Transparent and Amorphous W-Ti-O Nano-Coatings

The present work was performed on the Ti-doping effects in a small and controlled amount into WO3 to produce W0.80Ti0.20O3. The aim of study is to explore the effect of Titanium (Ti) coupled with growth temperature on the growth of behavior, microstructure and optical properties. W0.80Ti0.20O3 coatings were fabricated using RF magnetron sputter-deposition onto Silicon (Si-100) wafers and optical quality Quartz substrates. The depositions were made in a wide temperature ranging from room temperature (25 ˚C) to 500 ˚C. X-ray diffraction (XRD), high-resolution scanning electron microscopy (SEM), Optical spectrophotometery and Spectroscopic Ellipsometry (SE) were performed to study the effect of temperature on the growth behavior, crystal structure, texturing, surface morphology, and optical properties of W0.80Ti0.20O3 films. The results show that the effect of temperature is significant on the growth and microstructure of W0.80Ti0.20O3 coatings. XRD results indicate that the W0.80Ti0.20O3 coatings grown in the entire range of temperatures are amorphous. SEM imaging analysis indicates that there is no distinct change in surface morphology. Optical band gap (Eg) is found to 3.1 eV. From SE analysis, thickness of the coatings was ~ 90-100 nm. The microstructure and optical constants of the grown films were evaluated using spectroscopic ellipsometry. The results indicate that the Ti-doped WO3 films are highly transparent and exhibit low optical losses in the visible and near infrared regions. The index of refraction increases from 2.17 to 2.31 with increasing growth temperature from 25 to 500 ºC. The increased packing density in the films with increasing temperature is attributed to the linear trend observed in index of refraction. The results suggest that tuning transparency and optical band gap can be achieved by controlling the Ti amount and growth temperature