Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 12: Quantum Dots and Wires: Arsenides

HL 12.1: Talk

Monday, March 14, 2011, 12:00–12:15, POT 151

Calculation of the Diameter dependent Polytypism in GaAs Nanowires — •Volker Pankoke, Peter Kratzer, and Sung Sakong — Fakultät für Physik Universität Duisburg-Essen, Lotharstr. 1,47048 Duisburg, Germany

The formation energies of GaAs nanowires (NWs) have been calculated from a structural motif approach, supporteed by first-principles data of small diameter wires. The calculated nanowires are cut from the bulk material in [111] direction and [0001] direction for zinc blende (ZB) and wurtzite (WZ) structure, respectively. Afterwards the hydrogen free surfaces were completely relaxed. GaAs bulk material has ZB structure,but the ground state of nanowires also depends on surfaces and edges.We considered wires with hexagonal cross sections with {11-20} and {10-10} facets in case of wurtzite structure, and {10-1} and {11-2} for zinc blende structure.

We performed both density functional calculations and structural motif expansion for several of these different wires and found, that the wurtzite formation energy of small nanowires with diameters less than 80 Å is lower than the zinc blende one, due to the lower surface energy of wurtzite. This still holds if edges are negligible. The influence of additional dangling bonds at the edges and its effect on the WZ ZB transition is discussed.