Fabrication of high density metallic nanowires and nanotubes for cell culture studies

We report a simple method for the fabrication of high density metallic nanowires and nanotubes by electrodeposition using polycarbonate (PC) and anodic aluminum oxide (AAO) membrane as templates. The diameters and the aspect ratio of the fabricated features could be controlled by choosing the pore size of the template and adjusting the current density and the duration of the electrodeposition. To illustrate the biocompatibility of the fabricated metallic nanowires and nanotubes, cell adhesion and cell proliferation experiments were performed using HeLa cells. This assay strategy might be useful in cell-material interaction studies as well as genetic material transfer and drug delivery.     

Cu 纳米线的制备及其力学性能的研究

采用购买的直径为40～50 nm的AAO模板,利用直流电沉积方法在AAO模板上制备了Cu纳米线.TEM观察发现,Cu 纳米线的直径为(45±5)nm,与AAO模板的内孔 直径一致.利用碳膜卷曲的方法,在JEOL 2010F型场发射透射电子显微镜中对单根 Cu 纳米线进行了原位弯曲变形实验.实验发现,存在于纳米线内部的孪...     

Fabrication of integrated metallic MEMS devices

A simple and complementary metal oxide semiconductor (CMOS) compatible fabrication technique for microelectromechanical (MEMS) devices is presented. The fabrication technology makes use of electroplated metal layers. Among the fabricated devices, high quality factor microresonators are characterised with respect to the quality factor.     

Fabrication and application of metallic nano-cantilevers

A new approach was developed in this work to fabricate metallic nano-cantilevers using a one-mask process and a deep reactive ion etch (DRIE) technique. 40-nm-thick Al and 70-nm-thick Au cantilevers of lengths from 5 μm and widths in the range of 200-300 nm were fabricated on a silicon substrate. The silicon underneath the suspended beams was completely etched. Short Al nano-cantilevers were used to find local residual stress induced in rapid thermal oxidation and the oxidized spots according to the deflection profiles of the nano-cantilevers. The deflection profiles were determined with the aid of a scanning electron microscope (SEM). Compared with a single feedback in the existing cantilever-based static methods, i.e., the deflection of the open end of a cantilever, the whole deflection profile provides more information regarding the effect of surface stresses on a cantilever.     

Fabrication of nano-scale metallic photonic crystals using interference ablation

We demonstrate the fabrication and characterization of large area metallic photonic crystals (MPCs) in the form of gold nano-island grating structures. The spectroscopic properties of the MPCs characterized by the angle-resolved optical extinction spectrum measurements show strong couplings between the waveguide resonance modes and the particle plasmon resonance of the gold nanostructures, indicating the success of this fabrication method. The excellent optical responses of the nano-island MPCs with the advantages of large-area fabrication, low cost, and high speed make it show potential applications in optoelectronic devices and sensors.     

Fabrication of metallic nanocavities by soft UV nanoimprint lithography

We propose a process combining UV-assisted nanoimprint lithography (NIL) and shadow mask evaporation techniques to fabricate metallic nanoparticles with cavities. A bi-layer transparent soft stamp with a hard top layer containing the high resolution patterns was obtained by spin coating and casting methods of PDMS. Then, it was used to mold the top photo-curable resist on a thick PMMA layer. After removal of the residual NIL resist layer, high density and high aspect ratio PMMA nanopillar arrays were obtained by reactive ion etching. Afterward, a four step evaporation under oblique angle was performed to deposit the gold nanostructures at the top of nanopillars. After lift-off, uniformly sized gold nanocavities were collected. Dark-field microscopy imaging of the fabricated nanocavities shows a clear geometry dependence of the emission peak wavelength, thereby providing a novel types of bio-sensing nano-objects.     

Fabrication of GaN nanowires on porous GaN substrate by thermal evaporation

In this research, we used an inexpensive method to fabricate highly crystalline gallium nitride (GaN) nanowires (NWs) on porous GaN (PGaN) on a Si (1 1 1) wafer by thermal evaporation using commercial GaN powder using a combination of argon and nitrogen gas atmosphere without any catalyst. Microstructural studies using scanning electron microscopy and transmission electron microscope measurements revealed the role of porosity in the nucleation and alignment of the GaN NWs. The GaN NWs have diameters of 30–45 nm and lengths of around 1 μm. Further structural and optical characterizations were performed using high resolution X-ray diffraction, energy-dispersive X-ray spectroscopy, and photoluminescence spectroscopy. Results indicate that the NWs are of a single-crystal hexagonal GaN and have the growth direction of [0 0 0 1].     

Fabrication of optical fibre nanowires and their optical and mechanical characterisation

It is demonstrated for the first time that long nanowires with radii as small as 30 nm can be manufactured with a conventional coupler fabrication rig. The temporal deterioration of nanowire optical properties has been studied and correlated with its mechanical behaviour. The original transmission properties have been restored by a post-fabrication treatment.     

