Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 36: Poster Session II (Metals; Nanostructures at surfaces; Surface or interface magnetism; Spin-Orbit Interaction at Surfaces; Electron and spin dynamics; Surface dynamics; Methods; Theory and computation of electronic structure)

O 36.75: Poster

Dienstag, 15. März 2011, 18:30–22:00, P4

Selforganized periodic 2D-Nanotemplates in Surfactant Mediated Epitaxy of Ge on Si(111) — •Claudius Klein, Martin Kammler, and Michael Horn-von Hoegen — Department of Physics & Center for Nanointegration Duisburg Essen (CeNIDE), University Duisburg-Essen, D-47057 Duisburg, Germany

Surfactant mediated growth of epitaxial Ge heterofilms on Si(111) is utilized to create selforganized 2-dim. ordered nano templates. Using Sb as surfactant a honeycomb pattern like reconstruction of 4 x 4 nm size is formed between 1 - 2 bilayer Ge coverage. Employing the spot width in SPA-LEED the degree of order in the honeycomb pattern has been optimized at a growth temperature of 700°C. STM studies confirm the increase of periodicity with growth temperature. Relaxed Ge films were grown using Bi as surfactant at 450°C. For coverages above 4 bilayers of Ge the lattice mismatch of 4.2% is then accommodated by the formation of a 2-dim. ordered hexagonal dislocation array confined to the hetero interface. Each dislocation is surrounded by a strain field causing a lateral and vertical distortion of the film. The vertical displacement field causes a height undulation of about 1 Å of the surface which becomes apparent in LEED by spot splitting. The lateral displacement fields have been explored in STM and their amplitude determined by highly sophisticated image analysis. Above an interfacial dislocation line the lattice parameter of the Ge film is expanded by more than 10% with respect to the bulk value. Inbetween two dislocation lines the Ge is still compressed to the Si lattice parameter.