Lattice defects of organic molecular crystals affect their optical or electrical properties by changing the local energy structure. Lattice defects also playa very important role in the chemical and physical properties, for example, as an active site of a catalyst or an initiating point of a solid state reaction. However, very little has been reported on the defect structure of real organic crystals. In the past ten years it became clear that the origin and the structure of the defects depend on the geometrical and chemical nature of the building units of the crystal, the molecules. Molecular...

1.1 The Role of Silicon as a Semiconductor Silicon is unchallenged as a semiconductor base material in our present electronics indu stry. The reasons why it qualifies so strongly for this particular purpose are manyfold. The attractive combination of physical (electrical) properties of silicon and the unique properties of its native oxide layer have been the original factors for its breathtaking evolution in device technology. The majority of reasons, however, for its present status are correlated with industrial prosessing in terms of charge units ( economy), reliability (reproducibility),...

Our understanding of the basic processes of crystal growth has meanwhile reached the level of maturity at least in the phenomenological concepts. This concerns for example the growth of pure crystals from a low-density nutrient phase like vapor or dilute solution with various aspects of pattern formation like spiral and layer growth, facetting and roughening, and the stability of smooth macroscopic shapes, as well as basic mechanisms of impurity incorporation in melt growth of (in this sense) simple materials like silicon or organic model substances. In parallel the experimental techniques to...