In this study we investigate the effects of a thin Au interlayer on the formation of cobalt silicide thin films on (001)Si substrate. The presence of a thin Au interlayer in the Co/Au/Co/(001)Si samples was found to decrease the temperature needed for the formation of the COSi2 phase by about 100-190 degrees C compared to that needed for Co/(001)Si samples. The effect on the formation of COSi2 became more pronounced as the thickness of the Au interlayer increased. These results are explained in the context of classical nucleation theory. Cross-sectional transmission electron microscopy (TEM) observations show that both the COSi2 surface and COSi2/Si interface in Co/Au/Co/(001)Si samples are much smoother than those in Co/Au/Si samples. In addition, the TEM, energy dispersion spectrometry, and secondary ion mass spectroscopy analyses of the Co/Au/Co/(001)Si samples reveal that after annealing a large amount of Au atoms have diffused from the original interface position to be dispersed in the COSi2 layers and at the grain boundaries. (c) 2008 Elsevier B.V. All rights reserved.