Structure et cinetique de mise en ordre dans des couches minces epitaxiees d'alliage AuNi: etude par thermodiffractometrie des rayons X

摘要

The improvements in the Molecular Beam Epitaxy (MBE) techniques have allowed one to obtain super-lattices in metallic thin layers. Because some of these epitaxial structures are unstable in bulk, it is necessary to study such strained systems to understand and to predict their stability. Au-Ni has been chosen as a model system. An in-situ temperature X-ray diffraction study has already been carried out in our laboratory with AuNi alloys thin layers. It has been shown that a modulated structure develops along the growth direction of the AuNi layer. This structure consists of a periodic stacking of 1 Ni-rich plane and (n - 1) Au-rich planes. Then a focus would be given in this paper on the analysis of the superlattice structure. The most representative is the one formed by Au_(0.6)Ni_(0.4) on Au(001). The modelized structure would allow us to understand what kind of order settles in the layer. From our calculations, the description of the ordering process like the growing up of some small well-ordered domains seems more close to the reality than the progressive development of an homogeneous order.