Electron microscopy study of incommensurate modulated structures in misfitternary chalcogenides

The study of misfit structures by means of transmission electron microscopy and associated techniques is reviewed. It is complementary to X-ray crysta llography and provides a local and direct view of the beautiful complexity of these systems. Three different types are presented in this work. Misfit columnar structures can be contemplated as a case of one-dimensional misfit structures while misfit layer structures are considered as two-dimensional misfit structures. Some extra dimensionality is added when these misfit la yer structures wrap to give rise to tubular crystals. Electron microscopy/d iffraction shows clearly in many examples the presence of structural modula tions as weak satellite reflections that are very difficult to detect by X- ray diffraction methods. Besides, high-resolution images show the presence of stacking defects in some of these misfit layer structures. (C) 2001 Else vier Science Ltd. All rights: reserved.