Resistance Of Nanowires Research Articles

Remote plasmon-induced heat transfer probed by the electronic transport of a gold nanowire

We show in this paper that the heat generated by the optical excitation of resonant plasmonic antennas and diffusing along a simple glass/air interface disturbs the electron transport of a nearby conductive element. By probing the temperature-dependent resistance of a gold nanowire $R_{\rm nw}(T)$, we quantitatively analyze the impact of a resonant absorption of the laser by the antennas. We find that the temperature rise at the nanowire induced by the laser absorption of a distant nanoparticle may exceed that of a direct illumination of the nanowire itself. We also find that a global temperature calibration underestimates the heat generated locally by the laser. The temperature deduced from resistance variations are verified by numerical simulations with a very satisfactory agreement.

Enhancement of the electrical properties of silver nanowire transparent conductive electrodes by atomic layer deposition coating with zinc oxide

Transparent conductive electrodes for applications in optoelectronic devices such as solar cells and light-emitting diodes are important components and require low sheet resistance and high transmittance. Herein, we report an enhancement of the electrical properties of silver (Ag) nanowire networks by coating with zinc oxide using the atomic layer deposition technique. A strong decrease in the sheet resistance of Ag nanowires, namely from 20–40 Ω/□ to 7–15 Ω/□, was observed after coating with ZnO. Ag nanowire electrodes coated with 200-cycle ZnO by atomic layer deposition show the best quality, with a sheet resistance of 11 Ω/□ and transmittance of 75%.

Reducing Grain-Boundary Resistivity of Copper Nanowires by Doping

Grain-boundary scattering becomes a significant contribution to resistivity as copper interconnects are reduced to the nanoscale, presenting a major challenge to the scaling of modern electronics. Using a fully atomistic first-principles method, the authors study grain boundaries doped with other elements in a wide range of concentrations, and in certain cases see diminished resistivity compared to pristine boundaries. This suggests grain-boundary doping as a means to improve copper nanotechnology.

Large-scale synthesis and electrical transport properties of single-crystalline SmB6 nanowires

Topological Kondo insulator samarium hexaboride (SmB6) nanowires, with diameters of 60–150 nm and lengths up to 1–5 μm, were successfully synthesized in large scale by chemical vapor deposition using BCl3 and SmCl3 as precursors at 1070 °C. Transmission electron microscopy observation and selected area electron diffraction analysis indicate that SmB6 nanowires are single-crystalline and grow in a preferred direction of [1 0 0]. It also indicates that the growth of SmB6 nanowires might be governed by a vapor–solid mechanism. Conventional four-terminal resistance measurements show that the resistance of an SmB6 nanowire increases with decreasing temperature, but saturates at temperatures less than 10 K, which might be attributed to a true topological insulator with a metallic surface and fully insulating bulk states. Resistance measurements also indicate that the contribution of surface states to conductance in the SmB6 nanowire is enhanced remarkably; therefore the high-quality single-crystalline SmB6 nanowires with large surface-to-bulk ratio might be the best candidate for investigating the topological properties of this material.

A simulation study of silver nanowire for water and ethane vapor sensing

Purpose Nanowires, nanostructures with the diameter of the order of a nanometer, have recently attracted as gas sensors because of their interesting properties such as high sensitivity, fast response and high selectivity and stability. Among the different types of gas sensors, metallic nanowires used in high frequency applications because of their long mean free path that make the conduction ballistic. Design/methodology/approach This paper presents the results of simulations to find the effects of adsorbing some molecules by silver Ag nanowires. The mechanisms of the simulated gas sensor are implemented in the Atomistix Toolkit 13.2 (ATK 13.2). Findings The simulation results show high sensitivity of silver nanowires in adjacent with water and ethane. The resistance of the simulated nanowire increased to about 3.65 kΩ for ethane and 4.95 kΩ for water molecules. This result shows that the sensitivity of a silver nanowire is about triple for the case of adsorbing water in comparison to the adsorption of ethane molecules. Originality/value This paper presents a simulation study on silver nanowires and compares their sensitivities in adjacent with water and ethane molecules.

