Direct-current electrodeposition and characterization of Ni5Sb2 nanowires array

The fabrication of monocrystalline Ni₅Sb₂ nanowires array into porous anodic alumina membranes by using direct-current potentiostatic electrodeposition technique has been firstly reported. In this paper, the focus is on the effects of Sb content and the co-deposition voltage on the resultant. It was found that Ni₅Sb₂ nanowires array with a monoclinic structure could be successfully synthesized by regulating these two parameters. The analysis results displayed that the Ni₅Sb₂ nanowires array was highly filled and ordered, as well as around 80 nm in diameter. Structure analysis indicated that the as-deposited nanowires had a highly preferential orientation grown along [0 2 2] direction.     

Synthesis and characterization of GaN nanowires

In this work, GaN nanowires were fabricated on Si substrates coated with NiCl₂ thin films using chemical vapor deposition (CVD) method by evaporating Ga₂O₃ powder at 1100 °C in ammonia gas flow. X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscope (HRTEM) and photoluminescence (PL) spectrum are used to characterize the samples. The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure. The growth mechanism of GaN nanowires is also discussed.     

Preparation and characterization of CdS/Si coaxial nanowires

CdS/Si coaxial nanowires were fabricated via a simple one-step thermal evaporation of CdS powder in mass scale. Their crystallinities, general morphologies and detailed microstructures were characterized by using X-ray diffraction, scanning electron microscope, transmission electron microscope and Raman spectra. The CdS core crystallizes in a hexagonal wurtzite structure with lattice constants of a=0.4140 nm and c=0.6719 nm, and the Si shell is amorphous. Five Raman peaks from the CdS core were observed. They are 1LO at 305 cm⁻¹, 2LO at 601 cm⁻¹, A₁-TO at 212 cm⁻¹, E₁-TO at 234 cm⁻¹, and E₂ at 252 cm⁻¹. Photoluminescence measurements show that the nanowires have two emission bands around 510 and 590 nm, which originate from the intrinsic transitions of CdS cores and the amorphous Si shells, respectively.     

Synthesis and characterization of ultra-long silica nanowires

Large-scale synthesis of amorphous silica nanowires was achieved by using simple physical evaporation of a mixture of Si and Al₂O₃ powders. Scanning electron microscopy observations showed that the silica nanowires have lengths of several mm and diameters of 20–100 nm. X-ray photoelectron spectroscopy revealed that these nanowires consisted of Si and O elements in an atomic ratio of approximately 1:2, consistent with the stoichiometric formula SiO₂. Photoluminescence measurements showed a blue luminescence band in the wavelength range of 400–500 nm with three peaks at 420 nm, 440 nm, and 470 nm, respectively, which also differs from the previous reports of the photoluminescence for oxygen-deficient silica nanowires. This may suggest that the fully oxidized silica nanowires still have many structural defects that contribute to the photoluminescence. PACS 81.05.Ys; 78.55.Et; 78.30.Fs; 52.75.Rx; 81.15.Gh; 64.70.Fx     

Photoluminescence from amorphous silica nanowires synthesized using TiN/Ni/SiO2/Si and TiN/Ni/Si substrates

Photoluminescence characteristics of amorphous silica nanowires (a-SiONWs) grown on TiN/Ni/Si and TiN/Ni/SiO₂ substrates have been studied. A-SiONWs grown on TiN/Ni/Si substrates show a Si-rich composition compared to those grown from TiN/Ni/SiO₂/Si. The emission characteristics of the nanowires were found to depend on the type of substrate. By annealing the a-SiONWs grown on TiN/Ni/Si in air, emission bands shift from blue to green bands. It is likely that silicon to oxygen ratio is an important factor in deciding the types of defects and emission bands of amorphous silica nanowires.     

Synthesis and characterization of PbS nanorods and nanowires

 A surfactant assisted solvotermal approach for the controllable synthesis of PbS nanowires and nanorods is applied. The synthesis is based on decomposition of lead thiocyanate in boiling benzyl alcohol with Cetyl trimethyl ammonium bromide used as a surfactant. Nanowires of PbS (about 2–3 μm with an average diameter of 30–50 nm) and nanorods (200–300 nm in length with an axial ratio of 4–5) were synthesised. The nanostructures were characterized by high resolution transmission electron microscopy (HR-TEM), scanning electron microscopy (SEM), selected area electron diffraction (SAED) and X-ray diffraction analysis. The experimental results indicate that the reaction duration and concentration of surfactant play key roles in determining the final morphologies of PbS blocks building and also in their crystallinity. A possible mechanism for creation of PbS nanowires and nanorods is discussed.     

