Preparation and structural characterization of nickel oxide films for gas sensor devices

Nickel oxide (NiO) thin films were prepared on Si substrates by dc reactive magnetron sputtering from a nickel metal target in Ar+O₂ with O₂ content varied from 15 to 50%. The effects of the O₂ gas content on the deposition rate, structure, composition and electrical properties were investigated. We have found that the good NiO stoichiometric films are obtainable with a polycrystalline structure and a resistivity of near 300 Ωcm at 25% oxygen content. But either the resistivity or the composition and structure suffer variations with the discharge parameters. Depending on the oxygen content, the deposited films have both amorphous and polycrystalline structures and the Ni/O ratio ranges between 0.71 and 1.02