Tuning the oxidation state of titanium dioxide mesoporous film by 1000 eV argon ion beam irradiation

Abstract

This work proposes the creation of oxygen vacancies on the surface of TiO2 mesoporous film using a 1000 eV argon ion (Ar+) beam. After X-ray photoelectron spectroscopic characterization, the survey spectra of TiO2 nano-particles reveal the presence of oxygen (with chemical state O 1s), titanium (with chemical state Ti 2p), carbon (with chemical state C 1s) and argon (with chemical state Ar 2p) while the concentrations of each chemical states vary with an irradiation time of the Ar+ beam. The acquired Ti 2p spectra show five peaks at high resolution which correspond to Ti4+ 2p3/2, Ti4+ 2p1/2, Ti3+ 2p3/2, Ti3+ 2p1/2, and Ti2+ 2p1/2. The concentrations of Ti2+ and Ti3+ increase with irradiation time while the concentrations of Ti4+ decrease as the irradiation time increases. Three peaks characterize high-resolution spectra of O 1s which correspond to lattice oxygen, oxygen vacancy, and adsorbed oxygen. The peak area of lattice oxygen decreases with irradiation time while that of oxygen vacancies increases with irradiation time which shows the creation of oxygen vacancies at the expense of contaminant removal due to Ar+ exposure. Valence spectra analysis shows an insignificant effect on the valance band as the sample exposure to Ar+ increases. This proposed method of oxygen vacancy creation would facilitate the effective utilization of TiO2-based semiconductors in addressing many photo-catalytic challenges and widening the sunlight absorption capacity of the semiconductor.