Physical and structural characterization of NiO thin films for gas detection

We have studied physical and structural properties of NiO thin films produced by reactive DC magnetron sputtering of a Ni target in an Ar/O/sub 2/ mixture. The oxygen content in the gas mixture varied from 15 to 45%. The thin film deposition was controlled by the target voltage. 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. The NiO thin films were tested in order to investigate their response to NH/sub 3/ and CO in the interval 50-200 ppm at the different operating temperatures. The maximum value of CO response (30% to 200 ppm) was obtained at an operating temperature of 420/spl deg/C for sample prepared in oxide-sputtering mode.