TiOx-modified NiO thin films for H2 gas sensors: effects of TiOx-overlayer sputtering parameters

The sensitivity and selectivity of sputtered NiO thin films are found to be promoted by the addition of TiOx-overlayers. The sensing properties are strongly influenced by the sputtering parameters of the TiOx-overlayers. Among all studied films, the modified NiO thin films using TiOx-overlayers deposited in pure Ar gas with a sputtering power density of 1.59 W/cm2 have the best properties for H2 detection. The cross-sensitivity to other gases such as NO2 and NH3 is comparatively small. The response and recovery times of the sensor depend on operating temperature and gas concentrations. The sensor electrical response follows a power law behavior Rg=Ra(PH2)β with the coefficient β≈1.0.