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Published online by Cambridge University Press: 10 February 2011
The surface step structure of step graded Si1-xGex buffers was investigated by scanning tunneling microscopy (STM). On pseudomorphically grown samples, single atomic steps were found, with the 2×8 reconstruction indicating Ge segregation. Upon strain relaxation, surface slips and the development of the cross-hatched surface takes place. Here, close to the surface slips, the step structure was found to consist of double height DA steps. This feature is not simply kinematically driven step bunching but can be attributed to the anisotropic strain field on the surface and to the Ge segregation. Analysis of STM cross-sections were taken to estimate the relaxation of our samples. The obtained values agree well with x-ray measurements. The relaxation is found to depend exponentially on the temperature, as theoretically expected.