STRESS, STRAIN AND INTERDIFFUSION IN EPITAXIED Au-Ni MULTILAYERS

B. Gilles

LTPCM, ENSEEG, St Martin d'Heres BP 75 38402 FRANCE
E-mail : gilles@drfmc.ceng.cea.fr

X-ray quantitative measurements are performed on Au/Ni multilayers grown at room temperature (RT) by the Molecular Beam Epitaxy (MBE) technique, in both the (001) and the (111) growth directions. Combining the reflectivity analysis with the simulation of the large-angles diffraction pattern, an interdiffusion profile of the gold atoms in the Ni layers is extracted. This interdiffusion is also derived from the analysis of the strain in the Ni and Au individual layers, derived from asymetrical grazing-incidence X-ray diffraction maps. Moreover, a quantitative analysis of the intensity of the in-plane diffraction peaks puts also in evidence an alloying process in the Ni-rich layers.

The nature of this interdiffusion effect in a nearly immicible system at RT will be discussed, based on an Auger in-situ analysis. It is shown that there is a segregation of gold at the surface during the deposition of the nickel layers, which may probably induce the alloying of the layer. Finally, by combining the strain extracted from the RHEED pattern and the stress derived from the in-situ measurement of the curvature of the substrate, it is demonstrated that the interdiffusion releaves the misfit stress at the interface.