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Sample records for conductive bacterial nanowires

  1. Electrical conductivity measurements of bacterial nanowires from Pseudomonas aeruginosa

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthusamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2015-12-01

    The extracellular appendages of bacteria (flagella) that transfer electrons to electrodes are called bacterial nanowires. This study focuses on the isolation and separation of nanowires that are attached via Pseudomonas aeruginosa bacterial culture. The size and roughness of separated nanowires were measured using transmission electron microscopy (TEM) and atomic force microscopy (AFM), respectively. The obtained bacterial nanowires indicated a clear image of bacterial nanowires measuring 16 nm in diameter. The formation of bacterial nanowires was confirmed by microscopic studies (AFM and TEM) and the conductivity nature of bacterial nanowire was investigated by electrochemical techniques. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), which are nondestructive voltammetry techniques, suggest that bacterial nanowires could be the source of electrons—which may be used in various applications, for example, microbial fuel cells, biosensors, organic solar cells, and bioelectronic devices. Routine analysis of electron transfer between bacterial nanowires and the electrode was performed, providing insight into the extracellular electron transfer (EET) to the electrode. CV revealed the catalytic electron transferability of bacterial nanowires and electrodes and showed excellent redox activities. CV and EIS studies showed that bacterial nanowires can charge the surface by producing and storing sufficient electrons, behave as a capacitor, and have features consistent with EET. Finally, electrochemical studies confirmed the development of bacterial nanowires with EET. This study suggests that bacterial nanowires can be used to fabricate biomolecular sensors and nanoelectronic devices.

  2. Investigation on the electrical conductivity of ZnO nanoparticles-decorated bacterial nanowires

    NASA Astrophysics Data System (ADS)

    Maruthupandy, Muthuchamy; Anand, Muthusamy; Maduraiveeran, Govindhan; Suresh, Santhanakrishnan; Sait Hameedha Beevi, Akbar; Jeeva Priya, Radhakrishnan

    2016-12-01

    Electrical conductivity of zinc oxide nanoparticles (ZnO NPs)-decorated bacterial nanowires is investigated in the present work. The ZnO NPs are prepared through a simple precipitation method and characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, x-ray diffraction, atomic force microscopy (AFM), scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The SEM analysis discloses that the prepared ZnO NPs are spherical in shape with an average particle size of 3.5 nm. The ZnO NPs are decorated on the surface of bacterial nanowires and the same are characterized by AFM and HRTEM. The electrochemical performance of the bare bacterial nanowires and ZnO NPs-decorated bacterial nanowires is analyzed by cyclic voltammetry and linear sweep voltammetry, whereas their electrical conductivity is measured by electrochemical impedance spectroscopy. The results of the electrochemical investigations indicate that the ZnO NPs coating on the surface of bacterial nanowires improve the electrical conductivity of the bacterial nanowires.

  3. Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms.

    PubMed

    Gorby, Yuri A; Yanina, Svetlana; McLean, Jeffrey S; Rosso, Kevin M; Moyles, Dianne; Dohnalkova, Alice; Beveridge, Terry J; Chang, In Seop; Kim, Byung Hong; Kim, Kyung Shik; Culley, David E; Reed, Samantha B; Romine, Margaret F; Saffarini, Daad A; Hill, Eric A; Shi, Liang; Elias, Dwayne A; Kennedy, David W; Pinchuk, Grigoriy; Watanabe, Kazuya; Ishii, Shun'ichi; Logan, Bruce; Nealson, Kenneth H; Fredrickson, Jim K

    2006-07-25

    Shewanella oneidensis MR-1 produced electrically conductive pilus-like appendages called bacterial nanowires in direct response to electron-acceptor limitation. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA, and those that lacked a functional Type II secretion pathway displayed nanowires that were poorly conductive. These mutants were also deficient in their ability to reduce hydrous ferric oxide and in their ability to generate current in a microbial fuel cell. Nanowires produced by the oxygenic phototrophic cyanobacterium Synechocystis PCC6803 and the thermophilic, fermentative bacterium Pelotomaculum thermopropionicum reveal that electrically conductive appendages are not exclusive to dissimilatory metal-reducing bacteria and may, in fact, represent a common bacterial strategy for efficient electron transfer and energy distribution.

  4. Electrically conductive bacterial nanowires produced by Shewanella oneidensis strain MR-1 and other microorganisms

    PubMed Central

    Gorby, Yuri A.; Yanina, Svetlana; McLean, Jeffrey S.; Rosso, Kevin M.; Moyles, Dianne; Dohnalkova, Alice; Beveridge, Terry J.; Chang, In Seop; Kim, Byung Hong; Kim, Kyung Shik; Culley, David E.; Reed, Samantha B.; Romine, Margaret F.; Saffarini, Daad A.; Hill, Eric A.; Shi, Liang; Elias, Dwayne A.; Kennedy, David W.; Pinchuk, Grigoriy; Watanabe, Kazuya; Ishii, Shun’ichi; Logan, Bruce; Nealson, Kenneth H.; Fredrickson, Jim K.

    2006-01-01

    Shewanella oneidensis MR-1 produced electrically conductive pilus-like appendages called bacterial nanowires in direct response to electron-acceptor limitation. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA, and those that lacked a functional Type II secretion pathway displayed nanowires that were poorly conductive. These mutants were also deficient in their ability to reduce hydrous ferric oxide and in their ability to generate current in a microbial fuel cell. Nanowires produced by the oxygenic phototrophic cyanobacterium Synechocystis PCC6803 and the thermophilic, fermentative bacterium Pelotomaculum thermopropionicum reveal that electrically conductive appendages are not exclusive to dissimilatory metal-reducing bacteria and may, in fact, represent a common bacterial strategy for efficient electron transfer and energy distribution. PMID:16849424

  5. Structure of the type IVa major pilin from the electrically conductive bacterial nanowires of Geobacter sulfurreducens.

    PubMed

    Reardon, Patrick N; Mueller, Karl T

    2013-10-11

    Several species of δ proteobacteria are capable of reducing insoluble metal oxides as well as other extracellular electron acceptors. These bacteria play a critical role in the cycling of minerals in subsurface environments, sediments, and groundwater. In some species of bacteria such as Geobacter sulfurreducens, the transport of electrons is proposed to be facilitated by filamentous fibers that are referred to as bacterial nanowires. These nanowires are polymeric assemblies of proteins belonging to the type IVa family of pilin proteins and are mainly comprised of one subunit protein, PilA. Here, we report the high resolution solution NMR structure of the PilA protein from G. sulfurreducens determined in detergent micelles. The protein is >85% α-helical and exhibits similar architecture to the N-terminal regions of other non-conductive type IVa pilins. The detergent micelle interacts with the first 21 amino acids of the protein, indicating that this region likely associates with the bacterial inner membrane prior to fiber formation. A model of the G. sulfurreducens pilus fiber is proposed based on docking of this structure into the fiber model of the type IVa pilin from Neisseria gonorrhoeae. This model provides insight into the organization of aromatic amino acids that are important for electrical conduction.

  6. Structure of the Type IVa Major Pilin from the Electrically Conductive Bacterial Nanowires of Geobacter sulfurreducens

    SciTech Connect

    Reardon, Patrick N.; Mueller, Karl T.

    2013-10-11

    Several species of bacteria are capable of reducing insoluble metal oxides as well as other extracellular electron acceptors. These bacteria play a critical role in the cycling of minerals in subsurface environments, sediments, and groundwater. In some species of bacteria, such as Geobacter sulfurreducens, the transport of electrons is facilitated by filamentous fibers that are referred to as bacterial nanowires. These nanowires belong to the type IVa family of pilin proteins and are mainly comprised of one subunit protein, PilA. Here, we report the high resolution solution nuclear magnetic resonance (NMR) structure of the PilA protein from G. sulfurreducens determined in detergent micelles. The protein is over 85% α-helical and exhibits similar architecture to the N-terminal regions of other non-conductive type IVa pilins. The detergent micelle interacts with the first 21 amino acids of the protein, indicating that this region likely associates with the bacterial inner membrane prior to fiber formation. A model of the G. sulfurreducens pilus fiber is proposed based on docking of this structure into the fiber model of the type IVa pilin from Neisseria gonorrhoeae. This model provides insight into the organization of aromatic amino acids that are important for electrical conduction.

  7. Electrical transport along bacterial nanowires from Shewanella oneidensis MR-1

    PubMed Central

    El-Naggar, Mohamed Y.; Wanger, Greg; Leung, Kar Man; Yuzvinsky, Thomas D.; Southam, Gordon; Yang, Jun; Lau, Woon Ming; Nealson, Kenneth H.; Gorby, Yuri A.

    2010-01-01

    Bacterial nanowires are extracellular appendages that have been suggested as pathways for electron transport in phylogenetically diverse microorganisms, including dissimilatory metal-reducing bacteria and photosynthetic cyanobacteria. However, there has been no evidence presented to demonstrate electron transport along the length of bacterial nanowires. Here we report electron transport measurements along individually addressed bacterial nanowires derived from electron-acceptor–limited cultures of the dissimilatory metal-reducing bacterium Shewanella oneidensis MR-1. Transport along the bacterial nanowires was independently evaluated by two techniques: (i) nanofabricated electrodes patterned on top of individual nanowires, and (ii) conducting probe atomic force microscopy at various points along a single nanowire bridging a metallic electrode and the conductive atomic force microscopy tip. The S. oneidensis MR-1 nanowires were found to be electrically conductive along micrometer-length scales with electron transport rates up to 109/s at 100 mV of applied bias and a measured resistivity on the order of 1 Ω·cm. Mutants deficient in genes for c-type decaheme cytochromes MtrC and OmcA produce appendages that are morphologically consistent with bacterial nanowires, but were found to be nonconductive. The measurements reported here allow for bacterial nanowires to serve as a viable microbial strategy for extracellular electron transport. PMID:20937892

  8. Conducting polyaniline nanowire electrode junction

    NASA Astrophysics Data System (ADS)

    Gaikwad, Sumedh; Bodkhe, Gajanan; Deshmukh, Megha; Patil, Harshada; Rushi, Arti; Shirsat, Mahendra D.; Koinkar, Pankaj; Kim, Yun-Hae; Mulchandani, Ashok

    2015-03-01

    In this paper, a synthesis of conducting polyaniline nanowires electrode junction (CPNEJ) has been reported. Conducting polyaniline nanowires electrode junction on Si/SiO2 substrate (having 3 μm gap between two gold microelectrodes) is prepared. Polyaniline nanowires with diameter (ca. 140 nm to 160 nm) were synthesized by one step electrochemical polymerization using galvanostatic (constant current) technique to bridge this gap. The surface morphology of CPNEJ was studied by scanning electron microscope (SEM). The synthesized CPNEJ is an excellent platform for biosensor applications.

  9. Conductive Nanowires Templated by Molecular Brushes.

    PubMed

    Raguzin, Ivan; Stamm, Manfred; Ionov, Leonid

    2015-10-21

    In this paper, we report the fabrication of conductive nanowires using polymer bottle brushes as templates. In our approach, we synthesized poly(2-dimethylamino)ethyl methacrylate methyl iodide quaternary salt brushes by two-step atom transfer radical polymerization, loaded them with palladium salt, and reduced them in order to form metallic nanowires with average lengths and widths of 300 and 20 nm, respectively. The obtained nanowires were deposited between conductive gold pads and were connected to them by sputtering of additional pads to form an electric circuit. We connected the nanowires in an electric circuit and demonstrated that the conductivity of these nanowires is around 100 S·m(-1).

  10. Bacterial Nanowires Facilitate Extracellular Electron Transfer

    NASA Astrophysics Data System (ADS)

    Gorby, Y.

    2005-12-01

    Dissimilatory metal reducing bacteria, including Shewanella oneidensis and Geobacter sulfurreducens, produce electrically conductive nanowires that facilitate electron transfer to solid phase iron oxides. Nanowires produced by S. oneidensis strain MR-1 are functionalized by decaheme cytochromes MtrC and OmcA that are distributed along the length of the nanowires, as confirmed by immunolocalization experiments using peptide specific antibodies. Mutants lacking MtrC and OmcA produce nanowires that were poorly conductive, are unable to reduce solid phase iron oxides, and do not produce electric current in microbial fuel cells. Although less completely characterized, nanowires are also produced by organisms throughout a broad metabolic spectrum, from sulfate reducing bacteria to oxygenic, phototrophic cyanobacteria. Our research suggests that electrically conductive nanowires may be common throughout the microbial world and may serve as structures for efficient electron transfer and energy dissemination in complex communities such as microbial mats and biofilms.

  11. Conducting nanowires in insulating ceramics.

    PubMed

    Nakamura, Atsutomo; Matsunaga, Katsuyuki; Tohma, Jun; Yamamoto, Takahisa; Ikuhara, Yuichi

    2003-07-01

    Low-dimensional structures, such as microclusters, quantum dots and one- or two-dimensional (1D or 2D) quantum wires, are of scientific and technological interest due to their unusual physical properties, which are quite different from those in the bulk. Here we present a successful method for fabricating conducting nanowire bundles inside an insulating ceramic single crystal by using unidirectional dislocations. A high density of dislocations (10(9) cm(-2)) was introduced by activating a primary slip system in sapphire (alpha-Al2O3 single crystal) using a two-stage deformation technique. Plate specimens cut out from the deformed sapphire were then annealed to straighten the dislocations. Finally, the plates on which metallic Ti was evaporated were heat-treated to diffuse Ti atoms inside sapphire. As a result of this process, Ti atoms segregated along the unidirectional dislocations within about 5 nm diameter, forming unidirectional Ti-enriched nanowires, which exhibit excellent electrical conductivity. This simple technique could potentially to be applied to any crystal, and may give special properties to commonly used materials.

  12. Radiation Fluence dependent variation in Electrical conductivity of Cu nanowires

    SciTech Connect

    Gehlawat, Devender; Chauhan, R. P.; Sonkawade, R. G.

    2011-07-15

    Electrical conductivity of Cu nanowires varies with diameter of nanowires. However, keeping the diameter of nanowires constant, a variation in their electrical conductivity is observed after they irradiated with gamma rays and neutrons. On the basis of I-V characteristics drawn at room temperature, decrease in the conductivity of Cu nanowires is observed, as compared to that of pristine nanowires.

  13. Predicting the thermal conductivity of crystalline nanowires

    NASA Astrophysics Data System (ADS)

    Mingo, Natalio; Yang, Liu; Li, D.; Majumdar, A.

    2003-03-01

    We present quantitative calculations of the lattice thermal conductivity vs. temperature of Si nanowires, yielding good agreement with experimental measurements by Li et al.[1]. Our calculation method is predictive, since no experimental data from the nanowires are needed as input for the theoretical curves. The formalism is based on a transmission function approach, and makes use of the full phonon dispersion relations of the material [2]. Using the same method we also calculate curves for Ge nanowires, for which experiments have not yet been performed. In the talk we will explain the formalism of our Full Dispersions Transmission Function approach (FDTF). The traditional methods of Callaway and Holland [3] will also be discussed and compared with our FDTF method. Predictions with the latter method are considerably better than those using the traditional methods. In principle, the FDTF approach can be employed to calculate lattice thermal conductivity curves for nanowires of different materials. It may therefore constitute a very useful piece in the theoretical modeling of new thermoelectric materials based on nanowires. [1] D. Li et al., submitted. [2] N. Mingo et al., to be submitted. [3] M. Asen-Palmer et al., Phys. Rev. B 56, 9431 (1997).

  14. Isotropical conductive adhesives filled with silver nanowires

    NASA Astrophysics Data System (ADS)

    Tao, Y.; Xia, Y. P.; Zhang, G. Q.; Wu, H. P.; Tao, G. L.

    2009-07-01

    In this study, a solution-phase method was demonstrated to generate silver (Ag) nanowires with diameters in the range of 30~50nm and lengths of up to ~50μm, which was proceed by reducing silver nitrate with ethylene glycol in the presence of poly(vinyl pyrrolidone) (PVP). Fundamental material characterizations including X-ray diffraction transmission electro microscopy (TEM) and scanning electro microscopy (SEM) were conducted on these Ag nanowires. A novel kind of isotropical conductive adhesives (ICA) was prepared by using these Ag nanowires as conductive filler. Electrical property including bulk resistivity and mechanical property including shear strength were investigated and compared with that of conventional ICA filled with micrometer-sized Ag particles or nanometer-sized Ag particles. The average diameter of these Ag particles is about 1μm and 100 nm respectively. The results shown that ICA filled Ag nanowires exhibited higher conductivity, higher shear strength and low percolation threshold value than traditional ICA. Possible conductive mechanism was discussed based on theory calculation.

  15. Thermal conductivity in porous silicon nanowire arrays.

    PubMed

    Weisse, Jeffrey M; Marconnet, Amy M; Kim, Dong Rip; Rao, Pratap M; Panzer, Matthew A; Goodson, Kenneth E; Zheng, Xiaolin

    2012-10-06

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  16. Thermal conductivity in porous silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Weisse, Jeffrey M.; Marconnet, Amy M.; Kim, Dong Rip; Rao, Pratap M.; Panzer, Matthew A.; Goodson, Kenneth E.; Zheng, Xiaolin

    2012-10-01

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  17. The effect of nanowire length and diameter on the properties of transparent, conducting nanowire films.

    PubMed

    Bergin, Stephen M; Chen, Yu-Hui; Rathmell, Aaron R; Charbonneau, Patrick; Li, Zhi-Yuan; Wiley, Benjamin J

    2012-03-21

    This article describes how the dimensions of nanowires affect the transmittance and sheet resistance of a random nanowire network. Silver nanowires with independently controlled lengths and diameters were synthesized with a gram-scale polyol synthesis by controlling the reaction temperature and time. Characterization of films composed of nanowires of different lengths but the same diameter enabled the quantification of the effect of length on the conductance and transmittance of silver nanowire films. Finite-difference time-domain calculations were used to determine the effect of nanowire diameter, overlap, and hole size on the transmittance of a nanowire network. For individual nanowires with diameters greater than 50 nm, increasing diameter increases the electrical conductance to optical extinction ratio, but the opposite is true for nanowires with diameters less than this size. Calculations and experimental data show that for a random network of nanowires, decreasing nanowire diameter increases the number density of nanowires at a given transmittance, leading to improved connectivity and conductivity at high transmittance (>90%). This information will facilitate the design of transparent, conducting nanowire films for flexible displays, organic light emitting diodes and thin-film solar cells.

  18. Conducting Polyaniline Nanowire and Its Applications in Chemiresistive Sensing

    PubMed Central

    Song, Edward; Choi, Jin-Woo

    2013-01-01

    One dimensional polyaniline nanowire is an electrically conducting polymer that can be used as an active layer for sensors whose conductivity change can be used to detect chemical or biological species. In this review, the basic properties of polyaniline nanowires including chemical structures, redox chemistry, and method of synthesis are discussed. A comprehensive literature survey on chemiresistive/conductometric sensors based on polyaniline nanowires is presented and recent developments in polyaniline nanowire-based sensors are summarized. Finally, the current limitations and the future prospect of polyaniline nanowires are discussed. PMID:28348347

  19. Electrically Conductive Metal Nanowire Polymer Nanocomposites

    NASA Astrophysics Data System (ADS)

    Luo, Xiaoxiong

    This thesis investigates electrically conductive polymer nanocomposites formulated with metal nanowires for electrostatic discharge and electromagnetic interference shielding. Copper nanowires (CuNWs) of an average length of 1.98 mum and diameter of 25 +/- 4 nm were synthesized. The oxidation reaction of the CuNWs in air can be divided into two stages at weight of 111.2% on TGA curves. The isoconversional activation energies determined by Starink method were used to fit the different master plots. Johnson-Mehl-Avrami (JMA) equation gave the best fit. The surface atoms of the CuNWs are the sites for the random nucleation and the crystallite strain in the CuNWs is the driving force for the growth of nuclei mechanism during the oxidation process. To improve the anti-oxidation properties of the CuNWs, silver was coated onto the surface of the CuNWs in Ag-amine solution. The prepared silver coated CuNWs (AgCuNWs) with silver content of 66.52 wt. %, diameter of 28--33 nm exhibited improved anti-oxidation behavior. The electrical resistivity of the AgCuNW/low density polyethylene (LDPE) nanocomposites is lower than that of the CuNW/LDPE nanocomposites with the same volume percentage of fillers. The nanocomposites formulated with CuNWs and polyethylenes (PEs) were compared to study the different interaction between the CuNWs and the different types of PE matrices. The electrical conductivity of the different PE matrices filled with the same concentrations of CuNWs correlated well with the level of the CuNW dispersion. The intermolecular force and entanglement resulting from the different macromolecular structures such as molecular weight and branching played an important role in the dispersion, electrical properties and rheological behaviour of the CuNW/PE nanocomposites. Ferromagnetic polycrystalline nickel nanowires (NiNWs) were synthesized with uniform diameter of ca. 38 nm and an average length of 2.68 mum. The NiNW linear low density polyethylene (LLDPE

  20. Electrically conductive and optically active porous silicon nanowires.

    PubMed

    Qu, Yongquan; Liao, Lei; Li, Yujing; Zhang, Hua; Huang, Yu; Duan, Xiangfeng

    2009-12-01

    We report the synthesis of vertical silicon nanowire array through a two-step metal-assisted chemical etching of highly doped n-type silicon (100) wafers in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of the as-grown silicon nanowires is tunable from solid nonporous nanowires, nonporous/nanoporous core/shell nanowires, to entirely nanoporous nanowires by controlling the hydrogen peroxide concentration in the etching solution. The porous silicon nanowires retain the single crystalline structure and crystallographic orientation of the starting silicon wafer and are electrically conductive and optically active with visible photoluminescence. The combination of electronic and optical properties in the porous silicon nanowires may provide a platform for novel optoelectronic devices for energy harvesting, conversion, and biosensing.

  1. Composition, Reactivity, and Regulations of Extracellular Metal-Reducing Structures (Bacterial Nanowires) Produced by Dissimilatory Metal Reducing Bacteria

    SciTech Connect

    Scholten, Johannes

    2006-06-01

    This research proposal seeks to describe the composition and function of electrically conductive appendages known as bacterial nanowires. This project targets bacterial nanowires produced by dissimilatory metal reducing bacteria Shewanella and Geobacter. Specifically, this project will investigate the role of these structures in the reductive transformation of iron oxides as solid phase electron acceptors, as well as uranium as a dissolved electron acceptor that forms nanocrystalline particles of uraninite upon reduction.

  2. Impacts of atomistic coating on thermal conductivity of germanium nanowires.

    PubMed

    Chen, Jie; Zhang, Gang; Li, Baowen

    2012-06-13

    By using nonequilibrium molecular dynamics simulations, we demonstrated that thermal conductivity of germanium nanowires can be reduced more than 25% at room temperature by atomistic coating. There is a critical coating thickness beyond which thermal conductivity of the coated nanowire is larger than that of the host nanowire. The diameter-dependent critical coating thickness and minimum thermal conductivity are explored. Moreover, we found that interface roughness can induce further reduction of thermal conductivity in coated nanowires. From the vibrational eigenmode analysis, it is found that coating induces localization for low-frequency phonons, while interface roughness localizes the high-frequency phonons. Our results provide an available approach to tune thermal conductivity of nanowires by atomic layer coating.

  3. Synthesis of oxidation-resistant cupronickel nanowires for transparent conducting nanowire networks.

    PubMed

    Rathmell, Aaron R; Nguyen, Minh; Chi, Miaofang; Wiley, Benjamin J

    2012-06-13

    Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.

  4. Synthesis of Oxidation-Resistant Cupronickel Nanowires for Transparent Conducting Nanowire Networks

    SciTech Connect

    Rathmall, Aaron; Nguyen, Minh; Wiley, Benjamin J

    2012-01-01

    Nanowires of copper can be coated from liquids to create flexible, transparent conducting films that can potentially replace the dominant transparent conductor, indium tin oxide, in displays, solar cells, organic light-emitting diodes, and electrochromic windows. One issue with these nanowire films is that copper is prone to oxidation. It was hypothesized that the resistance to oxidation could be improved by coating copper nanowires with nickel. This work demonstrates a method for synthesizing copper nanowires with nickel shells as well as the properties of cupronickel nanowires in transparent conducting films. Time- and temperature-dependent sheet resistance measurements indicate that the sheet resistance of copper and silver nanowire films will double after 3 and 36 months at room temperature, respectively. In contrast, the sheet resistance of cupronickel nanowires containing 20 mol % nickel will double in about 400 years. Coating copper nanowires to a ratio of 2:1 Cu:Ni gave them a neutral gray color, making them more suitable for use in displays and electrochromic windows. These properties, and the fact that copper and nickel are 1000 times more abundant than indium or silver, make cupronickel nanowires a promising alternative for the sustainable, efficient production of transparent conductors.

  5. Interpretation of optical conductivity of zinc oxide nanowires

    SciTech Connect

    Choudhary, K. K.; Kaurav, N.

    2015-07-31

    The frequency dependent optical response of Zinc Oxide (ZnO) nanowires is theoretically analyzed within the two component schemes: one is the motion of coherent Drude electrons within the ZnO nanowire and the other is incoherent motion of electrons from one nanowire to other. The model has only one free parameter, the relaxation rate. The frequency dependent relaxation rates are expressed in terms of memory functions. The coherent Drude carriers form a sharp peak at zero frequency and a long tail at higher frequencies, i.e. in the infrared region. However, the hopping of carriers from one nanowire to other (incoherent motion of electrons) yields a peak value in the optical conductivity around mid infrared region. It is found that both the Drude and hopping carriers will contribute to the optical process of conduction in ZnO nanowire.

  6. Phonon thermal conductivity of a nanowire attached to leads

    NASA Astrophysics Data System (ADS)

    Hershfield, Selman; Muttalib, Khandker

    2015-03-01

    There is experimental evidence as well as theoretical proposals that nanowires can be made to have high thermoelectric efficiency by tuning the electronic properties; however, there is always a phonon contribution to the heat transport which reduces the thermoelectric efficiency. In the harmonic approximation we compute the transmission of phonons through a nanowire coupled to large leads. There is a finite thermal conductivity because of the restriction provided by the nanowire. The nanowire reduces the thermal transport because of the mismatch between the leads and wire modes. We examine the effect of disorder in three places: in the wire, in the leads near the wire, and in the leads far way from the wire. In some cases disorder can increase the thermal conduction because of enhanced mode coupling. We will discuss the implications of our results for thermoelectric nanowire devices.

  7. Ultralow thermal conductivity in Electrolessly Etched (EE) Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Hippalgaonkar, Kedar; Chen, Renkun; Budaev, Bair; Tang, Jinyao; Andrews, Sean; Murphy, Padraig; Mukerjee, Subroto; Moore, Joel; Yang, Peidong; Majumdar, Arun

    2009-03-01

    EE process produces single-crystalline Silicon nanowires with rough walls. We use suspended structures to directly compute the heat transfer through single nanowires. Nanowires with diameters less than the mean free path of phonons impede transport by boundary scattering. The roughness acts as a secondary scattering mechanism to further reduce phonon transport. By controlling the amount of roughness it is possible to push limits to the extent that nanowire conductance close to quanta of thermal conductance,πkB^2 T / πkB^2 T 6 . - 6 is observed. Traditionally, the lower limit of conductivity is amorphous Silicon at 1 W/mK at room temperature. The measured conductivity of our nanostructures challenges even this amorphous limit pointing towards previously unstudied mechanisms of thermal resistance. We measure thermal conductivity of ˜150nm diameter EE wires to be ˜1 W/mK.

  8. Enhanced Photoresponse of Conductive Polymer Nanowires Embedded with Au Nanoparticles.

    PubMed

    Zhang, Junchang; Zhong, Liubiao; Sun, Yinghui; Li, Anran; Huang, Jing; Meng, Fanben; Chandran, Bevita K; Li, Shuzhou; Jiang, Lin; Chen, Xiaodong

    2016-04-20

    A conductive polymer nanowire embedded with a 1D Au nanoparticle chain with defined size, shape, and interparticle distance is fabricated which demonstrates enhanced photoresponse behavior. The precise and controllable positioning of 1D Au nanoparticle chain in the conductive polymer nanowire plays a critical role in modulating the photoresponse behavior by excitation light wavelength or power due to the coupled-plasmon effect of 1D Au nanoparticle chain.

  9. Silver nanowire catalysts on carbon nanotubes-incorporated bacterial cellulose membrane electrodes for oxygen reduction reaction.

    PubMed

    Kim, Bona; Choi, Youngeun; Cho, Se Youn; Yun, Young Soo; Jin, Hyoung-Joon

    2013-11-01

    Silver nanowires have unique electrical, thermal and optical properties, which support their potential application in numerous fields including catalysis, electronics, optoelectronics, sensing, and surface-enhanced spectroscopy. Especially, their application such as catalysts for alkaline fuel cells (AFCs) have attracted much interest because of their superior electrical conductivity over that of any metal and their lower cost compared to Pt. In this study, multiwalled carbon nanotubes (MWCNTs)-incorporated bacterial cellulose (BC) membrane electrode with silver nanowire catalyst was prepared. First, acid-treated MWCNTs were incorporated into BC membranes and then freeze-dried after solvent exchange to tert-butanol in order to maintain the 3D-network macroporous structure. Second, silver nanowires synthesized by polyol process were introduced onto the surface of the MWCNTs-incorporated BC membrane through easy vacuum filtration. Finally, thermal treatment was carried out to confirm the effect of the PVP on the silver nanowire catalysts toward oxygen reduction reaction. The electrode with thermally treated silver nanowire had great electrocatalytic activity compared with non-treated one. These results suggest that the MWCNTs-incorporated BC electrode with silver nanowire catalysts after thermal treatment could be potentially used in cathodes of AFCs.

  10. Indirect measurement of thermal conductivity in silicon nanowires

    SciTech Connect

    Pennelli, Giovanni Nannini, Andrea; Macucci, Massimo

    2014-02-28

    We report indirect measurements of thermal conductivity in silicon nanostructures. We have exploited a measurement technique based on the Joule self-heating of silicon nanowires. A standard model for the electron mobility has been used to determine the temperature through the accurate measurement of the nanowire resistance. We have applied this technique to devices fabricated with a top-down process that yields nanowires together with large silicon areas used both as electrical and as thermal contacts. As there is crystalline continuity between the nanowires and the large contact areas, our thermal conductivity measurements are not affected by any temperature drop due to the contact thermal resistance. Our results confirm the observed reduction of thermal conductivity in nanostructures and are comparable with those previously reported in the literature, achieved with more complex measurement techniques.

