Scanning tunnelling microscopy observations of the evolution of small-scale topography on gold surfaces following irradiation with low-energy argon ions

Room-temperature irradiation of atomically flat gold films has been observed, using scanning tunnelling microscopy, to give rise to small faceted islands and pits (about 10 nm in lateral dimension and a few monolayers in height) which subsequently evolve by surface diffusion over a period of hours. The evolution on grains with different surface orientations is observed to be markedly different and, in particular, on what appears from symmetry consideration to be a (100) grain, the surface features are apparently in dynamic equilibrium under irradiation and subsequently thermally dissociate by the emission of small mobile clusters of atoms.