Effect on ethanol sensing ability of zinc oxide thin films with manganese doping

Undoped and Mn-doped ZnO nanostructured thin films were deposited on the glass substrate at 400 °C via spray pyrolysis technique. Films crystallinity and morphology were investigated using X-ray diffraction (XRD) analysis and field emission scanning electron microscopy (FESEM) analysis, respectively. From the XRD analysis, it is seen that prepared thin film samples are polycrystalline in nature, having a structure of hexagonal wurtzite. Undoped and Mn-doped ZnO samples showed (002) preferred orientation. FESEM study shows nanoflake structure formation. Elemental characterization was performed by Energy dispersive X-ray analysis (EDX). The elemental analysis results reveal the doping of manganese in Zinc oxide lattice. Also, an increase in doping percentages is clearly observed from the EDX spectra. It confirms the successful substitution of Mn in zinc oxide lattice. All the thin films samples were subjected to optical studies using UV–VIS spectroscopy. Transmittance data reveal a decrease in transmittance with an increase in dopant concentration. In addition, the Tauc’s plot illustrates the decrease in energy bandgap values with an increase in Mn content in ZnO. Gas sensing performance has been studied for ethanol at room temperature for all samples at various gas concentrations (5 ppm to 200 ppm). The maximum response is shown by a 2% Mn-doped ZnO thin film sample. High stability and improved gas response values of 2% Mn-doped ZnO samples make it a competitive gas sensing material.