The control of the SiGe NW composition is fundamental for the fabrication of high quality heterostructures. Raman spectroscopy has been used to analyse the composition of SiGe alloys. We present a study of the Raman spectrum of SiGe nanowires and SiGe/Si heterostructures. The inhomogeneity of the Ge composition deduced from the Raman spectrum is explained by the existence of a Ge-rich outer shell and by the interaction of the NW with the electromagnetic field associated with the laser beam.

We present a new approach to prepare Transmission Electron Microscopy (TEM) nanowire (NW) samples that addresses the core drawbacks of conventional techniques, which are based on mechanical polishing. The proposed method is time efficient and uses XeF2 isotropic and selective dry etching of Si to remove the host substrate from the NWs, after their embedding into a poly(methyl-methacrylate) (PMMA) matrix. Scanning electron microscopy (SEM) data suggest that NWs were grown through the gaps between the parasitic layer islands and that the stems are in direct contact with the Si substrate. This technique does not adversely affect the NWs and offers a convenient means of transferring the GaAs NWs onto other surfaces for post-process TEM analysis. It also offers excellent potential to facilitate their integration into device fabrication via a bottom-up approach, using the PMMA layer as a transfer medium.

This study aims at investigating the formation of nanofibers containing poly (vinylidene fluoride) (PVDF) and Fe3O4 nanoparticles using magnetic field assisted electrospinning. For this purpose, two Helmholtz coils were mounted on the electrospinning apparatus in order to create a uniform magnetic field. Different separations, angles and magnetic fields are being analyzed. Polymeric solutions containing PVDF, DMF and acetone with a concentration of 18 wt% were adopted (DMF to Acetone ratio of 3 to 1). Iron Oxide Nanopowder (Fe3O4, particle diameter of 20 nm to 30 nm) to PVDF ratios are 1:5, 1:10 and 1:15. The application of the electromagnetic field during fiber deposition results in better orientation of the polymer flow towards the grounded electrode and leads to smoother fibers with diameters in the range of hundreds of nanometers. Blisters, probably related to Fe3O4 agglomerates, were distributed on the surface of all samples of this study. A magnetic field response of the nanofibers with higher magnetic fields was clear observed. By adding more Fe3O4 to the polymeric solution the ferromagnetic response on thin films and nanofibers was improved. The analysis of circular capacitors revealed a full dielectric response.

Among the transition metal oxides, manganese oxides have been widely studied for electrochemical capacitors and batteries, because of their high energy density, low cost, natural abundance and environmentally friendliness. However, the poor electrical conductivity of manganese dioxide (MnO2) limits its capacitive response. Polyaniline becomes a unique and promising conducting polymer with a great potential application in supercapacitors due to easy synthesis and good conductivity of the conducting material. Combine the two properties can prepare nanocomposite materials in order to improve the conductivity and capacitive performance of the MnO2. MnO2 coated with polyaniline as the coaxial nanowires were prepared in this report. The polyaniline was synthesized via in situ polymerization and we got a controllable thin coating on the well-dispersed MnO2 nanowires. This hybrid nanostructure enhances the conductivity and capacitive performance of the supercapacitor electrode. The specific capacitance of MnO2/PANI composites is as high as 426 F g-1 at 1 A g-1, which is twice much higher than pure MnO2 (188 F g-1) .

Iron oxide nanotubes (Fe-ox-NTs) were prepared by a sol-gel technique using a mixture of an Fe(NO3)3·9H2O and a Pluronic F-127 nonionic surfactant in 1-propanol, gelatinizing at 35 °C for 5 days. Crude nanotubes thus obtained were well rinsed by deionized water in order to remove the surfactant. Transmission electron microscopy showed that the products have tubule structure with the outer (inner) diameter ∼10-15 (∼5-10) nm and the length ∼100 nm. X-ray diffraction profile of the crude nanotubes indicated a broadened feature characteristic for a defective or amorphous-like material, and whose profile may associate with the structure of ɣ-Fe2O3 (maghemite). By heating the crude nanotubes in open air, a phase transition occurs in a defective ɣ-Fe2O3 and its structure changes to a relaxed α-Fe2O3 (hematite) without morphological transformation. A further increase of the temperature results a destruction of the tube structure to the spherical nanoparticles without changing the crystallographic structure. A structurally relaxed Fe-ox-NT complex with fullerenols (C60(OH)n, n∼20) has larger photosensitive response under visible light irradiation, but the crude and defective Fe-ox-NTs and their complexes with fullerenols do not indicate noticeable response.

High yield nanomanufacturing is important to turning nanotechnology advances into industrial products. Electrospinning is a nanomanufacturing process that has been used to process advanced ceramic nanofibers suitable for functional applications in sensing and catalysis, yet it has been limited in its scalability thus far. In this study a novel design of the electrospinning process and related equipment that could produce large qualities of ceramic nanofibers is described. This scaled-up approach to traditional needle electrospinning allows the formation of 24 jets operating under the same conditions as those set in the single jet lab-based process. Due to a thin metallic disc design, with tiny (0.5mm) holes drilled at the bottom corner of the disc, all jets experience a uniform impact of the electrostatic field. Continuous replenishment of the source disk at higher flow rates allows for high yields of nanofibers.

