During the growth of nanometric metallic films, considerable stress can be generated. The mechanisms responsible for stress generation and relaxation are not well known. In particular, segregation of substrate atoms towards the surface may occur during deposition, leading to an interfacial concentration gradient. This work reports on the development of an apparatus allowing the determination of stress via in situ sample curvature measurements, and on the deposition of Ag on Si(111) in order to initiate the growth of metallic multilayers. The stress evolution during the deposition of silver, which cannot be interpreted through simple misfit accommodation, is confronted to structural analyses of the film. Complementing the determination of stress with RHEED measurements during growth, the stress and strain evolution in Cu-Ni(100) multilayers was studied. In spite of the weak misfit between Ni and Cu, partial relaxation takes place from the beginning of the growth. Moreover, the results reveal an interfacial mixing occurring when depositing Ni onto Cu. In the case of Au-Ni(111) multilayers, which are more highly mismatched, dynamical segregation occurs when depositing Ni onto Au, though Au and Ni are immiscible at room temperature. The comparison between x-ray anomalous diffraction spectra and numerical simulations reveal a composition gradient (associated with an interplanar distance gradient) extending on about six atomic planes around the Ni/Au interfaces, while the Au/Ni interfaces are abrupt. The local environment of atoms, and more particularly the first neighbour distance distribution, has been analyzed in these multilayers by x-ray absorption spectroscopy (EXAFS).
Study of stress and strain during growth of metallic films; analysis of interfaces structure and composition profile by x-ray scattering