The wetting layer formed during the early stages of Ge/Si(001) growth was found in recent experiments to undergo a roughening process, where the SA surface steps affect the spatial organization of vacancy lines (VLs) by increasing (stretching) or decreasing (squeezing) their average spacing. By using a combination of atomistic simulations and elastic theory of surface defects, the interaction energy of the SA steps and VLs were estimated for each of the observed defect configurations. It was found that the repulsive SA-VL interactions lead to an increase in the spacing of the VLs in the so-called stretch arrangement, but do not significantly affect the VL spacing in the so-called squeeze configuration thus providing an explanation for the observed correlations in the wetting layer roughness.

Self-Assembly of Steps and Vacancy Lines during the Early Stages of Ge/Si(001) Heteroepitaxy. D.T.Tambe, C.V.Ciobanu, V.B.Shenoy: Applied Physics Letters, 2005, 87[25], 251908 (3pp)