Size Of Nanowires Research Articles

Characterization and performance analysis of Li-doped ZnO nanowire as a nano-sensor and nano-energy harvesting element

A complete investigation of the effect of Li doping on the physical, material, electromechanical and piezoelectric properties of ZnO nanowires (NWs) is presented. Low temperature hydrothermal growth technique is used to grow vertically aligned crystalline ZnO NWs doped with different concentrations of Li. Characterization techniques reveal considerable physical, material and electromechanical property modifications of the ZnO NWs due to the incorporation of Li dopants. Atomic Force Microscope is utilized to apply controlled amount of force on the fabricated NWs to assess their piezoelectric response. More than twenty two-fold improvement is observed in sensitivity due to the combined effect of modifications in NW geometry and piezoelectric properties with the addition of Li. Finite element method simulations were performed to decouple the individual effect of Li doping on the NW size and on the piezoelectric coefficient and to see how much each effect plays a role in the sensitivity improvement. It is estimated that the changes in the material and electromechanical properties alone are responsible for more than seven-fold improvement in the sensitivity. The impact of ‘kick-out’ diffusion mechanism of Li in ZnO is one of the major factors responsible behind this sensitivity improvement. It is also observed that there is an optimum level of Li doping concentration which can lead to the best piezoelectric performance by the ZnO NWs. The novelty of this work lies on the detailed analyses to illustrate the physics and impact of Li dopants in ZnO NW structures from a piezoelectric point of view towards improving their application as a nano-sensing and nano-energy harvesting element.

Plasmonic Nanowires for Wide Wavelength Range Molecular Sensing.

In this paper, we propose the use of a standing nanowires array, constituted by plasmonic active gold wires grown on iron disks, and partially immersed in a supporting alumina matrix, for surface-enhanced Raman spectroscopy applications. The galvanic process was used to fabricate nanowires in pores of anodized alumina template, making this device cost-effective. This fabrication method allows for the selection of size, diameter, and spatial arrangement of nanowires. The proposed device, thanks to a detailed design analysis, demonstrates a broadband plasmonic enhancement effect useful for many standard excitation wavelengths in the visible and NIR. The trigonal pores arrangement gives an efficiency weakly dependent on polarization. The devices, tested with 633 and 830 nm laser lines, show a significant Raman enhancement factor, up to around 6 × 104, with respect to the flat gold surface, used as a reference for the measurements of the investigated molecules.

High-Switching-Ratio Photodetectors Based on Perovskite CH₃NH₃PbI₃ Nanowires.

Hybrid organic-inorganic perovskite materials have attracted extensive attention due to their impressive performance in photovoltaic devices. One-dimensional perovskite CH3NH3PbI3 nanomaterials, possessing unique structural features such as large surface-to-volume ratio, anisotropic geometry and quantum confinement, may have excellent optoelectronic properties, which could be utilized to fabricate high-performance photodetectors. However, in comparison to CH3NH3PbI3 thin films, reports on the fabrication of CH3NH3PbI3 nanowires for optoelectrical application are rather limited. Herein, a two-step spin-coating process has been utilized to fabricate pure-phase and single-crystalline CH3NH3PbI3 nanowires on a substrate without mesoporous TiO2 or Al2O3. The size and density of CH3NH3PbI3 nanowires can be easily controlled by changing the PbI2 precursor concentration. The as-prepared CH3NH3PbI3 nanowires are utilized to fabricate photodetectors, which exhibit a fairly high switching ratio of ~600, a responsivity of 55 mA/W, and a normalized detectivity of 0.5 × 1011 jones under 532 nm light illumination (40 mW/cm2) at a very low bias voltage of 0.1 V. The as-prepared perovskite CH3NH3PbI3 nanowires with excellent optoelectronic properties are regarded to be a potential candidate for high-performance photodetector application.

