Abstract
The formation and morphology of electrodeposited Au-Pd alloy films, which had been deposited from single hydrochloric acid baths on single and poly-crystal Cu substrates, were studied by electron microscopy and the following results were obtained. The films formed a solid solution alloy since the early stage of nucleation, and the density for nucleation was about 3×1012cm-2. The alloy nuclei of 20-40Å in diameter, which had been deposited in the early stage, showed no orientation to Cu substrate; but they gradually showed an epitaxy with the substrate in the process of their growth. The coherencies between electrodeposited films and Cu substrates were found to be of (001), (011), and (111) orientations and (111) Cu//{112} Au-Pd and ‹110›Cu/‹110› Au-Pd. In the films were observed many micro-twins, which contributed to relax the stress caused by the misfit between the film and substrate. When the current density for electrodeposition was low, plate crystals containing fine non-oriented crystallites in size of several tens of Å were formed; on the other hand, the crystals formed under a high current density were constituted by subgrains of uniform size. Under any current densities, a small number of fine nonoriented crystallites tended to coexist in the films deposited from the baths of rich in Au, but the number of such crystallites tended to increase in the films deposited from the baths of rich in Pd. The alloy constituents of electrodeposited films included more Au on the side of low current density, and the Pd content increased with the increase of current density. However, on the side of high current density, the alloy constituents of films were nearly identical with the composition of bath.
