Hydrogen sensing by sol-gel grown NiO and NiO:Li thin films

Hydrogen sensors have been prepared using nickel oxide (NiO) and lithium-doped nickel oxide (NiO:Li) thin films, deposited on glass substrates by the sol-gel spin coating technique. The surface morphology, structure, optical and electrical properties of the obtained films were studied. Hydrogen sensing results are presented for three operating temperatures (140, 160, and 180 {\deg}C) and for hydrogen concentrations ranging from 1000 to 15000 ppm in synthetic air. The NiO and NiO:Li (2% and 8% doping concentrations) sensors show maximum responses for the operating temperature of 180 {\deg}C. When tested at different hydrogen concentrations in air, the lithium-doped NiO sensors showed a higher response than the undoped NiO films.