title: Compositional characterization of GaAs/GaAsSb nanowires by quantitative HAADF-STEM.
abstract: The Sb concentration in axial GaAs(1-x)Sb(x) inserts of otherwise pure GaAs nanowires has been investigated with quantitative high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). The Sb concentration was quantified by comparing the experimental image intensities normalized to the incident beam intensity with intensities simulated with a frozen lattice multislice approach. Including static atomic displacements in the simulations was found to be crucial for correct compositional analysis of GaAs(1-x)Sb(x). HAADF intensities of individual nanowires were analysed both across the nanowires, exploiting their hexagonal cross-sectional shape, and along the evenly thick central part of the nanowires. From the cross-sectional intensity profiles, a decrease in the Sb concentration towards the nanowire outer surfaces was found. The longitudinal intensity profiles revealed a gradual build-up of Sb in the insert. The decrease of the Sb concentration towards the upper interface was either gradual or abrupt, depending on the growth routine chosen. The compositional analysis with quantitative HAADF-STEM was verified by energy dispersive X-ray spectroscopy.
authors.affiliation: Department of Physics, Norwegian University of Science and Technology (NTNU), Trondheim, Norway.
authors.forename: H
authors.initials: H
authors.lastname: Kauko
authors.forename: T
authors.initials: T
authors.lastname: Grieb
authors.forename: R
authors.initials: R
authors.lastname: Bjørge
authors.forename: M
authors.initials: M
authors.lastname: Schowalter
authors.forename: A M
authors.initials: AM
authors.lastname: Munshi
authors.forename: H
authors.initials: H
authors.lastname: Weman
authors.forename: A
authors.initials: A
authors.lastname: Rosenauer
authors.forename: A T J
authors.initials: AT
authors.lastname: van Helvoort