STRUCTURE-ANALYSIS OF GE DIMER ON SI(001) BY MEDIUM-ENERGY ION-SCATTERING BLOCKING PROFILES FROM EMBEDDED GE LAYERS

We propose a novel technique for determining the surface structure qua ntitatively and accurately by modifying the substrate, and apply it to the structure analysis of Ge dimers on the Si (001) surface. One or t wo atomic layers of Ge were embedded below 4-12 ML of Si overlayer by molecular-beam epitaxy and with atomic scale layer precision. The ions scattered from embedded Ge layers are blocked by the reconstructed su rface atoms. Since the origin of the signals are restricted, the scatt ering-blocking pairs are uniquely assigned. In addition, the effect of thermal vibration can be minimized by choosing a distance between sca ttering and blocking atoms that is suitable for analysis. Therefore, w e can observe the sharp and simple blocking profile of embedded Ge sig nals, and can determine the atomic displacements of reconstructed surf aces. The bond length of the Ge-Ge dimer on Si (001) surface was deter mined by this method to be 2.4 Angstrom. (C) 1997 American Vacuum Soci ety.