EVIDENCE FOR STRAIN-INDUCED SURFACE REARRANGEMENT - GE EPITAXIAL OVERLAYERS ON SI(001)

The structure of Ge dimers on well-oriented Si(001) has been studied b y surface-sensitive X-ray absorption fine structure (XAFS) technique i n situ after the growth by molecular beam epitaxy (MBE). For 1 monolay er (ML) Ge on Si(001), the elongated Ge dimer structure with the Ge-Ge bond length of 2.51 + 0.01 Angstrom was observed. The observed local structure around Ge atoms indicates that the adatoms take the p(3)-lik e configuration as a result of a substrate-to-adatom charge transfer i nduced by surface strain. The observed Ge/Si site exchange suggests th at the surface strain opens up a site-specific atomic migration channe l between the adjacent layers, serving as a driving force of interface mixing for Ge/Si and Si/Ge.