensity of the (101) diffraction peak and the crystallite size are found to increase with increasing substrate temperature, indicating a crystallinity improvement of the films. Raman peaks observed around 144, 197, 399, 515 and 639 cm−1 confirm that all samples possess anatase phase and the crystallinity is enhanced with increasing substrate temperatures. The analysis of scanning electron microscopy and atomic force microscopy images demonstrates that increasing the substrate temperature significantly affects the morphology, grain size and surface roughness of TiO2 films. The ultraviolet-visible spectroscopy analysis put into evidence that the film deposited at RT is highly transparent in the visible region with average transmittance greater than 84%. Higher substrate temperatures result in a slight decrease of transmittance. Moreover, the direct optical band gap decreases while the refractive index increases with increasing the substrate temperature. Thus, the obtained results reveal that ultraviolet-visible can be considered as a potential material for optical and photovoltaic applications.