Dresden 2009 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 9: Poster 1
HL 9.15: Poster
Montag, 23. März 2009, 14:30–17:00, P2
Phase separation and nanocrystal formation in bulk amorphous GeO — •Christoph J. Sahle1, Christian Sternemann1, Achim Hohl2, Ralph Wagner3, Dirk Lützenkirchen-Hecht3, Alexej Herdt3, Omid M. Feroughi1, Heiko Conrad1, and Metin Tolan1 — 1Fakultät Physik / DELTA, Technische Universität Dortmund, D-44221 Dortmund, Germany — 2Institute for Materials Science, Darmstadt University of Technology, D-64287 Darmstadt, Germany — 3Abteilung Physik, Bergische Universität Wuppertal, D-42097 Wuppertal, Germany
Bulk amorphous germanium monoxide (a–GeOx with x ≈ 1) is studied regarding the temperature–induced disproportionation, i.e phase separation of GeOx into Ge and GeO2, and formation of Ge nanocrystals by measurements of the Ge K–edge XANES employing fluorescence yield detection and x–ray diffraction. Germanium/oxygen systems are an interesting class of materials due to their potential as precursors for the synthesis of Ge nanocrystals in an oxide–matrix. The disproportionation of a–GeOx was characterized in the temperature range between 160∘C and 640∘C. Phase separation sets in at 250∘C and is almost completed at 440∘C. X–ray diffraction proves the occurrence of Ge nanocrystals of several nm diameter embedded in a GeO2 matrix for temperatures above 500∘C. The findings are discussed by a structural model of a–GeOx in which the native amorphous Ge monoxide is proposed to consist of nanoscaled regions of Ge and GeO2 which are separated by ultra–thin sub–oxide interfaces.