Anomalous nucleation and growth of metal and alloy particles during vapor deposition on amorphous substrates

The nucleation and growth of particles of various metals on amorphous carbon was investigated by in situ TEM techniques. Particles of Pd, Ni and Ag, in contrast to Au, Pt, Ph and Ir, were found to nucleate at unusually low number densities, and only with considerable delay, but exhibited high growth speeds thereafter, as well as growth transients upon interruptions of the vapour beam. During experiments with Pd-Ni alloy particles, growth transients were found to be influenced by the components. This peculiar behaviour is explained by the existence of special sites, at which adatoms may partly diffuse into the substrate, and may partly be re-emitted. The adatom binding energy to those sites is estimated to be in the range of 1.5 to 1.7 eV.