SPONTANEOUS ALLOYING OF COPPER INTO GOLD ATOM CLUSTERS

A double-source evaporator which can be set in the specimen chamber of a high voltage electron microscope has been constructed. With the use of the evaporator, isolated gold clusters of 5 approximately 10 nm in size were first prepared on a supporting film of amorphous carbon, and then copper atoms were deposited onto the film (and of the deposition of copper, the gold clusters changed into highly concentrated, homogeneously mixed Au-Cu alloy clusters. The copper atom diffusivity in gold clusters deduced from the present observations is at least 9 orders of magnitude faster than the copper solute diffusion in bulk gold.