Fabrication and photoluminescence properties of highly ordered ZnS nanowire arrays embedded in anodic alumina membrane

ZnS nanowire arrays embedded in anodic alumina membranes (AAM) were fabricated from an electrolyte containing ZnCl₂ and elemental S in dimethylsulfoxide. Photoluminescence (PL) measurements show a broadband with three peaks centered at about 353, 425, and 520 nm that are attributed to vacancies or interstitial, sulfur vacancy, and point defects respectively.     

Large-area In2O3 ordered pore arrays and their photoluminescence properties

Large-area In₂O₃ ordered pore arrays were prepared on glass and silicon substrates by the sol–gel technique based on colloidal monolayer spheres. The morphologies of such arrays are determined by precursor concentration used and colloidal sphere size, and are thus controllable. It has been shown that the formed ordered pore arrays consist of In₂O₃ polycrystallites. The photoluminescence measurement of the In₂O₃ ordered pore arrays shows that there is a strong photoluminescence band in the blue-green region centered around 465 nm, which does not exist in the bulk materials. Further experiments reveal that this peak originates from the oxygen deficiencies in In₂O₃ skeletons. This polydomain ordered pore-structured array could be of great potential for Si-based integrated nanophotonics and optoelectronic devices of the next generation, in addition to new gas sensors. PACS  01.30.-y; 78.20.-e; 78.55.-m; 78.55.Et     

Flow assisted synthesis of highly ordered silica nanowire arrays

Silica nanowires were synthesized through a self-supplied vapor–liquid–solid (VLS) mechanism. Unlike randomly entangled nanowires on the substrate, highly ordered nanowire arrays have been successfully fabricated using a sandwich-like configuration to define and enhance the local gas-flow. As-synthesized nanowires were characterized to be amorphous silicon dioxide with Au as catalysts. The role of the sandwich-like structure and the effect of gas-flow on the alignment of silica nanowires are demonstrated.     

Multiphoton route to ZnO nanowire lasers

With intense femtosecond laser excitation, multiphoton absorption-induced stimulated emission and laser emission in ZnO bulk crystal and nanowires have been demonstrated at room temperature. UV-stimulated emission peaks appeared in both bulk crystal and nanowires when the excitation exceeded certain thresholds, and a sharp lasing peak with a linewidth of ~0.5 nm was observed from ZnO nanowires. The emission properties were attributed to the band-edge emission of the recombination of carriers excited by two- and three-photon absorption processes in the wide-bandgap semiconductor.     

Synthesis of ordered ZnO nanowire arrays from aqueous solution using AAO template

In this paper we report a simple method that enables the easy fabrication of ordered ZnO nanowire arrays using Anodic Aluminium Oxide (AAO) template. We have used a vacuum injection technique to fill solution into the pores of an AAO template. The AAO template has been fabricated by a two-step anodization process using 0.3 M oxalic acid (H₂C₂O₄) solution under a constant voltage of 40 V. The AAO template formed through this process has been detached from Al substrate via an anodic voltage pulse using perchloric acid (HClO₄) solution (70%). The nanowires of ZnO have been synthesized by injecting the saturated Zn(NO₃)₂ solution into the pores of the detached AAO template using a vacuum pump. The ZnO nanowires synthesized by this technique have been found dense & continuous with uniform diameter throughout the length of the wire. The structural characteristics of AAO template and ZnO nanowires have been studied by Field Emission Scanning Electron Microscope (FESEM), Atomic force microscope (AFM) and Transmission Electron Microscope (TEM).     

Large-scale synthesis of ZnO nanowires using a low-temperature chemical route and their photoluminescence properties

Single-crystalline zinc oxide (ZnO) nanowires were synthesized from zinc powder and H₂O through a simple chemical route at 730 °C in Ar atmosphere. The potential exists for bulk synthesis of ZnO nanowires at temperatures significantly less than the 200–300 °C of thermal evaporation methods reported formerly. Scanning electron microscopy and transmission electron microscopy observations reveal that the ZnO nanowires are structurally uniform, have lengths up to several hundreds of micrometers and diameters of about 40–60 nm and crystallize in a hexagonal structure. The growth of ZnO nanowires is controlled by the vapor–solid crystal-growth mechanism. Photoluminescence measurements show that the ZnO nanowires have a strong near-band ultraviolet emission at 380 nm and a green light emission at 520 nm caused by oxygen vacancies. PACS 81.05.Ys; 78.55.Et     

Fabrication and magnetic properties of ordered 20 nm Co-Pb nanowire arrays

Ordered Co-Pb nanowire arrays embedded in anodic alumina template were successfully fabricated by electrodeposition. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) observations revealed that the Co-Pb nanowires were polycrystalline with uniform diameters around 20 nm and lengths up to several micrometers. Magnetic measurements showed that the coercivity and remanence of the as-deposited Co-Pb nanowires decreased with the increase of the Pb content. After annealing the Co-Pb nanowires present higher coercivities (2.4-2.5 kOe) than that of pure Co nanowires (2.1 kOe) and the dependence of coercivity and remanence on the Pb content is inconspicuous. A phase separation of Co and Pb occurred after annealing. The familiar pinning model was employed to explain the above experimental results.     

