All-electrochemical synthesis of tunable fine-structured nanoporous copper films

Nanoporous copper (np-Cu) films that feature fine ligament length scales and high surface area are prepared using an all-electrochemical approach. The two-step routine involves initially the electrodeposition of CuxZn(100-x) precursor alloy films with controlled thickness and composition from a pyrophosphate bath. This is followed by a selective oxidative removal or dealloying of Zn that leads to a surface area increase (by up to 22 times per one mu m thickness of the precursor alloy). In this article, we present a systematic investigation of the impact of three factors on the as-synthesized np-Cu structure: (1) dealloying bath composition, (2) atomic composition (at.%) of precursor alloy, and (3) addition of Ni. Our results show that varying the dealloying bath composition allows for tunable ligament and pore sizes that are due to the anion-induced (ClO4-, SO42-, or Cl-) modified surface diffusivity of Cu. The increase in surface area is also proportionally scalable by modifying the Cu content (12-42 at.%) in the precursor alloy. Thus, np-Cu films with porosity length scales in the range of 20-33 nm were obtained. A further np-Cu length scale refinement down to 10-12 nm was achieved after dealloying of a ternary Cu-Zn-Ni(3%) alloy. Overall, the strict parameter control yields a wide range of nano-scaled np-Cu films with specific surface characteristics, which may be suitable for various applications including microelectronic packaging, sensing, and catalysis.

Automated summary

Nanoporous copper films with fine ligament length scales and high surface area were prepared using an all-electrochemical approach. The parameters that were found to affect the resulting film structure were the composition of the dealloying bath, the atomic composition of the precursor alloy, and the addition of nickel. By controlling these parameters, a wide range of nano-scaled nanoporous copper films with specific surface characteristics were obtained.