Ordered arrays of Ni magnetic nanowires: Synthesis and investigation

The present study is focused on the synthesis and investigation of anodic aluminum oxide (AAO) films and magnetic nanocomposites Ni/AAO obtained by Ni electrodeposition into porous matrix. AAO membranes and magnetic nanocomposites were investigated by HRSEM, EDX microanalysis, XRD, nitrogen capillary adsorption method, SQUID magnetometry, and polarized small-angle neutron scattering (SANS). The influence of synthesis conditions and form factor effect on the magnetic properties of nanowire arrays is reported.     

Synthesis and electrical characterization of tungsten oxide nanowires

Tungsten oxide nanowires of diameters ranging from 7 to 200~nm are prepared on a tungsten rod substrate by using the chemical vapour deposition (CVD) method with vapour--solid (VS) mechanism. Tin powders are used to control oxygen concentration in the furnace, thereby assisting the growth of the tungsten oxide nanowires. The grown tungsten oxide nanowires are determined to be of crystalline W₁₈O₄₉. I--V curves are measured by an \textit{in situ} transmission electron microscope (TEM) to investigate the electrical properties of the nanowires. All of the I--V curves observed are symmetric, which reveals that the tungsten oxide nanowires are semiconducting. Quantitative analyses of the experimental I--V curves by using a metal--semiconductor--metal (MSM) model give some intrinsic parameters of the tungsten oxide nanowires, such as the carrier concentration, the carrier mobility and the conductivity.     

Synthesis and characterization of Ag-doped p-type ZnO nanowires

P-type ZnO nanowires with silver (Ag) doping were synthesized via a chemical vapor deposition process. The incorporation of Ag was confirmed by selected-area energy-dispersive x-ray spectroscopy. The formation of acceptor states was demonstrated by temperature and excitation power-dependent photoluminescence measurements. Characterization of field-effect transistors using Ag-doped ZnO nanowires as channels showed p-type conductivity of the nanowires with a hole concentration of 4.9×10¹⁷ cm⁻³ and a carrier mobility of approximately 0.18 cm² V⁻¹ s⁻¹.     

Synthesis and characterization of crystalline carbon nitride nanowires

Carbon nitride nanowires were synthesized by thermal nitridation of multiwalled carbon nanotubes in a horizontal tube furnace. Scanning electron microscopy and transmission electron microscopy images revealed the large-scale formation of nanowires. Selected-area electron diffraction images and high-resolution transmission electron microscopy images show that the as-synthesized nanowires grow preferentially along the [110] direction, with diameters of 15 to 100 nm and lengths from several tens of micrometers to several millimeters. Here, the growth mechanism of these nanowires is proposed.     

Formation of Si nanowires by the electrochemical reduction of porous Ni/SiO2 blocks in molten CaCl2

Silicon nanowires (SiNWs) were prepared by the electrochemical reduction of solid Ni/SiO₂ blocks in molten CaCl₂ at 1173 K. The SiNWs have diameter distributions ranging from 80 to 350 nm, and the nickel–silicon droplets are found on the tips of the nanowires. The growth mechanism of SiNWs was investigated, which confirmed that the nano-sized nickel–silicon droplets formed at the Ni/SiO₂/CaCl₂ three-phase interline. The droplets lead to the oriented growth of SiNWs. Formation of nano-sized nickel–silicon droplets suggests that this method could be a potential way to produce nano-sized metal silicides.     

Synthesis and photoluminescence of aligned straight silica nanowires on Si substrate

Aligned straight silica nanowires (NWs) have been synthesized on Si wafer by thermal evaporation of mixed powders of zinc carbonate hydroxide and graphite at 1100 °C and condensation on Si substrate without using any catalyst. The straight silica NWs have diameters ranging from 50 to 100 nm, and lengths of several micrometers, with cone-shaped tips at their ends. High deposition temperature and relatively high SiO_x vapor concentration near the growth substrate would be beneficial to the formation of the aligned straight silica NWs. Different morphologies of silica nanostructures have also been obtained by varying the deposition temperature and the vapor concentration of the SiO_x molecules. Room temperature photoluminescence measurements on the oriented silica NWs show that two green emission bands at 510 and 560 nm, respectively, revealing that the aligned straight silica NWs might have potential applications in the future optoelectronic devices.     