Ordered tellurium nanowire arrays and their optical properties

High-density tellurium (Te) nanowire arrays were prepared in the nanochannels of an anodic aluminum membrane (AAM) template using the electrochemical deposition method. The as-synthesized Te nanowires, typically 60 nm in diameter and up to 40 μm in length, possess a hexagonal single crystalline structure following [001] growth direction. The optical polarization properties of Te nanowire arrays embedded in AAM were investigated using an optic parameter oscillator in the wavelength range from 0.7 to 1 μm. The high optical polarization of the Te nanowire arrays embedded in the AAM assembly system was observed. PACS 81.05.Cy; 78.67.-n; 82.80.Fk.     

Synthesis and room temperature photoluminescence of ZnO/CTAB ordered layered nanocomposite with flake-like architecture

Flake-like ZnO/surfactant ordered layered nanocomposite has been synthesized by self-assembly at room temperature with the presence of cetyltrimethylammonium bromide (CTAB, CH₃(CH₂)₁₅N⁺(CH₃)₃Br⁻) surfactant. The procedure described in this study is attractive since it gives high yields of ordered layered nanocomposite with flake-like architecture. XRD results showed the formation of a layered structure with two layered spacings ca. 18.56 Å. SEM and FT-IR spectroscopy were used to further characterize ZnO/CTAB nanolayered composite. The ZnO/CTAB-ordered layered nanocomposite exhibits the room temperature photoluminescence (RTPL) characteristics. It is inferred that the RTPL of ZnO/CTAB-layered nanocomposite might be induced by the interfacial effect between the ZnO and the surfactant.     

Autocatalytic redox fabrication and magnetic studies of Co-Ni-P alloy nanowire arrays

Uniform and large-scale Co-Ni-P alloy nanowire arrays have been fabricated by autocatalytic redox reaction in an anodic alumina membrane (AAM). The images of Co-Ni-P alloy nanowire arrays and single nanowires are obtained by scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Selected area electron diffraction (SAED), X-ray diffraction (XRD) and energy dispersive spectra (EDS) are employed to study the morphology and chemical composition of the nanowires. The results indicate that the Co-Ni-P nanowire arrays are amorphous in structure. The magnetic property of Co-Ni-P nanowire arrays is characterized using a vibrating sample magnetometer (VSM). The hysteresis loops show that the easily magnetized direction of Co-Ni-P nanowire arrays is parallel to the nanowire arrays and that it has obvious magnetic anisotropy as a result of the shape anisotropy.     

Synthesis and magnetic properties of ordered barium ferrite nanowire arrays in AAO template

BaFe₁₂O₁₉ nanowire arrays having single magnetic domain size (≤460 nm) in anodic aluminum oxide (AAO) templates were prepared by sol-gel and self-propagating high-temperature synthesis techniques. The diameter of the nanowire arrays is approximately 70 nm and the length is about 2-4 μm. The specimens were characterized using X-ray diffraction, vibrating sample magnetometer, field emission scan electron microscope, atomic force microscopy and microwave vector network analyzer. The magnetic properties of BaFe₁₂O₁₉ nanowire arrays embedded in AAO templates were measured by VSM with a field up to 1274 KA/m at room temperature. The results indicate that the nanowire arrays exhibit large saturation magnetization and high coercivity in the range of 6000 Oe and an obvious magnetic anisotropy with the easy magnetizing axis along the length of the nanowire arrays, probably due to the shape anisotropy and magneto-crystalline anisotropy. Finally the microwave absorption properties of the nanowires were discussed.     

Fabrication and electrical properties of ordered two-dimensional hollow ZnO shells’ arrays

Colloidal templating and pulsed laser deposition (PLD) have been combined to fabricate arrays of ordered two-dimensional hollow ZnO cells. Based on a spin-coating method, a facile method has been developed to distribute colloidal bead in an ordered two-dimensional fashion between the fingers of inter-digital transducers. The underlying principle involved in the spin-coating method has been analyzed by obtaining Fourier transformation patterns from the arrangements of beads. The surfaces of oxide shells consist of protruding nano-crystallites, which have a würtzite structure of ZnO. Their electrical properties were measured as a function of annealing temperature. The change in the electrical properties upon grain growth has been attributed to alteration in the fraction site availability for defect formation at the grain boundaries.     

