Fig. 6.

a Average capacitance, $C_{\mathrm{dl}}$, b average area, $A_{\mathrm{ec}}$, and c ratio of capacitance to area, $C_{\mathrm{dl}}/A_{\mathrm{ec}}$, of each sample as a function of the average roughness factor, $\mathit{RF}$. Error bars represent the standard error of the mean for the measurements