Electrical limit of silver nanowire electrodes: Direct measurement of the nanowire junction resistance

We measure basic network parameters of silver nanowire (AgNW) networks commonly used as transparent conducting electrodes in organic optoelectronic devices. By means of four point probing with nanoprobes, the wire-to-wire junction resistance and the resistance of single nanowires are measured. The resistance RNW of a single nanowire shows a value of RNW=(4.96±0.18) Ω/μm. The junction resistance RJ differs for annealed and non-annealed NW networks, exhibiting values of RJ=(25.2±1.9) Ω (annealed) and RJ=(529±239) Ω (non-annealed), respectively. Our simulation achieves a good agreement between the measured network parameters and the sheet resistance RS of the entire network. Extrapolating RJ to zero, our study show that we are close to the electrical limit of the conductivity of our AgNW system: We obtain a possible RS reduction by only ≈20% (common RS≈10 Ω/sq). Therefore, we expect further performance improvements in AgNW systems mainly by increasing NW length or by utilizing novel network geometries.

Chemiresistors based on ultrathin gold nanowires for sensing halides, pyridine and dopamine

Two distinctively different approaches to the deposition of the ultrathin gold nanowires (NWs) on chips for the development of the chemiresistor sensors are studied. The first approach is the deposition of the pre-synthesized NWs on a chip using a microfluidic technique, and the second is the direct synthesis of the NWs on chips. It is shown that the 2nd approach ensures a better contact between the NWs and electrodes, lower resistance of the NW sensor device, and a longer life time of the devices. The current-voltage dependencies obtained for the chips with the NWs in contact with air, and aqueous solutions of NaF, NaCl, NaBr, NaI, pyridine, and dopamine indicate significant changes of the NWs resistance caused by sorption of halides, pyridine and dopamine on the NWs surface. This change of the NWs resistance can be used for quantification of Cl− over a concentration range of 10−5–10−3M and dopamine over a concentration range of 10−8–10−5M. Tentatively, it is concluded that the data obtained can be explained in terms of the Langmuir adsorption isotherm.

Top-Down Nanofabrication and Characterization of 20 nm Silicon Nanowires for Biosensing Applications.

A top-down nanofabrication approach is used to develop silicon nanowires from silicon-on-insulator (SOI) wafers and involves direct-write electron beam lithography (EBL), inductively coupled plasma-reactive ion etching (ICP-RIE) and a size reduction process. To achieve nanometer scale size, the crucial factors contributing to the EBL and size reduction processes are highlighted. The resulting silicon nanowires, which are 20 nm in width and 30 nm in height (with a triangular shape) and have a straight structure over the length of 400 μm, are fabricated precisely at the designed location on the device. The device is applied in biomolecule detection based on the changes in drain current (Ids), electrical resistance and conductance of the silicon nanowires upon hybridization to complementary target deoxyribonucleic acid (DNA). In this context, the scaled-down device exhibited superior performances in terms of good specificity and high sensitivity, with a limit of detection (LOD) of 10 fM, enables for efficient label-free, direct and higher-accuracy DNA molecules detection. Thus, this silicon nanowire can be used as an improved transducer and serves as novel biosensor for future biomedical diagnostic applications.

RF Characterization of Vertical Wrap-Gated InAs/High-$\kappa $ Nanowire Capacitors

This paper presents RF as well as low-frequency capacitance-voltage (C-V) characterization of vertical wrap-gated InAs/high-κ nanowire MOS capacitors. A full equivalent circuit model for traps is used to fit the low-frequency C-V characteristics, from which the interface trap density (D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> ) and border trap density (N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bt</sub> ) are evaluated separately. The results show comparable N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">bt</sub> but far lower D <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">it</sub> (<;10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> eV <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> near the conduction band edge) for a nanowire MOS gate-stack compared with planar references. In the RF domain, the influence of nanowire series resistances become significant, and by introducing a distributed RC-model, the nanowire resistivity (ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nw</sub> ) is evaluated from the capacitance data as a function of the gate bias. An ON/OFF ρ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">nw</sub> ratio of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> is obtained for the best device. Using the measured data, the quality factor is finally evaluated both for fabricated and ideal capacitors. The results agree well with simulated data.

