Exploring the influence of Zn impurities on the structural, optical, and H2 sensor properties of ultrasonic spray pyrolysis-grown MgO thin films

Magnesium oxide (MgO) thin films, both pure and zinc (Zn) doped, were fabricated on soda lime glass substrates using ultrasonic spray pyrolysis. Zn was introduced at concentrations of 0.5 %, 1 %, 2 %, 4 %, and 8 %. The effects of these doping levels on the films' structural, morphological, optical, and H2 gas sensing properties were studied using XRD, SEM, EDAX, UV–vis spectroscopy, PL spectroscopy, gas sensing measurements, and XPS. The films showed a cubic crystal structure without secondary phases, and grain sizes generally decreased with doping. Morphological changes in nanocrystal shapes were noted due to impurities. Optimal doping enhanced MgO's absorbance, with a slight increase in bandgap. The PL spectra showed increased luminescent emissions with higher doping, due to defects from Zn ions. Pure films were responsive to H2 gas, while Zn-doped samples showed weaker responses. The XPS confirmed the expected chemical compositions.