Self-organized ordering of $\mathrm{Si_{1-x}Ge_x}$ nanoscale islands studied by grazing incidence small-angle x-ray scattering

• Published in: Journal of Physics D: Applied Physics
• Main Authors: Schmidbauer, M., Wiebach, Th, Raidt, H., Hanke, M., Köhler, R., Wawra, H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: IOP Publ. 1999
• Subjects: info:eu-repo/classification/ddc/530; Low Island
• Online Access: https://bib-pubdb1.desy.de/record/390265; https://bib-pubdb1.desy.de/search?p=id:%22PUBDB-2017-09423%22

Highly regular islands of strained Si1-xGex have been grown on Si (001) by liquid phase epitaxy (LPE). The islands themselves are {111}-faceted truncated pyramids with a narrow base-width size distribution and coherent behaviour. In this study we report on the state of lateral ordering within a single layer of Si1-xGex islands. Grazing incidence small-angle x-ray scattering (GISAXS) was used to investigate the ordering as a function of island coverage. At very low island coverage the array behaves like a two-dimensional liquid exhibiting an increased number of island dimers which orient along the island base diagonal langle100rangle. On increasing the coverage these dimers develop into extended chains of islands oriented along langle100rangle. At high coverage there is strong ordering along both the langle100rangle and the langle110rangle directions. The self-organised ordering can be explained by two possible mechanisms: (i) that the observed ordering is driven by the anisotropy of the elastic constants where short-range order along the soft langle100rangle directions is expected, and (ii) that there is an underlying two-dimensional ripple pattern in the wetting layer aligned along the langle100rangle directions. At later stages of growth this pattern transforms into pseudomorphic islands.