Seiji Kamasaki

Growth Process and Structure of Gold Film Electrodeposited from HAuCl4-K2CO3 Bath

The nucleation, growth process and structure of gold film electrodeposited on iron from aqueous solution of HAuCl4 containing K2CO3 were examined by electron microscope. The results obtained were as follows: (1) The density of muclei formed at the initial stage of electrodeposition was about 2×1011cm-2. Among these nuclei, there were present pentagonal and hexagonal particles, which seemed to be multiply twinned particles. However, the ratio of these twinned particles to the total nuclei was very small. (2) The pentagonal and hexagonal particles grew up to about 400A in size. (3) The growth process was distiuguished into the following four stages: (a) Formation of nuclei. (b) Formation of insular crystals resulting from coalescence and growth of nuclei. (c) Formation of network structure resulting from two dimensional growths of insular crystals. (d) Accomplishment of plate crystals resulting from progressing of deposition in the non-covered area. (4) The normal micro-twins were formed in the gold plate crystals during the growth process. (5) The following coherency was found between the iron substrate and gold plate crystals: (001) Fe|| (001) Au and Fe|| Au. (6) The addition of K2CO3 to aqueous solution of HAuCl4 had an effect on the two dimensional growth of gold film; The effect increased the covering rate of substrate with gold film.

Electron Microscopic Examination of Au Films Electrodeposited from Hydrochloric Auric Chloride Baths

The effects of hydrochloric acid on Au films, which had been electrodeposited on Fe substrate from hydrochloric auric chloride baths, were examined by electron diffraction and direct electron microscopic observation.The following results were obtained:(1) The coherencies between the Au plate crystals and Fe substrate were the same as the results in the previous paper.(2) The growth rate of Au films was accelerated by addition of hydrochloric acid to the auric chloride bath.(3) The addition of hydrochloric acid was effective in cleaning of Fe substrate, owing to its removing action of oxide films, etc. on its surface. Accordingly, the Au films electrodeposited from the bath, containing 20cc HCl/100cc HAu Cl4, consisted of good single crystals, and the continuity of the film was also improved.