Au nanowires (AuNWs) were produced by electroless reduction of HAuCl4 in a micellar structure formed by oleylamine and investigated by means of high-resolution transmission electron microscopy (HRTEM). Micrometer long ultra-thin flexible AuNWs with 1—2 nm diameter and AuNWs with about 12 nm diameter and a few hundred nm length were produced. Their extremities show a characteristic bulging. In contradiction with previous work, the bodies of the 12 nm nanowires are defect-free along the axial direction, their extremities, however, show the presence of twin boundaries. Ultra-thin AuNWs were often found as bundles presenting lengths of few micrometers. Although they are stable in solution for months, they were found to be quite sensitive to electron beam irradiation during HRTEM experiments, with a tendency to break up into face centered cubic (fcc) Au droplets. It is proposed that the micellar configuration of oleylamine plays a fundamental role in the atomic arrangement of nanowires. Finally, we anticipate our results to be a starting point for a more realistic experimental investigation of surface effects on the mechanical properties of ultra-thin nanowires with high aspect ratio, which have been only widely exploited theoretically.

Growth orientation and type of internal structures are both observed to change abruptly as a function of growth temperature in catalyst free growth of gallium nitride nanowires. In the present work, corresponding temperature-dependent changes in the growth matrix substrate that can affect the availability of nucleation sites and influence the reactivity of constituent adatom materials in catalyst-free nanowire growth are investigated. The influence of Ga vapor pressure and an abrupt change in the availability of single versus molecular adatom constituents is identified as a possible controlling parameter.

In this study, well separated tapered CuO nanowires have been synthesized on copper grid using an easy and cost effective thermal oxidation method. A set of spectroscopic investigations have been performed on one single tapered CuO nanowire using Energy Dispersive X-ray, confocal Raman and confocal Photoluminescence spectroscopy to get insight into the mechanism of growth of the nanowires. Energy Dispersive X-ray studies reveal crystallization process of CuO nanowires occur from Cu/Cu2O mixed phase state to pure CuO structure. Raman measurements indicate a little sharpening of the Raman peaks with increasing growth temperature of the nanowires starting from 400°C to 600°C. Photoluminescence studies were carried out by mapping along the length of the nanowire to investigate the growth as well as optical properties of a single tapered CuO nanowire. As the diameter of the single tapered CuO nanowire decreases, the green emission of the nanowire gradually shifts towards the higher energy side. A steady blue shift of 20 nm of the photoluminescence peak has been attributed to the nanosize effect of the tapered nanowire along the length and enhanced surface defects.

We have fabricated carbon-containing nanowires by a gallium focused ion beam-induced deposition process from the precursor phenanthrene, C14H10. The electrical conductivity of the nanowires is only weakly temperature dependent below 300K, and reveals a superconducting state below Tc ˜ 7 K. We have measured the temperature dependence of the resistive upper critical field Hc2(T), and from those data, estimate the zero temperature critical field and coherence length to be 8.8 T and 6.1 nm, respectively. The Tc of this material is approximately 40% higher than that in any other FIB/direct write nanowire, such as those based on W(Ga), and thus offers the possibility of fabricating superconducting direct-write nanostructures that function at liquid helium temperature.

The incoherent transport model based on electron-phonon interaction was introduced for calculating the current-voltage characteristics of the nanowire conductor. The current-voltage characteristics of silicon nanowire calculated based on this model was discussed. The charge transport was described by the rate equation containing the coherent (tunneling) and incoherent (energy dissipation) rates, and the incoherent rate was calculated from the Hamiltonian in which the electron-phonon interaction was incorporated. The coherent transition corresponds to the electronic transition between electrode states and channel states without any energy dissipation. On the other hand, the incoherent transition corresponds to the electronic transition between electrode states and channel states where the energy difference of those two states means a thermal dissipation. Therefore, in order to carry out the calculation by the rate equation, the density of states (DOSs) of the carriers in electrode and the channel and the DOS of the phonon in the channel are needed. The current-voltage characteristics were calculated by using the DOS of n-type semiconductor for the electrode and by using intrinsic semiconductor DOS for the channel. In addition, the calculation was performed by using the DOS of the silicon nanowire phonon.

ZnO nanowires with strong green emission synthesized by chemical vapor deposition were treated using hydrogen plasma. The effect of hydrogen plasma treatment was studied by means of photoluminescence and photoconductivity. A strong passivation of the green emission and a significant enhancement of the near band edge emission were found after the hydrogen plasma treatment. The conductivity of the nanowires in dark was increased by more than 3 orders of magnitude. The photoconductivity also increased after the hydrogen plasma treatment. The observed changes in the luminescence and photoconductive properties of the ZnO nanowires were likely caused by hydrogen atoms occupying both oxygen vacancies and interstitial sites.

