Diffraction at GaAs/FeSi core/shell nanowires: the formation of nanofacets
arXiv:1512.02103 · doi:10.1063/1.4949009
Abstract
GaAs/FeSi core/shell nanowire structures were fabricated by molecular-beam epitaxy on oxidized Si(111) substrates and investigated by synchrotron x-ray diffraction. The surfaces of the FeSi shells exhibit nanofacets. These facets consist of well pronounced FeSi{111} planes. Density functional theory reveals that the Si-terminated FeSi{111} surface has the lowest energy in agreement with the experimental findings. We can analyze the x-ray diffuse scattering and diffraction of the ensemble of nanowires avoiding the signal of the substrate and poly-crystalline films located between the wires. FeSi nanofacets cause streaks in the x-ray reciprocal space map rotated by an azimuthal angle of 30° compared with those of bare GaAs nanowires. In the corresponding TEM micrograph the facets are revealed only if the incident electron beam is oriented along [10] in accordance with the x-ray results. Additional maxima in the x-ray scans indicate the onset of chemical reactions between FeSi shells and GaAs cores occurring at increased growth temperatures.
15 pages, 5 figures