Since the last five decades, semiconductor oxide materials are playing a big role in sensor industries, to detect harmful gases (CO, O_3, H_2S etc.) in petroleum industry, coal mine, etc. Still there are lots of challenges with MOX sensor like stability for the long time and sensitivity at the low temperature. On the other hand, these materials have great advantage in sensing field and have good detection probability with the target gases like ethanol (EtOH), H_2, CO, O_2 and acetone. During the last five decades, n-type semiconductor-based sensors were popular in the market and research field: metal oxides like ZnO, SnO_2 and TiO_2 were extensively investigated [1]. During the last two decades, p-type semiconductor oxide-based sensors have carved a niche in the sensor market and industries. We observed that p-type semi-conductor oxides have good potentials for sensor application. Wisitsoraat et al. tested the NiO sensing layer for ethanol and CO and confirmed the p-type semiconductor oxide [2]. NiO can be a promising oxide for sensor application [4], which is naturally a p-type semiconductor oxide because of the oxygen ions vacancy. We investigated preparation conditions of NiO thin films by sputtering from a NiO target and investigated them by glancing incidence X-ray diffraction (GIXRD) and scanning electron microscopy (SEM) techniques. Gas sensing properties were studied as a function of preparation conditions with volt-amperometric techniques: the gas sensing properties towards CO, ethanol and NO_2 are discussed.
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