During the last 20 years interest in high-resolution x-ray diffractometry and reflectivity has
grown as a result of the development of the semiconductor industry and the increasing interest
in material research of thin layers of magnetic organic and other materials. For example
optoelectronics requires a subsequent epitaxy of thin layers of different semiconductor
materials. Here the individuallayer thicknesses are scaled down to a few atomic layers in
order to exploit quantum effects. For reasons of electronic and optical confinement these thin
layers are embedded within much thicker cladding layers or stacks of multilayers of slightly
different chemical composition. It is evident that the interface quality of those quantum weHs
is quite important for the function of devices. Thin metallic layers often show magnetic
properties which do not ap pear for thick layers or in bulk material. The investigation of the
mutual interaction of magnetic and non-magnetic layers leads to the discovery of colossal
magnetoresistance for example. This property is strongly related to the thickness and
interface roughness of covered layers.
