Influence of Thermal Annealing to Material Properties of TiO₂, ZnO, and TiO₂/ZnO Bilayer Films by Sol-Gel Method

This study reported on the material properties of TiO₂, ZnO, and TiO₂/ZnO bilayer thin films fabricated by sol-gel spin coating technique after annealing. ZnO thin films were prepared by dissolving zinc acetate dehydrated into a solvent of ethanol and diethanolamine (DEA) was later added. Meanwhile, for TiO₂ films, titanium tetraisopropoxide (TTIP) was dissolved into ethanol and an acetate acid was added. Afterwards all film samples were annealed at different temperatures in the range of 400 – 600℃ for 60 minutes. For TiO₂/ZnO bilayer thin films, the structural properties showed that after annealing at 600℃, the XRD peak intensity was more pronounced compared to at 400 and 500℃. This indicated that the amorphous phase of the films decreased after annealing at 600℃. Furthermore, the crystallite sizes of the films increase as the annealing temperature increased to 600℃, while the strain reduces at this temperature. In the case of (UV-Vis) spectroscopy, it was seen that after annealing the transmittance value of the TiO₂/ZnO bilayer increase. The band gap energy of the films consists of low and high energy. The low energy which is around 3.30 eV refers to the transitions of valence conduction band in ZnO films and high energy was around 3.60 eV corresponding to the impurity transitions. In addition, the refractive index (n), the extinction coefficient (k), and the real and imaginary part of dielectric constant were determined from the transmittance and absorbance spectra results. Based on the SEM results indicate that there was no cluster in the surface of TiO₂/ZnO bilayer thin films. (author)