Hydrogen sensor of Pd-decorated tubular TiO2 layer prepared by anodization with patterned electrodes on SiO2/Si substrate

This study demonstrated a highly sensitive hydrogen sensor consisting of Pd-decorated TiO2 tubular structures on SiO2/Si substrate. Ti layer was deposited on a thermally oxidized Si substrate with patterned metal electrodes. TiO2 nanotubes were prepared by an anodization of Ti layer in an organic electrolyte containing NH4F 0.3 wt.% in ethylene glycol. Thin Pd layer was deposited on the detection area of the TiO2 layer to enhance detection abilities. The formation of the TiO2 layers on both the metal electrode and SiO2 layers was investigated by FESEM and EDS. After annealing at 500 °C, the crystalline phase transformation from amorphous to anatase was confirmed by XRD. The hydrogen sensing properties of the sensor were investigated in synthetic air, nitrogen and humid air at 140-180 °C. The Pd deposition effectively improved the hydrogen sensing abilities of the sensor due to catalytic effect of Pd. The sensor showed promising hydrogen sensing characteristics, such as a high response, a wide detection range (1 ppm-1%), a fast reaction time and a good selectivity. This sensor fabrication process can offer feasibility for mass production of micro scaled sensors using anodically prepared TiO2 sensors.