The effect of Nb doping on hydrogen gas sensing properties of capacitor-like Pt/Nb-TiO2/Pt hydrogen gas sensors

Hydrogen gas sensors with capacitor-like Pt/Nb-TiO2/Pt structure and various amount of Nb doping were successfully prepared by magnetron sputtering and lift-off photolithography. The Nb incorporation in the TiO2 layer has been confirmed by XPS and GIXRD measurements. It has been shown that the Nb doping delays the anatase to rutile phase transformation during annealing and according to the AFM measurements it also improves the homogeneity of the sensing films. However, unexpectedly the response of the sensors with Nb doped TiO2 film is lower compare to the undoped Pt/TiO2/Pt sensors, which exhibit highest response (2.08 x 10(4)) and shorter response time (49.4 s) to 1000 ppm hydrogen at 100 degrees C. This can be partially explained by the intrinsic characteristics (lower surface roughness and porosity) of Nb doped TiO2 films, which resulting in smaller active surface and lower diffusion of the oxygen and hydrogen gases into the films. Although the Nb doping did not improve the sensing performance, this study can be also useful for the future research on the capacitor-like metal oxide gas sensor. (C) 2019 Elsevier B.V. All rights reserved.