Total reflection X-ray topography for the observation of misfit dislocation strain at the surface of a Si/Ge-Si heterostructure

Abstract

Synchrotron X-Ray Topography has been used in Total Reflection Topography (TRT) mode to observe strain induced surface bumps due to the presence of underlying misfit dislocations in strained layer SiGe on Si epitaxial heterostructures. In these experiments the x-rays approached the sample surfaces at grazing incident angles below the total external reflection critical angles for a number of reflections and hence surface strain features nominally less than a few tens of Ångstroms from the sample surface have been observed. These are similar to the surface bumpiness observed by Atomic Force Microscopy, albeit on a much larger lateral length scale. The fact that TRT mode images were taken was confirmed by the observation of clear and conventional back reflection topographic images of misfit dislocations in all samples when the grazing incidence angle became greater than the critical angle.