Physicochemical and electrochemical properties of Gd3+-doped ZnSe thin films fabricated by single-step electrochemical deposition process

Abstract

Gd3+ (gadolinium)-doped ZnSe thin films (1 to 5 mol%) are grown onto indium-doped tin oxide (ITO) glass substrate by single-step electrochemical deposition process. X-ray diffraction analysis confirms the formation of hexagonal wurtzite structure with preferred growth orientation along (101) plane. A new antistructural modeling for describing active surface centers for ZnSe:Gd system is discussed for the first time. The new antistructural modeling shows that the dissolution of Gd cations increases the concentration of surface active centers $$ {\mathrm{Gd}}_{\mathrm{Zn}}^{\bullet } $$ and $$ {\mathrm{V}}_{\mathrm{Zn}}^{\prime \prime } $$ , which are located in the cationic sublattice. The surface morphology of thin films investigated using scanning electron microscopy reveals some agglomeration of grains with significant changes in particle size with varying Gd3+ concentrations. UV-vis and photoluminescence studies indicate a blue shift due to the incorporation of Gd3+ into ZnSe host lattice. Electrochemical impedance spectroscopy and photoelectrochemical measurements reveal that the 3 mol% Gd3+-doped ZnSe thin film possesses low charge transfer resistance (25.42 Ω) and faster migration of photoinduced electrons, resulting in high conductivity. Therefore, the optimum doping concentration, 3 mol% Gd3+-doped ZnSe, offers a positive synergistic effect for photoelectrochemical devices.