  11. Thermal conductivity of silicon nanowire arrays with controlled roughness

    SciTech Connect

    Feser, JP; Sadhu, JS; Azeredo, BP; Hsu, KH; Ma, J; Kim, J; Seong, M; Fang, NX; Li, XL; Ferreira, PM; Sinha, S; Cahill, DG

    2012-12-01

    A two-step metal assisted chemical etching technique is used to systematically vary the sidewall roughness of Si nanowires in vertically aligned arrays. The thermal conductivities of nanowire arrays are studied using time domain thermoreflectance and compared to their high-resolution transmission electron microscopy determined roughness. The thermal conductivity of nanowires with small roughness is close to a theoretical prediction based on an upper limit of the mean-free-paths of phonons given by the nanowire diameter. The thermal conductivity of nanowires with large roughness is found to be significantly below this prediction. Raman spectroscopy reveals that nanowires with large roughness also display significant broadening of the one-phonon peak; the broadening correlates well with the reduction in thermal conductivity. The origin of this broadening is not yet understood, as it is inconsistent with phonon confinement models, but could derive from microstructural changes that affect both the optical phonons observed in Raman scattering and the acoustic phonons that are important for heat conduction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767456

  12. Rolling silver nanowire electrodes: simultaneously addressing adhesion, roughness, and conductivity.

    PubMed

    Hauger, Tate C; Al-Rafia, S M Ibrahim; Buriak, Jillian M

    2013-12-11

    Silver nanowire mesh electrodes represent a possible mass-manufacturable route toward transparent and flexible electrodes for plastic-based electronics such as organic photovoltaics (OPVs), organic light emitting diodes (OLEDs), and others. Here we describe a route that is based upon spray-coated silver nanowire meshes on polyethylene terephthalate (PET) sheets that are treated with a straightforward combination of heat and pressure to generate electrodes that have low sheet resistance, good optical transmission, that are topologically flat, and adhere well to the PET substrate. The silver nanowire meshes were prepared by spray-coating a solution of silver nanowires onto PET, in air at slightly elevated temperatures. The as-prepared silver nanowire electrodes are highly resistive due to the poor contact between the individual silver nanowires. Light pressure applied with a stainless steel rod, rolled over the as-sprayed silver nanowire meshes on PET with a speed of 10 cm s(-1) and a pressure of 50 psi, results in silver nanowire mesh arrays with sheet resistances of less than 20 Ω/□. Bending of these rolled nanowire meshes on PET with different radii of curvature, from 50 to 0.625 mm, showed no degradation of the conductivity of the electrodes, as shown by the constant sheet resistance before and after bending. Repeated bending (100 times) around a rod with a radius of curvature of 1 mm also showed no increase in the sheet resistance, demonstrating good adherence and no signs of delamination of the nanowire mesh array. The diffuse and direct transmittance of the silver nanowires (both rolled and as-sprayed) was measured for wavelengths from 350 to 1200 nm, and the diffuse transmission was similar to that of the PET substrate; the direct transmission decreases by about 7-8%. The silver nanowires were then incorporated into OPV devices with the following architecture: transparent electrode/PEDOT:PSS/P3HT:PC61BM/LiF/Al. While slightly lower in efficiency than the

  13. Manipulating connectivity and electrical conductivity in metallic nanowire networks.

    PubMed

    Nirmalraj, Peter N; Bellew, Allen T; Bell, Alan P; Fairfield, Jessamyn A; McCarthy, Eoin K; O'Kelly, Curtis; Pereira, Luiz F C; Sorel, Sophie; Morosan, Diana; Coleman, Jonathan N; Ferreira, Mauro S; Boland, John J

    2012-11-14

    Connectivity in metallic nanowire networks with resistive junctions is manipulated by applying an electric field to create materials with tunable electrical conductivity. In situ electron microscope and electrical measurements visualize the activation and evolution of connectivity within these networks. Modeling nanowire networks, having a distribution of junction breakdown voltages, reveals universal scaling behavior applicable to all network materials. We demonstrate how local connectivity within these networks can be programmed and discuss material and device applications.

  14. Persistent ion beam induced conductivity in zinc oxide nanowires

    SciTech Connect

    Johannes, Andreas; Niepelt, Raphael; Gnauck, Martin; Ronning, Carsten

    2011-12-19

    We report persistently increased conduction in ZnO nanowires irradiated by ion beam with various ion energies and species. This effect is shown to be related to the already known persistent photo conduction in ZnO and dubbed persistent ion beam induced conduction. Both effects show similar excitation efficiency, decay rates, and chemical sensitivity. Persistent ion beam induced conduction will potentially allow countable (i.e., single dopant) implantation in ZnO nanostructures and other materials showing persistent photo conduction.

  15. Persistent ion beam induced conductivity in zinc oxide nanowires

    NASA Astrophysics Data System (ADS)

    Johannes, Andreas; Niepelt, Raphael; Gnauck, Martin; Ronning, Carsten

    2011-12-01

    We report persistently increased conduction in ZnO nanowires irradiated by ion beam with various ion energies and species. This effect is shown to be related to the already known persistent photo conduction in ZnO and dubbed persistent ion beam induced conduction. Both effects show similar excitation efficiency, decay rates, and chemical sensitivity. Persistent ion beam induced conduction will potentially allow countable (i.e., single dopant) implantation in ZnO nanostructures and other materials showing persistent photo conduction.

  16. DNA-templated nanowires: morphology and electrical conductivity

    NASA Astrophysics Data System (ADS)

    Watson, Scott M. D.; Pike, Andrew R.; Pate, Jonathan; Houlton, Andrew; Horrocks, Benjamin R.

    2014-03-01

    DNA-templating has been used to create nanowires from metals, compound semiconductors and conductive polymers. The mechanism of growth involves nucleation at binding sites on the DNA followed by growth of spherical particles and then, under favourable conditions, a slow transformation to a smooth nanowire. The final transformation is favoured by restricting the amount of templated material per unit length of template and occurs most readily for materials of low surface tension. Electrical measurements on DNA-templated nanowires can be facilitated using three techniques: (i) standard current-voltage measurements with contact electrodes embedded in a dielectric so that there is a minimal step height at the dielectric/electrode boundary across which nanowires may be aligned by molecular combing, (ii) the use of a dried droplet technique and conductive AFM to determine contact resistance by moving the tip along the length of an individual nanowire and (iii) non-contact assessment of conductivity by scanned conductance microscopy on Si/SiO2 substrates.

  17. Conducting polymer nanowire arrays for high performance supercapacitors.

    PubMed

    Wang, Kai; Wu, Haiping; Meng, Yuena; Wei, Zhixiang

    2014-01-15

    This Review provides a brief summary of the most recent research developments in the fabrication and application of one-dimensional ordered conducting polymers nanostructure (especially nanowire arrays) and their composites as electrodes for supercapacitors. By controlling the nucleation and growth process of polymerization, aligned conducting polymer nanowire arrays and their composites with nano-carbon materials can be prepared by employing in situ chemical polymerization or electrochemical polymerization without a template. This kind of nanostructure (such as polypyrrole and polyaniline nanowire arrays) possesses high capacitance, superior rate capability ascribed to large electrochemical surface, and an optimal ion diffusion path in the ordered nanowire structure, which is proved to be an ideal electrode material for high performance supercapacitors. Furthermore, flexible, micro-scale, threadlike, and multifunctional supercapacitors are introduced based on conducting polyaniline nanowire arrays and their composites. These prototypes of supercapacitors utilize the high flexibility, good processability, and large capacitance of conducting polymers, which efficiently extend the usage of supercapacitors in various situations, and even for a complicated integration system of different electronic devices.

  18. Sintering Behavior and Effect of Silver Nanowires on the Electrical Conductivity of Electrically Conductive Adhesives.

    PubMed

    Xie, H; Xiong, N N; Wang, Y H; Zhao, Y Z; Li, J Z

    2016-01-01

    In this paper, two kinds of silver nanowires with a 160 nm average diameter ranging from 30 to 90 µm length and a 450 nm average diameter up to 100 µm length were successfully synthesized by a polyol process with FeCl3 and Na₂S as reaction inhibitor, respectively. The experimental results indicate that the morphologies and sintering behaviors of both of silver nanowires are impacted by glutaric acid and sintering temperature. The isotropically conductive adhesives (ICAs) filled with micro-sized silver flakes and silver nanowires as hybrid fillers were fabricated and the electrical properties were investigated based on the fraction of the silver nanowires of the total of silver fillers and the curing temperature, etc. The in situ monitoring the variation in electrical resistance of the ICAs explores that silver nanowires have influence on the curing behavior of the ICAs. Silver nanowires synthesized with Na2S as reaction inhibitor and treated with glutaric acid can significantly improve the electrical conductivity of the ICAs in the case of the low loading of silver fillers in the appropriate proportion range of the weight ratio of micro-sized silver flakes and silver nanowires, primarily as a result of connecting effect. When the loading of silver fillers in the ICAs is high, the electrical conductivity is also enhanced slightly in the case of the proper fraction of silver nanowires of the total of silver fillers. The effect of the curing temperature on the electrical conductivity relates to the fraction of silver nanowires and the total loading of silver fillers. The electrical conductivity of the ICAs filled with micro-sized silver flakes and silver nanowires synthesized with FeCl₃ as reaction inhibitor is greatly damaged, indicating that the size of silver nanowires also is one of main factor to impact the electrical conductivity of the ICAs doped with silver nanowires. The electrical property of the ICAs filled with micro-sized silver flakes and silver

  19. Conductance of a proximitized nanowire in the Coulomb blockade regime

    NASA Astrophysics Data System (ADS)

    van Heck, B.; Lutchyn, R. M.; Glazman, L. I.

    2016-06-01

    We identify the leading processes of electron transport across finite-length segments of proximitized nanowires and build a quantitative theory of their two-terminal conductance. In the presence of spin-orbit interaction, a nanowire can be tuned across the topological transition point by an applied magnetic field. Due to a finite segment length, electron transport is controlled by the Coulomb blockade. Upon increasing of the field, the shape and magnitude of the Coulomb blockade peaks in the linear conductance are defined, respectively, by Andreev reflection, single-electron tunneling, and resonant tunneling through the Majorana modes emerging after the topological transition. Our theory provides the framework for the analysis of experiments with proximitized nanowires [such as reported in S. M. Albrecht et al., Nature (London) 531, 206 (2016), 10.1038/nature17162] and identifies the signatures of the topological transition in the two-terminal conductance.

  20. Copper nanowires as fully transparent conductive electrodes.

    PubMed

    Guo, Huizhang; Lin, Na; Chen, Yuanzhi; Wang, Zhenwei; Xie, Qingshui; Zheng, Tongchang; Gao, Na; Li, Shuping; Kang, Junyong; Cai, Duanjun; Peng, Dong-Liang

    2013-01-01

    In pondering of new promising transparent conductors to replace the cost rising tin-doped indium oxide (ITO), metal nanowires have been widely concerned. Herein, we demonstrate an approach for successful synthesis of long and fine Cu nanowires (NWs) through a novel catalytic scheme involving nickel ions. Such Cu NWs in high aspect ratio (diameter of 16.2 ± 2 nm and length up to 40 μm) provide long distance for electron transport and, meanwhile, large space for light transmission. Transparent electrodes fabricated using the Cu NW ink achieve a low sheet resistance of 1.4 Ohm/sq at 14% transmittance and a high transparency of 93.1% at 51.5 Ohm/sq. The flexibility and stability were tested with 100-timebending by 180°and no resistance change occurred. Ohmic contact was achieved to the p- and n-GaN on blue light emitting diode chip and bright electroluminescence from the front face confirmed the excellent transparency.

  1. Ionic conductivity enhancement of polymer electrolytes with ceramic nanowire fillers.

    PubMed

    Liu, Wei; Liu, Nian; Sun, Jie; Hsu, Po-Chun; Li, Yuzhang; Lee, Hyun-Wook; Cui, Yi

    2015-04-08

    Solid-state electrolytes provide substantial improvements to safety and electrochemical stability in lithium-ion batteries when compared with conventional liquid electrolytes, which makes them a promising alternative technology for next-generation high-energy batteries. Currently, the low mobility of lithium ions in solid electrolytes limits their practical application. The ongoing research over the past few decades on dispersing of ceramic nanoparticles into polymer matrix has been proved effective to enhance ionic conductivity although it is challenging to form the efficiency networks of ionic conduction with nanoparticles. In this work, we first report that ceramic nanowire fillers can facilitate formation of such ionic conduction networks in polymer-based solid electrolyte to enhance its ionic conductivity by three orders of magnitude. Polyacrylonitrile-LiClO4 incorporated with 15 wt % Li0.33La0.557TiO3 nanowire composite electrolyte exhibits an unprecedented ionic conductivity of 2.4 × 10(-4) S cm(-1) at room temperature, which is attributed to the fast ion transport on the surfaces of ceramic nanowires acting as conductive network in the polymer matrix. In addition, the ceramic-nanowire filled composite polymer electrolyte shows an enlarged electrochemical stability window in comparison to the one without fillers. The discovery in the present work paves the way for the design of solid ion electrolytes with superior performance.

  2. Magnetic and conductive magnetite nanowires by DNA-templating.

    PubMed

    Mohamed, Hasan Daw A; Watson, Scott M D; Horrocks, Benjamin R; Houlton, Andrew

    2012-09-28

    The synthesis of nanowires made of magnetite (Fe(3)O(4)) phase iron oxide was achieved using DNA as a template to direct formation of the metal oxide and confine its growth in two dimensions. This simple solution-based approach involves initial association of Fe(2+) and Fe(3+) to the DNA "template" molecules, and subsequent co-precipitation of the Fe(3)O(4) material, upon increasing the solution pH, to give the final metal oxide nanowires. Analysis of the DNA-templated material, using a combination of FTIR, XRD, XPS, and Raman spectroscopy, confirmed the iron oxide formed to be the Fe(3)O(4) crystal phase. Investigation of the structural character of the nanowires, carried out by AFM, revealed the metal oxide to form regular coatings of nanometre-scale thickness around the DNA templates. Statistical analysis showed the size distribution of the nanowires to follow a trimodal model, with the modal diameter values identified as 5-6 nm, 14-15 nm, and 23-24 nm. Additional scanning probe microscopy techniques (SCM, MFM) were also used to verify that the nanowire structures are electrically conducting and exhibit magnetic behaviour. Such properties, coupled with the small dimensions of these materials, make them potentially good candidates for application in a host of future nanoscale device technologies.

  3. A review of the electrical properties of semiconductor nanowires: insights gained from terahertz conductivity spectroscopy

    NASA Astrophysics Data System (ADS)

    Joyce, Hannah J.; Boland, Jessica L.; Davies, Christopher L.; Baig, Sarwat A.; Johnston, Michael B.

    2016-10-01

    Accurately measuring and controlling the electrical properties of semiconductor nanowires is of paramount importance in the development of novel nanowire-based devices. In light of this, terahertz (THz) conductivity spectroscopy has emerged as an ideal non-contact technique for probing nanowire electrical conductivity and is showing tremendous value in the targeted development of nanowire devices. THz spectroscopic measurements of nanowires enable charge carrier lifetimes, mobilities, dopant concentrations and surface recombination velocities to be measured with high accuracy and high throughput in a contact-free fashion. This review spans seminal and recent studies of the electronic properties of nanowires using THz spectroscopy. A didactic description of THz time-domain spectroscopy, optical pump–THz probe spectroscopy, and their application to nanowires is included. We review a variety of technologically important nanowire materials, including GaAs, InAs, InP, GaN and InN nanowires, Si and Ge nanowires, ZnO nanowires, nanowire heterostructures, doped nanowires and modulation-doped nanowires. Finally, we discuss how THz measurements are guiding the development of nanowire-based devices, with the example of single-nanowire photoconductive THz receivers.

  4. Thermal Conductivity of ZnO Single Nanowire.

    PubMed

    Yuldashev, Sh U; Yalishev, V Sh; Cho, H D; Kang, T W

    2016-02-01

    The thermal conductivity of a single ZnO nanowire with diameter of ~150 nm was measured using a four-point-probe 3omega method over a temperature range of 140-300 K. The measured ther- mal conductivity of ZnO nanowire is strongly reduced compared to bulk ZnO crystal due to the enhanced phonon-boundary and impurity (isotope) scattering. The maximum of the thermal conductivity is shifted to a higher temperature than that of bulk counterpart. Temperature dependent measurements show that beyond the low-temperature maximum, the thermal conductivity decreases with temperature as T(-1.5) indicating strong impurity (isotope) scattering at intermediate and high temperatures.

  5. Thermal conductivity modeling of core-shell and tubular nanowires.

    PubMed

    Yang, Ronggui; Chen, Gang; Dresselhaus, Mildred S

    2005-06-01

    The heteroepitaxial growth of crystalline core-shell nanostructures of a variety of materials has become possible in recent years, allowing the realization of various novel nanoscale electronic and optoelectronic devices. The increased surface or interface area will decrease the thermal conductivity of such nanostructures and impose challenges for the thermal management of such devices. In the meantime, the decreased thermal conductivity might benefit the thermoelectric conversion efficiency. In this paper, we present modeling results on the lattice thermal conductivity of core-shell and tubular nanowires along the wire axis direction using the phonon Boltzmann equation. We report the dependence of the thermal conductivity on the surface conditions and the core-shell geometry for silicon core-germanium shell and tubular silicon nanowires at room temperature. The results show that the effective thermal conductivity changes not only with the composition of the constituents but also with the radius of the nanowires and nanopores due to the nature of the ballistic phonon transport. The results in this work have implications for the design and operation of a variety of nanoelectronic devices, optoelectronic devices, and thermoelectric materials and devices.

  6. Theoretic analysis on electric conductance of nano-wire transistors

    NASA Astrophysics Data System (ADS)

    Tsai, N.-C.; Chiang, Y.-R.; Hsu, S.-L.

    2010-01-01

    By employing the commercial software nanoMos and Vienna ab Initio Simulation Package ( VASP), the performance of nano-wire field-effect transistors is investigated. In this paper, the Density-Gradient Model (DG Model) is used to describe the carrier transport behavior of the nano-wire transistor under quantum effects. The analysis of the drain current with respect to channel length, body dielectric constant and gate contact work function is presented. In addition, Fermi energy and DOS (Density of State) are introduced to explore the relative stability of carrier transport and electrical conductance for the silicon crystal with dopants. Finally, how the roughness of the surface of the silicon-based crystal is affected by dopants and their allocation can be illuminated by a few broken bonds between atoms near the skin of the crystal.

  7. Tunable metallic-like conductivity in microbial nanowire networks

    NASA Astrophysics Data System (ADS)

    Malvankar, Nikhil S.; Vargas, Madeline; Nevin, Kelly P.; Franks, Ashley E.; Leang, Ching; Kim, Byoung-Chan; Inoue, Kengo; Mester, Tünde; Covalla, Sean F.; Johnson, Jessica P.; Rotello, Vincent M.; Tuominen, Mark T.; Lovley, Derek R.

    2011-09-01

    Electronic nanostructures made from natural amino acids are attractive because of their relatively low cost, facile processing and absence of toxicity. However, most materials derived from natural amino acids are electronically insulating. Here, we report metallic-like conductivity in films of the bacterium Geobacter sulfurreducens and also in pilin nanofilaments (known as microbial nanowires) extracted from these bacteria. These materials have electronic conductivities of ~5 mS cm-1, which are comparable to those of synthetic metallic nanostructures. They can also conduct over distances on the centimetre scale, which is thousands of times the size of a bacterium. Moreover, the conductivity of the biofilm can be tuned by regulating gene expression, and also by varying the gate voltage in a transistor configuration. The conductivity of the nanofilaments has a temperature dependence similar to that of a disordered metal, and the conductivity could be increased by processing.

  8. Thermal Conductivity Suppression in Nanostructured Silicon and Germanium Nanowires

    NASA Astrophysics Data System (ADS)

    Özden, Ayberk; Kandemir, Ali; Ay, Feridun; Perkgöz, Nihan Kosku; Sevik, Cem

    2016-03-01

    The inherent low lattice thermal conductivity (TC) of semiconductor nanowires (s-NW) due to one-dimensional phonon confinement might provide a solution for the long-lasting figure-of-merit problem for highly efficient thermoelectric (TE) applications. Standalone diameter modulation or alloying of s-NW serve as a toolkit for TC control, but realizing the full potential of nanowires requires new atomic-scale designs, growth, characterization, and understanding of the physical mechanisms behind the structure-property (TC) relationship. Before undertaking time-consuming and expensive experimental work, molecular dynamics (MD) simulations serve as an excellent probe to investigate new designs and understand how nanostructures affect thermal transport properties through their capability to capture various phenomena such as phonon boundary scattering, phonon coherence resonance, and phonon backscattering. On the other hand, because different research groups use different structural and MD parameters in their simulations, it is rather difficult to make comparisons between different nanostructures and select appropriate ones for potential TE applications. Therefore, in this work, we systematically investigated pristine, core-shell (C-S), holey (H-N), superlattice (SL), sawtooth (ST), and superlattice sawtooth (SL-ST) nanowires with identical structural parameters. Specifically, we aim to compare the relative TC reduction achieved by these nanostructures with respect to pristine nanowires in order to propose the best structural design with the lowest lattice TC, using Green-Kubo method-based equilibrium molecular dynamics simulations at 300 K. Our results show that the TC can be minimized by changing specific parameters such as the core diameter and monolayer separation for C-S, H-N, and ST structures. In the case of SL structures, the TC is found to be independent of these parameters. However, surface roughness in the form of a ST morphology provides a TC value below 2 W

  9. Thermal conductivity of silicon nanowires embedded on thermoelectric platforms

    NASA Astrophysics Data System (ADS)

    Choi, JinYong; Cho, Kyoungah; Yoon, Dae Sung; Kim, Sangsig

    2016-10-01

    In this study, we propose a simple method for obtaining the thermal conductivity of silicon nanowires (SiNWs) embedded on a thermoelectric platform. The approximation of the heat flux in SiNWs with temperature differences enables the determination of thermal conductivity. Using this method, the thermal conductivities of our n- and p-type SiNWs are found to be 18.06  ±  0.12 and 20.29  ±  0.77 W m-1 · K-1, respectively. The atomic weight of arsenic ions in the n-type SiNWs is responsible for a lower thermal conductivity than that of boron ions in the p-type SiNWs. Our results demonstrate that this simple method is capable of measuring the thermal conductivity of thermoelectric nanomaterials embedded on thermoelectric devices.

  10. Local electric conductive property of Si nanowire models

    NASA Astrophysics Data System (ADS)

    Ikeda, Yuji; Senami, Masato; Tachibana, Akitomo

    2012-12-01

    Local electric conductive properties of Si nanowire models are investigated by using two local electric conductivity tensors, {{σ }limits^{leftrArr }}_{ext}(r) and {{σ }limits^{leftrArr }}_{int}(r), defined in Rigged QED. It is emphasized that {{σ }limits^{leftrArr }}_{int}(r) is defined as the response of electric current to the actual electric field at a specific point and does not have corresponding macroscopic physical quantity. For the Si nanowire models, there are regions which show complicated response of electric current density to electric field, in particular, opposite and rotational ones. Local conductivities are considered to be available for the study of a negative differential resistance (NDR), which may be related to this opposite response. It is found that {{σ }limits^{leftrArr }}_{int}(r) shows quite different pattern from {{σ }limits^{leftrArr }}_{ext}(r), local electric conductivity defined for the external electric field. The effects of impurities are also studied by using the model including a Ge atom, in terms of the local response to electric field. It is found that the difference from the pristine model is found mainly around the Ge atom.

  11. Effects of alkali treatments on Ag nanowire transparent conductive films

    NASA Astrophysics Data System (ADS)

    Kim, Sunho; Kang, Jun-gu; Eom, Tae-yil; Moon, Bongjin; Lee, Hoo-Jeong

    2016-06-01

    In this study, we employ various alkali materials (alkali metals with different base strengths, and ammonia gas and solution) to improve the conductivity of silver nanowire (Ag NW)-networked films. The alkali treatment appears to remove the surface oxide and improve the conductivity. When applied with TiO2 nanoparticles, the treatment appears more effective as the alkalis gather around wire junctions and help them weld to each other via heat emitted from the reduction reaction. The ammonia solution treatment is found to be quick and aggressive, damaging the wires severely in the case of excessive treatment. On the other hand, the ammonia gas treatment seems much less aggressive and does not damage the wires even after a long exposure. The results of this study highlight the effectiveness of the alkali treatment in improving of the conductivity of Ag NW-networked transparent conductive films.

  12. Tunable conductance of magnetic nanowires with structured domain walls.

    PubMed

    Dugaev, V K; Berakdar, J; Barnaś, J

    2006-02-03

    We show that in a magnetic nanowire with double magnetic domain walls, quantum interference results in spin-split quasistationary states localized mainly between the domain walls. Spin-flip-assisted transmission through the domain structure increases strongly when these size-quantized states are tuned on resonance with the Fermi energy, e.g., upon varying the distance between the domain walls which results in resonance-type peaks of the wire conductance. This novel phenomenon is shown to be utilizable to manipulate the spin density in the domain vicinity. The domain wall parameters are readily controllable, and the predicted effect is hence exploitable in spintronic devices.

  13. Helicity induced thermal conductivity reduction in superlattice nanowires

    NASA Astrophysics Data System (ADS)

    Varshney, Vikas; Roy, Ajit K.; Lee, Jonghoon; Dudis, Douglas S.; Farmer, Barry L.

    2012-12-01

    In this study, we have performed non-equilibrium molecular dynamics (NEMD) simulations to investigate thermal transport properties of 'model' bi-component helical nanowires. The results indicate that significant reduction in thermal conductivity, similar to that of flat superlattice nanostructures, can be achieved using a helical geometric configuration. The reduction is attributed to a plethora of transmissive and reflective phonon scattering events resulting from the steady alteration of phonon propagating direction that emerges from the continuous rotation of the helical interface. We also show that increasing the relative mass ratio of the two components lowers the phonon energy transmission at the interface (differences in vibrational frequency spectrum), thereby relatively 'easing' the phonon energy propagation along the helical pathway. While the proposed mechanisms result in a reduced lattice thermal conductivity, the continuous nature of the bi-component nanowire would not be expected to significantly reduce its electrical counterpart, as often occurs in superlattice/alloy nanostructures. Hence, we believe that the helical configuration of atomic arrangement should be a very attractive, general approach for improved thermoelectric material assemblies independent of the specific chemical composition.

  14. Strain- and defect-mediated thermal conductivity in silicon nanowires.

    PubMed

    Murphy, Kathryn F; Piccione, Brian; Zanjani, Mehdi B; Lukes, Jennifer R; Gianola, Daniel S

    2014-07-09

    The unique thermal transport of insulating nanostructures is attributed to the convergence of material length scales with the mean free paths of quantized lattice vibrations known as phonons, enabling promising next-generation thermal transistors, thermal barriers, and thermoelectrics. Apart from size, strain and defects are also known to drastically affect heat transport when introduced in an otherwise undisturbed crystalline lattice. Here we report the first experimental measurements of the effect of both spatially uniform strain and point defects on thermal conductivity of an individual suspended nanowire using in situ Raman piezothermography. Our results show that whereas phononic transport in undoped Si nanowires with diameters in the range of 170-180 nm is largely unaffected by uniform elastic tensile strain, another means of disturbing a pristine lattice, namely, point defects introduced via ion bombardment, can reduce the thermal conductivity by over 70%. In addition to discerning surface- and core-governed pathways for controlling thermal transport in phonon-dominated insulators and semiconductors, we expect our novel approach to have broad applicability to a wide class of functional one- and two-dimensional nanomaterials.

  15. Monte Carlo Simulation of Thermal Conductivity in Randomly Distributed Nanowire Composites

    NASA Astrophysics Data System (ADS)

    Tian, W.; Yang, R.

    2007-03-01

    In this paper, we investigated the thermal conductivity of composites made of two types of randomly stacked nanowires with high contrast ratio of bulk thermal conductivity. Thermal conductivity predictions based on solving the phonon Boltzmann transport equation by using the Monte Carlo method are presented for different contrast ratios of thermal conductivity, sizes of nanowires and the volumetric fractions in the composites. For composites made of nanowires with high contrast ratio thermal conductivity, the thermal conductivity of the nanocomposites increase dramatically when the volumetric fraction of high thermal conductivity nanowire is higher than the geometry percolation threshold, although existing correlations in percolation theory do not fit the results due to the phonon interface scattering. On the other hand, when the the size of nanowires is small and the volumetric fraction of high thermal conductivity nanowire is less than percolation threshold, the thermal conductivity of the nanocomposites decreases with increasing the volumetric fraction of the high thermal conductivity nanowires. The results of this study may help the development of nanoscale thermoelectric materials in which the figure of merit is optimized by choosing appropriate nanowire size, property contrast and composition. RY acknowledges the funding support for this work by DoD/AFOSR MURI grant FA9550-06-1-0326. The simulation was conducted on a 24-node cluster supported by Intel Corporation and managed by Prof. Gang Chen and Mr. Lu Hu at MIT.

  16. Highly transparent, conductive, flexible resin films embedded with silver nanowires.

    PubMed

    Jiang, Yaqiu; Xi, Jun; Wu, Zhaoxin; Dong, Hua; Zhao, Zhixu; Jiao, Bo; Hou, Xun

    2015-05-05

    In this article, a low sheet resistance and highly transparent silver nanowire (AgNW) resin composite film was demonstrated, which was prepared by a simple and efficacious two-step spin-coating method. By burying the AgNWs below the surface of the transparent resin matrix which was cured at 150 °C in air, we achieved a uniform, highly transparent, conductive, flexible film. Compared to the reported transparent electrodes, this composite transparent and conductive film showed 10 Ω/□ sheet resistance and nearly 90% mean optical transmittance over the UV-visible range simultaneously. Undergoing hundreds of cycles of tensile and compression folding, the composite film slightly increased its sheet resistance by less than 5%, displaying good electromechanical flexibility. These characteristics of the composite AgNW-resin films were expected to be used in applications of flexible optoelectronics.

