ROLE OF SUBSTRATE DISLOCATIONS AND GRAIN-BOUNDARIES IN THE NUCLEATION AND GROWTH OF THIN ELECTROCHEMICAL OVERGROWTHS - TEM AND FIM STUDIES

Thin coatings of nickel are electroplated onto annealed (0.2 mm grain size) copper substrates and annealed and shock‐loaded copper substrates. The shock loading produces a sub‐grain dislocation cell structure without distorting the grain boundaries. Selective chemical stripping produces thin nickel electrodeposits and thin nickel/copper composites which are observed by transmission electron microscopy. Neither the grain boundaries nor the dislocation substructure of the copper substrates are observed to directly influence the nucleation and growth of the defect structure of the nickel overgrowths. Thin films of aluminum and copper with various grain sizes and dislocation structure are also prepared by vapor deposition onto (001) NaCl crystals and when used as substrates to precipitate copper from an aqueous CuSO4 solution by electrochemical displacement reactions, and the copper nuclei upon the substrate films viewed simultaneously in the transmission electron microscope, there is also no observable influence of either the emerging dislocations in the substrate film surface or the grain boundaries on the density or disposition of the copper nuclei. Finally, grain boundaries in the surface of tungsten emission and forms used as substrates for the electroplating of nickel from a (NiSO4)6 · 6H2O‐aqueous solution, and systematically examined by field evaporation of individual overgrowth atomic layers in the field‐ion microscope also show that the grain boundary is not propagated directly into the overgrowth for any more than a few atom layers near the substrate. Copyright © 1979 WILEY‐VCH Verlag GmbH & Co. KGaA