Strains and stresses in an epitaxial Ni(111)/Mo(110) multilayer grown by direct ion beam sputtering

An epitaxial Ni(111)/Mo(110) multilayer was grown on a (1 1 2̄ 0) oriented monocrystalline sapphire substrate in a high vacuum sputtering deposition system. The strain and stress state of the layers has been measured with X-ray diffraction in symmetric and asymmetric geometries. Non-equal biaxial coherency stresses due to the Nishiyama–Wassermann epitaxial relation between both lattices are clearly evidenced. The values of the stress-free lattice parameters of molybdenum and nickel sublayers, deduced from the global stress analysis, supports the hypothesis of an interfacial alloying effect between layers with diffusion of nickel in the Mo layers and, to a lesser degree, of molybdenum in Ni layers. On the other hand, the Ni layers appear nearly fully relaxed. A detailed analysis of the stresses in the film shows a strong contribution of a compressive stress field due to possible post-growth atomic rearrangements occurring inside the multilayered film.