Morphology and Optical Properties of TiO2 Thin Films Acquired by Sol–gel Spin Coating Method Using Titanium (IV) Butoxide

Abstract

Titanium dioxide (TiO₂) is widely recognized for its excellent electronic properties, particularly in gas-sensing applications. However, its large optical band gap limits electron transitions between the valence and conduction bands, restricting its full potential. This study investigates the fabrication of TiO₂ thin films using the sol-gel spin-coating method, with varying concentrations of titanium (IV) butoxide: 1.0 ml, 1.5 ml, and 2.0 ml. The primary objective is to optimise the concentration and analyse its impact on the films', morphological, topography and optical properties. To achieve this, the films were characterised using Field Emission Scanning Electron Microscopy (FE-SEM) and Atomic Force Microscopy (AFM) to evaluate surface morphology, cross-sectional structure, grain size, and roughness. The optimised concentration of 2.0 ml titanium (IV) butoxide produced films with a uniform coating, enhanced by solution ageing and controlled annealing temperature. FE-SEM images revealed a combination of nano-sized and micro-sized particles, with an increase in grain size correlating to pile-up at grain boundaries and an increase in roughness (3.914 nm). Additionally, UV spectroscopy analysis showed a reduced optical band gap of 3.20 eV and high transmittance. These results suggest that TiO₂ thin films, with their promising electronic and optical properties, hold significant potential for applications in gas sensors and solar cells.