Cumulative disorder and x-ray line broadening in multilayers.

We have measured the high-angle x-ray diffraction from crystalline Pb-amorphous Ge multilayers. The experimental data in conjunction with a model calculation for the fluctuation in amorphous-layer thickness show that this fluctuation is larger than about 5%. A smaller thickness variation implies the existence of high-angle peaks which have not been observed in any amorphous-crystalline multilayers.