Step-debunching in Sn/Si(001) surfaces

Step-debunching, or the transformation of step structure from double atomic height to single atomic height, has been observed using scanning tunneling microscopy (STM) on the vicinal Si(001) surface upon adsorption of 0.8 ML Sn. The surface shows a two-domain c(8 x 4)-Sn structure containing defective features such as antiphase boundaries and so on. One of the causes of step-debunching is the release of misfit-induced strain between the substrate and adsorbates. The other is related to kinetics, where Sn replaces surface silicon layers during the formation of c(8 x 4) and the removed Si atoms are incorporated into the step to extend the terrace. The kinetics on the small terrace width is responsible for the observed defective surface structure. (C) 2004 Elsevier B.V. All rights reserved.