  17. Final Scientific Report: Bacterial Nanowires and Extracellular Electron Transfer to Heavy Metals and Radionuclides by Bacterial Isolates from DOE Field Research Centers

    SciTech Connect

    Nealson, Kenneth

    2016-12-20

    This proposal involved the study of bacteria capable of transferring electrons from the bacterial cells to electron acceptors located outside the cell. These could be either insoluble minerals that were transformed into soluble products upon the addition of electrons, or they could be soluble salts like uranium or chromium, that become insoluble upon the addition of electrons. This process is called extracellular electron transport or EET, and can be done directly by cellular contact, or via conductive appendages called bacterial nanowires. In this work we examined a number of different bacteria for their ability to perform EET, and also looked at their ability to produce conductive nanowires that can be used for EET at a distance away from the EET-capable cells. In the work, new bacteria were isolated, new abilities of EET were examined, and many new methods were developed, and carefully described in the literature. These studies set the stage for future work dealing with the bioremediation of toxic metals like uranium and chromium. They also point out that EET (and conductive nanowires) are far more common that had been appreciated, and may be involved with energy transfer not only in sediments, but in symbioses between different bacteria, and in symbiosis/pathogenesis between bacteria and higher organisms.

  18. Valence state of Ti in conductive nanowires in sapphire

    SciTech Connect

    Mizoguchi, Teruyasu; Nakamura, Atsutomo; Matsunaga, Katsuyuki; Ikuhara, Yuichi; Sakurai, Masaki; Tanaka, Isao; Yamamoto, Takahisa

    2004-10-15

    In order to reveal the valence state of Ti in conductive nanowires in sapphire, near-edge x-ray-absorption fine structures (NEXAFS) were observed. From experimental and theoretical studies on NEXAFS of reference compounds including rutile, anatase, and Ti{sub 2}O{sub 3}, it was found that the valence state of Ti can be identified by regarding the positions of the spectral onset and the shoulder in the main peak of Ti-K NEXAFS. The valence states of Ti doped Al{sub 2}O{sub 3} polycrystalline specimens which were annealed at oxidized and reduced atmospheres were determined to be +4 and +3, respectively. The solubility limit of Ti in Al{sub 2}O{sub 3} polycrystal was found to be between 1000 ppm to 1.0% at the both atmospheres. The spectrum from Ti nanowires in sapphire has a lot of similarities to the reduced specimen, the valence state was therefore concluded to be +3.

  19. Growth of gallium nitride and indium nitride nanowires on conductive and flexible carbon cloth substrates.

    PubMed

    Yang, Yi; Ling, Yichuan; Wang, Gongming; Lu, Xihong; Tong, Yexiang; Li, Yat

    2013-03-07

    We report a general strategy for synthesis of gallium nitride (GaN) and indium nitride (InN) nanowires on conductive and flexible carbon cloth substrates. GaN and InN nanowires were prepared via a nanocluster-mediated growth method using a home built chemical vapor deposition (CVD) system with Ga and In metals as group III precursors and ammonia as a group V precursor. Electron microscopy studies reveal that the group III-nitride nanowires are single crystalline wurtzite structures. The morphology, density and growth mechanism of these nanowires are determined by the growth temperature. Importantly, a photoelectrode fabricated by contacting the GaN nanowires through a carbon cloth substrate shows pronounced photoactivity for photoelectrochemical water oxidation. The ability to synthesize group III-nitride nanowires on conductive and flexible substrates should open up new opportunities for nanoscale photonic, electronic and electrochemical devices.

  20. Influence of magnetic domain walls and magnetic field on the thermal conductivity of magnetic nanowires.

    PubMed

    Huang, Hao-Ting; Lai, Mei-Feng; Hou, Yun-Fang; Wei, Zung-Hang

    2015-05-13

    We investigated the influence of magnetic domain walls and magnetic fields on the thermal conductivity of suspended magnetic nanowires. The thermal conductivity of the nanowires was obtained using steady-state Joule heating to measure the change in resistance caused by spontaneous heating. The results showed that the thermal conductivity coefficients of straight and wavy magnetic nanowires decreased with an increase in the magnetic domain wall number, implying that the scattering between magnons and domain walls hindered the heat transport process. In addition, we proved that the magnetic field considerably reduced the thermal conductivity of a magnetic nanowire. The influence of magnetic domain walls and magnetic fields on the thermal conductivity of polycrystalline magnetic nanowires can be attributed to the scattering of long-wavelength spin waves mediated by intergrain exchange coupling.

  1. Co-percolation to tune conductive behaviour in dynamical metallic nanowire networks.

    PubMed

    Fairfield, J A; Rocha, C G; O'Callaghan, C; Ferreira, M S; Boland, J J

    2016-11-03

    Nanowire networks act as self-healing smart materials, whose sheet resistance can be tuned via an externally applied voltage stimulus. This memristive response occurs due to modification of junction resistances to form a connectivity path across the lowest barrier junctions in the network. While most network studies have been performed on expensive noble metal nanowires like silver, networks of inexpensive nickel nanowires with a nickel oxide coating can also demonstrate resistive switching, a common feature of metal oxides with filamentary conduction. However, networks made from solely nickel nanowires have high operation voltages which prohibit large-scale material applications. Here we show, using both experiment and simulation, that a heterogeneous network of nickel and silver nanowires allows optimization of the activation voltage, as well as tuning of the conduction behavior to be either resistive switching, memristive, or a combination of both. Small percentages of silver nanowires, below the percolation threshold, induce these changes in electrical behaviour, even for low area coverage and hence very transparent films. Silver nanowires act as current concentrators, amplifying conductivity locally as shown in our computational dynamical activation framework for networks of junctions. These results demonstrate that a heterogeneous nanowire network can act as a cost-effective adaptive material with minimal use of noble metal nanowires, without losing memristive behaviour that is essential for smart sensing and neuromorphic applications.

  2. Thermal Conduction in Vertically Aligned Copper Nanowire Arrays and Composites.

    PubMed

    Barako, Michael T; Roy-Panzer, Shilpi; English, Timothy S; Kodama, Takashi; Asheghi, Mehdi; Kenny, Thomas W; Goodson, Kenneth E

    2015-09-02

    The ability to efficiently and reliably transfer heat between sources and sinks is often a bottleneck in the thermal management of modern energy conversion technologies ranging from microelectronics to thermoelectric power generation. These interfaces contribute parasitic thermal resistances that reduce device performance and are subjected to thermomechanical stresses that degrade device lifetime. Dense arrays of vertically aligned metal nanowires (NWs) offer the unique combination of thermal conductance from the constituent metal and mechanical compliance from the high aspect ratio geometry to increase interfacial heat transfer and device reliability. In the present work, we synthesize copper NW arrays directly onto substrates via templated electrodeposition and extend this technique through the use of a sacrificial overplating layer to achieve improved uniformity. Furthermore, we infiltrate the array with an organic phase change material and demonstrate the preservation of thermal properties. We use the 3ω method to measure the axial thermal conductivity of freestanding copper NW arrays to be as high as 70 W m(-1) K(-1), which is more than an order of magnitude larger than most commercial interface materials and enhanced-conductivity nanocomposites reported in the literature. These arrays are highly anisotropic, and the lateral thermal conductivity is found to be only 1-2 W m(-1) K(-1). We use these measured properties to elucidate the governing array-scale transport mechanisms, which include the effects of morphology and energy carrier scattering from size effects and grain boundaries.

  3. Effects of lithium insertion on thermal conductivity of silicon nanowires

    SciTech Connect

    Xu, Wen; Zhang, Gang; Li, Baowen

    2015-04-27

    Recently, silicon nanowires (SiNWs) have been applied as high-performance Li battery anodes, since they can overcome the pulverization and mechanical fracture during lithiation. Although thermal stability is one of the most important parameters that determine safety of Li batteries, thermal conductivity of SiNWs with Li insertion remains unclear. In this letter, using molecular dynamics simulations, we study room temperature thermal conductivity of SiNWs with Li insertion. It is found that compared with the pristine SiNW, there is as much as 60% reduction in thermal conductivity with 10% concentration of inserted Li atoms, while under the same impurity concentration the reduction in thermal conductivity of the mass-disordered SiNW is only 30%. With lattice dynamics calculations and normal mode decomposition, it is revealed that the phonon lifetimes in SiNWs decrease greatly due to strong scattering of phonons by vibrational modes of Li atoms, especially for those high frequency phonons. The observed strong phonon scattering phenomenon in Li-inserted SiNWs is similar to the phonon rattling effect. Our study serves as an exploration of thermal properties of SiNWs as Li battery anodes or weakly coupled with impurity atoms.

  4. Electric conductivity-tunable transparent flexible nanowire-filled polymer composites: orientation control of nanowires in a magnetic field.

    PubMed

    Nagai, Takayuki; Aoki, Nobuyuki; Ochiai, Yuichi; Hoshino, Katsuyoshi

    2011-07-01

    Cobalt compound nanowires were dispersed in a transparent nonconductive polymer film by merely stirring, and the film's transparency and electrical conductivity were examined. This composite film is a unique system in which the average length of the nanowires exceeds the film's thickness. Even in such a system, a percolation threshold existed for the electric conductivity in the direction of the film thickness, and the value was 0.18 vol%. The electric conductivity value changed from ∼1 × 10(-12) S/cm to ∼1 × 10(-3) S/cm when the volume fraction exceeded the threshold. The electric conductivity apparently followed the percolation model until the volume fraction of the nanowires was about 0.45 vol %. The visible light transmission and electric conductivity of the composite film of about 1 vol % nanowires were 92% and 5 × 10(-3) S/cm, respectively. Moreover, the electric conductivity in the direction parallel to the film surface did not depend on the amount of the dispersed nanowires, and its value was about 1 × 10(-14) S/cm. Even in a weak magnetic field of about 100 mT, the nanowires were aligned in a vertical and parallel direction to the film surface, and the electric conductivity of each aligned composite film was 2.0 × 10(-2) S/cm and 2.1 × 10(-12) S/cm. The relation between the average wire length and the electric conductivity was examined, and the effect of the magnetic alignment on that relation was also examined.

  5. Probing the low thermal conductivity of single-crystalline porous Si nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Yunshan; Lina Yang Collaboration; Lingyu Kong Collaboration; Baowen Li Collaboration; John T L Thong Collaboration; Kedar Hippalgaonkar Collaboration

    Pore-like structures provide a novel way to reduce the thermal conductivity of silicon nanowires, compared to both smooth-surface VLS nanowires and rough EE nanowires. Because of enhanced phonon scattering with interface and decrease in phonon transport path, the porous nanostructures show reduction in thermal conductance by few orders of magnitude. It proves to be extremely challenging to evaluate porosity accurately in an experimental manner and further understand its effect on thermal transport. In this study, we use the newly developed electron-beam based micro-electrothermal device technique to study the porosity dependent thermal conductivity of mesoporous silicon nanowires that have single-crystalline scaffolding. Based on the Casino simulation, the power absorbed by the nanowire, coming from the loss of travelling electron energy, has a linear relationship with it cross section. The relationship has been verified experimentally as well. Monte Carlo simulation is carried out to theoretically predict the thermal conductivity of silicon nanowires with a specific value of porosity. These single-crystalline porous silicon nanowires show extremely low thermal conductivity, even below the amorphous limit. These structures together with our experimental techniques provide a particularly intriguing platform to understand the phonon transport in nanoscale and aid the performance improvement in future nanowires-based devices.

  6. Conductive-probe atomic force microscopy characterization of silicon nanowire

    PubMed Central

    2011-01-01

    The electrical conduction properties of lateral and vertical silicon nanowires (SiNWs) were investigated using a conductive-probe atomic force microscopy (AFM). Horizontal SiNWs, which were synthesized by the in-plane solid-liquid-solid technique, are randomly deployed into an undoped hydrogenated amorphous silicon layer. Local current mapping shows that the wires have internal microstructures. The local current-voltage measurements on these horizontal wires reveal a power law behavior indicating several transport regimes based on space-charge limited conduction which can be assisted by traps in the high-bias regime (> 1 V). Vertical phosphorus-doped SiNWs were grown by chemical vapor deposition using a gold catalyst-driving vapor-liquid-solid process on higly n-type silicon substrates. The effect of phosphorus doping on the local contact resistance between the AFM tip and the SiNW was put in evidence, and the SiNWs resistivity was estimated. PMID:21711623

  7. Silver Nanowire Networks as Flexible, Transparent, Conducting Films: Extremely High DC to Optical Conductivity Ratios.

    PubMed

    De, Sukanta; Higgins, Thomas M; Lyons, Philip E; Doherty, Evelyn M; Nirmalraj, Peter N; Blau, Werner J; Boland, John J; Coleman, Jonathan N

    2009-07-28

    We have used aqueous dispersions of silver nanowires to prepare thin, flexible, transparent, conducting films. The nanowires are of length and diameter close to 6.5 μm and 85 nm, respectively. At low thickness, the films consist of networks but appear to become bulk-like for mean film thicknesses above ∼160 nm. These films can be very transparent with optical transmittance reaching as high as 92% for low thickness. The transmittance (550 nm) decreases with increasing thickness, consistent with an optical conductivity of 6472 S/m. The films are also very uniform; the transmittance varies spatially by typically <2%. The sheet resistance decreases with increasing thickness, falling below 1 Ω/◻ for thicknesses above 300 nm. The DC conductivity increases from 2 × 10(5) S/m for very thin films before saturating at 5 × 10(6) S/m for thicker films. Similarly, the ratio of DC to optical conductivity increases with increasing thickness from 25 for the thinnest films, saturating at ∼500 for thicknesses above ∼160 nm. We believe this is the highest conductivity ratio ever observed for nanostructured films and is matched only by doped metal oxide films. These nanowire films are electromechanically very robust, with all but the thinnest films showing no change in sheet resistance when flexed over >1000 cycles. Such results make these films ideal as replacements for indium tin oxide as transparent electrodes. We have prepared films with optical transmittance and sheet resistance of 85% and 13 Ω/◻, respectively. This is very close to that displayed by commercially available indium tin oxide.

  8. Ultralow thermal conductivity of silicon nanowire arrays by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Xiong, Xue; Liu, Meng; Cheng, Guoan; Zheng, Ruiting; Xu, Ju; Wei, Lei

    2017-02-01

    We investigate the thermal conductivities of silicon nanowires (SiNWs) and their arrays based on molecular dynamics simulations. It is found that diminishing diameter, roughing surface and doping impurity of SiNWs can reduce their thermal conductivities by two or three orders of magnitude compared with that of bulk silicon crystals due to the strong phonon boundary and phonon impurity scattering. The simulated thermal conductivities of SiNW arrays demonstrate that arraying nanowires can further lower the thermal conductivity owing to the laterally-coupled effect, and the thermal conductivity of arrays decreases notably with the increased nanowire volume fraction, resulting in an ultralow thermal conductivity for the doped SiNW arrays with rough surfaces, which provides theoretical guidance of thermal management for semiconductor nanowire based microelectronic and thermoelectric devices.

  9. Solid State Electron Transfer via Bacterial Nanowires: Contributions Toward a Mechanistic Understanding of Geophysical Response of Biostimulated Subsurface

    SciTech Connect

    Estella Atekwana

    2012-05-08

    The degradation of organic matter by microorganisms provides a source of electrical potential or so-called 'self potential' (SP) that can be measured by using a voltmeter. During this process electrons are being produced as a waste-product and bacterial cells have to dispose of these to allow for the complete biodegradation of organic matter. Especially in anaerobic microbial communities, exo-cellular electron transfer is the most important driving force behind this process and organisms have developed different, but also similar, ways to transfer electrons to other microorganisms. Recently, it has been postulated that direct electron transfer from cell-to-cell is actually done by 'hard-wired' microorganisms. This shuttling of electrons is most likely done by certain c-type cytochromes that form the functional part of electrically conductive nanowires. In this study we investigated if nanowires can explain the geoelectrical (self potential and spectral induced polarization) signals observed at some biostimulated environments such as DOE sites. The objectives of our project are to: (1) investigate any temporal changes in the geophysical signatures (Self Potential (SP) and Induced Polarization (IP)) associated with nanowires of the bacterium Shewanella oneidensis MR-1, wild type and mtrc/omcA deletion mutant, (2) demonstrate that mutant strains of bacteria that produce nonconductive nanowires do not contribute to geoelectrical responses. We accomplished the following: (1) Provided training to students and a postdoctoral fellow that worked on the project, (2) Conducted several SP & IP measurements correlating the distribution of nanowires and SIP/SP signals in partial fulfillment of object No. 1 and 2. On the following we will report and discuss the results of our last experiment with some emphasis on the source mechanisms of both SP and IP associated with Shewanella oneidensis MR-1, wild type in sand columns.

  10. Conductance fluctuations and disorder induced ν =0 quantum Hall plateau in topological insulator nanowires

    NASA Astrophysics Data System (ADS)

    Xypakis, Emmanouil; Bardarson, Jens H.

    2017-01-01

    Clean topological insulators exposed to a magnetic field develop Landau levels accompanied by a nonzero Hall conductivity for the infinite slab geometry. In this work we consider the case of disordered topological insulator nanowires and find, in contrast, that a zero Hall plateau emerges within a broad energy window close to the Dirac point. We numerically calculate the conductance and its distribution for a statistical ensemble of disordered nanowires, and use the conductance fluctuations to study the dependence of the insulating phase on system parameters, such as the nanowire length, disorder strength, and the magnetic field.

  11. Laser patterning of transparent conductive metal nanowire coatings: simulation and experiment.

    PubMed

    Henley, Simon J; Cann, Maria; Jurewicz, Izabela; Dalton, Alan; Milne, David

    2014-01-21

    Transparent and electrically conductive metal nanowire networks are possible replacements for costly indium tin oxide (ITO) films in many optoelectronic devices. ITO films are regularly patterned using pulsed lasers so similar technologies could be used for nanowire coatings to define electrode structures. Here, the effects of laser irradiation on conducting silver nanowire coatings are simulated and then investigated experimentally for networks formed by spray deposition onto transparent substrates. The ablation threshold fluence is found experimentally for such nanowire networks and is then related to film thickness. An effective model using finite-element heat transfer analysis is examined to look at energy dissipation through these nanowire networks and used to understand mechanisms at play in the laser-material interactions. It is demonstrated that the three-dimensional nature of these coatings and the relative ratios of the rates of lateral to vertical heat diffusion are important controlling parameter affecting the ablation threshold.

  12. Atomistic Simulation of the Size and Orientation Dependences of Thermal Conductivity in GaN Nanowires

    SciTech Connect

    Wang, Zhiguo; Zu, Xiaotao; Gao, Fei; Weber, William J.; Crocombette, J.-P.

    2007-04-16

    The thermal conductivity of GaN nanowires has been determined computationally, by applying nonequilibrium atomistic simulation methods using the Stillinger-Weber [Phys. Rev. B 31, 5262 (1985)] potentials. The simulation results show that the thermal conductivity of the GaN nanowires is smaller than that of a bulk crystal and increases with increasing diameter. Surface scattering of phonons and the high surface to volume ratios of the nanowires are primarily responsible for the reduced thermal conductivity and its size dependence behavior. The thermal conductivity is also found to decrease with increasing temperature, which is due to phonon-phonon interactions at high temperatures. The thermal conductivity also exhibits a dependence on axial orientation of the nanowires.

  13. Metal-conductive polymer hybrid nanostructures: preparation and electrical properties of palladium-polyimidazole nanowires.

    PubMed

    Al-Hinai, Mariam; Hassanien, Reda; Watson, Scott M D; Wright, Nicholas G; Houlton, Andrew; Horrocks, Benjamin R

    2016-03-04

    A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of PdCl4(-2) with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV-vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5-45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1-1.4 S cm(-1)), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm(-1)). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (E(a )= 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd.

  14. Metal-conductive polymer hybrid nanostructures: preparation and electrical properties of palladium-polyimidazole nanowires

    NASA Astrophysics Data System (ADS)

    Al-Hinai, Mariam; Hassanien, Reda; Watson, Scott M. D.; Wright, Nicholas G.; Houlton, Andrew; Horrocks, Benjamin R.

    2016-03-01

    A simple, convenient method for the formation of hybrid metal/conductive polymer nanostructures is described. Polyimidazole (PIm) has been templated on λ-DNA via oxidative polymerisation of imidazole using FeCl3 to produce conductive PIm/DNA nanowires. The PIm/DNA nanowires were decorated with Pd (Pd/PIm/DNA) by electroless reduction of {{{{PdCl}}}4}2- with NaBH4 in the presence of PIm/DNA; the choice of imidazole was motivated by the potential Pd(II) binding site at the pyridinic N atom. The formation of PIm/DNA and the presence of metallic Pd on Pd/PIm/DNA nanowires were verified by FTIR, UV-vis and XPS spectroscopy techniques. AFM studies show that the nanowires have diameters in the range 5-45 nm with a slightly greater mean diameter (17.1 ± 0.75 nm) for the Pd-decorated nanowires than the PIm/DNA nanowires (14.5 ± 0.89 nm). After incubation for 24 h in the polymerisation solution, the PIm/DNA nanowires show a smooth, uniform morphology, which is retained after decoration with Pd. Using a combination of scanned conductance microscopy, conductive AFM and two-terminal measurements we show that both types of nanowire are conductive and that it is possible to discriminate different possible mechanisms of transport. The conductivity of the Pd/PIm/DNA nanowires, (0.1-1.4 S cm-1), is comparable to the PIm/DNA nanowires (0.37 ± 0.029 S cm-1). In addition, the conductance of Pd/PIm/DNA nanowires exhibits Arrhenius behaviour (E a = 0.43 ± 0.02 eV) as a function of temperature in contrast to simple Pd/DNA nanowires. These results indicate that although the Pd crystallites on Pd/PIm/DNA nanowires decorate the PIm polymer, the major current pathway is through the polymer rather than the Pd.

  15. Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle-nanowires

    NASA Astrophysics Data System (ADS)

    Muhammed Ajmal, C.; Mol Menamparambath, Mini; Ryeol Choi, Hyouk; Baik, Seunghyun

    2016-06-01

    Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle-nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle-nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle-nanowires provided a greater maximum conductivity (54 390 S cm-1) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle-nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration.

  16. Extraordinarily high conductivity of flexible adhesive films by hybrids of silver nanoparticle-nanowires.

    PubMed

    Ajmal, C Muhammed; Menamparambath, Mini Mol; Choi, Hyouk Ryeol; Baik, Seunghyun

    2016-06-03

    Highly conductive flexible adhesive (CFA) film was developed using micro-sized silver flakes (primary fillers), hybrids of silver nanoparticle-nanowires (secondary fillers) and nitrile butadiene rubber. The hybrids of silver nanoparticle-nanowires were synthesized by decorating silver nanowires with silver nanoparticle clusters using bifunctional cysteamine as a linker. The dispersion in ethanol was excellent for several months. Silver nanowires constructed electrical networks between the micro-scale silver flakes. The low-temperature surface sintering of silver nanoparticles enabled effective joining of silver nanowires to silver flakes. The hybrids of silver nanoparticle-nanowires provided a greater maximum conductivity (54 390 S cm(-1)) than pure silver nanowires, pure multiwalled carbon nanotubes, and multiwalled carbon nanotubes decorated with silver nanoparticles in nitrile butadiene rubber matrix. The resistance change was smallest upon bending when the hybrids of silver nanoparticle-nanowires were employed. The adhesion of the film on polyethylene terephthalate substrate was excellent. Light emitting diodes were successfully wired to the CFA circuit patterned by the screen printing method for application demonstration.

  17. Stable and Controllable Synthesis of Silver Nanowires for Transparent Conducting Film.

    PubMed

    Liu, Bitao; Yan, Hengqing; Chen, Shanyong; Guan, Youwei; Wu, Guoguo; Jin, Rong; Li, Lu

    2017-12-01

    Silver nanowires without particles are synthesized by a solvothermal method at temperature 150 °C. Silver nanowires are prepared via a reducing agent of glycerol and a capping agent of polyvinylpyrrolidone (M w  ≈ 1,300,000). Both of them can improve the purity of the as-prepared silver nanowires. With controllable shapes and sizes, silver nanowires are grown continuously up to 10-20 μm in length with 40-50 nm in diameter. To improve the yield of silver nanowires, the different concentrations of AgNO3 synthesis silver nanowires are discussed. The characterizations of the synthesized silver nanowires are analyzed by UV-visible absorption spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and atomic force microscope (AFM), and silver nanowires are pumped on the cellulose membrane and heated stress on the PET. Then, the cellulose membrane is dissolved by the steam of acetone to prepare flexible transparent conducting thin film, which is detected 89.9 of transmittance and 58 Ω/□. Additionally, there is a close loop connected by the thin film, a blue LED, a pair of batteries, and a number of wires, to determinate directly the film if conductive or not.

  18. Surface states and conductivity of silicon nano-wires

    NASA Astrophysics Data System (ADS)

    Kumar Bhaskar, Umesh; Pardoen, Thomas; Passi, Vikram; Raskin, Jean-Pierre

    2013-04-01

    The transport characteristics of low dimensional semiconductors like silicon nano-wires (SiNWs) rarely conform to expectations from geometry and dopant density, exhibiting significant variations as a function of different surface terminations/conditions. The association of these mechanisms with surface states and their exact influence on practical SiNW devices still remains largely unclear. Herein, we report on the influence of surface state charge distributions on SiNW transport characteristics. For this study, p-type SiNW devices with widths of 50, 100, and 2000 nm are fabricated from 25, 50, and 200 nm-thick SOI wafers. A ˜five order difference in effective carrier concentration was observed in the initial SiNWs characteristics, when comparing SiNWs fabricated with and without a thermal oxide. The removal of the surface oxide by a hydrogen fluoride (HF) treatment results in a SiNW conductance drop up to ˜six orders of magnitude. This effect is from a surface depletion of holes in the SiNW induced by positive surface charges deposited as a result of the HF treatment. However, it is observed that this charge density is transient and is dissipated with the re-growth of an oxide layer. In summary, the SiNW conductance is shown to vary by several orders of magnitude, while comparing its characteristics for the three most studied surface conditions: with a native oxide, thermal oxide and HF induced H-terminations. These results emphasize the necessity to interpret the transport characteristics of SiNWs with respect to its surface condition, during future investigations pertaining to the physical properties of SiNWs, like its piezo-resistance. As a sequel, prospects for efficiently sensing an elementary reduction/oxidation chemical process by monitoring the variation of SiNW surface potential, or in practice the SiNW conductance, is demonstrated.

  19. Highly conductive indium nanowires deposited on silicon by dip-pen nanolithography

    SciTech Connect

    Kozhukhov, Anton; Volodin, Vladimir; Klimenko, Anatoliy; Shcheglov, Dmitriy; Karnaeva, Natalya; Latyshev, Alexander

    2015-04-14

    In this paper, we developed a new dip-pen nanolithography (DPN) method. Using this method, we fabricated conductive nanowires with diameters of 30–50 nm on silicon substrates. To accomplish this, indium was transferred from an atomic force microscopy tip to the surface by applying a potential difference between the tip and substrate. The fabricated indium nanowires were several micrometers in length. Unlike thermal DPN, our DPN method hardly oxidized the indium, producing nanowires with conductivities from 5.7 × 10{sup −3} to 4 × 10{sup −2} Ω cm.

  20. Chirality-Discriminated Conductivity of Metal-Amino Acid Biocoordination Polymer Nanowires.

    PubMed

    Zheng, Jianzhong; Wu, Yijin; Deng, Ke; He, Meng; He, Liangcan; Cao, Jing; Zhang, Xugang; Liu, Yaling; Li, Shunxing; Tang, Zhiyong

    2016-09-27

    Biocoordination polymer (BCP) nanowires are successfully constructed through self-assembly of chiral cysteine amino acids and Cd cations in solution. The varied chirality of cysteine is explored to demonstrate the difference of BCP nanowires in both morphology and structure. More interestingly and surprisingly, the electrical property measurement reveals that, although all Cd(II)/cysteine BCP nanowires behave as semiconductors, the conductivity of the Cd(II)/dl-cysteine nanowires is 4 times higher than that of the Cd(II)/l-cysteine or Cd(II)/d-cysteine ones. The origin of such chirality-discriminated characteristics registered in BCP nanowires is further elucidated by theoretical calculation. These findings demonstrate that the morphology, structure, and property of BCP nanostructures could be tuned by the chirality of the bridging ligands, which will shed light on the comprehension of chirality transcription as well as construction of chirality-regulated functional materials.

  1. Coffee ring effect resulted conductive nanowire patterns by evaporating colloidal suspension droplets without sintering process

    NASA Astrophysics Data System (ADS)

    Wang, Xiaofeng; Seong, Baekhoon; Yudistira, Hadi Teguh; Byun, Doyoung

    2015-11-01

    Drying colloidal suspensions containing non-volatile solute will form a ring like pattern, which is called ``coffee ring effect.'' Here, we present the coffee ring effect with silver nanowires dispersing into DI water, resulting in a highly dense-packed nanowire ring patterns. The effect of nanowire length, concentration, droplet size, and substrate temperature were investigated. With shorter nanowires, a distinct ring could be obtained. Meanwhile, the concentration of the colloidal suspension was found to affect the ring width. The droplet size and nanowire length played a significant role in affecting the occurrence of the coffee ring effect. When smaller droplets (i.e., less than 150 μm) containing long nanowires (~ 20 μm), the coffee ring effect was suppressed. While smaller droplets containing short nanowires (~ 1 μm), the coffee ring effect was not affected. By increasing the temperature of the substrate, multi-ring pattern was formed inside the original ring. The resistivity of the semi-circle of the nanowire ring was measured, and had a minimum value of 1.32 × 10-6 Ωm without any sintering process. These findings could be exploited to basic study of ring stain effect as well as the practical use, such as evaporative lithography and ink-jet printing for conductive film and display. This research was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) (Grant number: 2014-023284).

