Probing interface roughness by X-ray scattering

X-ray scattering at glancing angles can be exploited to probe interface roughness. Various theories for this technique will be reviewed. The applicability of the theories is shown to depend on the relevant length scales of sample and X-rays. Approximations are discussed and improvements of the theory are suggested. Both specular reflection, diffuse scattering and absorption of X-rays will be discussed. It will be shown that relevant roughness parameters, like root-mean-square roughness, lateral and perpendicular correlation lengths and the degree of jaggedness can be extracted from the experiments. Possible forms for the roughness correlation function are discussed. As an example, it is shown how the interface roughness of an oxidic multilayer has been probed by X-ray scattering.