Physical and structural characterization of NiO thin films for gas detection

Abstract

Nickel oxide (NiO) thin films, for use as function sensor layers for chemical sensors, have been deposited on Si and alumina substrates by DC magnetron sputtering from a pure metallic Ni target in an Ar/O/sub 2/ mixture. The oxygen content in the gas mixture varied from 15 to 45%. The influence of deposition parameters and annealing temperature on the structural properties and surface roughness of the undoped and doped NiO films has been analyzed by X-ray diffraction (XRD) and atomic force microscopy (AFM). XRD has confirmed the polycrystalline structure of NiO films and also revealed the changes of the lattice constant of polycrystalline NiO films depending on the annealing temperatures. The NiO thin films were tested in order to investigate their response to hydrogen in the interval 0-1.5 vol% and ethanol in the interval 0-1200 ppm at different operating temperatures.