  2. Scanning thermal microscopy with heat conductive nanowire probes.

    PubMed

    Timofeeva, Maria; Bolshakov, Alexey; Tovee, Peter D; Zeze, Dagou A; Dubrovskii, Vladimir G; Kolosov, Oleg V

    2016-03-01

    Scanning thermal microscopy (SThM), which enables measurement of thermal transport and temperature distribution in devices and materials with nanoscale resolution is rapidly becoming a key approach in resolving heat dissipation problems in modern processors and assisting development of new thermoelectric materials. In SThM, the self-heating thermal sensor contacts the sample allowing studying of the temperature distribution and heat transport in nanoscaled materials and devices. The main factors that limit the resolution and sensitivities of SThM measurements are the low efficiency of thermal coupling and the lateral dimensions of the probed area of the surface studied. The thermal conductivity of the sample plays a key role in the sensitivity of SThM measurements. During the SThM measurements of the areas with higher thermal conductivity the heat flux via SThM probe is increased compared to the areas with lower thermal conductivity. For optimal SThM measurements of interfaces between low and high thermal conductivity materials, well defined nanoscale probes with high thermal conductivity at the probe apex are required to achieve a higher quality of the probe-sample thermal contact while preserving the lateral resolution of the system. In this paper, we consider a SThM approach that can help address these complex problems by using high thermal conductivity nanowires (NW) attached to a tip apex. We propose analytical models of such NW-SThM probes and analyse the influence of the contact resistance between the SThM probe and the sample studied. The latter becomes particularly important when both tip and sample surface have high thermal conductivities. These models were complemented by finite element analysis simulations and experimental tests using prototype probe where a multiwall carbon nanotube (MWCNT) is exploited as an excellent example of a high thermal conductivity NW. These results elucidate critical relationships between the performance of the SThM probe on

  3. Cell number per spheroid and electrical conductivity of nanowires influence the function of silicon nanowired human cardiac spheroids.

    PubMed

    Tan, Yu; Richards, Dylan; Coyle, Robert C; Yao, Jenny; Xu, Ruoyu; Gou, Wenyu; Wang, Hongjun; Menick, Donald R; Tian, Bozhi; Mei, Ying

    2017-03-15

    Human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) provide an unlimited cell source to treat cardiovascular diseases, the leading cause of death worldwide. However, current hiPSC-CMs retain an immature phenotype that leads to difficulties for integration with adult myocardium after transplantation. To address this, we recently utilized electrically conductive silicon nanowires (e-SiNWs) to facilitate self-assembly of hiPSC-CMs to form nanowired hiPSC cardiac spheroids. Our previous results showed addition of e-SiNWs effectively enhanced the functions of the cardiac spheroids and improved the cellular maturation of hiPSC-CMs. Here, we examined two important factors that can affect functions of the nanowired hiPSC cardiac spheroids: (1) cell number per spheroid (i.e., size of the spheroids), and (2) the electrical conductivity of the e-SiNWs. To examine the first factor, we prepared hiPSC cardiac spheroids with four different sizes by varying cell number per spheroid (∼0.5k, ∼1k, ∼3k, ∼7k cells/spheroid). Spheroids with ∼3k cells/spheroid was found to maximize the beneficial effects of the 3D spheroid microenvironment. This result was explained with a semi-quantitative theory that considers two competing factors: 1) the improved 3D cell-cell adhesion, and 2) the reduced oxygen supply to the center of spheroids with the increase of cell number. Also, the critical role of electrical conductivity of silicon nanowires has been confirmed in improving tissue function of hiPSC cardiac spheroids. These results lay down a solid foundation to develop suitable nanowired hiPSC cardiac spheroids as an innovative cell delivery system to treat cardiovascular diseases.

  4. Atmospheric-Pressure Processed Silver Nanowire (Ag-NW)/ZnO Composite Transparent Conducting Contacts

    SciTech Connect

    Perkins, John D.; Aggarwal, Shruti; van Hest, Maikel F. A. M.; Ginley, David S.

    2015-06-14

    Composite transparent contacts (TCs) based on metal nanowires and metal oxide matrix materials hold great promise for high performance transparent contacts for photovoltaics and opto-electronic technologies with the potential of all-atmospheric pressure processing. The metal nanowire mesh can provide both electrical conductivity and mechanical robustness against bending while the matrix material can both control the electrical interface and protect the metal nanowires. Here, we demonstrate all atmospheric pressure processed Ag-NW/ZnO composite TCs that are 90% transparent in the visible with sheet resistance Rs ~= 10 Ohms/sq. In addition, the composite TCs have higher infrared transmission than conventional TCO films with the same sheet resistance.

  5. Modulation of thermal conductivity in kinked silicon nanowires: phonon interchanging and pinching effects.

    PubMed

    Jiang, Jin-Wu; Yang, Nuo; Wang, Bing-Shen; Rabczuk, Timon

    2013-04-10

    We perform molecular dynamics simulations to investigate the reduction of the thermal conductivity by kinks in silicon nanowires. The reduction percentage can be as high as 70% at room temperature. The temperature dependence of the reduction is also calculated. By calculating phonon polarization vectors, two mechanisms are found to be responsible for the reduced thermal conductivity: (1) the interchanging effect between the longitudinal and transverse phonon modes and (2) the pinching effect, that is, a new type of localization, for the twisting and transverse phonon modes in the kinked silicon nanowires. Our work demonstrates that the phonon interchanging and pinching effects, induced by kinking, are brand-new and effective ways in modulating heat transfer in nanowires, which enables the kinked silicon nanowires to be a promising candidate for thermoelectric materials.

  6. Highly stretchable and highly conductive metal electrode by very long metal nanowire percolation network.

    PubMed

    Lee, Phillip; Lee, Jinhwan; Lee, Hyungman; Yeo, Junyeob; Hong, Sukjoon; Nam, Koo Hyun; Lee, Dongjin; Lee, Seung Seob; Ko, Seung Hwan

    2012-07-03

    A highly stretchable metal electrode is developed via the solution-processing of very long (>100 μm) metallic nanowires and subsequent percolation network formation via low-temperature nanowelding. The stretchable metal electrode from very long metal nanowires demonstrated high electrical conductivity (~9 ohm sq(-1) ) and mechanical compliance (strain > 460%) at the same time. This method is expected to overcome the performance limitation of the current stretchable electronics such as graphene, carbon nanotubes, and buckled nanoribbons.

  7. Doping-Induced Universal Conductance Fluctuations in GaN Nanowires.

    PubMed

    Elm, Matthias T; Uredat, Patrick; Binder, Jan; Ostheim, Lars; Schäfer, Markus; Hille, Pascal; Müßener, Jan; Schörmann, Jörg; Eickhoff, Martin; Klar, Peter J

    2015-12-09

    The transport properties of Ge-doped single GaN nanowires are investigated, which exhibit a weak localization effect as well as universal conductance fluctuations at low temperatures. By analyzing these quantum interference effects, the electron phase coherence length was determined. Its temperature dependence indicates that in the case of highly doped nanowires electron-electron scattering is the dominant dephasing mechanism, while for the slightly doped nanowires dephasing originates from Nyquist-scattering. The change of the dominant scattering mechanism is attributed to a modification of the carrier confinement caused by the Ge-doping. The results demonstrate that the phase coherence length can be tuned by the donor concentration making Ge-doped GaN nanowires an ideal model system for studying the influence of impurities on quantum-interference effects in mesoscopic and nanoscale systems.

  8. Temperature dependence of electrical and thermal conduction in single silver nanowire.

    PubMed

    Cheng, Zhe; Liu, Longju; Xu, Shen; Lu, Meng; Wang, Xinwei

    2015-06-02

    In this work, the thermal and electrical transport in an individual silver nanowire is characterized down to 35 K for in-depth understanding of the strong structural defect induced electron scattering. The results indicate that, at room temperature, the electrical resistivity increases by around 4 folds from that of bulk silver. The Debye temperature (151 K) of the silver nanowire is found 36% lower than that (235 K) of bulk silver, confirming strong phonon softening. At room temperature, the thermal conductivity is reduced by 55% from that of bulk silver. This reduction becomes larger as the temperature goes down. To explain the opposite trends of thermal conductivity (κ) ~ temperature (T) of silver nanowire and bulk silver, a unified thermal resistivity (Θ ~ T/k ) is used to elucidate the electron scattering mechanism. A large residual Θ is observed for silver nanowire while that of the bulk silver is almost zero. The same Θ ~ T trend proposes that the silver nanowire and bulk silver share the similar phonon-electron scattering mechanism for thermal transport. Due to phonon-assisted electron energy transfer across grain boundaries, the Lorenz number of the silver nanowire is found much larger than that of bulk silver and decreases with decreasing temperature.

  9. Interfacial Engineering of Silicon Carbide Nanowire/Cellulose Microcrystal Paper toward High Thermal Conductivity.

    PubMed

    Yao, Yimin; Zeng, Xiaoliang; Pan, Guiran; Sun, Jiajia; Hu, Jiantao; Huang, Yun; Sun, Rong; Xu, Jian-Bin; Wong, Ching-Ping

    2016-11-16

    Polymer composites with high thermal conductivity have attracted much attention, along with the rapid development of electronic devices toward higher speed and better performance. However, high interfacial thermal resistance between fillers and matrix or between fillers and fillers has been one of the primary bottlenecks for the effective thermal conduction in polymer composites. Herein, we report on engineering interfacial structure of silicon carbide nanowire/cellulose microcrystal paper by generating silver nanostructures. We show that silver nanoparticle-deposited silicon carbide nanowires as fillers can effectively enhance the thermal conductivity of the matrix. The in-plane thermal conductivity of the resultant composite paper reaches as high as 34.0 W/m K, which is one order magnitude higher than that of conventional polymer composites. Fitting the measured thermal conductivity with theoretical models qualitatively demonstrates that silver nanoparticles bring the lower interfacial thermal resistances both at silicon carbide nanowire/cellulose microcrystal and silicon carbide nanowire/silicon carbide nanowire interfaces. This interfacial engineering approach provides a powerful tool for sophisticated fabrication of high-performance thermal-management materials.

  10. Silver Nanowire Transparent Conductive Films with High Uniformity Fabricated via a Dynamic Heating Method.

    PubMed

    Jia, Yonggao; Chen, Chao; Jia, Dan; Li, Shuxin; Ji, Shulin; Ye, Changhui

    2016-04-20

    The uniformity of the sheet resistance of transparent conductive films is one of the most important quality factors for touch panel applications. However, the uniformity of silver nanowire transparent conductive films is far inferior to that of indium-doped tin oxide (ITO). Herein, we report a dynamic heating method using infrared light to achieve silver nanowire transparent conductive films with high uniformity. This method can overcome the coffee ring effect during the drying process and suppress the aggregation of silver nanowires in the film. A nonuniformity factor of the sheet resistance of the as-prepared silver nanowire transparent conductive films could be as low as 6.7% at an average sheet resistance of 35 Ω/sq and a light transmittance of 95% (at 550 nm), comparable to that of high-quality ITO film in the market. In addition, a mechanical study shows that the sheet resistance of the films has little change after 5000 bending cycles, and the film could be used in touch panels for human-machine interactive input. The highly uniform and mechanically stable silver nanowire transparent conductive films meet the requirement for many significant applications and could play a key role in the display market in a near future.

  11. Prospects for nanowire-doped polycrystalline graphene films for ultratransparent, highly conductive electrodes.

    PubMed

    Jeong, Changwook; Nair, Pradeep; Khan, Mohammad; Lundstrom, Mark; Alam, Muhammad A

    2011-11-09

    Traditional transparent conducting materials such as ITO are expensive, brittle, and inflexible. Although alternatives like networks of carbon nanotubes, polycrystalline graphene, and metallic nanowires have been proposed, the transparency-conductivity trade-off of these materials makes them inappropriate for broad range of applications. In this paper, we show that the conductivity of polycrystalline graphene is limited by high resistance grain boundaries. We demonstrate that a composite based on polycrystalline graphene and a subpercolating network of metallic nanowires offers a simple and effective route to reduced resistance while maintaining high transmittance. This new approach of "percolation-doping by nanowires" has the potential to beat the transparency-conductivity constraints of existing materials and may be suitable for broad applications in photovoltaics, flexible electronics, and displays.

  12. Study of Thermal Conductivity of Si Nanowires with micro-Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, Bingqing; Murphy, Kathryn F.; Gianola, Daniel S.; Cheng, X. M.

    2013-03-01

    Nanowires have played an increasingly important role in thermoelectric technology due to their high figure of merit ZT resulting from the reduced thermal conductivity, K, and good electrical conductivity. In this work, we report the measurement of K of individual silicon nanowires (SiNWs) by mapping Raman temperature profiles along the testing nanowires using a microelectromechanical system (MEMS) device and a micro-Raman system with a 530 nm laser beam. Thermal conductivity was measured as a function of uniaxial tensile stress applied to the SiNWs, which was varied from 0 to 1.2 GPa. The measured K results for the unstrained nanowires agree well with the predictions based on diffuse phonon boundary scattering. The dependence of SiNWs' thermal conductivity on engineering stress can provide significant information for nanowires fabrication. The work at University of Pennsylvania is supported by the Department of Energy, Basic Energy Sciences, through an Early Career Award (DE-SC0008135). The work at Bryn Mawr College is supported by NSF Career Award (DMR- 1053854).

  13. UV light emitting transparent conducting tin-doped indium oxide (ITO) nanowires.

    PubMed

    Gao, J; Chen, R; Li, D H; Jiang, L; Ye, J C; Ma, X C; Chen, X D; Xiong, Q H; Sun, H D; Wu, T

    2011-05-13

    Multifunctional single crystalline tin-doped indium oxide (ITO) nanowires with tuned Sn doping levels are synthesized via a vapor transport method. The Sn concentration in the nanowires can reach 6.4 at.% at a synthesis temperature of 840 °C, significantly exceeding the Sn solubility in ITO bulks grown at comparable temperatures, which we attribute to the unique feature of the vapor-liquid-solid growth. As a promising transparent conducting oxide nanomaterial, layers of these ITO nanowires exhibit a sheet resistance as low as 6.4 Ω/[Symbol: see text] and measurements on individual nanowires give a resistivity of 2.4 × 10(-4) Ω cm with an electron density up to 2.6 × 10(20) cm(-3), while the optical transmittance in the visible regime can reach ∼ 80%. Under the ultraviolet excitation the ITO nanowire samples emit blue light, which can be ascribed to transitions related to defect levels. Furthermore, a room temperature ultraviolet light emission is observed in these ITO nanowires for the first time, and the exciton-related radiative process is identified by using temperature-dependent photoluminescence measurements.

  14. On the dependence of the thermal conductivity of width-modulated nanowires on the number of modulations

    NASA Astrophysics Data System (ADS)

    Zianni, Xanthippi; Termentzidis, Konstantinos; Lacroix, David

    2017-01-01

    Our previous Monte Carlo simulations on the thermal conductivity of width-modulated nanowires indicated two distinct dependences of the decrease of the thermal conductivity κ relative to that of the non-modulated nanowire: (i) in the case of multiple constrictions κ scales with the nanowire transmissivity, (ii) in the case of a single constriction κ is determined by the ballistic constriction resistance. Here, we report on the transition between the two regimes. We discuss the thermal conductivity of width modulated nanowires as a function of the number of modulations. Phenomenology has been derived to interpret the MC simulations.

  15. Redox-exchange induced heterogeneous RuO2-conductive polymer nanowires.

    PubMed

    Gui, Zhe; Duay, Jonathon; Hu, Junkai; Lee, Sang Bok

    2014-06-28

    A redox exchange mechanism between potassium perruthenate (KRuO4) and the functional groups of selected polymers is used here to induce RuO2 into and onto conductive polymer nanowires by simply soaking the polymer nanowire arrays in KRuO4 solution. Conductive polymer nanowire arrays of polypyrrole (PPY) and poly(3,4-ethylenedioxythiophene) (PEDOT) were studied in this work. SEM and TEM results show that the RuO2 material was distributed differently in the PPY and PEDOT nanowire matrices. Energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were used to confirm the dispersion and formation of RuO2 materials in these polymer nanowires. Cyclic voltammetry and galvanostatic charge-discharge experiments were used to characterize their electrochemical performance. RuO2-polymer samples prepared with a 6 min soaking time in 10 mM KRuO4 solution show a high specific capacitance of 371 F g(-1) and 500 F g(-1) for PEDOT-based and PPY-based composite nanowires, respectively. This is attributed to the high exposure area of the conductive RuO2 and the good conductivity of the polymer matrix. This work demonstrates a simple method to synthesize heterogeneous polymer based-materials through the redox reaction between conductive polymers and high oxidation state transition metal oxide ions. Different heterogeneous nanocomposites were obtained depending on the polymer properties, and high energy storage performance of the metal oxides can be achieved within these heterogeneous nanostructures.

  16. Rheological behavior of silver nanowire conductive inks during screen printing

    NASA Astrophysics Data System (ADS)

    Hemmati, Shohreh; Barkey, Dale P.; Gupta, Nivedita

    2016-08-01

    The rheological behavior of silver nanowire (AgNW) suspensions adapted for screen printing inks was investigated. Aqueous silver nanowire inks consisting of AgNW (length of 30 μm, and diameter of 40 and 90 nm), dispersant and binder were formulated. The effect of AgNW content on the rheological behavior of the ink and the build-up of ink structure after screen printing were examined as they depend on applied shear and temperature. Rheological measurements under conditions that mimic the screen printing process were done to assess viscoelastic properties induced by flow alignment of the wires and the subsequent recovery of the low shear structure. The Stretched Exponential model (SEmo) was used to model the recovery process after screen printing to obtain the characteristic time of the recovery or build-up process. The characteristic time was determined at several temperatures to obtain the activation energy of recovery. The domination of Brownian motion or non-Brownian motion behavior can be characterized by a Peclet number, which is the ratio of shear rate to the rotational diffusion coefficient. The Peclet number and the dimensionless concentration of wires were used to assess the recovery mechanism. The steady viscosity at low and high shear rates was also treated by an activation energy analysis.

  17. Electrical characterization of HgTe nanowires using conductive atomic force microscopy

    SciTech Connect

    Gundersen, P.; Kongshaug, K. O.; Selvig, E.; Haakenaasen, R.

    2010-12-01

    Self-organized HgTe nanowires grown by molecular beam epitaxy (MBE) have been characterized using conductive atomic force microscopy. As HgTe will degrade or evaporate at normal baking temperatures for electron beam lithography (EBL) resists, an alternative method was developed. Using low temperature optical lithography processes, large Au contacts were deposited on a sample covered with randomly oriented, lateral HgTe nanowires. Nanowires partly covered by the large electrodes were identified with a scanning electron microscope and then localized in the atomic force microscope (AFM). The conductive tip of the AFM was then used as a movable electrode to measure current-voltage curves at several locations on HgTe nanowires. The measurements revealed that polycrystalline nanowires had diffusive electron transport, with resistivities two orders of magnitude larger than that of an MBE-grown HgTe film. The difference can be explained by scattering at the rough surface walls and at the grain boundaries in the wires. The method can be a solution when EBL is not available or requires too high temperature, or when measurements at several positions along a wire are required.

  18. Hybrid solar cells with conducting polymers and vertically aligned silicon nanowire arrays: The effect of silicon conductivity

    NASA Astrophysics Data System (ADS)

    Woo, Sungho; Hoon Jeong, Jae; Kun Lyu, Hong; Jeong, Seonju; Hyoung Sim, Jun; Hyun Kim, Wook; Soo Han, Yoon; Kim, Youngkyoo

    2012-08-01

    Organic/inorganic hybrid solar cells, based on vertically aligned n-type silicon nanowires (n-Si NWs) and p-type conducting polymers (PEDOT:PSS), were investigated as a function of Si conductivity. The n-Si NWs were easily prepared from the n-Si wafer by employing a silver nanodot-mediated micro-electrochemical redox reaction. This investigation shows that the photocurrent-to-voltage characteristics of the n-Si NW/PEDOT:PSS cells clearly exhibit a stable rectifying diode behavior. The increase in current density and fill factor using high conductive silicon is attributed to an improved charge transport towards the electrodes achieved by lowering the device's series resistance. Our results also show that the surface area of the nanowire that can form heterojunction domains significantly influences the device performance.

  19. High frequency electromagnetic detection by nonlinear conduction modulation in graphene nanowire diodes

    NASA Astrophysics Data System (ADS)

    Winters, M.; Thorsell, M.; Strupiński, W.; Rorsman, N.

    2015-10-01

    We present graphene nanowires implemented as dispersion free self switched microwave diode detectors. The microwave properties of the detectors are investigated using vector corrected large signal measurements in order to determine the detector responsivity and noise equivalent power (NEP) as a function of frequency, input power, and device geometry. We identify two distinct conductance nonlinearities which generate detector responsivity: an edge effect nonlinearity near zero bias due to lateral gating of the nanowire structures, and a velocity saturation nonlinearity which generates current compression at high power levels. The scaling study shows that detector responsivity obeys an exponential scaling law with respect to nanowire width, and a peak responsivity (NEP) of 250 V/W (50 pW/ √{ Hz } ) is observed in detectors of the smallest width. The results are promising as the devices exhibit responsivities which are comparable to state of the art self switched detectors in semiconductor technologies.

  20. Electrical conduction mechanism of an individual polypyrrole nanowire at low temperatures.

    PubMed

    Yu, Gui-Feng; Pan, Wei; Yu, Miao; Han, Wen-Peng; Zhang, Jun-Cheng; Zhang, Hong-Di; Long, Yun-Ze

    2015-01-30

    Conducting polypyrrole (PPY) nanowires doped with p-toluene sulfonamide (PTSA) were synthesized by a template-free self-assembly method. Electrical transport characteristics, i.e. current-voltage (I-V) behavior, of an individual PPY/PTSA nanowire have been explored in a wide temperature range from 300 down to 40 K. The fitting results of I-V curves indicated that the electrical conduction mechanism can be explained by the space-charge-limited current (SCLC) theory from 300 down to 100 K. In this temperature range, traps play an important role for this non-crystalline system. The corresponding trap energy and trap concentration have also been calculated based on the SCLC theory. Interestingly, there is no trap at 160 K, different from other temperatures. The obtained carrier mobility for the polymer nanowires is 0.964 cm(2) V(-1) s(-1) on the basis of trap free SCLC theory. In the temperature range of 80-40 K, little current can flow through the nanowire especially at lower voltages, however, the current follows the equation I ∞ (V/Vt-1)(ζ) at higher bias, which could be attributed to Coulomb blockade effect. Additionally, the differential conductance dI/dV curves also show some clear Coulomb oscillations.

  1. Suppressed phase transition and giant ionic conductivity in La2Mo2O9 nanowires

    PubMed Central

    Liu, Wei; Pan, Wei; Luo, Jian; Godfrey, Andy; Ou, Gang; Wu, Hui; Zhang, Wei

    2015-01-01

    Improving the ionic conductivity of solid electrolytes at low temperatures represents a major challenge and an opportunity for enabling a variety of solid-state ionic devices for energy conversion and storage, as well as for environmental protection. Here we report a giant ionic conductivity of 0.20 Scm−1, achieved at 500 °C, in the La2Mo2O9 nanowires with a bamboo-wire morphology, corresponding to a 1000-fold enhancement in conductivity over conventional bulk material. Stabilization of the high-temperature phase is observed to account for about a 10-fold increase in the conductivity. We further demonstrate that fast surface conduction in ∼3 nm thick, partially ordered, surface ‘amorphous' films, under strain on the curved surfaces of the nanowires (as a non-autonomous surface phase or complexion), contributes to an enhancement of the conductivity by another two orders of magnitude. Exemplified here by the study of the La2Mo2O9 nanowires, new possibilities for improvement of conductivity and for miniaturization of solid-state ionic devices by the careful use of one-dimensional nanomaterials can be envisioned. PMID:26380943

  2. Suppressed phase transition and giant ionic conductivity in La2Mo2O9 nanowires.

    PubMed

    Liu, Wei; Pan, Wei; Luo, Jian; Godfrey, Andy; Ou, Gang; Wu, Hui; Zhang, Wei

    2015-09-18

    Improving the ionic conductivity of solid electrolytes at low temperatures represents a major challenge and an opportunity for enabling a variety of solid-state ionic devices for energy conversion and storage, as well as for environmental protection. Here we report a giant ionic conductivity of 0.20 Scm(-1), achieved at 500 °C, in the La2Mo2O9 nanowires with a bamboo-wire morphology, corresponding to a 1000-fold enhancement in conductivity over conventional bulk material. Stabilization of the high-temperature phase is observed to account for about a 10-fold increase in the conductivity. We further demonstrate that fast surface conduction in ∼3 nm thick, partially ordered, surface 'amorphous' films, under strain on the curved surfaces of the nanowires (as a non-autonomous surface phase or complexion), contributes to an enhancement of the conductivity by another two orders of magnitude. Exemplified here by the study of the La2Mo2O9 nanowires, new possibilities for improvement of conductivity and for miniaturization of solid-state ionic devices by the careful use of one-dimensional nanomaterials can be envisioned.

  3. Gallium ion implantation greatly reduces thermal conductivity and enhances electronic one of ZnO nanowires

    SciTech Connect

    Xia, Minggang; Cheng, Zhaofang; Han, Jinyun; Zhang, Shengli; Zheng, Minrui; Sow, Chorng-Haur; Thong, John T. L.; Li, Baowen

    2014-05-15

    The electrical and thermal conductivities are measured for individual zinc oxide (ZnO) nanowires with and without gallium ion (Ga{sup +}) implantation at room temperature. Our results show that Ga{sup +} implantation enhances electrical conductivity by one order of magnitude from 1.01 × 10{sup 3} Ω{sup −1}m{sup −1} to 1.46 × 10{sup 4} Ω{sup −1}m{sup −1} and reduces its thermal conductivity by one order of magnitude from 12.7 Wm{sup −1}K{sup −1} to 1.22 Wm{sup −1}K{sup −1} for ZnO nanowires of 100 nm in diameter. The measured thermal conductivities are in good agreement with those in theoretical simulation. The increase of electrical conductivity origins in electron donor doping by Ga{sup +} implantation and the decrease of thermal conductivity is due to the longitudinal and transverse acoustic phonons scattering by Ga{sup +} point scattering. For pristine ZnO nanowires, the thermal conductivity decreases only two times when its diameter reduces from 100 nm to 46 nm. Therefore, Ga{sup +}-implantation may be a more effective method than diameter reduction in improving thermoelectric performance.

  4. Interface bond relaxation on the thermal conductivity of Si/Ge core-shell nanowires

    SciTech Connect

    Chen, Weifeng; He, Yan; Ouyang, Gang; Sun, Changqing

    2016-01-15

    The thermal conductivity of Si/Ge core-shell nanowires (CSNWs) is investigated on the basis of atomic-bond-relaxation consideration and continuum mechanics. An analytical model is developed to clarify the interface bond relaxation of Si/Ge CSNWs. It is found that the thermal conductivity of Si core can be modulated through covering with Ge epitaxial layers. The change of thermal conductivity in Si/Ge CSNWs should be attributed to the surface relaxation and interface mismatch between inner Si nanowire and outer Ge epitaxial layer. Our results are in well agreement with the experimental measurements and simulations, suggesting that the presented method provides a fundamental insight of the thermal conductivity of CSNWs from the atomistic origin.

  5. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire

    PubMed Central

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C.; Luo, Tengfei

    2015-01-01

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics. PMID:26568511

  6. Ultra-low Thermal Conductivity in Si/Ge Hierarchical Superlattice Nanowire.

    PubMed

    Mu, Xin; Wang, Lili; Yang, Xueming; Zhang, Pu; To, Albert C; Luo, Tengfei

    2015-11-16

    Due to interfacial phonon scattering and nanoscale size effect, silicon/germanium (Si/Ge) superlattice nanowire (SNW) can have very low thermal conductivity, which is very attractive for thermoelectrics. In this paper, we demonstrate using molecular dynamics simulations that the already low thermal conductivity of Si/Ge SNW can be further reduced by introducing hierarchical structure to form Si/Ge hierarchical superlattice nanowire (H-SNW). The structural hierarchy introduces defects to disrupt the periodicity of regular SNW and scatters coherent phonons, which are the key contributors to thermal transport in regular SNW. Our simulation results show that periodically arranged defects in Si/Ge H-SNW lead to a ~38% reduction of the already low thermal conductivity of regular Si/Ge SNW. By randomizing the arrangement of defects and imposing additional surface complexities to enhance phonon scattering, further reduction in thermal conductivity can be achieved. Compared to pure Si nanowire, the thermal conductivity reduction of Si/Ge H-SNW can be as large as ~95%. It is concluded that the hierarchical structuring is an effective way of reducing thermal conductivity significantly in SNW, which can be a promising path for improving the efficiency of Si/Ge-based SNW thermoelectrics.

  7. Performance enhancement of metal nanowire transparent conducting electrodes by mesoscale metal wires.

    PubMed

    Hsu, Po-Chun; Wang, Shuang; Wu, Hui; Narasimhan, Vijay K; Kong, Desheng; Ryoung Lee, Hye; Cui, Yi

    2013-01-01

    For transparent conducting electrodes in optoelectronic devices, electrical sheet resistance and optical transmittance are two of the main criteria. Recently, metal nanowires have been demonstrated to be a promising type of transparent conducting electrode because of low sheet resistance and high transmittance. Here we incorporate a mesoscale metal wire (1-5 μm in diameter) into metal nanowire transparent conducting electrodes and demonstrate at least a one order of magnitude reduction in sheet resistance at a given transmittance. We realize experimentally a hybrid of mesoscale and nanoscale metal nanowires with high performance, including a sheet resistance of 0.36 Ω sq(-1) and transmittance of 92%. In addition, the mesoscale metal wires are applied to a wide range of transparent conducting electrodes including conducting polymers and oxides with improvement up to several orders of magnitude. The metal mesowires can be synthesized by electrospinning methods and their general applicability opens up opportunities for many transparent conducting electrode applications.

  8. Photoinduced conductivity of a porphyrin-gold composite nanowire

    SciTech Connect

    Kilina, Svletana; Balatsky, Alexander; Kilin, Dmitri S; Prezhdo, Oleg; Tsemekhman, Kiril

    2009-01-01

    Negatively charged phosphine groups on the backbone of DNA are known to attract gold nanoclusters from a colloid, assembling the clusters at fixed intervals. Bridging these intervals with porphyrin-dye linkers forms an infinite conducting chain, a quantum wire whose carrier mobility can be enhanced by photoexcitation. The resulting nanoassembly can be used as a gate: a wire with a controllable conductivity. The electronic structure of the porphyrin-gold wire is studied here by density functional theory, and the conductivity of the system is determined as a function of the photoexcitation energy. Photoexcitations of the dye are found to enhance the wire conductivity by orders of magnitude.

