The dependence of thin-film microstructures upon the curvature of the substrate was investigated by means of field-ion microscopy and transmission electron microscopy. Thus, Cu–Au multi-layers were deposited onto W single crystals which were prepared both as curved (radius of curvature ~50nm) and as planar substrates. Three-dimensional atom-probe analysis showed that the curved substrates led to heterogeneous reaction patterns by grain boundary reaction besides planar reaction patterns. This was explained by local variations in microstructure. The grain-boundary reaction was dependent upon the atomic structure of the grain boundary and could lead to the early formation of intermetallics. At temperatures which were too low for significant volume diffusion, interdiffusion between enriched grain boundaries and neighboring grains was observed during the formation of ordered compounds. The elastic strain, which was caused by a considerable atomic size mismatch, was found to hinder interdiffusion and to cause alloying during grain boundary motion. The introduction of a Co diffusion barrier between Au and Cu slowed the interdiffusion and resulted in higher reaction temperatures. Thus, it was observed that grain-boundary reaction in the Au layer disappeared at high temperatures, where the volume diffusion of Cu in Au became possible. In the case of Cu layers, the grain-boundary reaction was still observed.Microstructure-Controlled Interdiffusion of Cu/Co/Au Thin Films Investigated by Three-Dimensional Atom Probe. C.Lang, G.Schmitz: Materials Science and Engineering A, 2003, 353[1-2], 119-25