Phason and phonon contributions to the diffraction pattern of (√3 × √3)-type hexagonal layers

Abstract

The concept of an average unit cell has been used in the diffraction analysis of epitaxial hexagonal layers with frozen deviations from perfect symmetry, that is phasons and phonons. Appropriate probability distributions of atomic distances from the reference lattice lines have been calculated and used for the construction of a so-called envelope function, describing the maximum intensities of the diffraction peaks. For the (√3 × √3) hyperstructure the peak intensities have been interpreted as a result of phonons frozen in the hexagonal structure. It was also shown that these diffraction peak intensities could be described properly by the phonon–phason coupling approach.