Dresden 2017 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 90: Surface Dynamics: Experiments
O 90.2: Vortrag
Donnerstag, 23. März 2017, 10:45–11:00, WIL C107
Surface-morphology transition between step-flow growth and step bunching — •Konrad Bellmann1, Udo W. Pohl1, Alexander Sabelfeld1, Christian Kuhn1, Tim Wernicke1, and Michael Kneissl1,2 — 1Technische Universität Berlin, Institute of Solid State Physics — 2Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin
Epitaxially grown opto-electronic devices rely on smooth interfaces with step-flow morphology. The surface-morphology transition between step-flow growth and step bunching will be theoretically discussed by comparing two different boundary conditions to solve the differential equation for surface diffusion. Favored smooth surfaces rely on vicinal terraces which are characterized by a mean terrace width and terrace-edge conditions. An energy diffusion-barrier at the terrace edge, the Ehrlich-Schwöbel barrier, influences the adatom incorporation towards the lower terrace edge. The first approach simply considers an asymmetric equilibrium adatom-density at the edges which offers a simple analytic morphology transition relation. The second more-physical approach considers an asymmetric adatom-incorporation flux at the edges. Both approaches yield a similar qualitative behavior. However, the morphology transition does not only rely on the two adatom-incorporation rates at the edges and the surface diffusion, but also on the adatom-mean resident time on the surface. Finally, the morphology transition between step-flow growth and step bunching is experimentally confirmed by homoepitaxial growth of AlN.