LAUSR

Abstract Nanocrystalline NiO thin films were synthesized on ITO substrates by a sol–gel dip coating method using the mixture of NiC 4 H 6 O 4 ·4H 2 O, NH 3 ·H 2 O and C 3 H 8 O as the precursor. Structure of NiO thin films was characterized by means of X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible spectroscopy, and the results showed that the films were composed of cubic NiO nanocrystalline particles having diameters in the range of 20–30 nm, which provides a large specific surface area. NiO thin films showed p -type semiconductor behavior due to the non-stoichiometry. A band gap of 3.75 eV was obtained by UV–vis measurement. The sensor based on NiO thin films demonstrated a good reversibility and repeatability to NO 2 at evaluated operating temperatures. The films also showed an excellent NO 2 selectivity compared to formaldehyde, ethanol, methanol, xylene, hydrogen, ammonia and methane at 150 °C, demonstrating a potential application in low-energy consumption gas sensor devices.