Abstract: The Fe³⁺ doped TiO₂ oxygen sensitive thin films deposited on single crystal silicon substrates were prepared by a sol-gel method. The phase structure of the thin films was measured by X-ray
diffraction (XRD). The morphologies were observed by scanning electron microscope (SEM). The results showed that the anatase phase appeared with a small grain size dispersed homogeneously in the
thin film. The rutile phase appeared with a morphology of special clustered grains and large sizes in the thin film. It was exhibited evidently that the formation of the rutile phase in the thin film on a
single crystal substrate was dependent on Fe³⁺ doping in the system. The formation temperature was about 100℃ lower with 3mol% Fe³⁺ doped than that without Fe³⁺ doping.
The largest content of the rutile phase appeared in the thin film while Fe³⁺ doping of about 6mol%. In addition, the crystal lattice of both the anatas phase and the rutile phase decreased with the substitution
of a small size of Fe ions for a large size of Ti ions when doping Fe ions concentrantion below 6mol%. As Fe ions doped was above 6mol%, the c axis of the rutile phase increased while the c axis kept
almost constant with the increase of Fe and thus both oxygen vacancy and structure distortion increased. The oxygen sensitivity of Fe doped TiO₂ thin films was controled by the concentration of the oxygen
vacancies and the content of the rutile phase in TiO₂ thin films.The rutile phase and the sensitivity in the Fe doped TiO₂ thin film showed maximum while Fe doping was 6mol%, and its oxygen sensitivity
was 19 times more than that of the TiO₂ thin film with 3mol% Fe doped.

Key words: sol-gel, TiO₂ oxygen sensitive thin film, Fe doping, silicon substrate