Effect of O2 addition to Ar plasma and growth temperature on the phase and optical properties of TiO2 thin films deposited by RF sputtering
Precise control of various structural phases of TiO2 at low temperature is particularly important for practical applications. In this work, the deposition conditions for the growth of anatase phase at room temperature (RT) were optimized. TiO2 films was deposited by RF sputtering of ceramic TiO2 target in argon and argon-oxygen plasma (20 % O2) at various substrate temperatures (Tsub = RT-400 °C). The plasma properties were investigated using optical emission spectroscopy (OES) while the structural, chemical and optical properties were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible-near infrared (UV-VIS-NIR) spectroscopy respectively. Anatase phase was successfully grown for the films deposited in Ar-O2 plasma over the whole range of temperature. The prepared films were transparent (∼ 85 %) and the calculated optical band gap was around 3.25 eV. Our results demonstrate that oxygen negative ions and surface energy conditions at the substrate are the key parameters controlling the phase and optical properties of the prepared films at low temperature.