Comparative study of spin-coated and vapour deposited nickel oxides for detecting VOCs

Nickel oxide (p-type) sensors are developed to detect volatile organic compounds (VOCs). In the presented work, NiO sensors are fabricated and tested towards acetone, ethanol, toluene, hexane, methanol, and n-propanol vapours between 5 to 25 parts-per-million concentrations, under both dry and humid conditions. NiO films are deposited onto alumina substrates using both spin-coating (SC) and vapour deposition (AACVD) methods. The measured thickness of the spin coated and AACVD NiO films are approximately comparable at 10.3 μm and 6.7 μm, respectively. Both SC and AACVD sensors showed a maximum response at 350°C. No significant influence of humidity was observed on sensor response and baseline resistance for either SC or AACVD sensors. The sensitivity is found to be highest for ethanol, acetone, and methanol vapours than the rest.