268 ISSN 1063-7826, Semiconductors, 2020, Vol. 54, No. 2, pp. 268–273. © Pleiades Publishing, Ltd., 2020. Investigation of the Influences of Post-Thermal Annealing on Physical Properties of TiO 2 Thin Films Deposited by RF Sputtering H. E. Doghmane a , T. Touam a,b, *, A. Chelouche c , F. Challali d , and B. Bordji e a Laboratory of Semiconductors, University of Badji Mokhtar-Annaba, BP 12, Annaba, 23000 Algeria b Research Unit in Optics and Photonics (UROP), Centre for Development of Advanced Technologies (CDTA), University of Sétif 1, Sétif, 19000 Algeria c Laboratory of Environmental Engineering, University of Bejaia, Bejaia, 06000 Algeria d Laboratory of Sciences of Processes and Materials (LSPM), CNRS-UPR 3407, Paris 13 University, Villetaneuse, 93430 France e Laboratory of Materials and Structure of Electromechanical Systems and Their Reliability, Larbi Ben M’Hidi University, Oum El Bouaghi, 04000 Algeria *e-mail: touamt@gmail.com Received May 9, 2019; revised October 9, 2019; accepted October 9, 2019 Abstract—For this study, titanium dioxide (TiO 2 ) thin films were deposited on glass substrates at room tem- perature by the RF magnetron sputtering technique. The preparation parameters that offer better control and reproducibility of film fabrication were first optimized. Then, the effects of post-deposition annealing tem- perature at 350, 450, and 550°C on the microstructure, surface morphology, and optical properties of the pre- pared films were investigated using X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), atomic force microscopy (AFM), and UV–Visible (UV–Vis) spectrophotometry. Inter- estingly, XRD analysis shows that as-deposited and annealed TiO 2 film possess anatase crystal structure only with a preferential orientation along the (101) plane. The intensity of the (101) diffraction peak and crystallite size are found to increase with increasing annealing temperature, which indicates an improvement in the crystallinity of the films. Raman spectra confirm that all samples possess anatase phase and the crystallinity is enhanced with increasing thermal annealing. From the analysis of SEM and AFM images, it is revealed that the heat treatment significantly affects the morphology, grain size, and surface roughness of the TiO 2 films. The UV–Vis spectroscopy analysis shows that as-deposited TiO 2 thin film is highly transparent in the visible region with an average transmittance about 84%, whereas the transmission decreases slightly with an increase in annealing temperature. Moreover, the optical band gap energy shows a red shift with increasing the annealing temperature. Keywords: TiO 2 thin films, RF sputtering, annealing temperature, structure and morphology, optoelectronic applications DOI: 10.1134/S1063782620020086 1. INTRODUCTION Over the last few decades, metal oxide semicon- ductors have drawn tremendous attentions. Among them, titanium dioxide (TiO 2 ) has emerged as one of the most promising materials due to its outstanding chemical, electrical, and optical properties, such as non-toxicity, good chemical stability, excellent mechanical durability, wide band gap, high refractive index, and high transparency over a broad wavelength range including the visible and near-infrared. With such properties, TiO 2 has been considered for various applications such as solar cells [1], photonic sensors [2], antireflective coating [3], optoelectronics [4], photovoltaics [5], and microphotonic devices [6]. Various deposition techniques, including chemical and physical processes have been developed to pro- duce TiO 2 thin films, such as chemical spray pyrolysis [7], sol–gel process [8], electron-beam evaporation [9], atomic layer deposition [10], pulsed laser deposi- tion [11], and direct current (DC) and radio frequency (RF) magnetron sputtering [12, 13]. Among all these methods, the RF magnetron sputtering technique has attracted a great attention due to its efficiency and high deposition rates. In addition, this method produces at low substrate temperature uniform and dense TiO 2 thin films with well-controlled stoichiometry and high adhesion on large area of diverse type of substrates. Numerous investigations have been reported on the characterization of structural, morphological, and optical properties of sputtered TiO 2 thin films with various deposition parameters [14–21]. These studies showed that the properties of TiO 2 films strongly FABRICATION, TREATMENT, AND TESTING OF MATERIALS AND STRUCTURES