  9. Hybrid metal-organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly.

    PubMed

    Yan, Hao; Hohman, J Nathan; Li, Fei Hua; Jia, Chunjing; Solis-Ibarra, Diego; Wu, Bin; Dahl, Jeremy E P; Carlson, Robert M K; Tkachenko, Boryslav A; Fokin, Andrey A; Schreiner, Peter R; Vailionis, Arturas; Kim, Taeho Roy; Devereaux, Thomas P; Shen, Zhi-Xun; Melosh, Nicholas A

    2017-03-01

    Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal-organic frameworks and coordination polymers. However, the lack of 'solid' inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal-organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on addition of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. This discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal-organic framework linkers.

  10. Hybrid metal-organic chalcogenide nanowires with electrically conductive inorganic core through diamondoid-directed assembly

    NASA Astrophysics Data System (ADS)

    Yan, Hao; Hohman, J. Nathan; Li, Fei Hua; Jia, Chunjing; Solis-Ibarra, Diego; Wu, Bin; Dahl, Jeremy E. P.; Carlson, Robert M. K.; Tkachenko, Boryslav A.; Fokin, Andrey A.; Schreiner, Peter R.; Vailionis, Arturas; Kim, Taeho Roy; Devereaux, Thomas P.; Shen, Zhi-Xun; Melosh, Nicholas A.

    2016-12-01

    Controlling inorganic structure and dimensionality through structure-directing agents is a versatile approach for new materials synthesis that has been used extensively for metal-organic frameworks and coordination polymers. However, the lack of `solid’ inorganic cores requires charge transport through single-atom chains and/or organic groups, limiting their electronic properties. Here, we report that strongly interacting diamondoid structure-directing agents guide the growth of hybrid metal-organic chalcogenide nanowires with solid inorganic cores having three-atom cross-sections, representing the smallest possible nanowires. The strong van der Waals attraction between diamondoids overcomes steric repulsion leading to a cis configuration at the active growth front, enabling face-on addition of precursors for nanowire elongation. These nanowires have band-like electronic properties, low effective carrier masses and three orders-of-magnitude conductivity modulation by hole doping. This discovery highlights a previously unexplored regime of structure-directing agents compared with traditional surfactant, block copolymer or metal-organic framework linkers.

  11. Significant thermal conductivity reduction of silicon nanowire forests through discrete surface doping of germanium

    SciTech Connect

    Pan, Ying; Hong, Guo; Raja, Shyamprasad N.; Zimmermann, Severin; Poulikakos, Dimos; Tiwari, Manish K.

    2015-03-02

    Silicon nanowires (SiNWs) are promising materials for the realization of highly-efficient and cost effective thermoelectric devices. Reduction of the thermal conductivity of such materials is a necessary and viable pathway to achieve sufficiently high thermoelectric efficiencies, which are inversely proportional to the thermal conductivity. In this article, vertically aligned forests of SiNW and germanium (Ge)-doped SiNW with diameters around 100 nm have been fabricated, and their thermal conductivity has been measured. The results show that discrete surface doping of Ge on SiNW arrays can lead to 23% reduction in thermal conductivity at room temperature compared to uncoated SiNWs. Such reduction can be further enhanced to 44% following a thermal annealing step. By analyzing the binding energy changes of Ge-3d and Si-2p using X-ray photoelectron spectroscopy, we demonstrate that surface doped Ge interacts strongly with Si, enhancing phonon scattering at the Si-Ge interface as has also been shown in non-equilibrium molecular dynamics studies of single nanowires. Overall, our results suggest a viable pathway to improve the energy conversion efficiency of nanowire-forest thermoelectric nanomaterials.

  12. Enhanced ionic conductivity of AgI nanowires/AAO composites fabricated by a simple approach

    NASA Astrophysics Data System (ADS)

    Liu, Li-Feng; Lee, Seung-Woo; Li, Jing-Bo; Alexe, Marin; Rao, Guang-Hui; Zhou, Wei-Ya; Lee, Jae-Jong; Lee, Woo; Gösele, Ulrich

    2008-12-01

    AgI nanowires/anodic aluminum oxide (AgI NWs/AAO) composites have been fabricated by a simple approach, which involves the thermal melting of AgI powders on the surface of the AAO membrane, followed by the infiltration of the molten AgI inside the nanochannels. As-prepared AgI nanowires have corrugated outer surfaces and are polycrystalline according to scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations. X-ray diffraction (XRD) shows that a considerable amount of 7H polytype AgI exists in the composites, which is supposed to arise from the interfacial interactions between the embedded AgI and the alumina. AC conductivity measurements for the AgI nanowires/AAO composites exhibit a notable conductivity enhancement by three orders of magnitude at room temperature compared with that of pristine bulk AgI. Furthermore, a large conductivity hysteresis and abnormal conductivity transitions were observed in the temperature-dependent conductivity measurements, from which an ionic conductivity as high as 8.0 × 102 Ω-1 cm-1 was obtained at around 70 °C upon cooling. The differential scanning calorimetry (DSC) result demonstrates a similar phase transition behavior as that found in the AC conductivity measurements. The enhanced ionic conductivity, as well as the abnormal phase transitions, can be explained in terms of the existence of the highly conducting 7H polytype AgI and the formation of well-defined conduction paths in the composites.

  13. Atomistic calculation of the thermal conductance of large scale bulk-nanowire junctions

    SciTech Connect

    Duchemin, Ivan; Donadio, Davide

    2011-09-15

    We have developed a stable and efficient kernel method to compute thermal transport in open systems, based on the scattering-matrix approach. This method is applied to compute the thermal conductance of a junction between bulk silicon and silicon nanowires with diameter up to 10 nm. We have found that beyond a threshold diameter of 7 nm, transmission spectra and contact conductances scale with the cross section of the contact surface, whereas deviations from this general trend are observed in thinner wires. This result allows us to predict the thermal resistance of bulk-nanowire interfaces with larger cross sections than those tractable with atomistic simulations, and indicate the characteristic size beyond which atomistic systems can in principle be treated accurately by mean-field theories. Our calculations also elucidate how dimensionality reduction and shape affect interfacial heat transport.

  14. Kondo-like zero-bias conductance anomaly in a three-dimensional topological insulator nanowire

    PubMed Central

    Cho, Sungjae; Zhong, Ruidan; Schneeloch, John A.; Gu, Genda; Mason, Nadya

    2016-01-01

    Zero-bias anomalies in topological nanowires have recently captured significant attention, as they are possible signatures of Majorana modes. Yet there are many other possible origins of zero-bias peaks in nanowires—for example, weak localization, Andreev bound states, or the Kondo effect. Here, we discuss observations of differential-conductance peaks at zero-bias voltage in non-superconducting electronic transport through a 3D topological insulator (Bi1.33Sb0.67)Se3 nanowire. The zero-bias conductance peaks show logarithmic temperature dependence and often linear splitting with magnetic fields, both of which are signatures of the Kondo effect in quantum dots. We characterize the zero-bias peaks and discuss their origin. PMID:26911258

  15. Conductance oscillations of core-shell nanowires in transversal magnetic fields

    NASA Astrophysics Data System (ADS)

    Manolescu, Andrei; Nemnes, George Alexandru; Sitek, Anna; Rosdahl, Tomas Orn; Erlingsson, Sigurdur Ingi; Gudmundsson, Vidar

    2016-05-01

    We analyze theoretically electronic transport through a core-shell nanowire in the presence of a transversal magnetic field. We calculate the conductance for a variable coupling between the nanowire and the attached leads and show how the snaking states, which are low-energy states localized along the lines of the vanishing radial component of the magnetic field, manifest their existence. In the strong-coupling regime they induce flux periodic, Aharonov-Bohm-like, conductance oscillations, which, by decreasing the coupling to the leads, evolve into well-resolved peaks. The flux periodic oscillations arise due to interference of the snaking states, which is a consequence of backscattering at either the contacts with leads or magnetic or potential barriers in the wire.

  16. Kondo-like zero-bias conductance anomaly in a three-dimensional topological insulator nanowire

    SciTech Connect

    Cho, Sungjae; Zhong, Ruidan; Schneeloch, John A.; Gu, Genda; Mason, Nadya

    2016-02-25

    Zero-bias anomalies in topological nanowires have recently captured significant attention, as they are possible signatures of Majorana modes. Yet there are many other possible origins of zero-bias peaks in nanowires—for example, weak localization, Andreev bound states, or the Kondo effect. Here, we discuss observations of differential-conductance peaks at zero-bias voltage in non-superconducting electronic transport through a 3D topological insulator (Bi1.33Sb0.67)Se3 nanowire. The zero-bias conductance peaks show logarithmic temperature dependence and often linear splitting with magnetic fields, both of which are signatures of the Kondo effect in quantum dots. As a result, we characterize the zero-bias peaks and discuss their origin.

  17. On correlation between zero bias conductance peaks and topological invariants in semiconductor Rashba nanowires

    NASA Astrophysics Data System (ADS)

    Nag, Amit; Sau, Jay

    The observed zero bias peak in tunneling conductance experiments on semiconductor Rashba nanowire is a signature of presence of Majorana zero modes. Characteristics of zero bias conductance peak (ZBCP) namely, height, width and peak splitting, are a function of microscopic parameters. Zero modes have finite splitting as a result of finiteness of the nanowire rendering the ground state only approximately topological i.e. zero modes are only approximately Majoranas. We calculate the scattering matrix topological invariant to quantify the quality of approximate Majorana modes and study its relation to observed characteristics of ZBCP. Furthermore we study the effect of dephasing on the topological invariant. Finally, we draw connection between the characteristics of the ZBCP and probability of observing non-Abelian statistics in proposed future experiments involving braiding of Majorana modes. Work is done in collaboration with Sankar Das Sarma and supported by LPS-MPO-CMTC, Microsoft Q, Univ. of Maryland startup grants and JQI-NSF-PFC.

  18. Kondo-like zero-bias conductance anomaly in a three-dimensional topological insulator nanowire

    DOE PAGES

    Cho, Sungjae; Zhong, Ruidan; Schneeloch, John A.; ...

    2016-02-25

    Zero-bias anomalies in topological nanowires have recently captured significant attention, as they are possible signatures of Majorana modes. Yet there are many other possible origins of zero-bias peaks in nanowires—for example, weak localization, Andreev bound states, or the Kondo effect. Here, we discuss observations of differential-conductance peaks at zero-bias voltage in non-superconducting electronic transport through a 3D topological insulator (Bi1.33Sb0.67)Se3 nanowire. The zero-bias conductance peaks show logarithmic temperature dependence and often linear splitting with magnetic fields, both of which are signatures of the Kondo effect in quantum dots. As a result, we characterize the zero-bias peaks and discuss their origin.

  19. Structural Basis for Metallic-Like Conductivity in Microbial Nanowires

    SciTech Connect

    Malvankar, Nikhil S.; Vargas, Madeline; Nevin, Kelly; Tremblay, Pier-Luc; Evans-Lutterodt, Kenneth; Nykypanchuk, Dmytro; Martz, Eric; Tuominen, Mark T.; Lovley, Derek R.

    2015-03-03

    Direct measurement of multiple physical properties of Geobacter sulfurreducens pili have demonstrated that they possess metallic-like conductivity, but several studies have suggested that metallic-like conductivity is unlikely based on the structures of the G. sulfurreducens pilus predicted from homology models. In order to further evaluate this discrepancy, pili were examined with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction. Both techniques revealed a periodic 3.2-Å spacing in conductive, wild-type G. sulfurreducens pili that was missing in the nonconductive pili of strain Aro5, which lack key aromatic acids required for conductivity. The intensity of the 3.2-Å peak increased 100-fold when the pH was shifted from 10.5 to 2, corresponding with a previously reported 100-fold increase in pilus conductivity with this pH change. These results suggest a clear structure-function correlation for metallic-like conductivity that can be attributed to overlapping π-orbitals of aromatic amino acids. A homology model of the G. sulfurreducens pilus was constructed with a Pseudomonas aeruginosa pilus model as a template as an alternative to previous models, which were based on a Neisseria gonorrhoeae pilus structure. This alternative model predicted that aromatic amino acids in G. sulfurreducens pili are packed within 3 to 4 Å, consistent with the experimental results. Thus, the predictions of homology modeling are highly sensitive to assumptions inherent in the model construction. Finally, the experimental results reported here further support the concept that the pili of G. sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport.

  20. Structural Basis for Metallic-Like Conductivity in Microbial Nanowires

    PubMed Central

    Malvankar, Nikhil S.; Vargas, Madeline; Nevin, Kelly; Tremblay, Pier-Luc; Evans-Lutterodt, Kenneth; Nykypanchuk, Dmytro; Martz, Eric; Tuominen, Mark T.

    2015-01-01

    ABSTRACT Direct measurement of multiple physical properties of Geobacter sulfurreducens pili have demonstrated that they possess metallic-like conductivity, but several studies have suggested that metallic-like conductivity is unlikely based on the structures of the G. sulfurreducens pilus predicted from homology models. In order to further evaluate this discrepancy, pili were examined with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction. Both techniques revealed a periodic 3.2-Å spacing in conductive, wild-type G. sulfurreducens pili that was missing in the nonconductive pili of strain Aro5, which lack key aromatic acids required for conductivity. The intensity of the 3.2-Å peak increased 100-fold when the pH was shifted from 10.5 to 2, corresponding with a previously reported 100-fold increase in pilus conductivity with this pH change. These results suggest a clear structure-function correlation for metallic-like conductivity that can be attributed to overlapping π-orbitals of aromatic amino acids. A homology model of the G. sulfurreducens pilus was constructed with a Pseudomonas aeruginosa pilus model as a template as an alternative to previous models, which were based on a Neisseria gonorrhoeae pilus structure. This alternative model predicted that aromatic amino acids in G. sulfurreducens pili are packed within 3 to 4 Å, consistent with the experimental results. Thus, the predictions of homology modeling are highly sensitive to assumptions inherent in the model construction. The experimental results reported here further support the concept that the pili of G. sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport. PMID:25736881

  1. Structural Basis for Metallic-Like Conductivity in Microbial Nanowires

    DOE PAGES

    Malvankar, Nikhil S.; Vargas, Madeline; Nevin, Kelly; ...

    2015-03-03

    Direct measurement of multiple physical properties of Geobacter sulfurreducens pili have demonstrated that they possess metallic-like conductivity, but several studies have suggested that metallic-like conductivity is unlikely based on the structures of the G. sulfurreducens pilus predicted from homology models. In order to further evaluate this discrepancy, pili were examined with synchrotron X-ray microdiffraction and rocking-curve X-ray diffraction. Both techniques revealed a periodic 3.2-Å spacing in conductive, wild-type G. sulfurreducens pili that was missing in the nonconductive pili of strain Aro5, which lack key aromatic acids required for conductivity. The intensity of the 3.2-Å peak increased 100-fold when the pHmore » was shifted from 10.5 to 2, corresponding with a previously reported 100-fold increase in pilus conductivity with this pH change. These results suggest a clear structure-function correlation for metallic-like conductivity that can be attributed to overlapping π-orbitals of aromatic amino acids. A homology model of the G. sulfurreducens pilus was constructed with a Pseudomonas aeruginosa pilus model as a template as an alternative to previous models, which were based on a Neisseria gonorrhoeae pilus structure. This alternative model predicted that aromatic amino acids in G. sulfurreducens pili are packed within 3 to 4 Å, consistent with the experimental results. Thus, the predictions of homology modeling are highly sensitive to assumptions inherent in the model construction. Finally, the experimental results reported here further support the concept that the pili of G. sulfurreducens represent a novel class of electronically functional proteins in which aromatic amino acids promote long-distance electron transport.« less

  2. Effective passivation of Ag nanowire-based flexible transparent conducting electrode by TiO2 nanoshell

    NASA Astrophysics Data System (ADS)

    Lee, Dong Geon; Lee, Dongjun; Yoo, Jin Sun; Lee, Sangwook; Jung, Hyun Suk

    2016-08-01

    Silver nanowire-based flexible transparent electrodes have critical problem, in spite of their excellent electrical and optical properties, that the electrical conductance and transparency degrade within several days in air because of oxidation of silver. To prevent the degradation of the silver nanowire, we encapsulated Ag-NWs with thin TiO2 barrier. Bar-coated silver nanowires on flexible polymer substrate were laminated at 120 °C, followed by atomic layer deposition of TiO2 nanoshell. With 20 nm of TiO2 nanoshells on silver nanowires, the transparent electrode keeps its electrical and optical properties over 2 months. Moreover, the TiO2-encapsulated silver nanowire-based transparent electrodes exhibit excellent bending durability.

  3. Current imaging and electromigration-induced splitting of GaN nanowires as revealed by conductive atomic force microscopy.

    PubMed

    Li, Chun; Bando, Yoshio; Golberg, Dmitri

    2010-04-27

    Current images of electromigration-induced common vapor-liquid-solid-grown GaN nanowires were obtained using a conductive atomic force microscope. Structural characterization indicated that these wurtzite (ZW) [0110] nanowires contained longitudinal zinc blende (ZB) defects as stacking faults. The current was attributed to tunneling current through the Schottky barrier between the AFM tip and a nanowire, which was dominated by the local nanowire surface work function. Due to the electromigration induced by large current densities around the defects, the axial splitting process of the nanowires was directly observed under continuous current scanning. The electromigration was likely enhanced by non-uniformly distributed electrostatic pressure around the axial ZW/ZB domain interfaces.

  4. Self-templated synthesis and thermal conductivity investigation for ultrathin perovskite oxide nanowires

    NASA Astrophysics Data System (ADS)

    Yadav, Gautam G.; Zhang, Genqiang; Qiu, Bo; Susoreny, Joseph A.; Ruan, Xiulin; Wu, Yue

    2011-10-01

    The large thermal conductivity of bulk complex metal oxides such as SrTiO3, NaCo2O4, and Ca3Co4O9 has set a barrier for the improvement of thermoelectric figure of merit and the applications of these materials in high temperature (>=1000 K) thermoelectric energy harvesting and solid-state cooling. Here, we present a self-templated synthesis approach to grow ultrathin SrTiO3 nanowires with an average diameter of 6 nm in large quantity. The thermal conductivity of the bulk pellet made by compressing nanowire powder using spark plasma sintering shows a 64% reduction in thermal conductivity at 1000 K, which agrees well with theoretical modeling.The large thermal conductivity of bulk complex metal oxides such as SrTiO3, NaCo2O4, and Ca3Co4O9 has set a barrier for the improvement of thermoelectric figure of merit and the applications of these materials in high temperature (>=1000 K) thermoelectric energy harvesting and solid-state cooling. Here, we present a self-templated synthesis approach to grow ultrathin SrTiO3 nanowires with an average diameter of 6 nm in large quantity. The thermal conductivity of the bulk pellet made by compressing nanowire powder using spark plasma sintering shows a 64% reduction in thermal conductivity at 1000 K, which agrees well with theoretical modeling. Y. Wu thanks the support from the Purdue University new faculty startup grant, Kick Grant from Birck Nanotechnology Center, DuPont Young Faculty Award, Midwest Institute for Nanoelectronics Discovery (MIND), and NSF/DOE Thermoelectric Partnership (Award Number 1048616). Y. Wu acknowledges the help from Dr Douglas Dudis and Charles Cooke at Wright-Patterson Air Force Research Lab on the spark plasma sintering of nanowire powder. X.L. Ruan and B. Qiu acknowledge the partial support of Air Force Office of Scientific Research (Grant Number FA9550-11-1-0057).

  5. Preparation and dielectric properties of SiC nanowires self-sacrificially templated by carbonated bacterial cellulose

    SciTech Connect

    Wen, Lixia; Ma, Yongjun; Dai, Bo; Zhou, Yong; Liu, Jinsong; Pei, Chonghua

    2013-02-15

    Graphical abstract: Display Omitted Highlights: ► A new material – CBC is introduced as a template to prepare SiC nanowires. ► SiC nanowires are synthesized by the infiltration process of reactive vapor Si. ► The highest ε″ of β-SiC nanowires is obtained at 1400 °C. -- Abstract: SiC nanowires were synthesized by the infiltration process of reactive vapor Si in Ar atmosphere at 1350–1450 °C, using carbonated bacterial cellulose (CBC) as carbon template and a reactant. Scanning electron microscopy (SEM), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and vector network analyzer were employed to characterize the samples. The diameter of the resulting β-SiC nanowires changes with calcination temperatures, specifically, 35–60 nm for 1350 °C, 40–80 nm for 1400 °C, and 30–60 nm for 1450 °C. The β-SiC nanowires obtained at 1400 °C possess the highest ε″ of complex permittivity.

  6. Effective medium theory for the conductivity of disordered metallic nanowire networks.

    PubMed

    O'Callaghan, Colin; Gomes da Rocha, Claudia; Manning, Hugh G; Boland, John J; Ferreira, Mauro S

    2016-10-05

    Motivated by numerous technological applications, there is current interest in the study of the conductive properties of networks made of randomly dispersed nanowires. The sheet resistance of such networks is normally calculated by numerically evaluating the conductance of a system of resistors but due to disorder and with so many variables to account for, calculations of this type are computationally demanding and may lack mathematical transparency. Here we establish the equivalence between the sheet resistance of disordered networks and that of a regular ordered network. Rather than through a fitting scheme, we provide a recipe to find the effective medium network that captures how the resistance of a nanowire network depends on several different parameters such as wire density, electrode size and electrode separation. Furthermore, the effective medium approach provides a simple way to distinguish the sheet resistance contribution of the junctions from that of the nanowires themselves. The contrast between these two contributions determines the potential to optimize the network performance for a particular application.

  7. Biaxially stretchable silver nanowire conductive film embedded in a taro leaf-templated PDMS surface

    NASA Astrophysics Data System (ADS)

    Wu, Chunhui; Jiu, Jinting; Araki, Teppei; Koga, Hirotaka; Sekitani, Tsuyoshi; Wang, Hao; Suganuma, Katsuaki

    2017-01-01

    A biaxially wave-shaped polydimethylsiloxane (PDMS) surface was developed simply by using a taro leaf as the template. The resulting leaf-templated PDMS (L-PDMS) possesses a micro-sized curved interface structure, which is greatly beneficial for the exact embedding of a silver nanowire (AgNW) network conductive film covering the L-PDMS surface. The intrinsically curved AgNW/L-PDMS film surface, without any dangling nanowire, could prevent the fracture of AgNWs due to stretching stress even after cyclic stretching. More importantly, it also exhibited a biaxial stretchability, which showed ultra-stable resistance after continuous stretching for 100 cycles each in X- and Y-directions. This biaxially stretchable AgNW/L-PDMS film could extend the application fields in stretchable electronics.

  8. Enhanced lithium ion conductivity in lithium lanthanum titanate solid electrolyte nanowires prepared by electrospinning

    NASA Astrophysics Data System (ADS)

    Yang, Ting; Li, Ying; Chan, Candace K.

    2015-08-01

    Solid electrolytes have great potential to address the safety issues of Li-ion batteries, but better synthesis methods are still required for ceramics such as lithium lanthanum titanate (LLTO) since current techniques require high-temperature calcination for long times. Here we report a new approach that utilizes electrospinning to prepare phase-pure polycrystalline LLTO nanowires with well-crystallized tetragonal structure after only 3 h calcination at 1000 °C. Pellets prepared from the electrospun LLTO nanowires had higher density, less void space, and higher Li+ conductivity compared to those comprised of LLTO prepared with conventional sol-gel methods. This work demonstrates the potential that electrospinning can provide towards improving the properties of sol-gel derived ceramics.

  9. Temperature dependent conduction and UV induced metal-to-insulator transition in ZnO nanowires

    SciTech Connect

    Chang, P.-C.; Lu, Jia Grace

    2008-05-26

    Thin ZnO nanowires with diameters of less than 50 nm are configured as field effect transistors and studied for their transport mechanisms at different temperatures under UV illumination and gate modulation. The conductivity exhibits two regimes: at T>50 K, thermally activated transport dominates with activation energy around 30-60 meV attributed to the shallow donor states and at T<50 K, three dimensional variable range hopping reveals in the conduction. In addition, UV irradiation leads to a metal-to-insulator transition at {approx}210 K. Furthermore, electrostatic gating results in a band bending giving rise to a change in the activation energy.

  10. Flexibility and non-destructive conductivity measurements of Ag nanowire based transparent conductive films via terahertz time domain spectroscopy.

    PubMed

    Hwang, Gyujeong; Balci, Soner; Güngördü, M Zeki; Maleski, Alex; Waters, Joseph; Lee, Sunjong; Choi, Sangjun; Kim, Kyoungkook; Cho, Soohaeng; Kim, Seongsin M

    2017-02-20

    Highly stable and flexible transparent electrodes are fabricated based on silver nanowires (AgNWs) on both polyethylene-terephthalate (PET) and polyimide (PI) substrates. Terahertz time domain spectroscopy (THz-TDS) was utilized to probe AgNW films while bended with a radius 5 mm to discover conductivity of bended films which was further analyzed through Drude-Smith model. AgNW films experience little degradation in conductivity (<3%) before, after, and during 1000 bending cycles. Highly stable AgNW flexible electrodes have broad applications in flexible optoelectronic and electronic devices. THz-TDS is an effective technique to investigate the electrical properties of the bended and flattened conducting films in a nondestructive manner.

  11. Large scale, highly conductive and patterned transparent films of silver nanowires on arbitrary substrates and their application in touch screens.

    PubMed

    Madaria, Anuj R; Kumar, Akshay; Zhou, Chongwu

    2011-06-17

    The application of silver nanowire films as transparent conductive electrodes has shown promising results recently. In this paper, we demonstrate the application of a simple spray coating technique to obtain large scale, highly uniform and conductive silver nanowire films on arbitrary substrates. We also integrated a polydimethylsiloxane (PDMS)-assisted contact transfer technique with spray coating, which allowed us to obtain large scale high quality patterned films of silver nanowires. The transparency and conductivity of the films was controlled by the volume of the dispersion used in spraying and the substrate area. We note that the optoelectrical property, σ(DC)/σ(Op), for various films fabricated was in the range 75-350, which is extremely high for transparent thin film compared to other candidate alternatives to doped metal oxide film. Using this method, we obtain silver nanowire films on a flexible polyethylene terephthalate (PET) substrate with a transparency of 85% and sheet resistance of 33 Ω/sq, which is comparable to that of tin-doped indium oxide (ITO) on flexible substrates. In-depth analysis of the film shows a high performance using another commonly used figure-of-merit, Φ(TE). Also, Ag nanowire film/PET shows good mechanical flexibility and the application of such a conductive silver nanowire film as an electrode in a touch panel has been demonstrated.

  12. Silver nanowires decorated with silver nanoparticles for low-haze flexible transparent conductive films

    PubMed Central

    Mol Menamparambath, Mini; Muhammed Ajmal, C.; Hee Kim, Kwang; Yang, Daejin; Roh, Jongwook; Cheol Park, Hyeon; Kwak, Chan; Choi, Jae-Young; Baik, Seunghyun

    2015-01-01

    Silver nanowires have attracted much attention for use in flexible transparent conductive films (TCFs) due to their low sheet resistance and flexibility. However, the haze was too high for replacing indium-tin-oxide in high-quality display devices. Herein, we report flexible TCFs, which were prepared using a scalable bar-coating method, with a low sheet resistance (24.1 Ω/sq at 96.4% transmittance) and a haze (1.04%) that is comparable to that of indium-tin-oxide TCFs. To decrease the haze and maintain a low sheet resistance, small diameter silver nanowires (~20 nm) were functionalized with low-temperature surface-sintering silver nanoparticles (~5 nm) using bifunctional cysteamine. The silver nanowire-nanoparticle ink stability was excellent. The sheet resistance of the TCFs was decreased by 29.5% (from 34.2 to 24.1 Ω/sq) due to the functionalization at a low curing temperature of 85 °C. The TCFs were highly flexible and maintained their stability for more than 2 months and 10,000 bending cycles after coating with a protective layer. PMID:26575970

  13. Silver nanowires decorated with silver nanoparticles for low-haze flexible transparent conductive films.

    PubMed

    Menamparambath, Mini Mol; Ajmal, C Muhammed; Kim, Kwang Hee; Yang, Daejin; Roh, Jongwook; Park, Hyeon Cheol; Kwak, Chan; Choi, Jae-Young; Baik, Seunghyun

    2015-11-17

    Silver nanowires have attracted much attention for use in flexible transparent conductive films (TCFs) due to their low sheet resistance and flexibility. However, the haze was too high for replacing indium-tin-oxide in high-quality display devices. Herein, we report flexible TCFs, which were prepared using a scalable bar-coating method, with a low sheet resistance (24.1 Ω/sq at 96.4% transmittance) and a haze (1.04%) that is comparable to that of indium-tin-oxide TCFs. To decrease the haze and maintain a low sheet resistance, small diameter silver nanowires (~20 nm) were functionalized with low-temperature surface-sintering silver nanoparticles (~5 nm) using bifunctional cysteamine. The silver nanowire-nanoparticle ink stability was excellent. The sheet resistance of the TCFs was decreased by 29.5% (from 34.2 to 24.1 Ω/sq) due to the functionalization at a low curing temperature of 85 °C. The TCFs were highly flexible and maintained their stability for more than 2 months and 10,000 bending cycles after coating with a protective layer.

  14. Silver nanowires decorated with silver nanoparticles for low-haze flexible transparent conductive films

    NASA Astrophysics Data System (ADS)

    Mol Menamparambath, Mini; Muhammed Ajmal, C.; Hee Kim, Kwang; Yang, Daejin; Roh, Jongwook; Cheol Park, Hyeon; Kwak, Chan; Choi, Jae-Young; Baik, Seunghyun

    2015-11-01

    Silver nanowires have attracted much attention for use in flexible transparent conductive films (TCFs) due to their low sheet resistance and flexibility. However, the haze was too high for replacing indium-tin-oxide in high-quality display devices. Herein, we report flexible TCFs, which were prepared using a scalable bar-coating method, with a low sheet resistance (24.1 Ω/sq at 96.4% transmittance) and a haze (1.04%) that is comparable to that of indium-tin-oxide TCFs. To decrease the haze and maintain a low sheet resistance, small diameter silver nanowires (~20 nm) were functionalized with low-temperature surface-sintering silver nanoparticles (~5 nm) using bifunctional cysteamine. The silver nanowire-nanoparticle ink stability was excellent. The sheet resistance of the TCFs was decreased by 29.5% (from 34.2 to 24.1 Ω/sq) due to the functionalization at a low curing temperature of 85 °C. The TCFs were highly flexible and maintained their stability for more than 2 months and 10,000 bending cycles after coating with a protective layer.