A first-principles analysis of ballistic conductance, grain boundary scattering and vertical resistance in aluminum interconnects

We present an ab initio evaluation of electron scattering mechanisms in Al interconnects from a back-end-of-line (BEOL) perspective. We consider the ballistic conductance as a function of nanowire size, as well as the impact of surface oxidation on electron transport. We also consider several representative twin grain boundaries and calculate the specific resistivity and reflection coefficients for each case. Lastly, we calculate the vertical resistance across the Al/Ta(N)/Al and Cu/Ta(N)/Cu interfaces, which are representative of typical vertical interconnect structures with diffusion barriers. Despite a high ballistic conductance, the calculated specific resistivities at grain boundaries are 70-100% higher in Al than in Cu, and the vertical resistance across Ta(N) diffusion barriers are 60-100% larger for Al than for Cu. These results suggest that in addition to the well-known electromigration limitations in Al interconnects, electron scattering represents a major problem in achieving low interconnect line resistance at fine dimensions.

Position‐Controlled VLS Growth of Nanowires on Mask‐Patterned GaAs Substrates for Axial GaAsSb/InAs Heterostructures (Phys. Status Solidi A 8∕2018)

Nanowires III-V semiconductor nanowires (NWs) have attracted attention as a constituent of small electronic devices with high performance. In particular, the demand for GaAsSb/InAs NWs is increasing because the GaAsSb/InAs material system can afford structures with type-II and broken-bandgap alignment, depending on the Sb content of GaAsSb. In article number 1700429 Kenichi Kawaguchi and co-workers investigate position-controlled vaporliquid-solid (VLS) growth of nanowires (NWs) for GaAsSb/InAs system. On mask-patterned GaAs(111)B substrates, rod-like InAs NWs are obtained by the introduction of a small amount of HCl gas. The InAs NW diameter depends on the Au catalyst size and pitch of NWs, which can be explained by the VLS growth accompanied by lateral growth. A peculiar change in InAs NW shapes for additive HCl gas is revealed. The formation of axial GaAsSb/InAs heterostructure NWs is demonstrated.

Template-free fabrication of vertically-aligned polymer nanowire array on the flat-end tip for quantifying the single living cancer cells and nanosurface interaction

We fabricated vertically aligned polyaniline (PANI) nanowire arrays on flat-end AFM tips via template-free methods. 4-Aminothiophenol was used for tailoring the nucleation size, chain propagation and orientation of the PANI nanowires. The microscopy characterization indicated that diameter was centered at a mean of 33.7 nm with a standard deviation of 6.5 nm, and length was centered at a mean of 50.3 nm with a standard deviation of 7.6 nm. PANI nanowire arrays are non-toxic, low-cost, and tunable, and thus PANI nanowire-grown tips could perfectly simulate different nanosurfaces. Via the force spectroscopy, we demonstrate the feasibility in real-time quantifying the nanostructure-cell interactions at the single cell level with high reliability and accuracy. This work will enable a new tool in precisely quantifying the interactions of single living cells and nanosurface, and thus opens a new door to understand how single living cells sense and respond to the specific nanostructures.

Electrosynthesis of polypyrrole nano/micro structures using an electrogenerated oriented polypyrrole nanowire array as framework

The purpose of this paper is to show that it is possible to increase the diameter and length of the nanostructures of a framework formed of oriented polypyrrole nanowires that has been prepared by a templateless electrochemical method based on the use of a pyrrole solution containing a high concentration of weak-acid anion and a low concentration of non-acidic anion. The dimensions of the initial nanowires are increased by performing an additional electrosynthesis in a ‘classical’ monomer solution. Depending on the polarization time of this last synthesis (a few tens of seconds), wires with various diameters, from one hundred up to several hundred nanometers, are obtained. In addition to the variation of the nanowire size, these findings confirm, as outlined in the reaction mechanism we have proposed, that the base of the nanowires is surrounded by a thin non-conductive polymer i.e. by an overoxidized polypyrrole film. Actually this paper shows a proof-of-concept. Indeed one can imagine that the second polymeric electrodeposit could be performed using an organic monomer solution, using functionalized pyrrole monomer to fabricate a biosensor having large specific area, and/or using anions which could be drugs.

