American Chemical Society
ph5002022_si_005.avi (4.24 MB)

Nanospectroscopic Imaging of Twinning Superlattices in an Individual GaAs-AlGaAs Core–Shell Nanowire

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posted on 2014-11-19, 00:00 authored by Alexander V. Senichev, Vadim G. Talalaev, Igor V. Shtrom, Horst Blumtritt, George E. Cirlin, Jörg Schilling, Christoph Lienau, Peter Werner
GaAs nanowires (NWs) exhibit different, zinc blende (ZB) and wurzite (WZ), crystalline phases and one generally finds an uncontrolled switching between both phases on a scale of 1–10 nm. The change of crystalline structure and stacking fault density strongly affects the local confinement potential of GaAs NWs. Combining low temperature near-field spectroscopic imaging and transmission electron microscopy measurements performed on the very same individual GaAs nanowire allows us to gain an understanding of the local structure–property correlations in such wires. From the photoluminescence measurements at subwavelength spatial resolution local characteristics of the band structure are derived. In particular, our method enables us to assign the observed band gap reduction to the high level of impurity dopants and to distinguish emission from ZB-type regions and from periodically twinned superlattice regions. In this way we demonstrate the ability to trace spatial variations of the crystal structure along the wire axis by all-optical means. Our results provide direct and quantitative insight into the correlations between morphology and optics of GaAs nanowires and hence present an important step toward band gap engineering of nanowires by controlled crystal phase formation.