Effects of grazing incidence conditions on the x-ray diffuse scattering from self-assembled nanoscale islands

Abstract

Grazing incidence small-angle x-ray scattering and grazing incidence x-ray diffraction from SiGe nanoscale islands grown on Si(001) substrate were investigated. Experiments and corresponding theoretical simulations based on the distorted-wave Born approximation were carried out. The strain field inside and in the vicinity of the SiGe islands was calculated in the framework of linear elasticity theory using the numerical finite element method. The diffuse intensity pattern in reciprocal space reveals a well-resolved fine structure with prominent maxima and a complicated fringe pattern. The distribution of diffuse intensity in reciprocal space strongly depends on the angle of incidence with respect to the sample surface. The results obtained substantiate the important role of basically five (grazing incidence small-angle x-ray) and nine (grazing incidence diffraction) scattering channels that have to be considered for a complete understanding of the scattering scenario. A refined island model concerning shape, size, and Ge composition was elaborated.