Non-specular X-ray reflection from self-organized ripple structures in Si/Ge multilayers

The ripples at the interfaces of five-period Si/Ge multilayer samples, grown on 0.3° miscut (001) Si are studied systematically. Five samples with Si spacer layer thicknesses ranging from 12.6 to View the MathML source and View the MathML source Ge were investigated. From the X-ray reflectivity investigations a characteristic step bunching morphology is found, with a ripple period which increases by more than 30% if the Si spacer thickness is doubled from about 13 to View the MathML source, but does not change further with increasing spacer. These results shed light on the ongoing discussion about the relative importance of kinetic versus strain-related origin of the ripple pattern.