Templated electrodeposition was used to synthesize silver-zinc oxide nanowires and iron oxide (Fe2O3) nanotubes in polycarbonate track etched (PCTE) membranes. Metal/oxide segmented nanowires were made to produce hydrogen gas from a water/methanol mixture under ultraviolet irradiation. It was observed that gas production increased during irradiation. Iron oxide nanotubes were synthesized via a gel synthesis route, avoiding clogging of the membrane pores during growth. The nanotubes formed without thermal after-treatment. Transmission electron microscopy (TEM) analysis and selected area electron diffraction (SAED) revealed a completely amorphous iron oxide structure. By demonstrating the synthesis of photocatalytically active segmented nanowire and nanotubes without post-treatment steps, templated electrodeposition can be a versatile and low cost tool for nanowires with designed functionality or fast nanotube synthesis.

The morphology, phase and stability of titania-coated SiOX NWs are investigated for two coating methods: solution-based deposition of Ti-alkoxides and Atomic Layer Deposition (ALD). Analysis of as-deposited and annealed films shows that it is possible to produce stable coatings of the anatase phase of TiO2. The limitations of these two approaches are also discussed.

We present x-ray diffraction based methods to quantitatively determine the wurtzite content of nanowire ensembles and to investigate the effect of twinning. An increased lattice constant in growth direction is found for all investigated InAs and InP nanowire samples. This increase is independent of the wurtzite content. Using x-ray pole figures we find that twinning is present in GaAs/Si branched nanowires, which leads to 60° rotations of the lattice.

Recently, thermoelectric (TE) is ignited by enhancement of nano-science and engineering that uncovers the possibility of increasing of figure of merit (ZT). As a candidate for thermoelectric materials, metal could not be considered because of their high thermal conductivity. However, according to other research, it is feasible to decrease thermal conductivity of also metal without much degradation of the electrical conductivity, which strongly implies that nanoscale metal can be utilized to improve thermoelectric properties of devices, especially power factor. Semiconductor-semiconductor superlattice nanowire structure has been studied as one of the best candidates for thermoelectric devices, because of their photon scattering characteristics at the interfaces. In this research, instead of semiconductor-semiconductor superlattice structure, metal-semiconductor superlattice structure was synthesized, and its microstructure and electrical properties are investigated. With this structure, improvement of electrical conductivity as well as degradation of thermal conductivity with phonon scattering would be anticipated. Metal-semiconductor superlattice nanowires were acquired with electrochemical displacement method, which can exchange the material which has low reduction potential with more noble materials in aqueous electrolyte. To achieve this, Ni-Ag superlattice structure was firstly prepared as metal-metal superlattice structure. The electrolyte for the electrodeposition of Ni-Ag segmented nanowries was consisted of 0.3 mol/L C6H5Na3O7, 0.7mol/L NiSO4 and AgNO3. Electrodeposition was performed galvanostatically in two electrode cell configuration with anodized aluminum oxide(AAO) template. Cu layer was deposited at the one side of AAO template as a working electrode, platinum coated titanium stripe as counter electrode. The composition of electrodeposits could be controlled by applied potential which is directly related the applied current density. Ni-rich phase could be obtained when the applied current density was over 10mA/cm2 and Ag-rich phase at 0.5mA/cm2. After acquiring Ni-Ag segmented nanowire structure, we synthesized the metal-semiconductor segemented nanowries (Ag-BiTe segmented nanowire) by using galvanic-displacement method. Because standard reduction potential energy of nickel is more negative (-0.25V) than that of BiTe in Bi ion and Te ion contained bath, it is possible to make displacement of Ni with BiTe using galvanic displacement. The morphology was investigated by SEM and composition profile was observed by EDS. In conclusion, nanoscale metal-semiconductor segmented nanowires were synthesized by electrodeposition and electrochemical displacement method. Their structural characteristics and electrical properties were investigated to understand the possibility of this segmented nanowires as a thermelectrical materials.

The post-synthetic assembly of nanowires into desired configurations presents a unique challenge. Through the use of a microscope we observed the behaviors of different nanowires during the drying of their solutions. In addition, we also viewed the resulting dried patterns on substrates by AFM and SEM. We found that nanowires are deposited and aligned along the contact line. The evaporation-induced capillary flow carries the nanowires to the contact line and their alignment there is due to self-assembly directed by solvent evaporation. Based on our observations, we developed a contact-line-deposition process and successfully assembled aligned nanowires in proper patterns on substrates.

This paper describes lateral deformations of electrodeposited Ni nanowires as an atomic force microscope (AFM) probe tip. The maximum end deflections for nanowires to break the elasticity, which beam mechanics indicates, were applicable to our observed results.

We report on the photoluminescence (PL) of GaAs-Al0.32Ga0.68As core-shell nanowires grown by MOVPE, and their dependence on the precursors V:III molar ratio utilised in the vapor during growth. It is shown that the PL emission of the GaAs nanowire core red-shifts with decreasing the V:III ratio from 30:1 to 4:1, an effect tentatively ascribed to the build-up of a space-charge region at the core-shell hetero-interface, the latter associated to the unintentional incorporation of impurities, namely C in GaAs and Si in AlGaAs.