We investigate the effect of layer-thickness fluctuations on diffraction in compositionally modulated materials. Two types of fluctuation distributions are considered: continuous random fluctuations which result from disordered or amorphous interfaces and discrete fluctuations resulting from coherent interfaces. We show that these two types of fluctuations produce identical superlattice diffraction structure at small scattering vector, but entirely different structure at large scattering vector corresponding to the discrete fluctuation spacing. Both structures are observed in experimental x-ray diffraction spectra.

• Received 19 December 1986

DOI:https://doi.org/10.1103/PhysRevB.35.9337