Surface Wettability of Nitrogen-Doped TiO₂ Films Prepared by Atomic Layer Deposition Using NH₄OH as the Doping Source

Undoped and N-doped TiO₂ films were successfully deposited by atomic layer deposition on planar silicon substrates using TDMAT and NH₄OH as precursors. The nitrogen concentrations in the films were varied by using different concentrations of NH₄OH solution, which was used as a source of both oxygen and nitrogen dopants for the preparation of N-doped TiO₂. The surface wettability properties of the N-doped TiO₂ films were examined as a function of the incorporated nitrogen concentration. A change in the wettability of the oxide surface was observed when the N-doped TiO₂ film surfaces were exposed to UV light. The surface wettability investigations showed that the N-doped TiO₂ films exhibited superhydrophilicity under UV irradiation. The contact angles of all the TiO₂ thin films decreased to values less than 20° under UV irradiation, indicating that the surfaces became more hydrophilic. This behavior is attributed to the photo-generation of electrons and holes on the surface of the N-doped TiO₂ films during UV irradiation.