STRUCTURE AND PROPERTIES OF SURFACE-LAYERS - X-RAY-DIFFRACTION STUDIES

After a brief discussion of some aspects of X-Ray diffraction analysis of surface layers, attention is focused on investigations of stress development and interdiffusion. The behavior of surface layers depends largely on their state of (residual) macro- and microstress. The behavior of surface layers depends largely on their state of (residual) macro- and microstress. The development and possible relaxation of macrostress in surface layers can originate from the thermally imposed difference in shrink or expansion between layer and substrate, from developing concentration profiles and from structural changes, in particular phase transformations. Diffusion processes in multilayers, are highly affected by the multitude of interfaces and therefore differ from those in bulk material. The effective diffusion coefficients can be determined from the decrease of the intensity of the reflections corersponding to the composition-modulation period, and the change of the integrated intensities of reflections from produced or retained crystalline components. Examples of interdiffusion in an amorphous multilayer and in a crystalline multilayer are presented.