EXCHANGE MECHANISMS AT THE GE SI(001) INTERFACE FROM A MULTIPLE-SCATTERING ANALYSIS OF THE GE L-3 ABSORPTION-EDGE/

Intermixing in Ge/Si(001) systems has been recently observed and has e merged as a crucial and controversial topic in the study of Ge first s tages of interface formation. In this paper we investigated the struct ure of Ge overlayers epitaxially grown on Si(001) substrates by a refi ned approach to x-ray absorption spectroscopy (XAS) at the Ge L-3 edge . XAS experimental spectra, recorded in situ using plane polarized syn chrotron radiation, have been directly compared to several Ge L-3 near -edge spectral features calculated for different Ge/Si(001) growth mod els making use of a multiple-scattering approach. This analysis clearl y excludes a layer-by-layer Ge laminar growth and confirms the occurre nce-of intermixing processes even in the case of Ge room temperature d eposition. Moreover, information on the interface structure has been e videnced and the occurrence of a preferential double-layer ordering me chanism along the [111] crystallographic directions has been singled o ut.