Influence of heat treatment on H2S gas sensing features of NiO thin films deposited via thermal evaporation technique

In this study, NiO thin films are prepared on Ni foil using thermal evaporation method and the effect of deposition conditions on structural, morphological and H2S gas sensing properties of NiO thin films is investigated. Structural analysis of the NiO films are conducted by means of X-ray diffraction (XRD), and the films are found to have the FCC phase with preferred (111) and (200) Bragg reflections. Based on XRD and scanning electron microscopy results, it is shown that the crystallite size and the size of homogeneous nanoclusters on the surface of the films increase after increasing oxidation temperature. Also, the EDS patterns of NiO films demonstrate a rise in the intensity of O peak upon increasing the oxidation temperature due to the enhancement of oxygen in the NiO films. The Raman spectrum of NiO thin films several bands correspond to Ni-O vibrations. The obtained gas sensing results demonstrate the sensing response to 20 ppm of hydrogen sulfide at 700 degrees C. Upon increasing the amount of hydrogen sulfide gas to more than 20 ppm, the fabricated sensors show no significant change in their response, indicating that no additional active sites were exist to interplay with hydrogen sulfide molecules for the higher concentration of hydrogen sulfide. The response of the sensors, recorded 10 s after H2S gas exposure, depended on the deposition temperature. The current study shows that NiO thin films-based sensors prepared by a simple thermal evaporation method are potentially useful for the detection of H2S gas.

Automated summary

In this study, NiO thin films were prepared on Ni foil using thermal evaporation method to investigate their structural, morphological and H2S gas sensing properties. XRD analysis revealed a FCC phase with preferred (111) and (200) Bragg reflections. Increasing the oxidation temperature led to an increase in crystallite size and size of nanoclusters on the film surface. EDS patterns showed an increase in O peak intensity with increasing oxidation temperature, indicating enhanced oxygen content. Raman spectrum revealed Ni-O vibrations in the thin films. Gas sensing results demonstrated sensitivity to 20 ppm H2S at 700 degrees C and no significant change in response for higher concentrations. The deposition temperature influenced the response of the sensors.