Synthesis and Characterization of Al2O3 doped TiO2 Thin Films Prepared by Pulsed Laser Deposition Technique

Abstract

In this study, nanostructured titanium dioxide (TiO₂) thin films were synthesized on glass substrates using the Pulsed Laser Deposition (PLD) technique (utilizing a Nd: YAG laser). The impact of aluminum oxide (Al₂O₃) doping at various concentrations (0, 1, 3, 5 wt%) on the structural and optical properties was systematically investigated. X-ray Diffraction (XRD) analysis confirmed the formation of a polycrystalline tetragonal structure for all samples. It was observed that the average crystallite size decreased with higher doping levels, correlating with an increase in the Full Width at Half Maximum (FWHM) and lattice strain. Optical characterization revealed that the optical transmittance decreases as the Al₂O₃ content increases. The pure TiO₂ film exhibited the lowest absorbance in the UV region, whereas doped films showed enhanced absorption in the visible (VIS) spectrum. Notably, the optical energy gap (E g) significantly narrowed from 3.78 eV for the pure film to 2.98 eV at 5% doping, attributed to the introduction of new localized states within the band gap. Furthermore, an increase in the refractive index and both the real and imaginary parts of the dielectric constants was observed in tandem with the doping ratio in the visible range.