Fabrication of poly(3-hexylthiophene) nanowires for high-mobility transistors

Presented here is a novel and efficient method used to improve carrier mobilities of poly(3-hexylthiophene) (P3HT)-based organic field effect transistors by means of nanowire formation. The treatment, termed solvation, consists of depositing a small quantity of a solvent directly on top of a previously deposited semiconducting film, and allowing the solvent to evaporate slowly. Such treatment results in an increase of the saturation mobility by more than one order of magnitude, from 1.3 × 10⁻³ up to 3.4 × 10⁻² cm²/Vs, while devices preserve their high ON/OFF ratio of ∼10⁴. The atomic force and scanning electron microscopy studies show that solvated P3HT layers develop a network of nanowires, which exhibit increased degree of structural order, as demonstrated by micro Raman spectroscopy. The time-of-flight photoconductivity studies suggest that higher hole mobility stems from a reduced energy disorder of the transporting states in these structures.     

Synthesis of gallium oxide nanowires and their electrical properties

Gallium oxide (Ga₂O₃) nanowires have been synthesized using a novel method by high-frequency inductive heating in a room temperature environment. Nanowires with high-yield were grown on silicon substrates in less than 3 min, using Ga₂O₃/graphite as the source powder. Scanning electron microscopy showed nanowire diameters of 20-40 nm and lengths up to several tens of microns, and high-resolution transmission electron microscopy verified the single-crystalline lattice of the nanowires. Electrical properties were investigated by connecting a single Ga₂O₃ nanowire in the field-effect transistor configuration. This demonstration further illustrates the feasibility of an easy and large-scale synthesis of nanomaterials by using high-frequency inductive heating.     

Theoretical investigation of photonic crystal waveguide splitters incorporating ultralow refractive index metallic nanowires

The present letter theoretically investigates the optical properties, and provides design guidelines for optimum performance of a photonic crystal (PC) waveguide splitter composed of ultralow refractive index metamaterials, by utilizing a rigorous analytical modeling based on the scattering matrix technique. We believe that this type of nanocomposite metallic PC waveguide can bring additional degrees of design flexibility to ultradense optical integration, because of its compact size and relatively low-loss propagation characteristics, mainly for power-splitting applications in the visible frequency spectrum.     

Fully transparent flexible transistors built on metal oxide nanowires

Transparent electronics has attracted great research efforts in recent years due to its potential to make significant impact in many area, such as next generation displays, ultraviolet (UV) detectors, solar cells, charge-coupled devices (CCDs), and so on. Central to the realization of transparent electronics is the development of high performance fully transparent thin-film transistors (TFTs). One-dimensional (1-D) nanostructures have been the focus of current researches due to their unique physical properties and potential applications in nanoscale elec-tronics and optoelectronics. Among 1-D nanostructures, transparent metal oxide nanowires are one of the best candidates to make fully transparent TFTs. We provide in this paper the most recent development on the fabrication of fully transparent TFT using metal oxide nanowires as the device elements. First, the review article gives a general introduction about the development of transparent elec-tronics using different kinds of materials as the devices elements, including organic semiconductors, metal oxide thin films, and metal oxide nanowires. Second, the growth of metal oxide nanowires using vapor phase methods governed by two different growth mechanisms: vapor-solid mechanism and vapor-liquid-solid mechanism, respectively, are described. Third, the fabrication of transparent and flexible TFTs using different metal oxides nanowires is comprehensively described. In conclusion, the challenges and prospects for the future are discussed.     

Fabrication of CdS nanowires on TiO2 nanorods for solar cell application

A composition of CdS nanoparticles and nanowires were deposited on TiO₂ nanorods by successive ionic layer adsorption and reaction method grown on Ti substrate. CdS/TiO₂/Ti device were used as photoanode in solar cell. Efficiency, short circuit current, and open circuit voltage were measured. Also, electron life time in each Fermi level and order of recombination were obtained by open circuit voltage decay and short circuit photocurrent interrupt voltage; respectively. Our results showed that there is an optimum composition of CdS nanoparticles and nanowires which improves solar cell properties of this type of cell.     

Fabrication and characterization of PEDOT nanowires based on self-assembled peptide nanotube lithography

In this article we demonstrate the use of self-assembled peptide nanotube structures as masking material in a rapid, mild and low cost fabrication of polymerized p-toluenesulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT:TsO) nanowire device. In this new fabrication approach the PEDOT:TsO nanowire avoids all contact with any organic solvents otherwise traditionally used in clean room fabrication. This can be achieved due to the intriguing properties of the self-assembled peptide nanotubes utilized as a dry etching mask for the patterning of the PEDOT:TsO nanowire. The peptide nanotubes, despite remaining stable during the reactive ion etching procedure, can be dissolved rapidly in water afterwards. The fabricated PEDOT:TsO nanowire devices exhibit excellent electrical characteristics. Finally, the potential of PEDOT:TsO nanowires as temperature sensors has been demonstrated and the high resolution of the sensor was illustrated.     