Growth of Perovskite Nanorods from PbS Quantum Dots

ABSTRACTOrganolead iodide perovskites, CH3NH3PbI3, have attracted the attention of researchers around the world due to their optical and electrical properties. Their main characteristics include, direct band-gap (1.4 to 3.0 eV), large absorption coefficient in the visible spectrum, long carrier diffusion length and ambipolar charge transport. Aside that, perovskite thin films can be produced with low cost and are compatible with large-scale manufacture. Perovskite thin films have been synthesized mainly by spin-coating technique and thermal evaporation, which can be executed in one or two steps. Aiming to increase the light absorption, nanostructured perovskite thin films are also under intense study, since the nanostructures can absorb more light than a flat film. Thus, in this work, we reported the synthesis of perovskite (CH3NH3PbI3) nanorods by means of conversion of lead sulphide quantum dots (PbSQD). The perovskite nanorods were grown by exposing the PbSQD to a highly concentrated iodine atmosphere and then dipping the resulting film in methylammonium iodide (CH3NH3I) solution. The first step converts completely the PbSQD into lead iodide (PbI2) nanowires, ≈50 µm long and ≈200 nm diameter, through substitution of sulphur by iodine atoms and subsequent aggregation of the particles. The later step converts the PbI2 nanowires in perovskite nonorods (≈5 µm long and ≈400 nm diameter). The perovskite nanorods present a regular geometry along all its length. A preferential alignment of nanorods to the substrate plane was observed. The preliminary results show that we can control the size of nanorods through exposition time of PbSQD to iodine, which change the size of PbI2 nanowire as well. The conversion process was studied by x-ray diffraction, optical absorption, photoluminescence and scanning electron microscopy.

Twinning to slip transition in ultrathin BCC Fe nanowires

We report twinning to slip transition with decreasing size and increasing temperature in ultrathin <100> BCC Fe nanowires. Molecular dynamics simulations have been performed on different nanowire size in the range 0.404–3.634 nm at temperatures ranging from 10 to 900 K. The results indicate that slip mode dominates at low sizes and high temperatures, while deformation twinning is promoted at high sizes and low temperatures. The temperature, at which the nanowires show twinning to slip transition, increases with increasing size. The different modes of deformation are also reflected appropriately in the respective stress–strain behaviour of the nanowires.

Controlling the size of silver nanowires produced by a tetrabutylammonium dichlorobromide salt-based polyol process: Kinetics of silver crystal growth

Long silver nanowires (Ag NWs) with lengths of ∼65 μm and aspect ratios as high as 1500 were synthesized using a tetrabutylammonium dichlorobromide (TBADCB) salt-based polyol process. The kinetics of crystal growth was studied using stepwise scanning electron microscopy, X-ray diffraction, and surface Plasmon resonance spectroscopy. The diameters of the Ag NWs were shown to be strongly dependent on the molar concentration of TBADCB/AgNO3. We further demonstrated that the length of the Ag NWs could be controlled by adjusting the reaction temperature at the nucleation step or by varying the stirring speed. NWs with lengths of up to 60 μm and diameters as large as 32 nm were obtained when unidirectional axial stirring was performed at 1000 rpm using a T-shaped impeller, and at an initial nucleation temperature of 20°C. The obtained two-dimensional conducive Ag NW network films exhibited good optical properties, with a low haze of ≤1.0% and 98% transmittance at 60 Ω/sq, similar to the properties of the films compared of 20-nm-diameter Ag NWs (aspect ratio: ∼1000).

