How can one conclude from Figure 11.22 that Cu atoms can diffuse rapidly over a well-ord...

How can one conclude from Figure 11.22 that Cu atoms can diffuse rapidly over a well-ordered Au electrode in an electrochemical cell?

FIGURE 11.22 Image of a gold electrode in which a small amount of copper has been electrochemically deposited. Note that the Cu is deposited in the form of small islands that are anchored at step edges of the underlying gold electrode. The onset of the deposition is initiated by the horizontal arrow in the figure. At that point, the electrode potential was increased to a value that allows the reaction Cu²⁺⁽aq) + 2e^- → Cu(s) to proceed. [Kolb, D.M. Engelmann, G.E., Ziegler, J.C. “On the Unusual Electochemical Stability of Nanofabricated Copper Clusters.” Angewandte Chemie International Edition 39 (2000): 1123–1125.]