Two-dimensional nucleation according to an exponential law with surface diffusion-controlled growth in the phase formation of uracil on Au(hkl)

The kinetics of formation of a two-dimensional condensed physisorbed film of uracil on the three gold surfaces Au(100)-(hex), Au(111)-(p X root 3) and Au(100)-(1 X 1) in KClO4 have been investigated by potential step experiments. Double potential steps (primary transients) were applied in order to reduce the effect of pre-adsorption on the immediate phase transition kinetics. These primary transients could be modelled with an exponential raw of nucleation and an induction time in combination with 2D surface diffusion-controlled growth. The growth mechanism could be resolved separately with a set of double step secondary growth transients. In order to guarantee well-defined experimental conditions, we also monitored the structure and stability of the various substrate surfaces in the potential range of interest in the absence and presence of uracil using in situ STM. (C) 1997 Elsevier Science S.A.