  15. Mask-Free Patterning of High-Conductivity Metal Nanowires in Open Air by Spatially Modulated Femtosecond Laser Pulses.

    PubMed

    Wang, Andong; Jiang, Lan; Li, Xiaowei; Liu, Yang; Dong, Xianzi; Qu, Liangti; Duan, Xuanming; Lu, Yongfeng

    2015-10-28

    A novel high-resolution nanowire fabrication method is developed by thin-film patterning using a spatially modulated femtosecond laser pulse. Deep subwavelength (≈1/13 of the laser wavelength) and high conductivity (≈1/4 of the bulk gold) nanowires are fabricated in the open air without using masks, which offers a single-step arbitrary direct patterning approach for electronics, plasmonics, and optoelectronics nanodevices.

  16. Copper Nanowires and Their Applications for Flexible, Transparent Conducting Films: A Review

    PubMed Central

    Nam, Vu Binh; Lee, Daeho

    2016-01-01

    Cu nanowires (NWs) are attracting considerable attention as alternatives to Ag NWs for next-generation transparent conductors, replacing indium tin oxide (ITO) and micro metal grids. Cu NWs hold great promise for low-cost fabrication via a solution-processed route and show preponderant optical, electrical, and mechanical properties. In this study, we report a summary of recent advances in research on Cu NWs, covering the optoelectronic properties, synthesis routes, deposition methods to fabricate flexible transparent conducting films, and their potential applications. This review also examines the approaches on protecting Cu NWs from oxidation in air environments. PMID:28344304

  17. Polar surface effects on the thermal conductivity of ZnO nanowires: a shell-like surface reconstruction-induced preserving mechanism.

    PubMed

    Jiang, Jin-Wu; Park, Harold S; Rabczuk, Timon

    2013-11-21

    We perform molecular dynamics (MD) simulations to investigate the effect of polar surfaces on the thermal transport in zinc oxide (ZnO) nanowires. We find that the thermal conductivity of nanowires with free polar (0001) surfaces is much higher than that of nanowires that have been stabilized with reduced charges on the polar (0001) surfaces, and also hexagonal nanowires without any transverse polar surface, where the reduced charge model has been proposed as a promising stabilization mechanism for the (0001) polar surfaces of ZnO nanowires. From normal mode analysis, we show that the higher thermal conductivity is due to the shell-like reconstruction that occurs for the free polar surfaces. This shell-like reconstruction suppresses twisting motion in the nanowires such that the bending phonon modes are not scattered by the other phonon modes, and this leads to substantially higher thermal conductivity of the ZnO nanowires with free polar surfaces. Furthermore, the auto-correlation function of the normal mode coordinate is utilized to extract the phonon lifetime, which leads to a concise explanation for the higher thermal conductivity of ZnO nanowires with free polar surfaces. Our work demonstrates that ZnO nanowires without polar surfaces, which exhibit low thermal conductivity, are more promising candidates for thermoelectric applications than nanowires with polar surfaces (and also high thermal conductivity).

  18. Characterization of the oxygen oonosorption effect on a single SnO2 nanowire by using conductive atomic force microscopy.

    PubMed

    Heo, Jinhee; Lee, Junghwan

    2012-06-01

    We have verified that SnO2 nano-wire has an n-type semiconductor property and it can be a p-type one when it is exposed to O2. We employed conductive AFM system to measure the I-V curve and resistance of single SnO2 nano-wire which had been synthesized on the Au thin film by a thermal process. To analyze a effect of O2 ionosorption into nano-wire, resistance was measured with various O2 concentration and we observed increment and maintenance of resistance which caused by O2 ionosorption. Also, the O2 ionosorption causes a type transfer of semiconductor and this phenomenon was verified by comparing the Schottky property of nano-wire before and after O2 exposure.

  19. Regulation of Gene Expression in Shewanella oneidensis MR-1 during Electron Acceptor Limitation and Bacterial Nanowire Formation

    PubMed Central

    Barchinger, Sarah E.; Pirbadian, Sahand; Baker, Carol S.; Leung, Kar Man; Burroughs, Nigel J.; El-Naggar, Mohamed Y.

    2016-01-01

    using extensions of the outer membrane called bacterial nanowires. These bacterial nanowires link the cell's respiratory chain to external surfaces, including oxidized metals important in bioremediation, and explain why S. oneidensis can be utilized as a component of microbial fuel cells, a form of renewable energy. In this work, we use differential gene expression analysis to focus on which genes function to produce the nanowires and promote extracellular electron transfer during oxygen limitation. Among the genes that are expressed at high levels are those encoding cytochrome proteins necessary for electron transfer. Shewanella coordinates the increased expression of regulators, metabolic pathways, and transport pathways to ensure that cytochromes efficiently transfer electrons along the nanowires. PMID:27342561

  20. Bismuth nanowires with very low lattice thermal conductivity as revealed by the 3ω method.

    PubMed

    Holtzman, A; Shapira, E; Selzer, Y

    2012-12-14

    Thermoelectric materials transform temperature gradients to voltages and vise versa. Despite their many advantages, devices based on thermoelectric materials are used today only in a few applications, due to their low efficiency, which is described by the figure of merit ZT. Theoretical studies predict that scaling down these materials to the nanometric scale should enhance their efficiency partially due to a decrease in their lattice thermal conductivity. In this work we determine for the first time the lattice thermal conductivity of 40 nm bismuth (Bi) nanowires (NWs), i.e. NWs with a diameter comparable to the Fermi wavelength of charge carriers in this material. We find a surprisingly low lattice thermal conductivity of 0.13 ± 0.05 W K(-1) m(-1) at 77 K. A quantitative argument, which takes into account several unique properties of Bi, is given to explain this unusual finding.

  1. Assembly of Ultrathin Gold Nanowires into Honeycomb Macroporous Pattern Films with High Transparency and Conductivity.

    PubMed

    He, Ying; Chen, Yuan; Xu, Qingchi; Xu, Jun; Weng, Jian

    2017-03-01

    Because of its promising properties, honeycomb macroporous pattern (HMP) film has attracted increasing attention. It has been realized in many artificial nanomaterials, but the formation of these HMPs was attributed to templates or polymer/supermolecule/surfactant assistant assembly. Pure metal HMP film has been difficult to produce using a convenient colloidal template-free method. In this report, a unique template-free approach for preparation of Au HMP film with high transparency and conductivity is presented. Ultrathin Au nanowires, considered a linear polymer analogue, are directly assembled into HMP film on various substrates using a traditional static breath figure method. Subsequent chemical cross-linking and oxygen plasma treatment greatly enhance the stability and conductivity of the HMP film. The resulting HMP film exhibits great potential as an ideal candidate for transparent flexible conductive nanodevices.

  2. Preparation and Properties of Silver Nanowire-Based Transparent Conductive Composite Films

    NASA Astrophysics Data System (ADS)

    Tian, Ji-Li; Zhang, Hua-Yu; Wang, Hai-Jun

    2016-06-01

    Silver nanowire-based transparent conductive composite films with different structures were successfully prepared using various methods, including liquid polyol, magnetron sputtering and spin coating. The experimental results revealed that the optical transmittance of all different structural composite films decreased slightly (1-3%) compared to pure films. However, the electrical conductivity of all composite films had a great improvement. Under the condition that the optical transmittance was greater than 78% over the wavelength range of 400-800 nm, the AgNW/PVA/AgNW film became a conductor, while the AZO/AgNW/AZO film and the ITO/AgNW/ITO film showed 88.9% and 94% reductions, respectively, for the sheet resistance compared with pure films. In addition, applying a suitable mechanical pressure can improve the conductivity of AgNW-based composite films.

  3. Spray-Deposited Large-Area Copper Nanowire Transparent Conductive Electrodes and Their Uses for Touch Screen Applications.

    PubMed

    Chu, Hsun-Chen; Chang, Yen-Chen; Lin, Yow; Chang, Shu-Hao; Chang, Wei-Chung; Li, Guo-An; Tuan, Hsing-Yu

    2016-05-25

    Large-area conducting transparent conducting electrodes (TCEs) were prepared by a fast, scalable, and low-cost spray deposition of copper nanowire (CuNW) dispersions. Thin, long, and pure copper nanowires were obtained via the seed-mediated growth in an organic solvent-based synthesis. The mean length and diameter of nanowires are, respectively, 37.7 μm and 46 nm, corresponding to a high-mean-aspect ratio of 790. These wires were spray-deposited onto a glass substrate to form a nanowire conducting network which function as a TCE. CuNW TCEs exhibit high-transparency and high-conductivity since their relatively long lengths are advantageous in lowering in the sheet resistance. For example, a 2 × 2 cm(2) transparent nanowire electrode exhibits transmittance of T = 90% with a sheet resistance as low as 52.7 Ω sq(-1). Large-area sizes (>50 cm(2)) of CuNW TCEs were also prepared by the spray coating method and assembled as resistive touch screens that can be integrated with a variety of devices, including LED lighting array, a computer, electric motors, and audio electronic devices, showing the capability to make diverse sizes and functionalities of CuNW TCEs by the reported method.

  4. The Conductive Silver Nanowires Fabricated by Two-beam Laser Direct Writing on the Flexible Sheet.

    PubMed

    He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Jin, Feng; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng

    2017-02-02

    Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 10(3) V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two-beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices.

  5. The Conductive Silver Nanowires Fabricated by Two-beam Laser Direct Writing on the Flexible Sheet

    PubMed Central

    He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Jin, Feng; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng

    2017-01-01

    Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 103 V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two–beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices. PMID:28150712

  6. Intrinsic nanotwin effect on thermal boundary conductance in bulk and single-nanowire twinning superlattices

    NASA Astrophysics Data System (ADS)

    Porter, Aaron; Tran, Chan; Sansoz, Frederic

    2016-05-01

    Coherent twin boundaries form periodic lamellar twinning in a wide variety of semiconductor nanowires, and they are often viewed as near-perfect interfaces with reduced phonon and electron scattering behaviors. Such unique characteristics are of practical interest for high-performance thermoelectrics and optoelectronics; however, insufficient understanding of twin-size effects on thermal boundary resistance poses significant limitations for potential applications. Here, using atomistic simulations and ab initio calculations, we report direct computational observations showing a crossover from diffuse interface scattering to superlatticelike behavior for thermal transport across nanoscale twin boundaries present in prototypical bulk and nanowire Si examples. Intrinsic interface scattering is identified for twin periods ≥22.6 nm, but it also vanishes below this size to be replaced by ultrahigh Kapitza thermal conductances. Detailed analysis of vibrational modes shows that modeling twin boundaries as atomically thin 6 H -Si layers, rather than phonon scattering interfaces, provides an accurate description of effective cross-plane and in-plane thermal conductivities in twinning superlattices, as a function of the twin period thickness.

  7. Welded-Ag-nanowires/FTO conducting film with high transmittance and its application in transparent supercapacitors

    NASA Astrophysics Data System (ADS)

    Qiao, Zhensong; Yang, Xiaopeng; Liu, Feng; Duan, Guangbin; Cao, Bingqiang

    2017-03-01

    Silver nanowires (AgNW) with a small diameter were synthesized by a facile and novel polyol reduction method. Ag nanowires ink was then spun on the surface of F-doped SnO2 (FTO) to form the AgNW/FTO conducting film. Welding treatment of the AgNW/FTO conducting film not only increased the optical transmittance from 71.9 % to 79.3 % at 550 nm and decreased the sheet resistance from 11.4 ohm sq-1 to 9.8 ohm sq-1, but also improved the adhesivity of AgNW network on FTO substrate. Furthermore, MnO2 nanosheets were directly deposited on welded-AgNW/FTO (wAF) substrate to prepare a transparent MnO2/weled-AgNW/FTO (MwAF) composite electrode. The MwAF electrode displayed excellent electrochemical performance, including high specific capacitance (375 F g-1 at 5 mV s-1) and superior cycle stability (173.3 % of the initial capacitance after 20000 GCD cycles).

  8. The Conductive Silver Nanowires Fabricated by Two-beam Laser Direct Writing on the Flexible Sheet

    NASA Astrophysics Data System (ADS)

    He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Jin, Feng; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng

    2017-02-01

    Flexible electrically conductive nanowires are now a key component in the fields of flexible devices. The achievement of metal nanowire with good flexibility, conductivity, compact and smooth morphology is recognized as one critical milestone for the flexible devices. In this study, a two-beam laser direct writing system is designed to fabricate AgNW on PET sheet. The minimum width of the AgNW fabricated by this method is 187 ± 34 nm with the height of 84 ± 4 nm. We have investigated the electrical resistance under different voltages and the applicable voltage per meter range is determined to be less than 7.5 × 103 V/m for the fabricated AgNW. The flexibility of the AgNW is very excellent, since the resistance only increases 6.63% even after the stretched bending of 2000 times at such a small bending radius of 1.0 mm. The proposed two–beam laser direct writing is an efficient method to fabricate AgNW on the flexible sheet, which could be applied in flexible micro/nano devices.

  9. Predicting low-thermal-conductivity Si-Ge nanowires with a modified cluster expansion method

    NASA Astrophysics Data System (ADS)

    Kristensen, Jesper; Zabaras, Nicholas J.

    2015-02-01

    We introduce the cluster-expansion ghost-lattice method, which extends the applicability of existing cluster-expansion software, to cluster expand structures of arbitrary finite and infinite geometries in a fast, unique, and transferable way. The ghost site that is introduced zeroes the cluster function of any cluster which includes it. This enables the use of bulk clusters grouped by bulk symmetries in nonbulk systems and distinguishes the cluster-expansion ghost-lattice method from a regular ternary cluster expansion with an inactive vacuum atom type. Even though the method does not treat surface terms, it can be used as an efficient way to obtain the bulk term in D. Lerch et al. [Modell. Simul. Mater. Sci. Eng. 17, 055003 (2009), 10.1088/0965-0393/17/5/055003]. We use the method to learn the thermal conductivity of Si-Ge nanowires, oriented along the [111] direction on a diamond lattice, versus their configuration of Si and Ge atoms. Once learned, the ghost-lattice cluster-expansion method is shown to be able to predict the lowest-thermal-conductivity nanowire configuration, in agreement with the configuration found in M. Chan et al. [Phys. Rev. B 81, 174303 (2010), 10.1103/PhysRevB.81.174303].

  10. A novel nano-configuration for thermoelectrics: helicity induced thermal conductivity reduction in nanowires.

    PubMed

    Varshney, Vikas; Roy, Ajit K; Dudis, Douglas S; Lee, Jonghoon; Farmer, Barry L

    2012-08-21

    In this article, we propose a novel helical nano-configuration towards the designing of high ZT thermoelectric materials. Non-equilibrium molecular dynamics (NEMD) simulations for 'model' bi-component nanowires indicate that a significant reduction in thermal conductivity, similar to that of flat superlattice nanostructures, can be achieved using a helical geometric configuration. The reduction is attributed to a plethora of transmissive and reflective phonon scattering events resulting from the steady alteration of phonon propagating direction that emerges from the continuous rotation of the helical interface. We also show that increasing the relative mass ratio of the two components lowers the phonon energy transmission at the interface due to differences in vibrational frequency spectra, thereby relatively 'easing' the phonon energy propagation along the helical pathway. While the proposed mechanisms result in a reduced lattice thermal conductivity, the continuous nature of the bi-component nanowire would not be expected to significantly reduce its electrical counterpart, as often occurs in superlattice/alloy nanostructures. Hence, we postulate that the helical configuration of atomic arrangement provides an attractive and general framework for improved thermoelectric material assemblies independent of the specific chemical composition.

  11. Effect of molecular adsorption on the electrical conductance of single au nanowires fabricated by electron-beam lithography and focused ion beam etching.

    PubMed

    Shi, Ping; Zhang, Jingying; Lin, Hsin-Yu; Bohn, Paul W

    2010-11-22

    Metal nanowires are one of the potential candidates for nanostructured sensing elements used in future portable devices for chemical detection; however, the optimal methods for fabrication have yet to be fully explored. Two routes to nanowire fabrication, electron-beam lithography (EBL) and focused ion beam (FIB) etching, are studied, and their electrical and chemical sensing properties are compared. Although nanowires fabricated by both techniques exhibit ohmic conductance, I-V characterization indicates that nanowires fabricated by FIB etching exhibit abnormally high resistivity. In addition, the resistivity of nanowires fabricated by FIB etching shows very low sensitivity toward molecular adsorption, while those fabricated by EBL exhibit sensitive resistance change upon exposure to solution-phase adsorbates. The mean grain sizes of nanowires prepared by FIB etching are much smaller than those fabricated by EBL, so their resistance is dominated by grain-boundary scattering. As a result, these nanowires are much less sensitive to molecular adsorption, which mediates nanowire conduction through surface scattering. The much reduced mean grain sizes of these nanowires correlate with Ga ion damage caused during the ion milling process. Thus, even though the nanowires prepared by FIB etching can be smaller than their EBL counterparts, their reduced sensitivity to adsorption suggests that nanowires produced by EBL are preferred for chemical and biochemical sensing applications.

  12. Conduction Band Offset and Polarization Effects in InAs Nanowire Polytype Junctions.

    PubMed

    Chen, I-Ju; Lehmann, Sebastian; Nilsson, Malin; Kivisaari, Pyry; Linke, Heiner; Dick, Kimberly A; Thelander, Claes

    2017-02-08

    Although zinc-blende (ZB) and wurtzite (WZ) structures differ only in the atomic stacking sequence, mixing of crystal phases can strongly affect the electronic properties, a problem particularly common to bottom up-grown nanostructures. A lack of understanding of the nature of electronic transport at crystal phase junctions thus severely limits our ability to develop functional nanowire devices. In this work we investigated electron transport in InAs nanowires with designed mixing of crystal structures, ZB/WZ/ZB, by temperature-dependent electrical measurements. The WZ inclusion gives rise to an energy barrier in the conduction band. Interpreting the experimental result in terms of thermionic emission and using a drift-diffusion model, we extracted values for the WZ/ZB band offset, 135 ± 10 meV, and interface sheet polarization charge density on the order of 10(-3) C/m(2). The extracted polarization charge density is 1-2 orders of magnitude smaller than previous experimental results, but in good agreement with first principle calculation of spontaneous polarization in WZ InAs. When the WZ length is reduced below 20 nm, an effective barrier lowering is observed, indicating the increasing importance of tunneling transport. Finally, we found that band-bending at ZB/WZ junctions can lead to bound electron states within an enclosed WZ segment of sufficient length, evidenced by our observation of Coulomb blockade at low temperature. These findings provide critical input for modeling and designing the electronic properties of novel functional devices, such as nanowire transistors, where crystal polytypes are commonly found.

  13. How to infer non-Abelian statistics and topological visibility from tunneling conductance properties of realistic Majorana nanowires

    NASA Astrophysics Data System (ADS)

    Das Sarma, S.; Nag, Amit; Sau, Jay D.

    2016-07-01

    We consider a simple conceptual question with respect to Majorana zero modes in semiconductor nanowires: can the measured nonideal values of the zero-bias-conductance-peak in the tunneling experiments be used as a characteristic to predict the underlying topological nature of the proximity induced nanowire superconductivity? In particular, we define and calculate the topological visibility, which is a variation of the topological invariant associated with the scattering matrix of the system as well as the zero-bias-conductance-peak heights in the tunneling measurements, in the presence of dissipative broadening, using precisely the same realistic nanowire parameters to connect the topological invariants with the zero-bias tunneling conductance values. This dissipative broadening is present in both (the existing) tunneling measurements and also (any future) braiding experiments as an inevitable consequence of a finite braiding time. The connection between the topological visibility and the conductance allows us to obtain the visibility of realistic braiding experiments in nanowires, and to conclude that the current experimentally accessible systems with nonideal zero-bias conductance peaks may indeed manifest (with rather low visibility) non-Abelian statistics for the Majorana zero modes. In general, we find that a large (small) superconducting gap (Majorana peak splitting) is essential for the manifestation of the non-Abelian braiding statistics, and in particular, a zero-bias conductance value of around half the ideal quantized Majorana value should be sufficient for the manifestation of non-Abelian statistics in experimental nanowires. Our work also establishes that as a matter of principle the topological transition associated with the emergence of Majorana zero modes in finite nanowires is always a crossover (akin to a quantum phase transition at finite temperature) requiring the presence of dissipative broadening (which must be larger than the Majorana energy

  14. Structural basis underlying the metallic-like conductivity of microbial nanowires

    NASA Astrophysics Data System (ADS)

    Malvankar, Nikhil; Vargas, Madeline; Tuominen, Mark; Lovley, Derek

    2014-03-01

    Microbial nanowires are electrically conductive proteinaceous pili nanofilaments secreted by Geobacter sulfurreducens. In contrast to current biochemical understanding that proteins are insulators, G. sulfurreducens pili show organic metallic-like conductivity. Pili also enable direct exchange of electrons among Geobacter co-cultures. Site-directed mutagenesis studies revealed that aromatic amino acids confer conductivity to pili. In order to develop a structural understanding of the pili to probe the conduction mechanism at a molecular level, we employed three complementary structural methods - X-ray microdiffraction using synchrotron radiation, rocking curve X-ray diffraction, and electron diffraction. Studies performed with all these three methods revealed a 3.2 Å periodic spacing in wild-type G. sulfurreducens pili, expected for metal-like conductivity and a lack of such spacing in genetically modified non-conductive pili. Notably, both the peak intensity and the conductivity increased 100-fold with lowering the pH from pH 10.5 to pH 2, demonstrating a structure-function correlation in pili. We also reconstructed the three dimensional tertiary structure of pili with homology modeling, which further suggested the 3.2 Å spacing among aromatics associated with metal-like conductivity. Funded by Office of Naval Research, DOE Genomic Sciences and NSF-NSEC Center for Hierarchical Manufacturing grant no. CMMI-1025020.

  15. DNA nanotubes self-assembled from triple-crossover tiles as templates for conductive nanowires

    PubMed Central

    Liu, Dage; Park, Sung Ha; Reif, John H.; LaBean, Thomas H.

    2004-01-01

    DNA-based nanotechnology is currently being developed as a general assembly method for nanopatterned materials that may find use in electronics, sensors, medicine, and many other fields. Here we present results on the construction and characterization of DNA nanotubes, a self-assembling superstructure composed of DNA tiles. Triple-crossover tiles modified with thiol-containing double-stranded DNA stems projected out of the tile plane were used as the basic building blocks. Triple-crossover nanotubes display a constant diameter of ≈25 nm and have been observed with lengths up to 20 μm. We present high-resolution images of the constructs, experimental evidence of their tube-like nature as well as data on metallization of the nanotubes to form nanowires, and electrical conductivity measurements through the nanowires. DNA nanotubes represent a potential breakthrough in the self-assembly of nanometer-scale circuits for electronics layout because they can be targeted to connect at specific locations on larger-scale structures and can subsequently be metallized to form nanometer-scale wires. The dimensions of these nanotubes are also perfectly suited for applications involving interconnection of molecular-scale devices with macroscale components fabricated by conventional photolithographic methods. PMID:14709674

  16. Anisotropic Electroless Deposition on DNA Origami Templates To Form Small Diameter Conductive Nanowires.

    PubMed

    Uprety, Bibek; Westover, Tyler; Stoddard, Michael; Brinkerhoff, Kamron; Jensen, John; Davis, Robert C; Woolley, Adam T; Harb, John N

    2017-01-24

    An improved method for the metallization of DNA origami is examined in this work. DNA origami, a simple and robust method for creating a wide variety of nanostructured shapes and patterns, provides an enabling template for bottom-up fabrication of next-generation nanodevices. Selective metallization of these DNA templates is needed to make nanoelectronic devices. Here, we demonstrate a metallization process that uses gold nanorod seeds followed by anisotropic plating to provide improved morphology and greater control of the final metallized width of the structure. In our approach, gold nanorods are attached to an origami template to create a seed layer. Electroless gold deposition is then used to fill the gaps between seeds in order to create continuous, conductive nanowires. Importantly, growth during electroless deposition occurs preferentially in the length direction at a rate that is approximately 4 times the growth rate in the width direction, which enables fabrication of narrow, continuous wires. The electrical properties of 49 nanowires with widths ranging from 13 to 29 nm were characterized, and resistivity values as low as 8.9 × 10(-7) Ω·m were measured. The anisotropic metallization process presented here represents important progress toward the creation of nanoelectronic devices by molecularly directed placement of functional components onto self-assembled biological templates.

  17. TiO2 nanocrystals shell layer on highly conducting indium tin oxide nanowire for photovoltaic devices.

    PubMed

    Han, Hyun Soo; Kim, Ju Seong; Kim, Dong Hoe; Han, Gil Sang; Jung, Hyun Suk; Noh, Jun Hong; Hong, Kug Sun

    2013-04-21

    We demonstrated a highly efficient conducting indium tin oxide (ITO) core-TiO2 nanocrystals shell nanowire array for a photoelectrode in dye-sensitized solar cells with regard to light harvest and charge collection. The TiO2 shell layer, consisting of anatase nanocrystals of ~2 nm, were successfully formed on a single crystalline ITO nanowire prepared via a vapor transport method using repetitive TiCl4 aqueous solution treatments at 50 °C. We found that the nanocrystal size and number of Cl(-) ions remaining on the formed shell layer critically influence the dye loading properties. Moreover, these factors can be controlled by means of a post-annealing process. We also found that the dye loading and the back electron transport from the conductive ITO nanowire to the electrolyte mainly determine the final cell performance. The proposed double-shell layer structure consisting of dense and porous layers showed significantly improved cell performance.

  18. Realizing field-dependent conduction in ZnO nanowires without annealing.

    PubMed

    Burke-Govey, C P; Castanet, U; Warring, H; Nau, A; Ruck, B J; Majimel, J; Plank, N O V

    2017-03-24

    We report on the low-temperature fabrication of field-effect transistors by bridging pre-patterned electrodes using ZnO nanowires grown in situ, which operate without requiring post-growth processing or annealing. The devices show good performance using as-grown nanowires, with on-off ratios of 10(5) and threshold voltages of 2 V. Electron microscopy shows the field-dependent nanowires hierarchically nucleate from larger ZnO nanorods, and both are oriented along a common c-axis. A high nanowire surface-to-volume ratio allows depleting electron traps on the nanowire surface to compensate intrinsic electron donors present throughout the nanowire bulk. This eliminates the need to reduce the electron concentration through high-temperature annealing, making the nanowires naturally field-dependent in their as-grown state.

  19. Realizing field-dependent conduction in ZnO nanowires without annealing

    NASA Astrophysics Data System (ADS)

    Burke-Govey, C. P.; Castanet, U.; Warring, H.; Nau, A.; Ruck, B. J.; Majimel, J.; Plank, N. O. V.

    2017-03-01

    We report on the low-temperature fabrication of field-effect transistors by bridging pre-patterned electrodes using ZnO nanowires grown in situ, which operate without requiring post-growth processing or annealing. The devices show good performance using as-grown nanowires, with on–off ratios of 105 and threshold voltages of 2 V. Electron microscopy shows the field-dependent nanowires hierarchically nucleate from larger ZnO nanorods, and both are oriented along a common c-axis. A high nanowire surface-to-volume ratio allows depleting electron traps on the nanowire surface to compensate intrinsic electron donors present throughout the nanowire bulk. This eliminates the need to reduce the electron concentration through high-temperature annealing, making the nanowires naturally field-dependent in their as-grown state.

  20. A novel 3D sandwich structure of hybrid graphite nanosheets and silver nanowires as fillers for improved thermal conductivity

    NASA Astrophysics Data System (ADS)

    Zhuang, Xiao; Zhou, Yongcun; Liu, Feng

    2017-01-01

    We explored a novel 3D sandwich structure of fillers in the polymer matrix to enhance thermal conductivity. A variety of fillers in the polymer matrix play a significant role in the physical properties of the composite. Fillers containing particle and line structures are popular, and enhance the thermal and electrical conductivities. Therefore, filler-based matrix network improves conductivity. We propose a sandwich structure consisting of hybrid graphite nanosheets (two dimensions), and silver nanowires (AgNWs) (one dimension), to create a 3D sandwich structure of polyimide matrix with improved thermal conductivity. Surface treatment of graphite and silver nanowires were conducted to reduce the dielectric constant of the composite. We designed the filler of 20 wt% resulting in a high thermal conductivity of 3.21 W m‑1 K‑1 with 15% C@SiO2 and 5% AgNWs@SiO2 filler loading. The novel combination and structure markedly enhanced the thermal conductivity of the composite.

  1. Size-dependent photoconductivity and dark conductivity of m-axial GaN nanowires with small critical diameter

    NASA Astrophysics Data System (ADS)

    Chen, Hsin-Yi; Chen, Reui-San; Chang, Fu-Chieh; Chen, Li-Chyong; Chen, Kuei-Hsien; Yang, Ying-Jay

    2009-10-01

    The size effects on both the photoconductivity and dark conductivity have been observed in m-axial GaN nanowires grown by chemical vapor deposition (CVD). For these nanowires with diameters at 50-130 nm, the products of carrier lifetime (τ) and mobility (μ) derived from the photocurrent measurements are typically at (2-8)×10-1 cm2/V, which are over two orders of magnitude higher than the maximal reported values [τμ=(1-5)×10-4 cm2/V] for their thin film counterparts. A significant decrease of τμ value at diameter below the critical values (dcrt) at 30-40 nm is observed. Similar size dependence is also found from the dark conductivity study. The temperature-dependent measurements further indicate two different thermal activation mechanisms in GaN nanowires with sizes above and below the dcrt. These results suggest a surface-dominant transport property in GaN nanowires both in dark and under light illumination due to the presence of surface depletion and band bending. Probable reasons leading to the smaller dcrt of the CVD-grown m-axial GaN nanowires, compared to the c-axial ones grown by molecular beam epitaxy are discussed as well.

