Electrodeposition and mechanical properties of Ir and Ir-Ni films from aqueous solutions.

Iridium (Ir) has some unique excellent properties and many special applications in high-tech fields. Herein, Ir and Ir Ni films were electrodeposited on copper substrates from aqueous solutions containing Ir3+, [Ir(III)Br 6 ]3− or [Ir(IV)Br 6 ]2−. The electrochemical behaviors of the electrolytes were studied. The surface morphology, phase and chemical composition of the selected films were investigated by SEM, TEM, XRD, XPS and EDS, respectively. The composition of Ir Ni film was regulated by bath components. Ir and Ir-rich Ir Ni films were deposited electrochemically from hexabromoiridate solutions. Although the quality of Ir film from IrCl 3 solution was poor, Ni-rich Ir Ni films obtained from IrCl 3 solution exhibited good quality and good adhesion. The deposition rate, crystallinity and appearance quality of the films were improved in oxalic acid solutions. Under the same deposition conditions, Ir Ni deposits from [Ir(III)Br 6 ]3- electrolyte had similar composition to the films from [Ir(IV)Br 6 ]2- electrolyte, while the deposition rate and efficiency tended to be high in [Ir(III)Br 6 ]3- electrolyte. The top-surface of the film was composed of Ir oxide and metallic Ir, or Ni and Ni oxide. However, the depth composition in the film mainly consisted of metallic Ir and Ni. The selected Ir-0–90 at.% Ni films consisted of nanocrystalline and amorphous phases. The hardness and elastic modulus of the films decreased with the decrease in Ir-content. The mechanical properties of Ni-rich Ir Ni alloys from citrate solutions are higher than those of Ir-rich Ir Ni deposit from oxalic acid solutions. The films from acid electrolytes with a low pH value had poor interfaces, resulting in poor adhesion. However, the adhesion force of Ni-rich Ir Ni alloys from citrate solutions was up to 35 - 45 N. • Ir films were electrodeposited from aqueous solutions with three kinds of Ir salts. • Ir-rich and Ni-rich Ir-Ni alloy films were plated from different solution systems. • Microstructure, phase and composition of Ir and Ir-Ni films were characterized. • Hardness and modulus of the film decreased with the decrease in Ir-content. • Adhesion force of Ni-rich Ir-Ni deposit from citrate solution was 35–45 N. [ABSTRACT FROM AUTHOR]