Preparation and characterization of SiO2 nanowires using a SnO2 catalyst

SiO₂ nanowires have been successfully synthesized on the surface of the silicon substrate via a thermal evaporation method using SnO₂ powders as the catalysts. The final synthesized product was systematically studied by X-ray powder diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy (SEM), and electron energy dispersive X-ray (EDX), UV-Visible absorption and photoluminescence (PL) spectroscopy. The results reveal that in the reaction and growth process, the real catalytic effect is Sn and SnO_x, and the growth of SiO₂ nanowire is most likely controlled by VLS mechanism. The PL spectral results indicate the obtained products have a stable yellow-green emission range. The products have improved performance and can be used in optoelectronic semiconductor devices.     

Local structure of Ni2Si

The local structure around the Ni atom in Ni₂Si has been studied by measuring and analyzing the Extended Energy Loss Fine Structure above the Ni M_2,3 edge. The radial distribution function we found is characterized by the efficiency of the only nearest neighbours Si atoms. We also obtained the phase shift of the Ni-Si pair and the backscattering amplitude.     

Synthesis and characterization of GaN nanowires by a catalyst assisted chemical vapor deposition

GaN nanowires have been fabricated on Si(1 1 1) substrates by chemical vapor deposition (CVD) method with NiCl₂ as catalyst and their compositions, microstructures, morphologies and light emitting properties were characterized by X-ray diffraction (XRD), FT-IR spectrophotometer (FTIR), scanning electron microscope (SEM), high-resolution transmission electron microscope (HRTEM), Raman spectroscopy and photoluminescence (PL). The results demonstrate that the nanowires are single-crystal GaN with hexagonal wurtzite structure and high crystalline quality, having the size of 20-50 nm in diameter and several tens of microns in length with some nano-droplets on their tips, which reveals that the growth mechanism of GaN nanowires agrees with vapor-liquid-solid (VLS) process. Five first-order Raman active phonon bands move to low shift and A₁(TO), E₁(TO), and E₂ (high) bands are overlapped and broaden, which is caused by uncertainty in the phonon wave vector. Five non-first-order active Raman phonons also appear, which is caused by the small dimension and high surface disorder degree. A blue-shift of the band-gap emission occurs due to quantum confinement effect.     

One-step synthesis of CdTe branched nanowires and nanorod arrays

Single crystalline CdTe branched nanowires and well-aligned nanorod arrays were simultaneously synthesized by a simple chemical vapor deposition (CVD) technique. X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electronic microscopy (TEM) and selected area electronic diffraction (SAED) were used to study the crystalline structure, composition and morphology of different samples. Vapor-liquid-solid (VLS) and vapor-solid (VS) processes were proposed for the formation of the CdTe branched nanowires and nanorod arrays, respectively. As-grown CdTe nanorod arrays show a strong red emission band centered at about 620 nm, which can be well fitted by two Gaussian curves centered at 610 nm and 635 nm, respectively.     

Synthesis, characterization and photoluminescence of tin oxide nanoribbons and nanowires

In this work we report the successful formation of tin oxide nanowires and tin oxide nanoribbons with high yield and by using simple cheap method. We also report the formation of curved nanoribbon, wedge-like tin oxide nanowires and star-like nanowires. The growth mechanism of these structures has been studied. Scanning electron microscope was used in the analysis and the EDX analysis showed that our samples is purely Sn and O with ratio 1:2. X-ray analysis was also used in the characterization of the tin oxide nanowire and showed the high crystallinity of our nanowires. The mechanism of the growth of our1D nanostructures is closely related to the vapor–liquid–solid (VLS) process. The photoluminescence PL measurements for the tin oxide nanowires indicated that there are three stable emission peaks centered at wavelengths 630, 565 and 395 nm. The nature of the transition may be attributed to nanocrystals inside the nanobelts or to Sn or O vacancies occurring during the growth which can induce trapped states in the band gap.     

Synthesis and characterization of the SnS nanowires via chemical vapor deposition

Single-crystal SnS nanowires have been successfully synthesized by catalysis-assistant chemical vapor deposition. Applying Au nanoparticles which were applied on the ITO surface as the catalysator, using SnS powder and S powder as precursors and the Ar+H₂ mixed atmosphere as the shielding and carrier gas, the SnS nanowires were obtained. X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectra (XPS) and Raman spectroscopy were employed to characterize the as-synthesized SnS nanostructures. The room-temperature photoluminescence properties of these as-prepared SnS nanowires were presented.