Characterization of the local structure of Ge quantum dots by X-ray absorption

Analysis of Ge K-edge extended X-ray absorption fine structure (EXAFS) of strained and relaxed germanium quantum dots (QDs) in "sandwich" Si/Ge/Si structures, is reported. The QDs were formed in germanium monolayers (ML) grown with different thickness at the very low temperature (210degreesC). The presence of Si cap on the Ge ML induces additional stresses and modifies the shape and composition of formed structures. Formation of monocrystal Ge core inside the QDs is suggested on the basis of the results of fitting and from the estimation of contribution of Si atoms from the QDs surface. The reduction of Ge layer growth temperature to 210degreesC limits the Si interdiffusion inside the QDs. (C) 2004 Elsevier B.V. All rights reserved.