Effect of doping concentration on the structural and optical properties of nanostructured Cu-doped Mn3O4 films obtained by SILAR technique

In this study, the effect of Cu doping on the optical, structural and wettability properties of the nanostructured Cu-doped Mn3O4 (CMO) thin films obtained by using successive ionic layer adsorption and reaction technique was systematically investigated. The optical, morphological, structural and wettability properties of the nanostructured CMO films were determined using scanning electron microscopy (SEM), X-ray diffraction (XRD), UV-Vis spectroscopy, and water contact angle (WCA) measurements. There were significant differences in the crystal structure of the nanostructured CMO thin films. The Cu doping disrupted this structure of pure (undoped) Mn3O4 films and caused the formation of the porous structure. Optical properties such as extinction coefficient, refractive index, and dielectric constants and optical band gap, were determined for nanostructured CMO films. Compared with pure films, the band gap of Cu-doped films decreased from 2.06 to 1.71 eV with increasing Cu concentration. The dielectric constants of the films showed that the nanostructured CMO films have a transparent structure. At 300 nm wavelength, the dielectric constants of pure Mn3O4 films were 2.22 while the calculated dielectric constants at increasing doping concentrations were 3.55, 2.41 and 2.25. It was also found from the WCA measurements that the thin films were hydrophilic in character and the WCA values for the nanostructured CMO thin films were measured as 24, 29 and 40 of degree.