Gas sensing properties of p-type semiconducting Cr-doped TiO2 thin films

Cr2O3-TiO2 thin films were prepared from the sol-gel process. Titanium butoxide was used as the precursor material. The solution was mixed with a chromium compound then spun onto sapphire and silicon substrates at 2500 rpm for 30 s. The films were annealied at temperatures of between 400 and 700 °C for 1 h. The X-ray diffraction (XRD), scanning electronic microscope (SEM), Rutherford backscatter spectrometry (RBS) and X-ray photoelectron spectroscopy (XPS) techniques were employed for microstructural characterazations. The responses to both NO2 and O2 gases confirmed that the films are of a p-type behaviour at operating temperatures between 350 and 400 °C. The films showed a good response to oxygen, in the range from 100 ppm to 10% of O2 at an operating temperature of 370 °C. The response is also fast and stable. The p-type Cr-doped TiO2 thin films have potential for development of a novel gas sensors.