Cu catalyst assisted growth of GaN nanowires on sapphire substrate for p-type behavior

Copper catalyst assisted growth of GaN nanowires (NWs) on c-plane sapphire substrate has been investigated using Chemical Vapor Deposition Method. The impact of different reaction temperatures on the crystallinity have been studied by high resolution X-ray diffraction and Raman spectroscopy. The results has confirmed that the crystalline structure of GaN NWs are wurtzite. The surface morphology of the GaN nanowires have been analysed by scanning electron microscopy. The transmission electron microscopy (TEM) analysis reveals that the grown nanowires are single crystalline in nature. The diameter of NW decreases gradually from 1μm to 65nm and length is ∼7μm. Composition and impurities in GaN NWs have been studied by EDX analysis. The resistivity (ρ=5×101Ωcm), hole mobility (μp=2.97cm2/Vs) and hole concentration (p=4.17×1016cm−3) of GaN nanowires have been estimated by Hall measurement. Room temperature photoluminescence study shows that the near band edge emission of GaN NWs was red shifted to 3.26eV.

Fabrication of ultra-high-sensitivity flexible strain sensor based on single ZnO nanowire

An ultra-high-sensitivity strain sensor based on a single ZnO nanowire (NW) was developed by nanowelding the NW onto a flexible substrate using a custom-built nano-manipulation system inside a scanning electron microscope (SEM). Onto the two ends of the NW were sputtered Au electrodes, to which conducting wires that connect to a multi-meter were glued. A thin methyl methacrylate polymer layer was used to insulate the strain sensor. The strain gauge was evaluated by attaching the sensor to a cantilever beam ex situ of the SEM, providing flexibility for repeated measurements. An applied force to the cantilever synchronously deformed and altered the NW resistance. The resistance variation of the strain gauge against the known strain on the cantilever showed that a gauge factor that is 200 times higher than that of a commercial strain sensor is feasible for the proposed device. The developed strain sensor is applicable for ultra-small mechanical strain on the order of 10−6.

Electronic transportation properties and magnetoresistance effects on single TiO2 nanowire under ultraviolet irradiation

The polycrystalline anatase TiO2 nanowires with a diameter of about 300 nm are successfully prepared by the sol-gel method together with electrospinning method under a heat treatment at 500℃. The effect of illumination on electronic transport property and magnetoresistance (MR) effect are studied via voltage-current (V-I) curves measured at room temperature in the cases of the dark and the ultraviolet irradiation. The results show that the V-I plots are straight lines without passing through zero point and the resistance of the nanowire is as high as 7.51011 in the dark. The resistance decreases gradually with the magnetic field increasing and after reaching a minimum 4.71011 at B=0.7 T it turns to increase rapidly, but is still smaller than the resistance without magnetic field, indicating a negative MR effect. With the increase of the magnetic field, the negative MR effect increases and then decreases, and the negative MR achieves a maximum value of -37.5% under B=0.7 T. Interestingly, the resistance of nanowires in the ultraviolet irradiation is reduced by about 10 times compared with that in the dark without applying a magnetic field. As the magnetic field increases, the resistance increases monotonically, presenting a positive MR effect. The MR increases rapidly with the increase of magnetic field, and reaches the maximum positive MR effect 620% under B=1.0 T. At room temperature only a few carriers are generated by the thermal excitation in the TiO2 nanowires, which leads to a large resistance in the dark situation. In the ultraviolet irradiation case, the carrier concentration of the nanowires increases because of the generation of a large number of electron-hole pairs, resulting in huge decrease of resistance compared with in the dark. We attribute the change of the MR to the competition betwen two MR mechanisms: negative MR effect due to the localization of d electron and positive MR effect due to spin splitting of the conduction band. In the dark, due to the low carrier concentration, the negative MR mechanism caused by the localization of d electron is dominant under the magnetic field. However, in the ultraviolet irradiation, because carrier concentration increases hugely due to the irradiation, the positive MR mechanism caused by spin splitting of the conduction band is dominant. The fact that the V-I curves does not pass through zero point implies that the contact between TiO2 nanowire and Pt metal is Schottky contact due to the difference in work function. In the dark, the initial voltage first increases with the increase of magnetic field, and then remains steady. In the ultraviolet irradiation the initial voltage is smaller than in the dark and increases monotonically with the magnetic field increasing. In this paper, the physical mechanism of the electrical transport property and MR effect of TiO2 nanowire are discussed, which may provide a meaningful exploration for developing the new electronic device based on the oxide nanowires.

