Studies On Hydrophilicity Property Of N-TiO₂ And Al/N-TiO₂ Films Prepared By Magnetron Sputtering

TiO₂ involves a unique aspect of photo-induced hydrophilicity with a water contact angle of 0o. This phenomenon has been applied to various items, such as self-cleaning tites and anti-fogging mirror. Recent investigations have focussed on the improvement of hydrophilic property of TiO₂ under visible light. The aim of this investigation is to explore N-TiO₂ and Al/N-TiO₂ films with excellent hydrophilic property prepared by magnetron sputtering. The followings are included in this work:(1) N-TiO₂ film was prepared by RF reaction magnetron sputtering, using TiN target, with O2 and Ar as sputtering gas. XRD, SEM, XPS, UV-Vis absorption, CA test(contact angle) measurements were used to analysis structure and properties of the N-TiO₂ film.The results indicate that: the N-TiO₂ film exhibits excellent optical and hydrophilic property; the improvement of optical property and hydrophilic property should be enhanced by nitrogen substitution at oxygen sites, forming Ti-N bond and leading to more oxygen vacancies.(2) Al/N-TiO₂ film was prepared by DC reaction magnetron sputtering, using Al/Ti target, with O2, N2 and Ar as sputtering gas. The effect of Al and N dopant on the structure and properties of TiO₂ film were studied by means of XRD, SEM, XPS, PL(photoluminescence), UV-Vis absorption and CA test. The results show that:(a) The lattice bulk of TiO₂ increases with Al dopant, while decreases with N dopant; lattice bulk of Al/N-TiO₂ is between Al-TiO₂ and N-TiO₂;(b) The surface morphologies of TiO₂ film were effected by Al and N dopant: both Al and N suppress particle growth; the surface of TiO₂ film becomes smoother and compacter with Al dopant, while becomes looser and rougher with N dopant. Al/N- TiO₂ film exhibits looser and rougher surface compared to pure TiO₂ film;(c) In the crystal lattice of TiO₂, Al is at Ti site, N is at O site, which generate additional oxygen vacancies;(d) The absorption edges of TiO₂ films show a red shift with Al and N dopant. The absorption edges decrease in the order of Al/N-TiO2 > N-TiO2 > Al-TiO2 > TiO2.(e) The hydrophilicity of the Al/N-TiO2 is superior to the pure TiO2, Al-TiO2 and N-TiO2. This may be ascribed to more oxygen vacancies produced by Al, N codoping.