Mechanistic study on electrochemical codeposition of mixed zinc–erbium oxide films on the cathodic surface

Abstract

Erbium doped zinc oxide thin films were prepared from aqueous solutions containing Zn(NO 3) 2 and Er(NO 3) 3 by the potentiostatic technique using a three-electrode system. The pH changes at the cathode/solution interface were in-situ measured during the electrodeposition process of mixed erbium–zinc hydroxide or oxide films. The solution- and solid-phase speciation distributions of the two metal ions and their hydroxides as a function of pH values, which were calculated and plotted according to the thermodynamic constants for these species, were used to explain the reaction mechanism for electrocodeposition of mixed erbium–zinc hydroxides or oxides on cathodic surfaces and predict the composition for the mixed zinc–erbium oxide films.