DIFFRACTION FROM SURFACES WITH RANDOMLY DISTRIBUTED STRUCTURAL DEFECTS

Diffraction techniques are powerful tools to probe surfaces with respe ct to structural defects. Basing our calculation on the kinematic appr oximation valid for the analysis of spot profiles we present a general closed-form solution for the spot profile for surfaces with randomly displaced domains. Generally both lateral and vertical displacements o f domains are considered. On the other hand within one domain all atom s are arranged perfectly with respect to each other. The spot profiles depend only on the distribution of displacements and domain sizes sup posing that these are not correlated. From analyzing spot profiles at different scattering conditions (order of the spot and varying the ver tical scattering condition) one can conclude the kind of defects, eval uate their distribution and the distribution of domain sizes. Finally, we present a detailed analysis of spot profiles for strongly distorte d surfaces (all atoms are displaced) and for surfaces with grain bound aries. While for strongly distorted surfaces the spots vanish with inc reasing scattering vector for surfaces with grains, the spot profiles can be obtained from the incoherent interference of the grains for the se scattering conditions.