Investigating the chemical and physical aspects: optical and electrical properties of TiO₂, TiO₂: Fe, and Fe/TiO₂ (111) through DFT analysis

The development of a thin film titanium dioxide (TiO2) depends on an understanding of complex electronic structure and charge transport properties. The utilization of simulation studies will help us understand the complicated system at the atomic level. Here, utilizing Hubbard's modified first-principles density functional theory (DFT + U), a theoretically created thin film TiO2 (111) interface model is provided. Generalized gradient approximation with Perdew-Burke-Ernzerhof assistance (GGA + PBE) was used to model structural properties, while Hubbard's modified (GGA + U) exchange correlation functional was used to simulate optoelectronic properties. The addition, i.e., doping and adsorption, of Fe to the TiO2 rutile (111) surface transfers its bandgap energy from 2.95 eV to a metallic nature, thereby enhancing its responsiveness to visible light by lowering the energy required for electron transitions. The enhanced visible light absorption and efficient charge separation worked together to significantly improve the hybrid photo catalyst's photocatalytic performance. The research utilized the DFT method along with the (GGA + U) technique to evaluate both the band structure and density of states (DOS). The analysis of the electronic structure shows that the band gap for the pristine but for the doped and adsorbed systems the nature of the materials changes to metallic. The DOS calculations indicate hybridization between O-orbitals and Fe-orbitals in the vicinity of the conduction band minimum for both channels due to the doped system, and for the maximum in the case of the adsorbed system, the impurity introduces an energy level that lowers the band gap. The research carried out computations to determine the band structure and density of states for (TiO2) doped with Fe and Fe-adsorbed. The results demonstrate that the doped and adsorption is considered to be a more advantageous approach than the pristine because of the maximum absorption in visible region. When the Fe atoms are adsorbed on TiO2 (111), there is a maximum increase in the adsorption energy. The study examines the photo activity mechanism by investigating the impact of Fe on the semiconductor's absorption edge. This type of semiconductor, with Fe adsorbed on TiO2 (111), has potential applications in the fields of photovoltaic, photocells, and electronics.