Crystallography of surfaces and interfaces

Each solid is bounded by surfaces. An atom or molecule located directly on the surface has an altered atomic environment compared to a particle located in the middle of the solid due to its interfacial environment. Molecules impinging from the adjacent gas or liquid phase can enter into a chemical interaction and cause a further change in the surface structure. These processes form the basis of heterogeneous catalysis or corrosion processes; in microelectronics, too, surfaces and interfaces are becoming increasingly important as the dimensions are reduced. In addition to direct imaging with electron microscopy or scanning tunneling microscopy, the key to understanding the properties of surfaces and interfaces lies in the analysis of their structure using crystallographic methods.

Technically used solids, such as those used as catalysts, are usually polycrystalline. It makes sense to use single crystals as model systems to investigate the elementary processes taking place on them. The clarification of the atomic structure is preferably carried out by using the diffraction of low-energy electrons (LEED). But also methods of X-ray structure analysis, including synchrotron radiation, have recently become increasingly important.