  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.
