Effect of thermal annealing on the structural and optical properties of TiO2 nanostructures

In this work, TiO nanostructure films were deposited via vacuum thermal evaporation at a temperature of 80 degrees C. The TiO thin films were annealed under vacuum for 1 h at three different degrees (200, 300, and 400 degrees C) in addition to the thin film prepared at 80 degrees C. X-ray Diffraction (XRD) showed that all the deposited and annealed TiO films had anatase polycrystalline diffraction patterns with a predominant reflection of the (200) plane. As a result, the particle size increased with annealing temperature. Scanning Electron Microscopy (SEM) measurements showed that at the annealed temperature of 200 degrees C, the shape of the TiO nanostructures began to change from a condensed cluster distribution to a conical shape. As the annealing temperature was increased to 400 degrees C, all the conical shapes transformed into clear spherical shapes. The spherical shapes recorded 45 (nm) height and (20) (nm) base width. Optical measurements were performed using Ultraviolet-Visible spectroscopy (UV-Vis). The transmittance is reduced from 79.63% for the TiO sample prepared at 80 degrees C to 71.91% for the TiO sample annealed at 400 degrees C. The optical energy gap values decrease from 3.279 eV for the prepared TiO sample at 80 degrees C to 3.115 eV for the TiO sample annealed at 400 degrees C.