A conventional X-ray diffraction can be utilized for the determination of the structure of interfaces. Since X-rays do not interact strongly with the material they are probing, there are some difficulties with X-ray diffraction in two-dimensional physical systems. In recent years, two approaches have been developed. One is to deposit layers on powdered adsorbents while the other is to use grazing incidence scattering. The method is contrasted to electron diffraction to show why it offers unique advantages for certain classes of problems such as the phase transitions of physisorbed layers, the crystallography of clean reconstructed surfaces and the structures of solid-solid, solid-liquid and liquid-gas interfaces. The application of the method, as well as the principle and the instrumentation is described.
