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 0.3degrees miscut (0 0 1) Si are studied systematically. Five samples with Si spacer layer thicknesses ranging from 12.6 to 102.7 nm and 6 monolayer 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 25 nm, 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. (C) 2002 Elsevier Science B.V. All rights reserved.