Nanoscopic crystallography of chalcopyrite CulnS₂ by techniques of convergent-beam electron diffraction

Abstract

We investigate the crystallography of CuInS₂ single crystals on a nanoscopic scale in space by transmission electron microscopy. We combine several convergent-beam electron diffraction techniques (CBED). Microdiffraction, a variant of CBED with a moderate convergent beam, is used for a space-group analysis. The arrangements of so-called defect and excess lines as visible in (000) and high-order Laue zone CBED discs are utilized for the determination of the lattice parameters and for the exact atom positions within the crystallographic unit cell respectively. Therefore the experimental CBED patterns are compared with simulations based on the dynamical diffraction theory. These investigations reveal the analysed CulnS₂ material to be a reliable model substance for chalcopyrites (contrary to CuInSe₂). We utilize this model substance to determine reflections that occur owing to ‘Umweganregungen’. The unambiguous identification of such reflections is indispensable for the differentiation between chalcopyrites and related crystal structures.