2000-eV argon ion beam induced formation of multiple chemical states in titanium dioxide mesoporous film

Oxygen vacancies were created on the surface of TiO₂ mesoporous film after exposure to a 2000 eV argon ion beam. Confirmation of the presence of the vacancies was conducted through x-ray photoelectron spectroscopy analysis which reveals Ti 2p, O 1s, C 1s, and Ar 2p chemical states at different binding energies. Ti 2p spectra show five distinct peaks corresponding to Ti²⁺ 2p_1/2, Ti³⁺ 2p_3/2, Ti⁴⁺ 2p_3/2, Ti³⁺ 2p_1/2, and Ti⁴⁺ 2p_1/2 states while the Ti⁴⁺ continuously reduced to Ti³⁺ and Ti²⁺ as the irradiation time of Ar⁺ increases. The Ar⁺ irradiation leads to the lower binding energy of the Ti 2p state with an increase in irradiation time while the binding energy of O 1s becomes higher with irradiation time. The peaks correspond to lattice oxygen; oxygen vacancy and adsorbed oxygen were observed in high-resolution O 1s spectra while the peak area ratio of oxygen vacancy with lattice oxygen increases with irradiation time. The atomic percentage of C 1s decreases with irradiation time while that of Ti 2p, O 1s, and Ar 2p increases with irradiation time. An increase in irradiation time leads to insignificantly shifting of the valence band edge towards the conduction band. The observed response of the prepared nano-particle TiO₂ after 2000 eV Ar⁺ exposure which conveniently creates oxygen vacancies in the crystallographic structure of the semiconductor could be a versatile approach to enhancing the photocatalytic activity of the semiconductor for various industrial and technological applications.