Physical characterization of Nickel-doped zinc oxide thin solid films deposited by the ultrasonic chemically sprayed technique: Gas-sensing performance in a propane atmosphere

Nickel doped by zinc oxide [ZnO:Ni] thin films have been deposited at different temperatures on soda-lime glass substrates by the ultrasonic spray pyrolysis technique. Selected starting reactants were zinc acetylacetonate and nickel acetylacetonate. The thin solid films were polycrystalline, fitting all well with the ZnO wurtzite type structure, with (002) preferential orientation that show a (101) switching for high substrate temperatures. The morphology studies showed that ZnO:Ni thin films were formed of nanostructured thin slices with hexagonal-shape geometry, irrespective of the substrate temperature. Band gap values ranging from 3.3 to 3.4 eV were estimated. Gas sensing characteristics of ZnO:Ni thin films, in propane gas, were analyzed at different gas concentration as well as different operating temperatures. Variation in the resistance of ZnO:Ni thin films started from an operation temperature of 100 °C, increasing up to 4 magnitude orders at 300 °C. The results that we obtained showed potential applications of ZnO:Ni as reliable gas sensors.