Unusual Formation of CoO@C “Dandelions” Derived from 2D Kagóme MOLs for Efficient Lithium Storage

AbstractDespite great breakthroughs, the search for anode materials with high performance for lithium‐ion batteries (LIBs) remains challenging. Hence, engineering advantageous structures via effective routes can bring new possibilities to the development of the LIB field. Herein, the precise synthesis of three‐dimensional (3D) hybrids of ultrathin carbon‐wrapped CoO (CoO@C) dandelions is reported by the pyrolysis of two‐dimensional (2D) Kagóme metal–organic layers (MOLs) at 400 °C under an Ar atmosphere. Due to the special coordination structure of the paternal MOLs, the resulting CoO nanowires show a small diameter of 5–10 nm and are uniformly confined within the ultrathin carbon layer. Based on the time‐dependent pyrolysis experiments, a crystal transformation mechanism of in situ self‐templated‐recrystallization‐self‐assembly accompanied by phase and morphology changes is first presented to reveal the formation of the 3D dandelion‐like spheres with assembly of nanowire arrays from a 2D Kagóme MOL. By virtue of structural and compositional features, including a 3D array structure, the small size of the primary ultrathin nanowires, and a uniform ultrathin graphitic carbon layer, these unique CoO@C dandelions display high specific capacity, good rate capability, and excellent cycling stability. Importantly, this approach can be extended to accurately synthesize other desired composite structures.

Enhanced AC conductivity and dielectric properties of ultrathin β-silver vanadium oxide/aniline nanowires

Ultrathin β-silver vanadium oxide nanowires synthesized by electrochemical polymerization of aniline were studied for their alternating current conductivity and dielectric properties. The structural morphology and the size of the hybrid nanowires before and after the adsorption of aniline were analyzed by using X-ray diffractometer, and an inductor–capacitor–resistance (LCR) measurement system. Moreover, electrical characterization was carried out to study the dielectric parameters as a function of frequency between 100 Hz and 5 MHz at room temperature.

Tunable structure of nanowire-grid polarizer for deep ultraviolet region

As the performance of nanowire-grid polarizer is determined by the characteristic size of nanowire, the polarizer for full ultraviolet (UV) region requires the characteristic size less than 50 nm, which is challengeable to the current fabrication level. In this letter, two pieces of nanowire-grid polarizers sandwiching a layer of polymer-dispersed liquid crystal (PDLC) was proposed as a tunable structure of nanowire-grid polarizer for high performance in deep ultraviolet region with 100 nm of nanowire period. In this structure, the transmittance of transverse electric (TE) mode (TTE) and transverse magnetic (TM) mode (TTM), and also the transmission extinction ratio (Ex) could be tuned by the optical path of the PDLC layer. Assuming the refractive index of PDLC layer could be varied from 1.5 to 1.6 as its applied voltage changed from saturation voltage to zero, we calculated the TTM and Ex, which varies periodically as the PDLC layer refractive index increasing. For a given incident wavelength, the maximums of TTM and Ex could be attained easily by tuning the applied voltage on PDLC layer. The simulation results show that the tunable structure has a short starting wavelength than that of single layer and double-layer structure nanowire-grid polarizer at a given transmission or extinction requirement with same characteristic size of nanowire, because of the constructive interference of TM polarization and the destructive interference of TE polarization in these two layers of nanowire, similar to a Fabry-Perot cavity, which makes it excellent to be applied in deep UV region.

Position‐Controlled VLS Growth of Nanowires on Mask‐Patterned GaAs Substrates for Axial GaAsSb/InAs Heterostructures

Position‐controlled vapor‐liquid‐solid (VLS) growth of nanowires (NWs) is investigated using GaAs substrates with SiN‐patterned masks and Au catalysts for the realization of axial GaAsSb/InAs heterostructures. Rod‐like InAs NWs are obtained by the introduction of a small amount of HCl gas. The InAs NW diameter depends on the Au catalyst size and pitch of NWs, which can be explained by the VLS growth accompanied by lateral growth. A peculiar change in NW shapes for additive HCl gas is also revealed. Moreover, the formation of axial GaAsSb/InAs heterostructure NWs, by controlling the growth temperature of GaAsSb segments is demonstrated. These results indicate that this growth method is promising for the development of NWs suitable for vertical nano‐scale devices with Sb‐containing heterostructures.

