Nanostructured TiO2 films: Enhanced NH3 detection at room temperature

The influence of substrate bias on the ammonia (NH3) sensing properties of reactive dc magnetron sputtered titanium dioxide (TiO2) films has been investigated. The films deposited at floating potential and −100 V substrate bias exhibited a mixed phase (anatase and rutile) as analysed by X-ray diffraction (XRD) while the films deposited at −200 V substrate bias had only rutile phase. On increasing the substrate bias voltage the grain size increased from 15 to 31 nm and the optical band gap value decreased. The TiO2 films had an enhanced response towards NH3 in the concentration range 5−100 ppm at room temperature. The enhanced performances are correlated to the high surface-to-bulk ratio and crystal structure. The TiO2 film deposited at lower bias has enhanced sensitivity of (S-7857) towards NH3 at room temperature with quick response and recovery time.