Accommodation of misfit across the interface between single-crystal films of various face-centred cubic metals

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Abstract
Specimens consisting of a pair of single-crystal films in contact and in parallel orientation were prepared by successive evaporation of the film materials in ultra-high vacuum onto the (001) surfaces of hot sodium chloride crystals. The combinations of film materials used were gold-palladium, gold-silver and platinum-gold. Examination of the specimens by transmission electron microscopy revealed that the difference between the lattice parameters of the pairs of metals was divided between elastic strain and misfit dislocations in approximately the manner predicted by van der Merwe (1963). Most of the 4·6% misfit between a 100 Å gold film and its 400 Å palladium substrate was accommodated by misfit dislocations. The 0·19% misfit between a gold film and its 1500 Å silver substrate was entirely taken up by elastic strain until the thickness of the gold reached between 250 Å and 300 Å. When the thickness of the gold film exceeded 250 to 300 Å some misfit was accommodated by dislocations that moved by glide from either the upper or lower specimen surface into the (001) interface between the two metals. The dislocations often cross-slipped during their glide to the interface, and their density increased as the thickness of the gold deposit increased.

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