Discrete and continuous disorder in superlattices

Publisher Website
Google Scholar
Abstract
We have derived a general diffraction relation for crystalline-crystalline superlattices including discrete fluctuations on the number of atoms in a layer and continuous fluctuations on the interface distance, both of a Gaussian type. We show that discrete fluctuations can markedly increase the linewidth of high-angle (large-q) diffraction peaks in lattice-mismatched systems. Moreover, we show that this line broadening increases strongly with increasing lattice mismatch and prove that these fluctuations on lattice-matched systems such as semiconductor superlattices are difficult to detect by high-angle diffraction techniques. These results have serious implications for the classical interpretation of x-ray diffraction from superlattices regarding the determination of elastic strains and the reconstruction of composition profiles.