Indium and tin oxide nanowires by vapor-liquid-solid growth technique

Regular three-dimensional (3-D) arrays of crystalline SnO₂-In₂O₃ nanowires were produced on m-sapphire using a gold catalyst-assisted vapor-liquid-solid growth process. The growth characteristics at multiple growth conditions were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray photoemission spectroscopy (XPS), and Rutherford backscattering spectroscopy (RBS) to evaluate the functional dependence of nanowire structure and composition on growth parameters such as temperature and source composition. The results indicate that nanowires of mixed composition are not possible from the catalytic clusters; rather, a mixture of indium and tin oxide wires are formed in the range of conditions investigated here.     

Synthesis of low-melting metal oxide and sulfide nanowires and nanobelts

The bulk nucleation and basal growth of semiconducting nanowires from molten Ga pools has been demonstrated earlier using oxygen/hydrogen plasma over molten Ga pools. Herein, we extend the above concept for bulk synthesis of oxide and sulfide nanowires of low-melting metal melts such as Sn and In. Specifically, nanowires of β-Ga₂O₃, β-In₂O₃, SnO₂, α-Ga₂S₃, and β-In₂S₃ were synthesized using direct reactions between respective molten metal pools and the gases such as oxygen/hydrogen mixture for oxides and H₂S for sulfides. In the case of β-Ga₂O₃ and SnO₂, a change in the morphology from nanowires to nanobelts was observed with an increase in the synthesis temperature. No such behavior was observed in the case of β-In₂O₃. Furthermore, we present evidence for α-Ga₂S₃ nanowires, which to our knowledge is being reported for the first time in the literature. Our studies with the sulfide nanowires suggest that H₂S reacts directly at the molten metal surface to form gallium sulfide. Finally, we discuss the role of chamber pressure and hydrogen on the size distribution of nanostructured β-Ga₂O₃ and SnO₂.     

Fabrication of 1.55 μm VCSELs on Si using metallic bonding

Using AuGeNiCr multilayered metals as the wafer bonding medium, long-wavelength GaInAsP/InP vertical cavity surface emitting lasers employing Al-oxide/Si as the upper and lower distributed Bragg reflectors were fabricated on Si substrate with the bonding interface formed outside the vertical cavity surface emitting laser cavity. Laser emission at 1.545 μm was measured under pulsed operations near room temperature. The low-temperature metallic bonding process demonstrates a great potential in device fabrication     

Fabrication of nanoscale metallic air-bridges by introducing a SiO2 sacrificial layer

A new method to fabricate nanoscale metallic air-bridges has been investigated. The pillar patterns of the air-bridge were defined on a SiO₂ sacrificial layer by electron-beam lithography combined with inductively coupled plasma etching. Thereafter, the span (suspended part between the pillars) patterns were defined with a second electron-beam exposure on a PMMA/PMMA–MAA resist system. The fabrication process was completed by subsequent metal electron-beam evaporation, lift-off in acetone, and removal of the sacrificial layer in a buffered hydrofluoric (HF) solution. Air-bridges with two different geometries (line-shaped and cross-shaped) were studied in detail. The narrowest width of the air-bridges was around 200 nm, and the typical length of the air-bridges was 2–5 μm. The advantages of our method are the simplicity of carrying out electron-beam exposure with good reproducibility and the capability of more accurate control of the pillar sizes and shapes of the air-bridge.     

Vertically aligned ZnO nanowires prepared by thermal oxidation of RF magnetron sputtered metallic zinc films

ZnO nanowires have been successfully grown by thermal oxidation of metallic zinc films at 430 °C. Polycrystalline zinc films were deposited on Si (100) substrates by RF magnetron sputtering utilizing discharge power from 70 to 180 W. Experimental results show that 70 W discharge power results in the formation of porous zinc nanoparticles that prevent zinc atom from diffusion and thus does not result in the formation of ZnO nanowires by subsequent thermal oxidation. By increasing discharge power to 120 W the zinc film transforms to Zone II with a columnar structure, while further increase in discharge power to 180 W results in re-crystallization and formation of micron-sized hexagonal structures on the surface. Vertically aligned ZnO nanowires can only be obtained by thermal oxidation of columnar zinc films that exhibit a field emission threshold of 5.3 V/μm (at a current density of 10 μA/cm²) with a field enhancement factor of 1834. A target current density of 0.75 mA/cm² is achieved with a bias field less than 10 V/μm.