X-ray and neutron reflectivity

The general concepts of x-ray and neutron reflectivity are outlined. Theoretical principles are discussed at the beginning where both, the optical treatment based on the solution of the Helmholtz equation and the kinematical scattering formalism are given. Afterwards experimental standard setups are presented, and a small fraction of the work that has been done in the past is discussed. The examples deal with scattering from liquid thin films and polymer films where x-ray and neutron reflectivity are almost unique probes to obtain structural information. This is in particular true for polymer/polymer interfaces where neutron reflectivity has one of its most prominent applications. Other examples show how oxidation processes can be monitored by x-ray reflectivity and how layer systems of technological importance, here CoSi2 layers, can be quantitatively characterized. Furthermore off-specular scattering is briefly discussed and its importance for a complete analysis emphazised.