The influences of preparation parameters on NiO thin film properties for gas-sensing application

Nickel oxide (NiO) thin films have been prepared by dc reactive magnetron sputtering from a metallic Ni target in an Ar+O2 mixed atmosphere in two sputtering modes. The oxygen content in the gas mixture varied from 15 to 45%. Rutherford backscattering spectrometry (RBS) and X-ray photoelectron spectroscope (XPS) investigations have been used for the study of the chemical composition and to detect different chemical states of bond elements. TEM observations revealed a dense fine-grained structure with the grain size in the range 4–10 nm. Atomic force microscopy (AFM) showed that the surface morphology NiO films can be modified by the process parameters as the oxygen content and the pumping speed. Scanning electron microscope (SEM) observation and energy dispersive X-ray (EDX) analyses revealed uniform morphology and homogenous dispersion of NiO, Pt and Al2O3 phases. In addition, the NiO thin films were tested in order to investigate their response to CO in the range 50–200 ppm at different operating temperatures.