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The heteroepitaxial growth of InAs nanowires (NWs) on GaAs [formula] substrate was investigated by metal-organic vapor phase epitaxy. The vapor-liquid-solid (VLS) growth mechanism was applied with gold as seed material. InAs NW with two types of morphology were observed. The first morphology type exhibited a tapered NW shape. In a distinct region below the alloy particle the shape was influenced by the precursor surface diffusion. The NW growth was attributed to Au-rich liquid alloy particles containing gallium as a result of the initial Au–GaAs interaction. Differential scanning calorimetry measurements revealed the lowest eutectic temperature of the Au–Ga–In liquid alloy for different compositions. For a considerable amount of gallium inside the ternary alloy, the eutectic temperature was found to be below the InAs NW growth temperature window. A second type of morphology with a more columnlike shape was related to a very high indium fraction inside the liquid alloy particle during VLS growth. These NW exhibited a change in the side facet orientation from [formula] to [formula] below the droplet. Additionally, the sample structure was studied by transmission electron microscopy. A change in the InAs NW crystal structure from sphalerite-type to mainly wurtzite-type was observed with an increase in the growth temperature. [ABSTRACT FROM AUTHOR]

The heteroepitaxial growth process of InAs nanowires (NW) on GaAs $[\bar{1}\bar{1}\bar{1}]_{\mathrm{B}}$ substrate was investigated by X-ray grazing-incidence diffraction using synchrotron radiation. For crystal growth we applied the vapor–liquid–solid (VLS) growth mechanism via gold seeds. The general sample structure was extracted from various electron microscopic and X-ray diffraction experiments. We found a closed Ga xIn1− xAs graduated alloy layer at the substrate to NW interface which was formed in the initial stage of VLS growth with a Au–Ga–In liquid alloy. With ongoing growth time a transition from this VLS layer growth to the conventional VLS NW growth was observed. The structural properties of both VLS grown crystal types were examined. Furthermore, we discuss the VLS layer growth process. [ABSTRACT FROM AUTHOR]

In analogy to PbS–Sb2S3-minerals nanowires of synthetic boulangerite (Pb5Sb4S11) with diameters ranging from 100 to 500 nm and lengths up to 100 μm were crystallized from the melt. In most cases these nanowires are arranged like bundles and microtubes, which are inspected by scanning electron microscopy. The chemical composition of these materials was analysed by electron microprobe and transmission electron microscope adapted energy dispersive X-ray analysis. The lattice parameters of natural and synthetic boulangerite nanomaterials were determined by powder X-ray diffraction. The crystal structure was examined by means of high resolution transmission electron microscopy, whereby the relation between structure and morphology was studied and the material was checked regarding cation ordering. [Copyright &y& Elsevier]

Abstract: Nanowires of an iodine containing Pb–Sb-sulfosalt have been synthesized by chemical vapor transport. Their structure was studied using high-resolution transmission electron microscopy and X-ray powder diffraction. The lattice parameters show values equal to a=4.9801(4)nm, b=0.41132(8)nm (with two-fold superstructure), c=2.1989(1)nm and β=99.918(6)°. These parameters and the results of a multislice simulation are in good agreement with the mineral pillaite, Cu0.10Pb9.16Sb9.84S22.94Cl1.06O0.5 (space group , a=4.949(1)nm, b=0.41259(8)nm, c=2.1828(4)nm, and β=99.62(3)°). Microprobe and EDX analyses yielded a chemical composition of Cu0.507(5)Pb8.73(9)Sb8.15(8)I1.6S20.0(2) which is close to natural pillaite but contains no oxygen and iodine instead of chlorine. The structure of the investigated material is based on chains of M–S polyhedra (M=Pb or Sb) typical for the architecture of sulfosalts implying iodine atoms in trigonal prismatic coordination with Pb atoms from the M–S polyhedra of neighboring chains. The [010] superstructure of the specimen was found to be unstable under electron beam irradiation with a rapid decrease of the b lattice parameter from 0.8 to 0.4nm within 5min. [Copyright &y& Elsevier]