EFFECT OF STRUCTURAL INCOHERENCE ON THE LOW-ANGLE DIFFRACTION PATTERNOF SYNTHETIC MULTILAYER MATERIALS

The sequential, layering techniques used to prepare multilayer materia ls result in significant structural incoherence due to deviations from the intended thicknesses within an elemental layer and local deviatio ns from the average due to islanding of the depositing elements during deposition. We demonstrate that if the domain size of the structural incoherence is large compared with the wavelength of the scattering ra diation, the structural incoherence manifests itself in the low-angle diffraction pattern by attenuating the intensity of the subsidiary max ima relative to the Bragg maxima. We also show that the subsidiary max ima in the low-angle diffraction pattern of a multilayer result from i ncomplete destructive interference from all of the interfaces, not jus t from the top and bottom surface of the film. A technique for incorpo rating structural incoherence when modeling the diffraction pattern of a multilayer structure is presented. The ability of this model to sim ulate the experimental diffraction pattern of an iron-silicon multilay er is demonstrated.