Nanowire length and diameter dependent electrical and optical properties of transparent conductive silver nanowires films

Sheet resistance reduction in the Ag nanowire (NW) coated films was demonstrated without significant degradation of optical properties using two different types of geometry. The maximum decrease in the sheet resistance of Ag NW-coated films was observed to be 27%. We found that the rate of change in the sheet resistance depended on the size of the Ag NWs used. Films with thinner NWs had higher electric resistance due to surface scattering. We also demonstrated that the addition of short NWs was more effective in decreasing the sheet resistance than the long NWs up to an optimum point. Once the sheet resistance passed the optimum point, it increased rapidly.

Current Collapse-Free and Self-Heating Performances in Normally Off GaN Nanowire GAA-MOSFETs

Normally off lateral GaN nanowire gate-all-around MOSFETs have been fabricated on the GaN-on-insulator substrate. The dynamic measurement proved that the devices with various nanowire heights exhibit current collapse-free characteristics implying that the electrons in the isolated nanowire channel do not suffer from trapping effects. However, the dc current level measured at high drain and gate voltage is reduced to approximately one half of the value measured in dynamic mode. This is attributed to the difficulty in heat dissipation because the suspended lateral nanowire channel is thermally isolated from the substrate. However, the heat dissipation is mitigated as the nanowire size increases.

Magnetic Properties of a Mixed Spin-3/2 and Spin-1/2 Ising Nanowire with Nearest and Next-Nearest Neighbour Interactions

The magnetic properties and the hysteresis behaviours of a mixed spin-3/2 and spin-1/2 cubic Ising nanowire have been studied by the use of the Monte Carlo simulations. To investigate the effects of the exchange interaction (J A), the crystal field (ΔA) and the nanowire size (N), we have plotted the variation of the magnetizations (m A and m B) of the two sublattices and the total magnetization (M T) with temperature for different values of J A, ΔA and N. The corresponding phase diagrams and the hysteresis loops behaviour are also presented and discussed.

Modeling of Quantum Confinement and Capacitance in III–V Gate-All-Around 1-D Transistors

In this paper, a physics-based compact model for calculating the semiconductor charges and gate capacitance of III–V nanowire (NW) MOS transistors is presented. The model calculates the subband energies and the semiconductor charges by considering the wave function penetration into the gate insulator, effective mass discontinuity at the semiconductor–oxide interface, 2-D confinement in the NW, and Fermi–Dirac statistics. The semiconductor charge expression proposed in this paper is completely explicit in terms of applied gate voltage, therefore, making it highly suitable for large circuit simulations. The model is also compared with the results from self-consistent Schrodinger–Poisson solver for different NW sizes and materials and found to be accurate over a wide range of gate voltages.

Dependence on size and curvature of sputtering yield in nanowires

Bombardment of different <110> Co nanowires with 1-k eV argon ions along a <100> direction is simulated by molecular dynamics. Sputtering yield is analysed for different surface curvatures. For that purpose, results on three cross-section shapes were obtained, namely: circular, square and rhomboid. A low dose is used to avoid great surface damage. Yield increases with increasing curvature. However, if the cross-section size decreases, this dependence is modified and other phenomena such as spike sputtering occur. In particular, this effect causes an abundant sputtering. The Sigmund theoretical model was used to compare predictions. Results for sputtering yield show a maximum and an asymptotic behaviour for large nanowire sizes. These asymptotic values confirm the dependence on curvature. This dependence for small sizes differs from the simulation model. The Sigmund model does not take into account the local heating, besides it assumes that the energy deposition profile does not depend on target size. The angular distributions of the speed vector show that the lattice structure determines the directions of ejection, and therefore, this structure would also influence the sputtering yield.

Analysis of optical scattering for the nanowire

Nanowires selected to be a preferable candidate for displacement detection due to some merits. This research investigates optical scattering of a homogeneous medium cylinder nanowire. Size of nanowires can affect the scattering light field. Our scheme involving the optical scattering and optical interference with the changing location and the changing radius of the nanowire. We transform the radius of the nanowire to obtain a optimal and suitable size to achieve a high maximal light intensity within a suitable range of radius.