Nanocrystalline TiO/sub 2/ thin films for O/sub 2/ gas sensing

Titanium dioxide (TiO/sub 2/) thin films have been prepared using a nanosized TiO/sub 2/ suspension and a spin-coating process. The morphology, microstructure, crystalline structure and chemical composition of the TiO/sub 2/ thin films have been investigated using SEM, XRD, and RBS. SEM analysis showed that the films are smooth and uniform with an average particle size of 25 nm. The crystal structure of the films is a mixture of 70% anatase and 30% rutile phases. RBS characterisation has revealed that the film is sub-stoichiometric TiO/sub 2-n/. The variation of electrical resistance of the thin films has been examined at different oxygen concentrations from 1 ppm to 1%. The response of the sensor to 100 ppm, 1000 ppm, and 1% O/sub 2/ gas is 1.4, 2.4, and 4.9, respectively. The response and recovery times (t/sub 0.90%/) are about 2 minutes.