Coherent diffraction patterns of individual dislocation strain fields

The coherent x-ray diffraction (CXD) method is particularly attractive for understanding structures that can be represented as phase objects. Diffraction from a crystal acquires a phase whenever atoms are displaced from lattice sites, even by small fractions of an angstrom, so CXD measured around a Bragg peak is ideal for studying strain. We have succeeded in using these coherent beams to study the strain field arising from individual misfit dislocations located at an interface between a GeSi thin film and its Si(001) substrate. The data have not yet been inverted to images, but we show how the asymmetric CXD diffraction patterns can be explained qualitatively by a model phase structure.