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Open Access Nano Express

Lattice parameter accommodation between GaAs(111) nanowires and Si(111) substrate after growth via Au-assisted molecular beam epitaxy

Anton Davydok1*, Steffen Breuer2, Andreas Biermanns1, Lutz Geelhaar2 and Ullrich Pietsch1

Author Affiliations

1 Festkörperphysik, Universität Siegen, Walter-Flex-Str. 3, Siegen, 57072, Germany

2 Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, Berlin, 10117, Germany

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Nanoscale Research Letters 2012, 7:109  doi:10.1186/1556-276X-7-109

Published: 8 February 2012

Abstract

Using out-of-plane and in-plane X-ray diffraction techniques, we have investigated the structure at the interface between GaAs nanowires [NWs] grown by Au-assisted molecular beam epitaxy and the underlying Si(111) substrate. Comparing the diffraction pattern measured at samples grown for 5, 60, and 1,800 s, we find a plastic strain release of about 75% close to the NW-to-substrate interface even at the initial state of growth, probably caused by the formation of a dislocation network at the Si-to-GaAs interface. In detail, we deduce that during the initial stage, zinc-blende structure GaAs islands grow with a gradually increasing lattice parameter over a transition region of several 10 nm in the growth direction. In contrast, accommodation of the in-plane lattice parameter takes place within a thickness of about 10 nm. As a consequence, the ratio between out-of-plane and in-plane lattice parameters is smaller than the unity in the initial state of growth. Finally the wurtzite-type NWs grow on top of the islands and are free of strain.

Keywords:
nanowires; MBE growth; X-ray diffraction