Preparation of nanocrystalline nickel oxide thin films by sol-gel process for hydrogen sensor applications

► We fabricate thin films of NiO by a sol-gel coating method. ► We characterize films at different calcination temperatures and substrate materials. ► Gas sensing characteristics are measured for hydrogen in air. ► A correlation is established between microstructure and the gas sensitivity. ► We find that NiO has high sensitivity and fast response toward hydrogen gas.