APS 1996 March Meeting Abstract

TITLE: Determination of Near-surface Ge and Si Site Occupation in
Ge/Si(100)

AUTHORS:  Michael A. Leskovar, Shuang Meng, Uwe Hessinger and Marjorie A.
Olmstead

ABSTRACT:

When Ge is deposited on Si(001), the larger size and lower surface energy
of the Ge should impede intermixing. However, the strain
induced by the surface reconstruction has been predicted to result in a
preference for Si in some near-surface sites. The specifics of the
predicted site segregation depend on whether an empirical or ab-initio
potential is used. We have investigated the near-surface site
occupation of well-annealed <= 2 ML Ge films on single-domain Si(100)4\deg
2x1 surfaces using X-ray photoelectron diffraction (XPD)
and low energy electron diffraction (LEED). Sub-monolayer Ge deposition at
500\degC results in the Ge residing in the top layer (no
forward scattering in Ge XPD) while the LEED pattern remains mostly 2x1.
This implies Ge exchange with the surface Si layer, followed
by transport of the displaced Si to preserve the dimer row orientation
relative to that of the steps. At higher temperatures and/or coverages
some Si-Ge intermixing may be observed.