Electronic transport properties of ultra-thin Ni and Ni-C nanowires.

The structures and electronic transport properties of ultra-thin Ni and Ni-C nanowires obtained from carbon nanotube (CNT) templates are theoretically investigated. C atoms tend to locate at the central positions of nanowires and are surrounded by Ni atoms. Spin polarization at the Fermi level is not responsible for the spin filtration of these nanowires. Increasing C concentration can improve the resistance of nanowires by abating the number of electronic transmission channels and the coupling of electron orbitals between Ni atoms. Moreover, with the increase of diameter, the conductance of these nanowires increases as well. This study is helpful for guiding the synthesis of nanowires with desired applications.

Direct electrical transport measurement on a single thermoelectric nanowire embedded in an alumina template.

Electrical conductivity is a key parameter to increase the performance of thermoelectric materials. However, the measurement of such performance remains complex for 1D structures, involving tedious processing. In this study, we present a non-destructive, rapid and easy approach for the characterization of electrical conductivity of Bi2Te3 based single nanowires. By controlling the nanowire overgrowth, each nanowire emerges in the form of a micrometric hemisphere constituting a unique contact zone for direct nanoprobing. As nanowires need no preliminary preparation and remain in their template during measurement, we avoid oxidation effects and time-consuming processing. Electrical transport results show a low nanowire resistivity for compact nanowires obtained at low overpotential. Such values are comparable to bulk materials and thin films. This method not only confirmed its reliability, but it could also be adopted for other semiconducting or metallic electrodeposited nanowires.

Transmission type flat-panel X-ray source using ZnO nanowire field emitters

A transmission type flat-panel X-ray source in diode structure was fabricated. Large-scale patterned ZnO nanowires grown on a glass substrate by thermal oxidation were utilized as field emitters, and tungsten thin film coated on silica glass was used as the transmission anode. Uniform distribution of X-ray generation was achieved, which benefited from the uniform electron emission from ZnO nanowires. Self-ballasting effect induced by the intrinsic resistance of ZnO nanowire and decreasing of screening effect caused by patterned emitters account for the uniform emission. Characteristic X-ray peaks of W-L lines and bremsstrahlung X-rays have been observed under anode voltages at a range of 18–20 kV, the latter of which were the dominant X-ray signals. High-resolution X-ray images with spatial resolution less than 25 μm were obtained by the flat-panel X-ray source. The high resolution was attributed to the small divergence angle of the emitted X-rays from the transmission X-ray source.

Single ZnO Nanowire-Based Gas Sensors to Detect Low Concentrations of Hydrogen.

Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H2 pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H2.

Structural and electrical properties of catalyst-free Si-doped InAs nanowires formed on Si(111).