  2. Copper Nanowires as Conductive Ink for Low-Cost Draw-On Electronics.

    PubMed

    Jason, Naveen Noah; Shen, Wei; Cheng, Wenlong

    2015-08-05

    This work tackles the complicated problem of clump formation and entanglement of high aspect ratio copper nanowires, due to which a well dispersed solution for use as a true ink for drawable electronics has not been made until now. Through rheology studies even a hard to use material like copper nanowires was tailored to be made into a highly efficient conductive ink with only 2 vol % or 18.28 wt % loading which is far lower than existing nanoparticle based inks. This versatile ink can be applied onto various substrates such as paper, PET, PDMS and latex. By using the ink in a roller ball pen, a bending sensor device was simply drawn on paper, which demonstrated detection of various degrees of convex bending and was highly durable as shown in the 10,000 bending cycling test. A highly sensitive strain sensor which has a maximum gauge factor of 54.38 was also fabricated by simply painting the ink onto latex rubber strip using a paintbrush. Finally a complex conductive pattern depicting the Sydney Opera House was painted on paper to demonstrate the versatility and robustness of the ink. The use of Cu NWs is highly economical in terms of the conductive filler loading in the ink and the cost of copper itself as compared to other metal NPs, CNT, and graphene-based inks. The demonstrated e-ink, devices, and facile device fabrication methods push the field one step closer to truly creating cheap and highly reliable skin like devices "on the fly".

  3. Electrically conductive nano graphite-filled bacterial cellulose composites.

    PubMed

    Erbas Kiziltas, Esra; Kiziltas, Alper; Rhodes, Kevin; Emanetoglu, Nuri W; Blumentritt, Melanie; Gardner, Douglas J

    2016-01-20

    A unique three dimensional (3D) porous structured bacterial cellulose (BC) can act as a supporting material to deposit the nanofillers in order to create advanced BC-based functional nanomaterials for various technological applications. In this study, novel nanocomposites comprised of BC with exfoliated graphite nanoplatelets (xGnP) incorporated into the BC matrix were prepared using a simple particle impregnation strategy to enhance the thermal properties and electrical conductivity of the BC. The flake-shaped xGnP particles were well dispersed and formed a continuous network throughout the BC matrix. The temperature at 10% weight loss, thermal stability and residual ash content of the nanocomposites increased at higher xGnP loadings. The electrical conductivity of the composites increased with increasing xGnP loading (attaining values 0.75 S/cm with the addition of 2 wt.% of xGnP). The enhanced conductive and thermal properties of the BC-xGnP nanocomposites will broaden applications (biosensors, tissue engineering, etc.) of BC and xGnP.

  4. Enhanced electrical and thermal conduction in graphene-encapsulated copper nanowires.

    PubMed

    Mehta, Ruchit; Chugh, Sunny; Chen, Zhihong

    2015-03-11

    Highly conductive copper nanowires (CuNWs) are essential for efficient data transfer and heat conduction in wide ranging applications like high-performance semiconductor chips and transparent conductors. However, size scaling of CuNWs causes severe reduction in electrical and thermal conductivity due to substantial inelastic surface scattering of electrons. Here we report a novel scalable technique for low-temperature deposition of graphene around CuNWs and observe strong enhancement of electrical and thermal conductivity for graphene-encapsulated CuNWs compared to uncoated CuNWs. Fitting the experimental data with the theoretical model for conductivity of CuNWs reveals significant reduction in surface scattering of electrons at the oxide-free CuNW surfaces, translating into 15% faster data transfer and 27% lower peak temperature compared to the same CuNW without the graphene coating. Our results provide compelling evidence for improved speed and thermal management by adapting the Cu-graphene hybrid technology in future ultrascaled silicon chips and air-stable flexible electronic applications.

  5. Disorder-free localization around the conduction band edge of crossing and kinked silicon nanowires

    SciTech Connect

    Keleş, Ümit; Çakan, Aslı; Bulutay, Ceyhun

    2015-02-14

    We explore ballistic regime quantum transport characteristics of oxide-embedded crossing and kinked silicon nanowires (NWs) within a large-scale empirical pseudopotential electronic structure framework, coupled to the Kubo-Greenwood transport analysis. A real-space wave function study is undertaken and the outcomes are interpreted together with the findings of ballistic transport calculations. This reveals that ballistic transport edge lies tens to hundreds of millielectron volts above the lowest unoccupied molecular orbital, with a substantial number of localized states appearing in between, as well as above the former. We show that these localized states are not due to the oxide interface, but rather core silicon-derived. They manifest the wave nature of electrons brought to foreground by the reflections originating from NW junctions and bends. Hence, we show that the crossings and kinks of even ultraclean Si NWs possess a conduction band tail without a recourse to atomistic disorder.

  6. Luminance behavior of lithium-doped ZnO nanowires with p-type conduction characteristics.

    PubMed

    Ko, Won Bae; Lee, Jun Seok; Lee, Sang Hyo; Cha, Seung Nam; Sohn, Jung Inn; Kim, Jong Min; Park, Young Jun; Kim, Hyun Jung; Hong, Jin Pyo

    2013-09-01

    The present study describes the room-temperature cathodeluminescence (CL) and temperature-dependent photoluminescence (PL) properties of p-type lithium (Li)-doped zinc oxide (ZnO) nanowires (NWs) grown by hydrothermal doping and post-annealing processes. A ZnO thin film was used as a seed layer in NW growth. The emission wavelengths and intensities of undoped ZnO NWs and p-type Li-doped ZnO NWs were analyzed for comparison. CL and PL observations of post-annealed p-type Li-doped ZnO NWs clearly exhibited a dominant sharp band-edge emission. Finally, a n-type ZnO thin film/p-type annealed Li-doped ZnO NW homojunction diode was prepared to confirm the p-type conduction of annealed Li-doped ZnO NWs as well as the structural properties measured by transmission electron microscopy.

  7. Highly conductive and flexible silver nanowire-based microelectrodes on biocompatible hydrogel.

    PubMed

    Ahn, Yumi; Lee, Hyungjin; Lee, Donghwa; Lee, Youngu

    2014-01-01

    We successfully fabricated silver nanowire (AgNW)-based microelectrodes on various substrates such as a glass and polydimethylsiloxane by using a photolithographic process for the first time. The AgNW-based microelectrodes exhibited excellent electrical conductivity and mechanical flexibility. We also demonstrated the direct transfer process of AgNW-based microelectrodes from a glass to a biocompatible polyacrylamide-based hydrogel. The AgNW-based microelectrodes on the biocompatible hydrogel showed excellent electrical performance. Furthermore, they showed great mechanical flexibility as well as superior stability under wet conditions. We anticipate that the AgNW-based microelectrodes on biocompatible hydrogel substrates can be a promising platform for realization of practical bioelectronics devices.

  8. Disorder-free localization around the conduction band edge of crossing and kinked silicon nanowires

    NASA Astrophysics Data System (ADS)

    Keleş, Ümit; ćakan, Aslı; Bulutay, Ceyhun

    2015-02-01

    We explore ballistic regime quantum transport characteristics of oxide-embedded crossing and kinked silicon nanowires (NWs) within a large-scale empirical pseudopotential electronic structure framework, coupled to the Kubo-Greenwood transport analysis. A real-space wave function study is undertaken and the outcomes are interpreted together with the findings of ballistic transport calculations. This reveals that ballistic transport edge lies tens to hundreds of millielectron volts above the lowest unoccupied molecular orbital, with a substantial number of localized states appearing in between, as well as above the former. We show that these localized states are not due to the oxide interface, but rather core silicon-derived. They manifest the wave nature of electrons brought to foreground by the reflections originating from NW junctions and bends. Hence, we show that the crossings and kinks of even ultraclean Si NWs possess a conduction band tail without a recourse to atomistic disorder.

  9. Preparation of conductive gold nanowires in confined environment of gold-filled polymer nanotubes.

    PubMed

    Mitschang, Fabian; Langner, Markus; Vieker, Henning; Beyer, André; Greiner, Andreas

    2015-02-01

    Continuous conductive gold nanofibers are prepared via the "tubes by fiber templates" process. First, poly(l-lactide) (PLLA)-stabilized gold nanoparticles (AuNP) with over 60 wt% gold are synthesized and characterized, including gel permeation chromatography coupled with a diode array detector. Subsequent electrospinning of these AuNP with template PLLA results in composite nanofibers featuring a high gold content of 57 wt%. Highly homogeneous gold nanowires are obtained after chemical vapor deposition of 345 nm of poly(p-xylylene) (PPX) onto the composite fibers followed by pyrolysis of the polymers at 1050 °C. The corresponding heat-induced transition from continuous gold-loaded polymer tubes to smooth gold nanofibers is studied by transmission electron microscopy and helium ion microscopy using both secondary electrons and Rutherford backscattered ions.

  10. Fingerprints of a size-dependent crossover in the dimensionality of electronic conduction in Au-seeded Ge nanowires

    PubMed Central

    Koleśnik-Gray, Maria; Collins, Gillian; Holmes, Justin D

    2016-01-01

    We studied the electrical transport properties of Au-seeded germanium nanowires with radii ranging from 11 to 80 nm at ambient conditions. We found a non-trivial dependence of the electrical conductivity, mobility and carrier density on the radius size. In particular, two regimes were identified for large (lightly doped) and small (stronger doped) nanowires in which the charge-carrier drift is dominated by electron-phonon and ionized-impurity scattering, respectively. This goes in hand with the finding that the electrostatic properties for radii below ca. 37 nm have quasi one-dimensional character as reflected by the extracted screening lengths. PMID:28144508

  11. Transparent-conducting-oxide nanowire arrays for efficient photoelectrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Lee, Sangwook; Park, Sangbaek; Han, Gill Sang; Kim, Dong Hoe; Noh, Jun Hong; Cho, In Sun; Jung, Hyun Suk; Hong, Kug Sun

    2014-07-01

    We report one dimensional (1-D) transparent-conducting-oxide arrays coated with light-absorbing semiconductors to simultaneously maximize light harvesting and charge collection in a photoelectrochemical (PEC) system. Tin-doped indium oxide (ITO) nanowire (NW) arrays are prepared on ITO thin-film substrates as the transparent-conducting-oxide, and TiO2 or CdSe/CdS/TiO2 thin layers were coated on the ITO NW arrays as the solar light-absorbing layers. The optimal PEC performance, 0.85% under 100 mW cm-2 of light illumination, is obtained from ~30 μm-long ITO NW, which is covered with ~20 nm-thick TiO2 nanoshell. We finally demonstrate that the ITO NW-based photoelectrode is also compatible with one of the most efficient visible-light sensitizers, the CdS/CdSe quantum dot. Our approach using the transparent conducting 1-D array has wide potential to improve the PEC performances of conventional semiconducting materials through liberation from the poor charge transport.We report one dimensional (1-D) transparent-conducting-oxide arrays coated with light-absorbing semiconductors to simultaneously maximize light harvesting and charge collection in a photoelectrochemical (PEC) system. Tin-doped indium oxide (ITO) nanowire (NW) arrays are prepared on ITO thin-film substrates as the transparent-conducting-oxide, and TiO2 or CdSe/CdS/TiO2 thin layers were coated on the ITO NW arrays as the solar light-absorbing layers. The optimal PEC performance, 0.85% under 100 mW cm-2 of light illumination, is obtained from ~30 μm-long ITO NW, which is covered with ~20 nm-thick TiO2 nanoshell. We finally demonstrate that the ITO NW-based photoelectrode is also compatible with one of the most efficient visible-light sensitizers, the CdS/CdSe quantum dot. Our approach using the transparent conducting 1-D array has wide potential to improve the PEC performances of conventional semiconducting materials through liberation from the poor charge transport. Electronic supplementary information

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

    PubMed

    Pham, Anh-Tuan; Nguyen, Xuan-Quang; Tran, Duc-Huy; Ngoc Phan, Vu; Duong, Thanh-Tung; Nguyen, Duy-Cuong

    2016-08-19

    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%.

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

    NASA Astrophysics Data System (ADS)

    Pham, Anh-Tuan; Nguyen, Xuan-Quang; Tran, Duc-Huy; Phan, Vu Ngoc; Duong, Thanh-Tung; Nguyen, Duy-Cuong

    2016-08-01

    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%.

  14. Correlative infrared-electron nanoscopy reveals the local structure-conductivity relationship in zinc oxide nanowires

    NASA Astrophysics Data System (ADS)

    Stiegler, J. M.; Tena-Zaera, R.; Idigoras, O.; Chuvilin, A.; Hillenbrand, R.

    2012-10-01

    High-resolution characterization methods play a key role in the development, analysis and optimization of nanoscale materials and devices. Because of the various material properties, only a combination of different characterization techniques provides a comprehensive understanding of complex functional materials. Here we introduce correlative infrared-electron nanoscopy, a novel method yielding transmission electron microscope and infrared near-field images of one and the same nanostructure. While transmission electron microscopy provides structural information up to the atomic level, infrared near-field imaging yields nanoscale maps of chemical composition and conductivity. We demonstrate the method's potential by studying the relation between conductivity and crystal structure in ZnO nanowire cross-sections. The combination of infrared conductivity maps and the local crystal structure reveals a radial free-carrier gradient, which inversely correlates to the density of extended crystalline defects. Our method opens new avenues for studying the local interplay between structure, conductivity and chemical composition in widely different material systems.

  15. Silver Nanowire-IZO-Conducting Polymer Hybrids for Flexible and Transparent Conductive Electrodes for Organic Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Yun, Ho Jun; Kim, Se Jung; Hwang, Ju Hyun; Shim, Yong Sub; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2016-10-01

    Solution-processed silver nanowire (AgNW) has been considered as a promising material for next-generation flexible transparent conductive electrodes. However, despite the advantages of AgNWs, some of their intrinsic drawbacks, such as large surface roughness and poor interconnection between wires, limit their practical application in organic light-emitting diodes (OLEDs). Herein, we report a high-performance AgNW-based hybrid electrode composed of indium-doped zinc oxide (IZO) and poly (3,4-ethylenediowythiophene):poly(styrenesulfonate) [PEDOT:PSS]. The IZO layer protects the underlying AgNWs from oxidation and corrosion and tightly fuses the wires together and to the substrate. The PEDOT:PSS effectively reduces surface roughness and increases the hybrid films’ transmittance. The fabricated electrodes exhibited a low sheet resistance of 5.9 Ωsq‑1 with high transmittance of 86% at 550 nm. The optical, electrical, and mechanical properties of the AgNW-based hybrid films were investigated in detail to determine the structure-property relations, and whether optical or electrical properties could be controlled with variation in each layer’s thickness to satisfy different requirements for different applications. Flexible OLEDs (f-OLEDs) were successfully fabricated on the hybrid electrodes to prove their applicability; their performance was even better than those on commercial indium doped tin oxide (ITO) electrodes.

  16. Silver Nanowire-IZO-Conducting Polymer Hybrids for Flexible and Transparent Conductive Electrodes for Organic Light-Emitting Diodes

    PubMed Central

    Yun, Ho Jun; Kim, Se Jung; Hwang, Ju Hyun; Shim, Yong Sub; Jung, Sun-Gyu; Park, Young Wook; Ju, Byeong-Kwon

    2016-01-01

    Solution-processed silver nanowire (AgNW) has been considered as a promising material for next-generation flexible transparent conductive electrodes. However, despite the advantages of AgNWs, some of their intrinsic drawbacks, such as large surface roughness and poor interconnection between wires, limit their practical application in organic light-emitting diodes (OLEDs). Herein, we report a high-performance AgNW-based hybrid electrode composed of indium-doped zinc oxide (IZO) and poly (3,4-ethylenediowythiophene):poly(styrenesulfonate) [PEDOT:PSS]. The IZO layer protects the underlying AgNWs from oxidation and corrosion and tightly fuses the wires together and to the substrate. The PEDOT:PSS effectively reduces surface roughness and increases the hybrid films’ transmittance. The fabricated electrodes exhibited a low sheet resistance of 5.9 Ωsq−1 with high transmittance of 86% at 550 nm. The optical, electrical, and mechanical properties of the AgNW-based hybrid films were investigated in detail to determine the structure-property relations, and whether optical or electrical properties could be controlled with variation in each layer’s thickness to satisfy different requirements for different applications. Flexible OLEDs (f-OLEDs) were successfully fabricated on the hybrid electrodes to prove their applicability; their performance was even better than those on commercial indium doped tin oxide (ITO) electrodes. PMID:27703182

  17. Doping controlled roughness and defined mesoporosity in chemically etched silicon nanowires with tunable conductivity

    NASA Astrophysics Data System (ADS)

    McSweeney, W.; Lotty, O.; Mogili, N. V. V.; Glynn, C.; Geaney, H.; Tanner, D.; Holmes, J. D.; O'Dwyer, C.

    2013-07-01

    By using Si(100) with different dopant type (n++-type (As) or p-type (B)), we show how metal-assisted chemically etched (MACE) nanowires (NWs) can form with rough outer surfaces around a solid NW core for p-type NWs, and a unique, defined mesoporous structure for highly doped n-type NWs. We used high resolution electron microscopy techniques to define the characteristic roughening and mesoporous structure within the NWs and how such structures can form due to a judicious choice of carrier concentration and dopant type. The n-type NWs have a mesoporosity that is defined by equidistant pores in all directions, and the inter-pore distance is correlated to the effective depletion region width at the reduction potential of the catalyst at the silicon surface in a HF electrolyte. Clumping in n-type MACE Si NWs is also shown to be characteristic of mesoporous NWs when etched as high density NW layers, due to low rigidity (high porosity). Electrical transport investigations show that the etched nanowires exhibit tunable conductance changes, where the largest resistance increase is found for highly mesoporous n-type Si NWs, in spite of their very high electronic carrier concentration. This understanding can be adapted to any low-dimensional semiconducting system capable of selective etching through electroless, and possibly electrochemical, means. The process points to a method of multiscale nanostructuring NWs, from surface roughening of NWs with controllable lengths to defined mesoporosity formation, and may be applicable to applications where high surface area, electrical connectivity, tunable surface structure, and internal porosity are required.

  18. Carbon Nanotube/Cu Nanowires/Epoxy Composite Mats with Improved Thermal and Electrical Conductivity.

    PubMed

    Xing, Yajuan; Cao, Wei; Li, Wei; Chen, Hongyuan; Wang, Miao; Wei, Hanxing; Hu, Dongmei; Chen, Minghai; Li, Qingwen

    2015-04-01

    Polymer composites with carbon nanofillers have been regarded as a promising candidate for electronic package materials. The challenge for such materials is to increase the electrical and thermal conductivity of the composites. Herein, we reported an epoxy composite film with high thermal and electrical conductivity that were prepared by loading high volume fraction of well-dispersed multi-walled carbon nanotubes (MWCNTs, around 50 nm in diameter, 1-10 µm in length) and copper nanowires (Cu NWs, 60-70 nm in diameter, 1-5 µm in length) in epoxy matrix. The MWCNT-Cu NW hybrid mats were prepared by a vacuum filtration method with an optimum Cu NW content of 50 wt%. The hybrid mats was then impregnated by epoxy solution to prepare epoxy composite films. The epoxy was modified by the toughening agent to make the composite films tough and flexible. The loading fraction of MWCNTs and Cu NWs was tuned by controlling the viscosity of epoxy solution. A remarkable synergetic effect between the MWCNTs and Cu NWs in improving the electrical and thermal conductivity of epoxy composites was demonstrated. The results showed that the electrical conductivity of nanocomposites with 42.5 wt% epoxy was 1500 S/m, and the thermal conductivity was 2.83 W/m K, which was 10.1 times of the neat epoxy. Its thermal resistance was as low as 1% of the pure epoxy. And the mechanical properties of composites were also investigated. These robust and flexible nanocomposites showed prospective applications as thermal interface materials (TIMs) in the electronic industry.

  19. Carbon Nanotube Networks Reinforced by Silver Nanowires with Improved Optical Transparency and Conductivity

    NASA Astrophysics Data System (ADS)

    Martine, Patricia; Fakhimi, Azin; Lin, Ling; Jurewicz, Izabela; Dalton, Alan; Zakhidov, Anvar A.; Baughman, Ray H.

    2015-03-01

    We have fabricated highly transparent and conductive free-standing nanocomposite thin film electrodes by adding silver nanowires (AgNWs) to dry-spun Multiwall Carbon Nanotube (MWNT) aerogels. This nanocomposite exhibits desirable properties such as high optical transmittance, excellent flexibility and enhanced electrical conductivity. The incorporation of the AgNWs to the MWNT aerogels was accomplished by using a spray coating method. The optical transparency and sheet resistance of the nanocomposite was tuned by adjusting the concentration of AgNWs, back pressure and nozzle distance of the spray gun to the MWNT aerogel during deposition. As the solvent evaporated, the aerogel MWNT bundles densified via surface tension which caused the MWNT bundles to collapse. This adjustable process was responsible in forming well defined apertures that increased the nanocomposite's transmittance up to 90 percent. Via AgNWs percolation and random interconnections between separate MWNT bundles in the aerogel matrix, the sheet resistance decreased from 1 K ohm/sq to less than 100 ohm/sq. Alan G. MacDiarmid NanoTech Institute

  20. Self-aligned nanoforest in silicon nanowire for sensitive conductance modulation.

    PubMed

    Seol, Myeong-Lok; Ahn, Jae-Hyuk; Choi, Ji-Min; Choi, Sung-Jin; Choi, Yang-Kyu

    2012-11-14

    A self-aligned and localized nanoforest structure is constructed in a top-down fabricated silicon nanowire (SiNW). The surface-to-volume ratio (SVR) of the SiNW is enhanced due to the local nanoforest formation. The conductance modulation property of the SiNWs, which is an important characteristic in sensor and charge transfer based applications, can be largely enhanced. For the selective modification of the channel region, localized Joule-heating and subsequent metal-assisted chemical etching (mac-etch) are employed. The nanoforest is formed only in the channel region without misalignment due to the self-aligned process of Joule-heating. The modified SiNW is applied to a porphyrin-silicon hybrid device to verify the enhanced conductance modulation. The charge transfer efficiency between the porphyrin and the SiNW, which is caused by external optical excitation, is clearly increased compared to the initial SiNW. The effect of the local nanoforest formation is enhanced when longer etching times and larger widths are used.

  1. Nanoscale Chemical and Electrical Stabilities of Graphene-covered Silver Nanowire Networks for Transparent Conducting Electrodes

    PubMed Central

    Kim, Seong Heon; Choi, Woon Ih; Kim, Kwang Hee; Yang, Dae Jin; Heo, Sung; Yun, Dong-Jin

    2016-01-01

    The hybrid structure of Ag nanowires (AgNWs) covered with graphene (Gr) shows synergetic effects on the performance of transparent conducting electrodes (TCEs). However, these effects have been mainly observed via large-scale characterization, and precise analysis at the nanoscale level remains inadequate. Here, we present the nanoscale verification and visualization of the improved chemical and electrical stabilities of Gr-covered AgNW networks using conductive atomic force microscopy (C-AFM), Auger electron spectroscopy (AES), and X-ray photoelectron spectroscopy (XPS) combined with the gas cluster ion beam (GCIB) sputtering technique. Specifically by transferring island Gr on top of the AgNW network, we were able to create samples in which both covered and uncovered AgNWs are simultaneously accessible to various surface-characterization techniques. Furthermore, our ab initio molecular dynamics (AIMD) simulation elucidated the specific mechanistic pathway and a strong propensity for AgNW sulfidation, even in the presence of ambient oxidant gases. PMID:27620453

  2. Novel method of ordering silver nanowires for synthesizing flexible films and their conductivity

    NASA Astrophysics Data System (ADS)

    Liu, Silin; Liu, Haitao; Huang, Zhaohui; Fang, Minghao; Liu, Yan-gai; Wu, Xiaowen; He, Can

    2016-11-01

    In this research, ordered silver nanowires (NWs) were transferred to flexible, freestanding nanofibrillated cellulose (NFC) thin film. Silver NWs were synthesized via a solution chemistry method and arranged by a novel assemble method at the oil-water-air, three phase interface. The transparent nanopaper was made of NFC through vacuum suction filtrated method. Then the arranged Ag NWs were transferred to the surface of the nanopaper using a relatively simple method to form a compound, nanopaper/Ag NWs. X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, atomic force microscopy, and transmission electron microscope were taken to characterize the phase and the morphology of the as-prepared products. Characterization of the as-synthesized nanopaper/Ag NWs indicated that they were compounded physically and the Ag NWs were well crystalline. The as-synthesized nanopaper showed well translucency. The nanopaper/Ag NWs showed excellent flexibility and conductivity. The as-synthesized products have the potential application in flexible conductor. This study may provide an effective strategy to design and construct nano-metallic materials with multitudinous features and potential applications in electric devices sensors, flexible devices and conductive materials.

  3. Thermal conductivity of bulk and nanowire Mg₂SixSn1–x alloys from first principles

    DOE PAGES

    Li, Wu; Lindsay, L.; Broido, D. A.; ...

    2012-11-29

    The lattice thermal conductivity (κ) of the thermoelectric materials, Mg₂Si, Mg₂Sn, and their alloys, are calculated for bulk and nanowires, without adjustable parameters. We find good agreement with bulk experimental results. For large nanowire diameters, size effects are stronger for the alloy than for the pure compounds. For example, in 200 nm diameter nanowires κ is lower than its bulk value by 30%, 20%, and 20% for Mg₂Si₀.₆Sn₀.₄, Mg₂Si, and Mg₂Sn, respectively. For nanowires less than 20 nm thick, the relative decrease surpasses 50%, and it becomes larger in the pure compounds than in the alloy. At room temperature, κmore » of Mg₂SixSn1–x is less sensitive to nanostructuring size effects than SixGe1–x, but more sensitive than PbTexSe1–x. This suggests that further improvement of Mg₂SixSn1–x as a nontoxic thermoelectric may be possible.« less

  4. Rheology of cellulose nanofibrils/silver nanowires suspension for the production of transparent and conductive electrodes by screen printing

    NASA Astrophysics Data System (ADS)

    Hoeng, Fanny; Denneulin, Aurore; Reverdy-Bruas, Nadège; Krosnicki, Guillaume; Bras, Julien

    2017-02-01

    With the aim of processing silver nanowires-based electrodes using screen printing process, this study proposes to evaluate the suitability of cellulose nanofibrils (CNF) as a thickening agent for providing a high viscosity silver nanowires screen printing ink. Rheology of CNF suspension has been specifically investigated according to screen printing process requirements using both rotational and oscillating rheology. It has been found that CNF indeed act as a thickener and stabilizer for the silver nanowires suspension. However, the solid dominant visco-elastic behavior of the CNF suspension was not suitable for screen printing and leads to defects within the printed film. CNF visco-elastic properties were modified by adding hydroxypropylmethyl cellulose (HPMC) to the suspension. Homogeneous transparent conductive layers have been obtained when using CNF-HPMC as a matrix for silver nanowires. The screen printed layers were characterized and performances of Rsh = 12 ± 5 Ω□-1 and T%500nm = 74,8% were achieved without any additional post-treatment to the film.

  5. Effect of Ag nanowire addition into nanoparticle paste on the conductivity of Ag patterns printed by gravure offset method.

    PubMed

    Ok, Ki-Hun; Lee, Chan-Jae; Kwak, Min-Gi; Choi, Duck-Kyun; Kim, Kwang-Seok; Jung, Seung-Boo; Kim, Jong-Woong

    2014-11-01

    This paper focuses on the effect of Ag nanowire addition into a commercial Ag nanopaste and the printability evaluation of the mixed paste by the gravure offset printing methodology. Ag nanowires were synthesized by a modified polyol method, and a small amount of them was added into a commercial metallic paste based on Ag nanoparticles of 50 nm in diameter. Two annealing temperatures were selected for comparison, and electrical conductivity was measured by four point probe method. As a result, the hybrid mixture could be printed by the gravure offset method for patterning fine lines up to 15 μm width with sharp edges and scarce spreading. The addition of the Ag nanowires was significantly efficient for enhancement of electrical conductivity of the printed lines annealed at a low temperature (150 degrees C), while the effect was somewhat diluted in case of high temperature annealing (200 degrees C). The experimental results were discussed with the conduction mechanism in the printed conductive circuits with a schematic description of the electron flows in the printed lines.

  6. Investigation of optimal silver nanowires film as conductive wires for LED

    NASA Astrophysics Data System (ADS)

    Wu, I. C.; Yang, T. L.; Pan, C. T.; Chen, Y. C.; Hung, K. H.

    2015-03-01

    In the study, the Polyol reduction process was used to fabricate silver nanowires (AgNWs). In the experiment, the ratio of PVP/Ag, silver seed, AgNO3 and the amount of ethylene glycol (EG) were adopted to design orthogonal array with a constant temperature and heating time and the synthesis parameters of AgNWs were obtained. Therefore, the optimal AgNWs solution was obtained, followed by centrifuging to obtain AgNWs which were used to fabricate AgNWs film. The scanning electron microscope (SEM), Fourier Transform Infrared Spectroscope (FTIR), Energy Dispersive Spectrometer (EDS) and four-point probe were used to measure the sheet resistant and transmittance of AgNWs film. Moreover, the AgNWs film was adopted to be the conductive wires of LED. From the experiment results, the synthesis parameter of 15ml EG, 0.01g AgCl, ratio 2 of PVP/Ag and 0.22g AgNO3 could be used to fabricate optimal AgNWs with 45nm average diameter, 5μm average length and aspect ratio of 110. The sheet resistance and transmittance of film fabricated by centrifuged AgNWs was 0.1252 Ω/sq and 70%, respectively. Furthermore, the luminance of LED with conductive wires made of AgNWs film was better than that made of commercial silver plastic. In the future, the AgNWs film can be broadly applied to the conductive films of touch electric products, LCD display and solar panels.

