Nucleation and Growth Characteristics of Thin Metal Films
This paper reports observations of nucleation and growth characteristics of thin metal films vapor deposited onto heated sodium chloride substrates. An attempt is made to explain the differences in nucleation and growth characteristics on the basis of classical nucleation theory.Thin metal films were prepared by vapor deposition onto heated NaCl (001) substrates in a commercial vacuum unit using a constant evaporation rate of approximately 1000 Å/sec. In the case of discontinuous thin films, approximately 200 Å of carbon was deposited for support. Samples for electron microscopy were prepared by standard techniques and were observed at 125 kV. Figs. 1(a) to (c) show a growth sequence of gold thin films characterized by 1) the formation of random, three dimensional, isolated nuclei at initial deposition, and their growth with further deposition predominantly by surface diffusion; 2) coalescence of these nuclei forming bigger islands; 3) the flattening of islands and formation of network structure : and 4) the filling up of these network structures with further deposition forming a continuous film.