The early stages of thin film formation were studied at the atomic scale by using scanning tunnelling microscopic imaging. To this end, Au was sputter-deposited onto a graphite substrate by means of the Cs+ ion bombardment of a Au target, using a few keV of energy. Stable Au nuclei were formed at defect sites which were produced by the impact of Au atoms with energies that were greater than 180eV. This energy was required in order to displace a C atom from the lattice during a binary collision. Three-dimensional clusters grew via the attachment of additional Au atoms to the nuclei. The fraction of Au atoms which had an energy of more than 180eV depended upon the Cs+ ion energy, and was typically less than 1% of the incident Au flux. After 1s of deposition time, the average size of the clusters was 10 atoms. The cluster number density was 1012/cm2, and a few percent of the incident flux was condensed in the clusters. These results were attributed to the weak interaction strength between Au and graphite.

Y.O.Ahn, M.Seidl: Journal of Applied Physics, 1995, 77[11], 5558-62