Electron microscopic studies showed that Au crystallites (2 to 3nm in diameter), when deposited under ultra-high vacuum onto a (100) cleavage plane at 20C to an initial surface concentration of 2.2 x 1011grains/cm2, migrated as separate entities at 100C. Their diffusivity was equal to 4 x 10-13cm2/s. This increased with decreasing particle size.

Brownian Movement of Au Crystallites Adhering to a (100) Cleavage Plane of KCl. A.Masson, J.J.Metois, R.Kern: Comptes Rendus de l’Academie des Sciences – C, 1970, 271[3], 235-8

Figure 11

Diffusion of Au Crystallites on the (100) Plane of KCl