The alloying of Cu atoms into Au clusters, at temperatures below 300K, was studied by using a 200kV transmission electron microscope which was equipped with a double-source evaporator. Isolated Au clusters of about 4nm in mean diameter were prepared on a supporting film and were cooled down to 245, 215, 165, or 125K. Atoms of Cu were then deposited onto the same film. Upon depositing the Cu, the Au clusters quickly changed into completely or partially alloyed clusters; depending upon the substrate temperature. The Cu diffusivity (2.0 x 10-19m2/s at 245K) which was estimated from the spontaneous alloying behavior was many orders of magnitude higher than that in bulk Au.

H.Yasuda, H.Mori, M.Komatsu, K.Takeda: Journal of Applied Physics, 1993, 73[3], 1100-3