Structure and kinetics of order in thin epitaxial layers of AuNi alloy - Study using X-ray thermodiffractometry

The improvements in the Molecular Beam Epitaxy MBE) techniques have allowed one to obtain super-lattices in metallic thin layers. Because some of thes e epitaxial structures are unstable in bulk it is necessary to study such s trained systems to understand and to predict their stability. Au-Ni has bee n chosen as a model system An in situ temperature X-ray diffraction study h as already been carried out in our laboratory with AuNi alloys thin layers. It has been shown that a modulated structure develops along the growth lay er. This structure consists of aperiodic stacking of 1 Ni-rich plane and (n -1) Au-rich planes. Then a focus would be given in this paper on the analys is of the superlattice structure. The most representative is the one formed by Au0.6Ni0.4 on Au(001). The modelized structure would allow us to unders tand what kind of order settles in the layer From our calculations, the des cription of the ordering process like the growing up of some snail well-ord ered domains seems more close to the reality than the progressive developme nt of an homogeneous order.