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O: Oberflächenphysik

O 32: Epitaxie und Wachstum (II)

O 32.4: Vortrag

Donnerstag, 29. März 2001, 16:15–16:30, C

Stability and adatom dynamics on surfactant-covered growing Ge(111) films — •K. Schroeder, Y. Cao, A. Antons, R. Berger, Wi. Kromen, and S. Blügel — Institut für Festkörperforschung, Forschungszentrum Jülich, 52425 Jülich

The heteroepitaxy of Ge on Si(111) is greatly modified by surfactant layers like As or Sb. It has been found, that during growth the surfactant covered Ge film relaxes and the structure changes [ N. Theuerkauf, Ph.D.-thesis RWTH Aachen 1999; M. Horn-von Hoegen, Z. Kristallogr. 214, 1-75 (1999)]. By ab initio calculations we have investigated the stability of different structures of Ge(111):Sb(1ML) as a function of the lateral lattice constant. We find that the (2×1)-reconstruction of Ge(111):Sb experimentally found to be stable at the equilibrium lattice constant of Ge is also the stable structure for slightly dilated Ge films (< 1%), for larger dilatations the (1×1)-structure becomes stable. For compressed Ge films the (√3×√3)T4-structure (found experimentally on Si(111):Sb) becomes competitive. It is stable for lattice constants smaller than a_Si (compression > 4%). Generally, we find that a surfactant covered thin film has a different equilibrium lattice constant than the bulk crystal. We have also investigated the dependence of diffusion and exchange barriers on As-covered Ge(111) which show a drastic dependence on the lateral lattice constant of the film. These results are relevant for the understanding of surfactant mediated island growth on stressed films.