X-ray optics of surfaces (reflection and diffraction at grazing angles of incidence)

A new direction in the field of x-ray optics is discussed. This new direction is associated with diffraction at grazing angles of incidence and diffraction; it is associated with the excitation of x-ray surface waves and quasiwaveguide modes, and with the study of the angular and energy dependences of the reflection spectra. An analysis of theoretical and experimental investigations in this area is carried out with the aim of determining the possibility of using these diffraction and reflection features for the study of surface layers, thin films and interfaces. The extremely asymmetric two- and multiwave diffraction schemes and the two-wave symmetric noncoplanar diffraction scheme are analyzed, as is the anomalous reflection of the x-rays. The angular dependences of the anomalous reflection are calculated on the basis of a model of a nonuniform surface layer. It is shown to be possible to use the angular dependence of the reflection for the determination of the statistical characteristics of surface nonuniformities. Experiments for the determination of short range order in surface films on the basis of the analysis of the extended fine structure of reflection spectra are discussed.