Structure–Property Relationships and Toxic Gas Sensing Ability of Reactively Sputtered NiO Thin Films Deposited with Variation in O ₂ Gas Flow

NiO thin films are deposited by reactive magnetron sputtering of a Ni target at 100 W D.C. power using four different oxygen gas partial pressures, while keeping argon gas flow constant. The films are deposited for a fixed time on glass substrates at room temperature without any further annealing treatment. The influence of various gas flow ratios on the structural, optical, morphological, and electrical properties of the films is examined. All of the films crystallize in the cubic phase corresponding to crystal planes of bulk NiO, with preferred growth orientation in the (200) direction. The effect of increase in oxygen flow is observed to reduce both growth rate and crystallite sizes of the films, enhance optical transmittivity, modify surface structures, and heighten electrical resistance. These nanostructured films are also tested for toxic gas sensitivity. This article reports that for a particular gas flow ratio, the corresponding NiO film selectively exhibits very good sensor response toward the detection of NO 2 gas at room temperature, creating an energy‐efficient system. The film could also undergo complete recovery between sequential gas doses of increasing concentration.