COMPARISON BETWEEN DIFFERENT X-RAY-DIFFRACTION METHODS TO EXTRACT STRAINS IN METALLIC MULTILAYERS

It is well known that, in multilayers, the information on perpendicula r lattice strains is hidden in the intensity of the superlattice peaks , whereas the positions of the diffraction lines are related to the su perperiod. This calls for some refinement. A standard way to extract s tresses in a variety of materials is to perform a ''Sin(2) psi analysi s'' (psi is the angle between the lattice plane normal and the sample surface normal). This method relies on the measurement of asymmetric B ragg peaks which may contain superlattice reflections. On the other ha nd, the in-plane directions, as measured by X-ray diffraction in the g razing incidence or the transmission modes, do not involve any superst ructure; thus they can lead straightforwardly to in-plane distances. A detailed comparison between the Sin(2) psi technique, i.e. lattice st rain measurements from asymmetric Bragg peaks, and the epsilon(perpend icular to)/epsilon(parallel to) method will be presented. This study i s performed on Au-Ni multilayers. One of the major conclusions is that the Sin(2) psi analysis is always valid but the measurement of lattic e strain becomes more complicated when the layers are epitaxial.