International Journal of Scientific Research and Engineering Development

The increasing demand for high-efficiency solar cells has highlighted titanium dioxide (TiO₂) thin films as a promising material for emerging photovoltaic technologies. In this study, TiO₂ thin films were deposited on silicon substrates using the sol-gel spin-coating technique, with hydrochloric acid (HCl) concentrations varied from 1 to 5 mL in the precursor solution. The films were subsequently annealed at 200°C and 500°C to investigate structural, optical, and morphological changes. Raman spectroscopy revealed a characteristic TiO₂ peak at 513 cm⁻¹ after annealing at 500°C, confirming recrystallization. XRD analysis identified anatase and rutile phases at 2θ = 33° (110) and 62° (204), respectively, with crystallite sizes increasing from 51.13 nm at 200°C to 58.55 nm at 500°C. FTIR spectra showed Ti-O stretching bands near 600 and 750 cm⁻¹ for all samples. Surface analysis indicated improved homogeneity and increased roughness (up to 0.45 µm) with higher HCl volume at 500°C. UV-vis measurements demonstrated a reduction in direct band gap energy to 2.25-2.30 eV at 500°C. Ellipsometry results showed a decrease in film thickness with increasing HCl concentration, though overall thickness increased to approximately 3.3 nm at 500°C. The dielectric constant rose to values between 3 and 4, while the refractive index decreased from 3.7 to 3.3 with higher annealing temperature. These findings demonstrate the significant impact of acid concentration and thermal treatment on the properties of TiO₂ thin films, underscoring their strong potential for next-generation photovoltaic applications.