We report structural and electrical properties of catalyst-free Si-doped InAs nanowires (NWs) formed on Si(111) substrates. The average diameter of Si-doped InAs NWs was almost similar to that of undoped NWs with a slight increase in height. In the previous works, the shape and size of InAs NWs formed on metallic catalysts or patterned structures were significantly changed by introducing dopants. Even though the external shape and size of the Si-doped NWs in this work were not changed, crystal structures inside the NWs were significantly changed. For the undoped InAs NWs, both zincblende (ZB) and wurzite (WZ) structures were observed in transmission-electron microscope images, where the portion of WZ structure was estimated to be more than 30%. However, only ZB was observed with an increase in stacking fault (SF) for the Si-doped NWs. The undoped and Si-doped InAs NWs were used as channels of four-point electrical measurements with Al/Ni electrodes to investigate electrical properties. The resistivity calculated from the current-voltage curve of a Si-doped InAs NW showed 1.32 × 10−3 Ωcm, which was dramatically decreased from 10.14 × 10−3 Ωcm for the undoped InAs NW. A relatively low resistivity of catalyst-free Si-doped InAs NWs was achieved without significant change in structural dimensions.

Lithographically Patterned PEDOT Nanowires for the Detection of Iron(III) with Nanomolar Sensitivity.

Arrays of nanowires of an electronically conductive polymeric affinity medium tailored to the detection of Fe(III) are prepared, and their properties for detecting Fe(III) are evaluated. This polymeric affinity medium consists of poly(3,4-ethylenedioxythiophene) (PEDOT) into which an iron chelator, deferoxamine (DFA), has been doped during the polymerization process. PEDOT-DFA nanowires are potentiostatically deposited from a solution containing both EDOT and DFA using lithographically patterned nanowire electrodeposition (LPNE). The through-nanowire electrical resistance of PEDOT-DFA nanowires is measured as a function of the Fe(III) concentration. In parallel with measurements on PEDOT-DFA nanowire arrays, the electrochemical impedance of PEDOT-DFA films is characterized as a function of the Fe(III) concentration and the frequency of the impedance measurement in order to better understand the mechanism of transduction. PEDOT-DFA nanowires detect Fe(III) from 10(-4) to 10(-8) M with a limit of detection of 300 pM (calculated) and 10 nM (measured).

Growth Conditions Control the Elastic and Electrical Properties of ZnO Nanowires.

Great efforts have been made to synthesize ZnO nanowires (NWs) as building blocks for a broad range of applications because of their unique mechanical and mechanoelectrical properties. However, little attention has been paid to the correlation between the NWs synthesis condition and these properties. Here we demonstrate that by slightly adjusting the NW growth conditions, the cross-sectional shape of the NWs can be tuned from hexagonal to circular. Room temperature photoluminescence spectra suggested that NWs with cylindrical geometry have a higher density of point defects. In situ transmission electron microscopy (TEM) uniaxial tensile-electrical coupling tests revealed that for similar diameter, the Young's modulus and electrical resistivity of hexagonal NWs is always larger than that of cylindrical NWs, whereas the piezoresistive coefficient of cylindrical NWs is generally higher. With decreasing diameter, the Young's modulus and the resistivity of NWs increase, whereas their piezoresistive coefficient decreases, regardless of the sample geometry. Our findings shed new light on understanding and advancing the performance of ZnO-NW-based devices through optimizing the synthesis conditions of the NWs.

Carrier Mobility Enhancement of Tensile Strained Si and SiGe Nanowires via Surface Defect Engineering.

Changes in the carrier mobility of tensile strained Si and SiGe nanowires (NWs) were examined using an electrical push-to-pull device (E-PTP, Hysitron). The changes were found to be closely related to the chemical structure at the surface, likely defect states. As tensile strain is increased, the resistivity of SiGe NWs deceases in a linear manner. However, the corresponding values for Si NWs increased with increasing tensile strain, which is closely related to broken bonds induced by defects at the NW surface. Broken bonds at the surface, which communicate with the defect state of Si are critically altered when Ge is incorporated in Si NW. In addition, the number of defects could be significantly decreased in Si NWs by incorporating a surface passivated Al2O3 layer, which removes broken bonds, resulting in a proportional decrease in the resistivity of Si NWs with increasing strain. Moreover, the presence of a passivation layer dramatically increases the extent of fracture strain in NWs, and a significant enhancement in mobility of about 2.6 times was observed for a tensile strain of 5.7%.