Surface enhanced Raman scattering and photoluminescence properties of catalytic grown ZnO nanostructures

Sword-like (diameter ranging from 40 nm to 300 nm) and needle-like zinc oxide (ZnO) nanostructures (average tip diameter ∼40 nm) were synthesized on annealed silver template over silicon substrate and directly on silicon wafer, respectively via thermal evaporation of metallic zinc followed by a thermal annealing in air. The surface morphology, microstructure, chemical analysis and optical properties of the grown samples were investigated by field emission scanning electron microscopy, X-ray diffraction, energy dispersive X-ray analysis, room temperature photoluminescence and Raman spectroscopy. The sword-like ZnO nanostructures grown on annealed silver template are of high optical quality compared to needle-like ZnO nanorods for UV emission and show enhanced Raman scattering.     

Electroless synthesis of large scale Co-Zn-P nanowire arrays and the magnetic behaviour

Co-Zn-P nanowire arrays have been synthesized by electroless deposition in an anodic alumina membrane (AAM). The images of Co-Zn-P nanowire arrays and single nanowires are obtained by both scanning electron microscope (SEM) and transmission electron microscope (TEM), respectively. Selected area electron diffraction (SAED), X-ray diffraction (XRD) and energy dispersive spectra (EDS) are employed to study the morphology and chemical composition of the nanowires. The results indicate that Co-Zn-P nanowire arrays are amorphous in structure. The hysteresis loops characterized by a vibrating sample magnetometer (VSM) show that the easily magnetized direction of Co-Zn-P nanowire arrays is parallel to the nanowire arrays and that there exhibits clearly a magnetic anisotropy as a result of the shape anisotropy.     

Comparative research on the optical properties of three surface patterning ZnO ordered arrays

We fabricate three surface patterning zinc oxide(ZnO) ordered arrays on glass substrates by using nanosphere lithography technique and dc magnetron sputtering technique. The crescent, tube and honeycomb surface morphologies of the samples are observed by scanning electron microscopy. The transmittance, fluorescence and confocal Raman spectra of the sample are measured. Obviously, when the angle between the plume and the substrate is 90?, the honeycomb arrays have a better transmission. Additionally, the PL intensity of honeycomb arrays is superior. With the increasing of the angle between the substrate and the sputtering plume, the fluorescence peak shows blue shift. The Raman peak located at438 cm-1belongs to ZnO E2(high) mode, which corresponds to the characteristic band of the hexagonal wurtzite phase.The tube arrays have the best Raman spectrum intensity.     

Effects of thermal annealing temperature and duration on hydrothermally grown ZnO nanorod arrays

In this study, the effects of thermal annealing temperature and duration on ZnO nanorod arrays fabricated by hydrothermal method were investigated. The annealed ZnO/Si(1 1 1) substrate was used for ZnO nanorod array growth. The effects of annealing treatment on the structural and optical properties were investigated by scanning electron microscopy, X-ray diffraction, and room-temperature photoluminescence measurements. With the annealing temperature of 750 °C and the annealing duration of 10 min, both the structural and optical properties of the ZnO nanorod arrays improved significantly, as indicated in the X-ray diffraction and photoluminescence measurement.     

Effect of synthesis conditions on microstructures and photoluminescence properties of Ga doped ZnO nanorod arrays

Ga doped ZnO nanorod arrays were prepared on silicon substrates in a mixture solution of zinc nitrate hexahydrate, methenamine, and gallium nitrate hydrate. Effect of synthesis conditions on crystal structures, morphologies, surface compositions, and optical properties was analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence techniques (PL). Experimental results reveal that Ga doping amount can reach 1.67 at% with the increase of gallium nitrate concentration. Ga doping greatly affects the morphologies of ZnO nanorod arrays. The photoluminescence spectra show a sharp UV emission and a broad visible emission. With Ga doping, UV emission has an apparent broadening effect and its peak shifts from 3.27 eV to 3.31 eV. The intensity ratio of UV emission to visible emission demonstrates that appropriate Ga doping amount is beneficial for the improvement of ZnO crystalline quality.     

Preparation of transparent conductive ZnO:Tb films and their photoluminescence properties

Tb-doped Zinc oxide (ZnO:Tb) films were prepared by RF reactive magnetron sputtering of a Zn target with some Tb-chips attached. The results show that the appropriate Tb ions incorporated into ZnO films can improve the structural and electrical properties of ZnO films. Photoluminescence (PL) measurements show that the characteristic emission lines correspond to the intra-4f^n-shell transitions in Tb^{3+} ions at room temperature. Under the optimal conditions, the ZnO:Tb films were prepared with the lowest resistivity (ρ) of 9.34×10^{ -4}Ωcm, transmittance over 80% at the visible region and the strong blue emission.     

Large-scale boron nanowire nanojunctions and their highly-oriented arrays

One-dimensional (1D) nanostructures, such as nanotubes and nanowires, have gen-erated worldwide interest due to their nano-scale sizes, high length-to-diameter ratios, highly anisotropic properties, various unique structures, and wide technological applica-tions. 1D nanostructures are the smallest dimension structures that can be used for effi-cient transport of electrons, vacancies, and excitations, and are thus critical building blocks in the construction of nanoscale electronic and mechanic…