Dresden 2011 – wissenschaftliches Programm

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KR: Fachgruppe Kristallographie

KR 7: Crystallography in Materials Science (jointly with DF)

KR 7.3: Vortrag

Donnerstag, 17. März 2011, 15:00–15:15, HSZ 101

X-ray characterization of Au-free grown GaAs nanowires on Si — •Andreas Biermanns¹, Steffen Breuer², Anton Davydok¹, Lutz Geelhaar², and Ullrich Pietsch¹ — ¹Universität Siegen, Festkörperphysik, Germany — ²Paul-Drude-Institut für Festkörperelektronik, Berlin, Germany

Semiconductor nanowires (NW) are of particular interest due to the ability to synthesize single-crystalline 1D epitaxial structures and heterostructures in the nanometer range. However, many details of the growth mechanism are not well understood. In this contribution we present a x-ray diffraction study of the early stage of Au-free GaAs nanowire growth on Si(111)-substrates with native oxide using the nano-focus setup available at the ID1 beamline of ESRF. The GaAs NWs were grown by molecular beam epitaxy (MBE), and their formation was induced by Ga droplets. Using a nanometer-sized x-ray beam, size and lattice parameters of individual wires were measured separately. Using asymmetric x-ray diffraction on particular zinc-blende (ZB) and wurtzite (W) sensitive reflections, we show that under the used conditions the NW growth starts with predominantly WZ phases and continues mainly in ZB phase. In addition we can show that the WZ segments of the NWs exhibit a different vertical lattice parameter compared to the zinc-blende segments. A combination of x-ray diffraction from single wires and grazing incidence diffraction shows that the base of the NW is compressively strained along the inplane direction. This strain is released within 20nm from the substrate-interface.