Interdependence of elastic strain and segregation in metallic multilayers:An x-ray diffraction study of (111) Au/Ni multilayers

This study concerns the analysis of elastic strains in Au/Ni multilayers wh ose periods lie in the range 1-5 nm. Lattice parameter measurements have be en performed by x-ray diffraction in various directions. The results are in terpreted in terms of elastic strain and interfacial mixing. It is shown th at considerable strains (several percent) are encountered within these very thin layers. In the Au sublayers, coherence is never observed with the und erlying Ni film and the residual strain relaxes progressively as the Au fil m thickens. In the Ni sublayers, interfacial mixing controls the lattice pa rameter and the elastic strain is a function of this mixing. Out of equilib rium mixing of Au into Ni is ascribed to dynamic segregation during the gro wth of Ni on Au. All these results bring new insights on the still open que stion of stress relaxation mechanisms in ultrathin films. (C) 2000 American Institute of Physics. [S0021-8979(00)04703-4].