X-RAY-DIFFRACTION STUDY OF SILVER NICKEL SUPERLATTICES

Silver-nickel multilayers, with elementary layers comprising a few to a few ten atomic planes, have been prepared by cathodic sputtering on glass substrates. X-ray diffraction experiments show that highly textured, polycrystalline superlattices are formed. For a deposition temperature of 100 K, there exists a critical number of atomic planes n(c) = 3, below which noncrystalline samples are obtained. This critical number can even be lowered in samples with nonequal numbers of Ag and Ni atomic planes. Transmission x-ray and electron diffraction experiments show that equivalent crystallographic directions are aligned in the Ag and Ni (111) planes, with a noticeable relaxation of the in-plane distances at the interfaces. The simulation of the periodic structure assuming a rectangular composition profile with interplanar distances slightly larger than the bulk values leads to a very good agreement with the experimental diffraction spectra.