Position-controlled InP nanowires (NWs) with separations of 10-100 μm were grown by the vapor-liquid-solid (VLS) method using Au-deposited SiO2-mask-patterned InP substrates. Excess indium species diffused from the large mask region formed plural tilted NW-like structures from single openings in addition to the vertical VLS NWs formed by Au catalyst. The introduction of HCl gas during the NW growth was found to efficiently suppress the tilted NW-like structures. Vertical InP NWs without anomalous growth were successfully formed by controlling the HCl flow rate. Moreover, single InP/InAsP/InP quantum wells (QWs) with wurtzite crystal phase structure were epitaxially grown on the sidewall of the position-controlled InP NWs, and two-dimensional arrayed patterns of photoluminescence (PL) coming from the radial QWs were clearly observed in the 1.3-μm wavelength region at room temperature.

Dirac materials are characterized by exceptional mobility, orders of magnitude higher than any semiconductor, due to the massless pseudorelativistic nature of the Dirac fermions. These systems being semimetallic, the lack of a genuine band-gap poses a serious limitation to their possible applications in electronics. We recently demonstrated that thin TiO2 nanowires can exhibit 1D Dirac states similar to metallic carbon nanotubes, with the crucial difference that these states lie inside the conduction band in proximity of a wide band gap. We analyze the robustness of the Dirac states respect to an Anderson disorder model and substitutional impurity and compare to different one dimensional systems. The results suggest that thin anatase TiO2 nanowires can be a promising candidate material for switching devices.

An Ultraviolet (UV) photodetector with high responsivity and relative fast response speed was fabricated from three dimensional WO3 nanowires/reduced graphene oxide (3D WO3 NWs/RGO) composite materials. The 3D WO3 NDs/GN composite was synthesized using a facile three-step synthesis. First, the Na2WO4/Graphene Oxide (GO) precursor was synthesized by homogeneous precipitation. Second, the Na2WO4/GO precursor was transformed into H2WO4/GO composites by acidification. Finally, the H2WO4/GO composites were reduced to 3D WO3 NWs/RGO via hydrothermal reduction process. A maximum photoresponsivity of 4.2 A/W at 374 nm was observed under 20 V bias. The UV photodetector showed relative fast transient response, which is at least 2 orders of magnitude faster than UV photodetectors fabricated from WO3 nanowires. The good photoresponsivity and fast transient response are attributed to improved carrier transport and collection efficiency through graphene.

We present calculation of electronic structure of impurity in nanowire. Ionization energy of impurities are calculated in dependence on nanowire radius. Direct Hamiltonian matrix diagonalization method with the physically reasonable approximate potential is employed for finding the exact solution of Schrödinger equation in the effective-mass approximation. It is shown that shallow donors are strongly influences by space confinement, which is expressed in sharp increase of ionization energy. Calculations show that effect of space confinement on deep impurities is less pronounced. The obtained results give hope that by selecting optimal value of nanowire radius compensation processes can be suppressed.

In recent years, studies have shown that single crystal metallic nanowires (NWs) can exhibit unique pseudoelastic behavior when their cross-sectional area is smaller than a certain critical value, which is on the order of a few nms. The mechanism responsible for this behavior is the formation of partial dislocations (twinning). In this paper we demonstrate using molecular dynamics simulations that thicker composite nanowires can exhibit pseudoelastic behavior at large cross-sectional dimensions to 28 nm and higher, as long as the individual layer thickness do not exceed a critical value of 1.8-2 nm, thus making their manufacturing feasible and more attractive.

A layered composite coating material with favorable properties for application as a transparent conductor is presented. It is composed of layers of three nanoscopic materials, namely zinc oxide nanoparticles, single wall nanotubes, and graphene oxide nanosheets. The electrically conducting layer consists of single wall nanotubes (SWNTs). The layer of zinc oxide nanoparticles acts as a primer. It increases the adhesion and the stability of the films against mechanical stresses. The top layer of graphene oxide enhances the conductivity of such coatings. Such three-layer composite coatings show better conductivity (without compromising transparency) and improved mechanical stability compared to pure SWNT films. The processes used in the preparation of such coatings are easily scalable.

Assembly of nanowires into ordered macroscopic structures has attracted great scientific interests in the past decade. In this work, we report a rapid low-cost scalable oil-water interfacial self assembly process for fabricating aligned Ag nanowires (AgNWs) films on solid substrates. This process is much simpler than the traditional Langmuir-Blodgett (LB) techniques and allows the assembly of one–dimensional Ag nanowires onto any solid substrates without extra pretreatment of the surface of silver nanowires or the solid substrate. The present aligned AgNW films can serve as robust surface-enhanced Raman scattering (SERS) sensors for chemical and bimolecular detection with improved spectra quality and demonstrated uniformity of SERS signal using R6G dye as probe.

Reconfigurable nanowire transistors provide the operation of unipolar p-type and n-type FETs freely selectable within a single device. The enhanced functionality is enabled by controlling the currents through two individually gated Schottky junctions. Here we analyze the impact of the Schottky barrier height on the symmetry of Silicon nanowire RFET transfer characteristics and their performance within circuits. Prospective simulations are carried out, indicating that germanium nanowire based RFETs of the same dimensions will show a distinctly increased performance, making them a promising material solution for future reconfigurable electronics.