High Zr doping effects on the microstructural and optical properties of Mn3 O4 thin films along with ethanol sensing

•Zr doped Mn3O4 thin films were successfully synthesized by spray pyrolysis at 350 °C•XRD study reveals that all the films are polycrystalline with spinel orthorhombic structure.•The band gap energy of the films varies from 2.20 to 2.92 eV with the Zr content.•6.0 at.% Zr doped Mn3O4 based sensor showed excellent sensitivity toward 0.1% ethanol at the operating temperature of 175 °C.•The performance of the sensor is discussed in terms of the morphology feature.-

Transition metal oxides as transparent conducting oxides (TCOs) films, with high optical transparency (≥ 82%), various valence states and p-type conductivity are used in a several physical domains. This work covers the physical study of Zr doped Mn3O4 semiconductor thin films using a spray pyrolysis method where Zr content varies in starting solutions from 0 to 20 at.%. The impact of this work is to offer some understanding of microscopic effects of relatively high doping Zr and then correlate these effects with the macroscopic properties for interesting applications especially gas sensor. In fact, the addition of Zr ions pointed out the reduction of crystallite size (24.1 (nm)) with 20 at.% doping allowing a better adsorption of gas molecules. In addition, it promotes the increase of optical gap (2.92 eV) with 6 at.% doping which is a useful parameter for some optical devices. X-ray diffraction (XRD), Raman spectroscopy, FTIR spectroscopy, atomic force microscopy (AFM) and EDAX techniques were used. It is found that these films crystallized in spinel type tetragonal hausmmanite structure. The gas sensing activity of these thin films (0, 6, 12 and 20 at.% Zr) was examined with Ethanol. The performances of these last four sensing layers were compared. All the tests were performed at different working temperatures Twork = 125, 150, 175 and 225 °C and under two gas concentrations: 0.1% and 0.5% ethanol using dry air as carrier gas. The films exhibited noticeably ethanol sensing especially the sample doped with 6% of zirconium exhibits the most excellent sensing performance since it showed a clear response already at a low ethanol concentration of 0.1%.

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