Comparative study of structural, optical and electrical properties of electrochemically deposited Eu, Sm and Gd doped ZnSe thin films

A facile approach involving electrochemical deposition method was utilized to coat ITO substrate with zinc selenide thin films at different rare earth metal (Eu3+, Sm3+ and Gd3+) ions. The characteristics of deposited films were studied in relation with the doped metal ions. The structure of the coating was confirmed to be hexagonal wurtzite in (101) plane by X-ray analysis. The new antistructural modeling shows that the doping of ZnSe lattice by rare earth cations increases the concentration of the surface active centers such as , which are located in the cationic sublattice. XRD data revealed that the average crystallite size of ZnSe and ZnSe:Eu, ZnSe:Sm, and ZnSe:Gd was 63, 54, 47, and 49 nm, respectively. The morphological results by scanning electron microscopy indicate that the spherical-like structure with agglomeration of grains and a slight increase in the particle size. Energy dispersive X-ray, UV-Visible and photoluminescence spectroscopy were used to study the composition and optical properties of the films. A blue-shift was observed in ZnSe thin films. The bandgap energy of undoped ZnSe and ZnSe:Eu, ZnSe:Sm, and ZnSe:Gd were found to be 2.28, 2.44, 2.68 and 2.75 eV, respectively. Among the different coated films, the Gd3+ ion doped ZnSe thin film exhibited a lesser charge transfer resistance of 25.5 abroken vertical bar as analyzed from the electrochemical impedance measurement. The photoelectrochemical studies reveal that the rate of photoinduced charge carriers was higher in Gd3+ ion doped thin film. The present studies suggested that the Gd3+ ion doped ZnSe thin film can be a promising material for electrochemical device applications.