Physical and Electrochemical Area Determination of Electrodeposited Ni, Co, and NiCo Thin Films

TL;DR

This study compares methods for determining the surface area of electrodeposited Ni, Co, and NiCo thin films, finding that electrochemical double-layer capacitance is a practical and versatile approach.

Contribution

It evaluates and compares three surface area measurement techniques, highlighting the effectiveness of in situ double-layer capacitance measurements for metal thin films.

Findings

Double-layer capacitance correlates with AFM roughness factors.

Electrochemical area measurements are less consistent across compositions.

Double-layer capacitance is a practical method for surface area estimation.

Abstract

The surface area of electrodeposited thin films of Ni, Co, and NiCo was evaluated using electrochemical double-layer capacitance, electrochemical area measurements using the [Ru(NH$_3$)$_6$]$^{3+}$/[Ru(NH$_3$)$_6$]$^{2+}$ redox couple, and topographic atomic force microscopy (AFM) imaging. These three methods were compared to each other for each composition separately and for the entire set of samples regardless of composition. Double-layer capacitance measurements were found to be positively correlated to the roughness factors determined by AFM topography. Electrochemical area measurements were found to be less correlated with measured roughness factors as well as applicable only to two of the three compositions studied. The results indicate that in situ double-layer capacitance measurements are a practical, versatile technique for estimating the accessible surface area of a metal sample.