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O: Oberflächenphysik
O 20: Epitaxy and growth II
O 20.3: Vortrag
Dienstag, 28. März 2006, 11:45–12:00, WIL B321
Epitaxial growth of Bi(111) on Si(001) studied by SPA-LEED: Morphology and Lattice Accomodation — •Giriraj Jnawali, Hichem Hattab, Boris Krenzer, and Michael Horn von Hoegen — Universität Duisburg-Essen, Fachbereich Physik, Lotharstr. 1, 47057 Duisburg
Deposition of Bismuth at 150 K results in the formation of epitaxial films. The LEED pattern shows diffuse spots reflecting a hexagonal orientation in two Bi(111) domains rotated by 90∘. With increasing coverage only a ring of intensity remains, reflecting rotational disorder. The ring disappears after annealing to 200 K. Annealing to 350 K reduces surface roughness and very flat surfaces are obtained with sharp LEED spots. Further annealing to 470 K leads to dewetting of the film which can be observed from LEED pattern. The surface morphology is studied by Spot Profile Analysing Low Energy Electron Diffraction during deposition and annealing. The lattice constant a0,Bi(111) = 4,54 Å of Bi(111) matches perfectly by a factor of 11:13 with the lattice constant a0,Si(001) = 3,84 Å of the Si(001) surface in one direction. In the perpendicular direction the row distance a0,Bi(111) sin60∘= 3,94 Å of the Bi(111) film almost matches the Si(001) lattice constant. For the films thicker than 2 nm the remaining lattice mismatch of 2.5 % is relieved by a disordered array of interfacial dislocations which is observed by spot splitting in the LEED pattern. From the distance between the satellite spots we conclude an almost strain relieved growth of the Bi(111)-film on the Si(001) surface.