Growth and stability of cobalt nanostructures on gold (111)

The nucleation, growth and stability of cobalt nanostructures on the (∼22 × √3) reconstructed Au(111) surface have been studied using thermal energy helium-atom scattering (TEAS) and Auger electron spectroscopy (AES) in the temperature range 50–700 K. Helium atom diffraction provides information on the island distribution and step heights. The composition of the surface region was checked by AES. In addition, the presence of cobalt in the topmost layer was investigated by the adsorption of carbon monoxide, as monitored by the specularly reflected helium intensity. From the change in the CO adsorption characteristics on the Co-covered Au(111) surface and the AES data, we conclude that surface alloy formation or Au capping takes place between 300 and 350 K, whereas Co diffusion into the Au bulk only occurs above 450 K.