Surface modification nanoporous titanium oxide films using continuous wave CO2 laser

Abstract

This study investigated the characteristics of titanium dioxide (TiO2) films modified through laser annealing by using a CO2 laser source (CSS 500 AIR, Spectral Inc., Italy) with a wavelength of 10,600 nm and a continuous wave mode. Commercial TiO2 thin films with a thickness of 100 nm were prepared through radio-frequency magnetron sputtering on soda-lime glass substrates. The optical properties (optical absorption and transmittance spectra), surface morphology, and surface chemical composition characteristics of the TiO2 films depended on the laser irradiation conditions. The characteristics of the films were systematically analyzed using a ultraviolet–visible near-infrared spectrophotometer, an X-ray photoelectron spectroscope, and a field emission scanning electron microscope. The experimental results demonstrated that the experimental transmittance spectra exhibited slight changes caused by laser annealing and a maximum transmittance in the visible region of approximately 91.4 %. The absorbance of all annealed TiO2 films exceeded that of as-deposited films. Moreover, the absorption band edge moved toward the long-wavelength side (red shift) as the annealing speed decreased because the heat applied during annealing caused the TiO2 film grains to grow. Diffusion and mobility between the films and glass substrates during laser annealing segregated elemental Ag.