Effect of manganese concentration on physical and electrochemical properties of Mn2+-doped ZnS thin films deposited onto ITO-(glass) substrates by electrodeposition technique

Abstract

In this work, Mn2+-doped ZnS onto (ITO)-coated glass substrates have been prepared by electrodeposition technique. Various samples of the ZnS with different Mn contents 0, 0.5, 1, 2, and 3 at.% were prepared. XRD analysis shows that all films crystallize in a cubic phase of ZnS with a preferential orientation along (200) direction. The variation in peak positions of X-ray diffraction shows that the Manganese element is well incorporated into ZnS matrix and does not remain in the interstitial sites. Surface morphology studies by Atomic Force Microscopy showed that an increase in the concentration doping causes an increase in the grain size and the mean square roughness. Moreover, the optical analysis reveals that the band gap energy varied between 3.54 and 3.76 eV in terms of Mn content. On the other hand, the electrochemical impedance spectroscopy data have been modeled using an equivalent circuit approach. Finally, from Mott–Schottky plot, the flat-band potential and carrier density of Mn-doping ZnS thin films have been determined. The results reveal that all the films showed n-type semiconductor character with a flat band potential and a carrier density varying from −0.46 V to −0.57 V and 3.20 × 1016 cm−3 to 4.34 × 1016 cm−3, respectively.