  7. Improved Flexible Transparent Conductive Electrodes based on Silver Nanowire Networks by a Simple Sunlight Illumination Approach

    PubMed Central

    Kou, Pengfei; Yang, Liu; Chang, Cheng; He, Sailing

    2017-01-01

    Silver nanowire (Ag NW) networks have attracted wide attention as transparent electrodes for emerging flexible optoelectronics. However, the sheet resistance is greatly limited by large wire-to-wire contact resistances. Here, we propose a simple sunlight illumination approach to remarkably improve their electrical conductivity without any significant degradation of the light transmittance. Because the power density is extremely low (0.1 W/cm2, 1-Sun), only slight welding between Ag NWs has been observed. Despite this, a sheet resistance of <20 Ω/sq and transmittance of ~87% at wavelength of 550 nm as well as excellent mechanical flexibility have still been achieved for Ag NW networks after sunlight illumination for 1 hour or longer, which are significant upgrades over those of ITO. Slight plasmonic welding together with the associated self-limiting effect has been investigated by numerical simulations and further verified experimentally through varied solar concentrations. Due to the reduced resistance, high-performance transparent film heaters as well as efficient defrosters have been demonstrated, which are superior to the previously-reported Ag NW based film heaters. Since the sunlight is environmentally friendly and easily available, sophisticated or expensive facilities are not necessary. Our findings are particularly meaningful and show enormous potential for outdoor applications. PMID:28169343

  8. Silver Nanowire Transparent Conductive Electrodes for High-Efficiency III-Nitride Light-Emitting Diodes

    PubMed Central

    Oh, Munsik; Jin, Won-Yong; Jun Jeong, Hyeon; Jeong, Mun Seok; Kang, Jae-Wook; Kim, Hyunsoo

    2015-01-01

    Silver nanowires (AgNWs) have been successfully demonstrated to function as next-generation transparent conductive electrodes (TCEs) in organic semiconductor devices owing to their figures of merit, including high optical transmittance, low sheet resistance, flexibility, and low-cost processing. In this article, high-quality, solution-processed AgNWs with an excellent optical transmittance of 96.5% at 450 nm and a low sheet resistance of 11.7 Ω/sq were demonstrated as TCEs in inorganic III-nitride LEDs. The transmission line model applied to the AgNW contact to p-GaN showed that near ohmic contact with a specific contact resistance of ~10−3 Ωcm2 was obtained. The contact resistance had a strong bias-voltage (or current-density) dependence: namely, field-enhanced ohmic contact. LEDs fabricated with AgNW electrodes exhibited a 56% reduction in series resistance, 56.5% brighter output power, a 67.5% reduction in efficiency droop, and a approximately 30% longer current spreading length compared to LEDs fabricated with reference TCEs. In addition to the cost reduction, the observed improvements in device performance suggest that the AgNWs are promising for application as next-generation TCEs, to realise brighter, larger-area, cost-competitive inorganic III-nitride light emitters. PMID:26333768

  9. Universal conductance fluctuations in Dirac semimetal C d3A s2 nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Li-Xian; Wang, Shuo; Li, Jin-Guang; Li, Cai-Zhen; Yu, Dapeng; Liao, Zhi-Min

    2016-10-01

    Three-dimensional Dirac semimetals host bulk Dirac fermions characterized by a linear dispersion relation in momentum space along all three dimensions. It has been theoretically predicted that the breaking of C4 rotational crystalline symmetry in the Dirac semimetal C d3A s2 may give rise to the massive Dirac fermions. Here we report the phase-coherent transport in C d3A s2 nanowires studied by measuring the universal conductance fluctuations (UCFs). It is found that the UCF amplitude is largely suppressed at the Dirac point by sweeping the magnetic field at different gate voltages, which is ascribed to the breaking of the C4 rotational symmetry-induced band-gap opening. The temperature dependence of resistance demonstrates a magnetic-field-induced metal-insulator transition, consisting of the band-gap opening. Moreover, the UCF amplitude is reduced by a factor of ˜2 √{2 } in the presence of a magnetic field, suggesting the phase transition from a Dirac-to-Weyl semimetal by breaking time-reversal symmetry.

  10. Silver nanowires for transparent conductive electrode to GaN-based light-emitting diodes

    SciTech Connect

    Jeong, Gyu-Jae; Lee, Jae-Hwan; Han, Sang-Hyun; Lee, Sung-Nam; Jin, Won-Yong; Kang, Jae-Wook

    2015-01-19

    Transparent, conductive, and uniform Ag nanowires (NWs) were introduced to improve the optical performance of GaN-based light-emitting diodes (LEDs) by a spin-coating technique. The Ag NWs acted as a current spreading layer, exhibiting high transmittance and low sheet resistance, and ultimately leading to high performance GaN-based LEDs with an ultra large size of 5 × 5 mm{sup 2}. Compared to the transmittance of conventional LEDs without Ag NWs, the relative transmittance of LEDs with Ag NWs was approximately 90% of the overall wavelength region. However, the electroluminescence (EL) intensity of LED with Ag NWs was much higher than that of conventional LEDs without Ag NWs for injection current above 45 mA. In addition, the EL full width at half maximum of LEDs with Ag NWs was much lower than that of conventional LEDs without Ag NWs. Based on these results, we believe that the enhanced optical performance of ultra large LEDs was due to an increase in the current spreading effect.

  11. Reduced haze of transparent conductive films by smaller diameter silver nanowires.

    PubMed

    Menamparambath, Mini Mol; Yang, Kihyuk; Kim, Hyeong Hoon; Bae, Oh Seung; Jeong, Mun Seok; Choi, Jae-Young; Baik, Seunghyun

    2016-11-18

    Silver nanowires (Ag NWs) have received considerable attention for flexible transparent conductive films (TCFs) since they provide a relatively low sheet resistance at a high transmittance. However, the diffuse light scattering, haze, has been regarded as a hurdle to achieve clarity of films. Here we revisit the Mie scattering theory to calculate the extinction and scattering coefficients of Ag NWs which were employed to estimate haze of TCFs. The theory predicted a decrease in haze with a decrease in Ag NW diameter which was supported by experimental investigations carried out using Ag NWs with 5 different diameters (17.6, 19.9, 22.5, 24.3, and 29.6 nm). Overall, excellent properties of TCFs (haze = 0.21%-1.8%, transmittance = 95.33%-98.45%, sheet resistance = 20.87-81.76 Ω sq(-1)) were obtained. Ag NWs with a diameter of 17.6 nm provided minimum haze values at equivalent sheet resistances (e.g., haze = 0.21%, transmittance = 98.45%, sheet resistance = 77.36 Ω sq(-1)) compared with ones with lager diameters and the controls in literatures. This work investigated the interdependence between haze and NW diameter and might provide a design guide for flexible Ag NW TCFs.

  12. Improved Flexible Transparent Conductive Electrodes based on Silver Nanowire Networks by a Simple Sunlight Illumination Approach.

    PubMed

    Kou, Pengfei; Yang, Liu; Chang, Cheng; He, Sailing

    2017-02-07

    Silver nanowire (Ag NW) networks have attracted wide attention as transparent electrodes for emerging flexible optoelectronics. However, the sheet resistance is greatly limited by large wire-to-wire contact resistances. Here, we propose a simple sunlight illumination approach to remarkably improve their electrical conductivity without any significant degradation of the light transmittance. Because the power density is extremely low (0.1 W/cm(2), 1-Sun), only slight welding between Ag NWs has been observed. Despite this, a sheet resistance of <20 Ω/sq and transmittance of ~87% at wavelength of 550 nm as well as excellent mechanical flexibility have still been achieved for Ag NW networks after sunlight illumination for 1 hour or longer, which are significant upgrades over those of ITO. Slight plasmonic welding together with the associated self-limiting effect has been investigated by numerical simulations and further verified experimentally through varied solar concentrations. Due to the reduced resistance, high-performance transparent film heaters as well as efficient defrosters have been demonstrated, which are superior to the previously-reported Ag NW based film heaters. Since the sunlight is environmentally friendly and easily available, sophisticated or expensive facilities are not necessary. Our findings are particularly meaningful and show enormous potential for outdoor applications.

  13. Reduced haze of transparent conductive films by smaller diameter silver nanowires

    NASA Astrophysics Data System (ADS)

    Mol Menamparambath, Mini; Yang, Kihyuk; Kim, Hyeong Hoon; Bae, Oh Seung; Jeong, Mun Seok; Choi, Jae-Young; Baik, Seunghyun

    2016-11-01

    Silver nanowires (Ag NWs) have received considerable attention for flexible transparent conductive films (TCFs) since they provide a relatively low sheet resistance at a high transmittance. However, the diffuse light scattering, haze, has been regarded as a hurdle to achieve clarity of films. Here we revisit the Mie scattering theory to calculate the extinction and scattering coefficients of Ag NWs which were employed to estimate haze of TCFs. The theory predicted a decrease in haze with a decrease in Ag NW diameter which was supported by experimental investigations carried out using Ag NWs with 5 different diameters (17.6, 19.9, 22.5, 24.3, and 29.6 nm). Overall, excellent properties of TCFs (haze = 0.21%-1.8%, transmittance = 95.33%-98.45%, sheet resistance = 20.87-81.76 Ω sq-1) were obtained. Ag NWs with a diameter of 17.6 nm provided minimum haze values at equivalent sheet resistances (e.g., haze = 0.21%, transmittance = 98.45%, sheet resistance = 77.36 Ω sq-1) compared with ones with lager diameters and the controls in literatures. This work investigated the interdependence between haze and NW diameter and might provide a design guide for flexible Ag NW TCFs.

  14. Improved Flexible Transparent Conductive Electrodes based on Silver Nanowire Networks by a Simple Sunlight Illumination Approach

    NASA Astrophysics Data System (ADS)

    Kou, Pengfei; Yang, Liu; Chang, Cheng; He, Sailing

    2017-02-01

    Silver nanowire (Ag NW) networks have attracted wide attention as transparent electrodes for emerging flexible optoelectronics. However, the sheet resistance is greatly limited by large wire-to-wire contact resistances. Here, we propose a simple sunlight illumination approach to remarkably improve their electrical conductivity without any significant degradation of the light transmittance. Because the power density is extremely low (0.1 W/cm2, 1-Sun), only slight welding between Ag NWs has been observed. Despite this, a sheet resistance of <20 Ω/sq and transmittance of ~87% at wavelength of 550 nm as well as excellent mechanical flexibility have still been achieved for Ag NW networks after sunlight illumination for 1 hour or longer, which are significant upgrades over those of ITO. Slight plasmonic welding together with the associated self-limiting effect has been investigated by numerical simulations and further verified experimentally through varied solar concentrations. Due to the reduced resistance, high-performance transparent film heaters as well as efficient defrosters have been demonstrated, which are superior to the previously-reported Ag NW based film heaters. Since the sunlight is environmentally friendly and easily available, sophisticated or expensive facilities are not necessary. Our findings are particularly meaningful and show enormous potential for outdoor applications.

  15. Ultra-high aspect ratio copper nanowires as transparent conductive electrodes for dye sensitized solar cells

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaozhao; Mankowski, Trent; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2016-09-01

    We report the synthesis of ultra-high aspect ratio copper nanowires (CuNW) and fabrication of CuNW-based transparent conductive electrodes (TCE) with high optical transmittance (>80%) and excellent sheet resistance (Rs <30 Ω/sq). These CuNW TCEs are subsequently hybridized with aluminum-doped zinc oxide (AZO) thin-film coatings, or platinum thin film coatings, or nickel thin-film coatings. Our hybrid transparent electrodes can replace indium tin oxide (ITO) films in dye-sensitized solar cells (DSSCs) as either anodes or cathodes. We highlight the challenges of integrating bare CuNWs into DSSCs, and demonstrate that hybridization renders the solar cell integrations feasible. The CuNW/AZO-based DSSCs have reasonably good open-circuit voltage (Voc = 720 mV) and short-circuit current-density (Jsc = 0.96 mA/cm2), which are comparable to what is obtained with an ITO-based DSSC fabricated with a similar process. Our CuNW-Ni based DSSCs exhibit a good open-circuit voltage (Voc = 782 mV) and a decent short-circuit current (Jsc = 3.96 mA/cm2), with roughly 1.5% optical-to-electrical conversion efficiency.

  16. Copper nanowire-graphene core-shell nanostructure for highly stable transparent conducting electrodes.

    PubMed

    Ahn, Yumi; Jeong, Youngjun; Lee, Donghwa; Lee, Youngu

    2015-03-24

    A copper nanowire-graphene (CuNW-G) core-shell nanostructure was successfully synthesized using a low-temperature plasma-enhanced chemical vapor deposition process at temperatures as low as 400 °C for the first time. The CuNW-G core-shell nanostructure was systematically characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, Raman, and X-ray photoelectron spectroscopy measurements. A transparent conducting electrode (TCE) based on the CuNW-G core-shell nanostructure exhibited excellent optical and electrical properties compared to a conventional indium tin oxide TCE. Moreover, it showed remarkable thermal oxidation and chemical stability because of the tight encapsulation of the CuNW with gas-impermeable graphene shells. The potential suitability of CuNW-G TCE was demonstrated by fabricating bulk heterojunction polymer solar cells. We anticipate that the CuNW-G core-shell nanostructure can be used as an alternative to conventional TCE materials for emerging optoelectronic devices such as flexible solar cells, displays, and touch panels.

  17. Parametric optimization of Nd-YVO4 laser for straight scribing on silver nanowire based conductive thin films by Taguchi method

    NASA Astrophysics Data System (ADS)

    Chuang, Ho-Chiao; Lee, Wen-Fu

    2014-04-01

    This study presents parameter optimization of laser scribing on silver nanowire based conductive thin films and a high-precision Nd-YVO4 (wavelength, 532 nm) laser is used to perform scribing experiments to replace the traditional wet etching process. The laser beam is directly focused on conductive thin films and vaporizes the silver nanowire which is coated on the thin film; consequently it is a non-polluting processes. The main objective of this study is to perform laser scribing experiments to cut off the silver nanowire on the thin film without damaging the flexible PET (Polyethylene terephthalate) substrate.

  18. High carrier concentration ZnO nanowire arrays for binder-free conductive support of supercapacitors electrodes by Al doping.

    PubMed

    Zheng, Xin; Sun, Yihui; Yan, Xiaoqin; Sun, Xu; Zhang, Guangjie; Zhang, Qian; Jiang, Yaru; Gao, Wenchao; Zhang, Yue

    2016-12-15

    Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. Here, we prepared in situ Al-doped ZnO nanowire arrays by using continuous flow injection (CFI) hydrothermal method to promote the conductivity. This reasonable method offers highly stable precursor concentration for doping that effectively avoid the appearance of the low conductivity ZnO nanosheets. Benefit from this, three orders of magnitude rise of the carrier concentration from 10(16)cm(-3) to 10(19)cm(-3) can be achieved compared with the common hydrothermal (CH) mothed in Mott-Schottky measurement. Possible effect of Al-doping was discussed by first-principle theory. On this basis, Al-doped ZnO nanowire arrays was developed as a binder-free conductive support for supercapacitor electrodes and high capacitance was triggered. It is owing to the dramatically decreased transfer resistance induced by the growing free-moving electrons and holes. Our results have a profound significance not merely in the controlled synthesis of other doping nanomaterials by co-precipitation method but also in the application of binder-free energy materials or other materials.

  19. Electron-beam irradiation induced conductivity in ZnS nanowires as revealed by in situ transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Liu, Baodan; Bando, Yoshio; Wang, Mingsheng; Zhi, Chunyi; Fang, Xiaosheng; Tang, Chengchun; Mitome, Masanori; Golberg, Dmitri

    2009-08-01

    Electron transport variations in individual ZnS nanowires synthesized through a chemical vapor deposition process were in situ studied in transmission electron microscope under convergent electron-beam irradiation (EBI). It was found that the transport can dramatically be enhanced using proper irradiation conditions. The conductivity mechanism was revealed based on a detailed study of microstructure and composition evolutions under irradiation. EBI-induced Zn-rich domains' appearance and related O doping were mainly responsible for the conductivity improvements. First-principles theoretical calculations additionally indicated that the generation of midbands within a ZnS band gap might also contribute to the improved conductivity.

  20. Conducting properties of nearly depleted ZnO nanowire UV sensors fabricated by dielectrophoresis.

    PubMed

    García Núñez, C; García Marín, A; Nanterne, P; Piqueras, J; Kung, P; Pau, J L

    2013-10-18

    ZnO nanowires (NWs) with different radii (rNW) have been aligned between pre-patterned electrodes using dielectrophoresis (DEP) for the fabrication of high gain UV sensors. The DEP conditions (voltage amplitude and frequency) and electrode material, geometry and size were optimized to enhance the efficiency during the DEP process. To understand the alignment mechanism of the ZnO NWs, the dielectrophoretic force (FDEP) was analyzed as a function of the DEP conditions and NW dimensions. These studies showed that the DEP alignment process tends to trap NWs with a smaller radius. The effects of NW size on device performance were analyzed by means of I-V measurements in darkness and under illumination (200 nm < λ < 600 nm). In darkness, the NW resistance increases as rNW decreases due to the reduction of the conduction volume, until saturation is reached for rNW < 65 nm. On the other hand, the NW spectral photoresponse shows high values around 10(8) A W(-1) (measured at 5 V and λ < 370 nm) and follows a linear trend as a function of the NW cross section. In addition, the cut-off wavelength depends on rNW, presenting a clear blue-shift for NWs with a lower radius (rNW < 50 nm). Transient photoresponse studies show that NWs with lower radii have longer rise times and shorter decay times mainly due to surface trapping effects. Regardless of NW size, passivation of the surface using a dielectric capping layer of SiO2 reduces the dynamic range of the photoresponse due to a strong increase of the dark current.

  1. Effect of Surface Layer on Electromechanical Stability of Tweezers and Cantilevers Fabricated from Conductive Cylindrical Nanowires

    NASA Astrophysics Data System (ADS)

    Keivani, Maryam; Koochi, Ali; Sedighi, Hamid M.; Abadyan, Mohamadreza; Farrokhabadi, Amin; Shahedin, Abed Moheb

    2016-12-01

    Herein, the impact of surface layer on the stability of nanoscale tweezers and cantilevers fabricated from nanowires with cylindrical cross section is studied. A modified continuum based on the Gurtin-Murdoch surface elasticity is applied for incorporating the presence of surface layer. Considering the cylindrical geometry of the nanowire, the presence of the Coulomb attraction and dispersion forces are incorporated in the derived formulations. Three different approaches, i.e. numerical differential quadrature method (DQM), an approximated homotopy perturbation method (HPM) and developing lumped parameter model (LPM) have been employed to solve the governing equations. The impact of surface layer on the instability of the system is demonstrated.

  2. Welding of silver nanowire networks via flash white light and UV-C irradiation for highly conductive and reliable transparent electrodes

    NASA Astrophysics Data System (ADS)

    Chung, Wan-Ho; Kim, Sang-Ho; Kim, Hak-Sung

    2016-08-01

    In this work, silver nanowire inks with hydroxypropyl methylcellulose (HPMC) binders were coated on polyethylene terephthalate (PET) substrates and welded via flash white light and ultraviolet C (UV-C) irradiation to produce highly conductive transparent electrodes. The coated silver nanowire films were firmly welded and embedded into PET substrate successfully at room temperature and under ambient conditions using an in-house flash white light welding system and UV-C irradiation. The effects of light irradiation conditions (light energy, irradiation time, pulse duration, and pulse number) on the silver nanowire networks were studied and optimized. Bending fatigue tests were also conducted to characterize the reliability of the welded transparent conductive silver nanowire films. The surfaces of the welded silver nanowire films were analyzed via scanning electron microscopy (SEM), while the transmittance of the structures was measured using a spectrophotometer. From the results, a highly conductive and transparent silver nanowire film with excellent reliability could be achieved at room temperature under ambient conditions via the combined flash white light and UV-C irradiation welding process.

  3. Welding of silver nanowire networks via flash white light and UV-C irradiation for highly conductive and reliable transparent electrodes

    PubMed Central

    Chung, Wan-Ho; Kim, Sang-Ho; Kim, Hak-Sung

    2016-01-01

    In this work, silver nanowire inks with hydroxypropyl methylcellulose (HPMC) binders were coated on polyethylene terephthalate (PET) substrates and welded via flash white light and ultraviolet C (UV-C) irradiation to produce highly conductive transparent electrodes. The coated silver nanowire films were firmly welded and embedded into PET substrate successfully at room temperature and under ambient conditions using an in-house flash white light welding system and UV-C irradiation. The effects of light irradiation conditions (light energy, irradiation time, pulse duration, and pulse number) on the silver nanowire networks were studied and optimized. Bending fatigue tests were also conducted to characterize the reliability of the welded transparent conductive silver nanowire films. The surfaces of the welded silver nanowire films were analyzed via scanning electron microscopy (SEM), while the transmittance of the structures was measured using a spectrophotometer. From the results, a highly conductive and transparent silver nanowire film with excellent reliability could be achieved at room temperature under ambient conditions via the combined flash white light and UV-C irradiation welding process. PMID:27553755

  4. Very long Ag nanowire synthesis and its application in a highly transparent, conductive and flexible metal electrode touch panel.

    PubMed

    Lee, Jinhwan; Lee, Phillip; Lee, Hyungman; Lee, Dongjin; Lee, Seung Seob; Ko, Seung Hwan

    2012-10-21

    The future electronics will be soft, flexible and even stretchable to be more human friendly in the form of wearable computers. However, conventional electronic materials are usually brittle. Recently, carbon based materials are intensively investigated as a good candidate for flexible electronics but with limited mechanical and electrical performances. Metal is still the best material for electronics with great electrical properties but with poor transparency and mechanical performance. Here we present a simple approach to develop a synthesis method for very long metallic nanowires and apply them as new types of high performance flexible and transparent metal conductors as an alternative to carbon nanotubes, graphene and short nanowire based flexible transparent conductors and indium tin oxide based brittle transparent conductors. We found that very long metallic nanowire network conductors combined with a low temperature laser nano-welding process enabled superior transparent flexible conductors with high transmittance and high electrical conductivity. Further, we demonstrated highly flexible metal conductor LED circuits and transparent touch panels. The highly flexible and transparent metal conductors can be mounted on any non-planar surfaces and applied for various opto-electronics and ultimately for future wearable electronics.

  5. Enhancing the optical properties of silver nanowire transparent conducting electrodes by the modification of nanowire cross-section using ultra-violet illumination

    NASA Astrophysics Data System (ADS)

    Hwang, J.; Lee, H.; Woo, Y.

    2016-11-01

    Improvement in the haze and transmittance of the silver nanowire (Ag NW) based transparent conducting electrodes is achieved by illuminating UV light after the Ag NW network formation. The evidences from the experimental analyses and numerical calculations indicate that the enhancement of the optical properties is derived from the modification of the Ag NW cross-section from a pentagonal to a circular shape, as well as the removal of the polyvinylpyrrolidone capping layer on the Ag NW surface. The deformation of the Ag NW cross-section occurs due to heat generation induced by the UV light absorption in the Ag NW, and it provides thermal energy for recrystallization to the Ag atoms on the NW surface, specifically near the corners of the pentagon, resulting in an increase in the radius of the rounded corners.

  6. Enhancement of Interface Characteristics of Neural Probe Based on Graphene, ZnO Nanowires, and Conducting Polymer PEDOT.

    PubMed

    Ryu, Mingyu; Yang, Jae Hoon; Ahn, Yumi; Sim, Minkyung; Lee, Kyung Hwa; Kim, Kyungsoo; Lee, Taeju; Yoo, Seung-Jun; Kim, So Yeun; Moon, Cheil; Je, Minkyu; Choi, Ji-Woong; Lee, Youngu; Jang, Jae Eun

    2017-03-29

    In the growing field of brain-machine interface (BMI), the interface between electrodes and neural tissues plays an important role in the recording and stimulation of neural signals. To minimize tissue damage while retaining high sensitivity, a flexible and a smaller electrode with low impedance is required. However, it is a major challenge to reduce electrode size while retaining the conductive characteristics of the electrode. In addition, the mechanical mismatch between stiff electrodes and soft tissues creates damaging reactive tissue responses. Here, we demonstrate a neural probe structure based on graphene, ZnO nanowires, and conducting polymer that provides flexibility and low impedance performance. A hybrid Au and graphene structure was utilized to achieve both flexibility and good conductivity. Using ZnO nanowires to increase the effective surface area drastically decreased the impedance value and enhanced the signal-to-noise ratio (SNR). A poly[3,4-ethylenedioxythiophene] (PEDOT) coating on the neural probe improved the electrical characteristics of the electrode while providing better biocompatibility. In vivo neural signal recordings showed that our neural probe can detect clearer signals.

  7. Temperature Dependence of Electrical and Thermal Conduction in Single Silver Nanowire

    DTIC Science & Technology

    2015-06-02

    sound speed (2600 m/s) is used to estimate the phonon velocity of silver39. At low temperatures , the phonon-phonon scattering mean free path becomes...depth understanding of the strong structural defect induced electron scattering. The results indicate that, at room temperature , the electrical...resistivity increases by around 4 folds from that of bulk silver. The Debye temperature (151 K) of the silver nanowire is found 36% lower than that (235 K) of

  8. Mussel-Inspired Polydopamine-Functionalized Graphene as a Conductive Adhesion Promoter and Protective Layer for Silver Nanowire Transparent Electrodes.

    PubMed

    Miao, Jinlei; Liu, Haihui; Li, Wei; Zhang, Xingxiang

    2016-05-31

    For the scalable fabrication of transparent electrodes and optoelectronic devices, excellent adhesion between the conductive films and the substrates is essential. In this work, a novel mussel-inspired polydopamine-functionalized graphene/silver nanowire hybrid nanomaterial for transparent electrodes was fabricated in a facile manner. Graphene oxide (GO) was functionalized and reduced by polydopamine while remaining stable in water without precipitation. It is shown that the polydopamine-functionalized GO (PFGO) film adhered to the substrate much more easily and more uniformly than the GO film. The PFGO film had a sheet resistance of ∼3.46 × 10(8) Ω/sq and a transparency of 78.2%, with excellent thermal and chemical stability; these characteristics are appropriate for antistatic coatings. Further reduced PFGO (RPFGO) as a conductive adhesion promoter and protective layer for the Ag nanowire (AgNW) significantly enhanced the adhesion force between AgNW networks and the substrate. The RPFGO-AgNW electrode was found to have a sheet resistance of 63 Ω/sq and a transparency of 70.5%. Moreover, the long-term stability of the RPFGO-AgNW electrode was greatly enhanced via the effective protection of the AgNW by RPFGO. These solution-processed antistatic coatings and electrodes have tremendous potential in the applications of optoelectronic devices as a result of their low production cost and facile processing.

  9. Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials.

    PubMed

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2014-07-21

    To date, there is no experimental characterization of thermal conductivity of semiconductor polymeric individual nanowires embedded in a matrix. This work reports on scanning thermal microscopy measurements in a 3ω configuration to determine how the thermal conductivity of individual nanowires made of a model conjugated polymer (P3HT) is modified when decreasing their diameters. We observe a reduction of thermal conductivity, from λNW = 2.29 ± 0.15 W K(-1) m(-1) to λNW = 0.5 ± 0.24 W K(-1) m(-1), when the diameter of nanowires is reduced from 350 nm to 120 nm, which correlates with the polymer crystal orientation measured by WAXS. Through this work, the foundations for future polymer thermal transport engineering are presented.

  10. A solution-processed molybdenum oxide treated silver nanowire network: a highly conductive transparent conducting electrode with superior mechanical and hole injection properties.

    PubMed

    Chang, Jung-Hao; Chiang, Kai-Ming; Kang, Hao-Wei; Chi, Wei-Jung; Chang, Jung-Hung; Wu, Chih-I; Lin, Hao-Wu

    2015-03-14

    We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq(-1), a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole injection in optoelectronic applications. By utilizing these s-MoOx-treated AgNW TCEs as the anode in ITO-free organic light emitting diodes, promising performance of 29.2 lm W(-1) and 10.3% external quantum efficiency are demonstrated. The versatile, multi-functional s-MoOx treatment presented here paves the way for the use of low-temperature, solution-processed MoOx as both a nanowire linker and a hole injection interfacial layer for future flexible optoelectronic devices.

  11. Paper-based silver-nanowire electronic circuits with outstanding electrical conductivity and extreme bending stability

    NASA Astrophysics Data System (ADS)

    Huang, Gui-Wen; Xiao, Hong-Mei; Fu, Shao-Yun

    2014-07-01

    Here a facile, green and efficient printing-filtration-press (PFP) technique is reported for room-temperature (RT) mass-production of low-cost, environmentally friendly, high performance paper-based electronic circuits. The as-prepared silver nanowires (Ag-NWs) are uniformly deposited at RT on a pre-printed paper substrate to form high quality circuits via vacuum filtration and pressing. The PFP circuit exhibits more excellent electrical property and bending stability compared with other flexible circuits made by existing techniques. Furthermore, practical applications of the PFP circuits are demonstrated.Here a facile, green and efficient printing-filtration-press (PFP) technique is reported for room-temperature (RT) mass-production of low-cost, environmentally friendly, high performance paper-based electronic circuits. The as-prepared silver nanowires (Ag-NWs) are uniformly deposited at RT on a pre-printed paper substrate to form high quality circuits via vacuum filtration and pressing. The PFP circuit exhibits more excellent electrical property and bending stability compared with other flexible circuits made by existing techniques. Furthermore, practical applications of the PFP circuits are demonstrated. Electronic supplementary information (ESI) available: Video of rolling tests; video of the PFP circuit used as flexible cable in a cell phone; video of the application of the circuit as a RFID tag; a detailed method for synthesizing silver nanowires; details of the PFP technique; folding tests for the circuits; air humidity test for the circuit. See DOI: 10.1039/c4nr00846d

  12. Paper-based silver-nanowire electronic circuits with outstanding electrical conductivity and extreme bending stability.

    PubMed

    Huang, Gui-Wen; Xiao, Hong-Mei; Fu, Shao-Yun

    2014-08-07

    Here a facile, green and efficient printing-filtration-press (PFP) technique is reported for room-temperature (RT) mass-production of low-cost, environmentally friendly, high performance paper-based electronic circuits. The as-prepared silver nanowires (Ag-NWs) are uniformly deposited at RT on a pre-printed paper substrate to form high quality circuits via vacuum filtration and pressing. The PFP circuit exhibits more excellent electrical property and bending stability compared with other flexible circuits made by existing techniques. Furthermore, practical applications of the PFP circuits are demonstrated.

  13. Hybrid transparent conductive electrodes with copper nanowires embedded in a zinc oxide matrix and protected by reduced graphene oxide platelets

    NASA Astrophysics Data System (ADS)

    Zhu, Zhaozhao; Mankowski, Trent; Balakrishnan, Kaushik; Shikoh, Ali Sehpar; Touati, Farid; Benammar, Mohieddine A.; Mansuripur, Masud; Falco, Charles M.

    2016-02-01

    Transparent conductive electrodes (TCE) were fabricated by combining three emerging nano-materials: copper nanowires (CuNWs), zinc oxide (ZnO) nano-particulate thin films, and reduced graphene oxide (rGO) platelets. Whereas CuNWs are responsible for essentially all of the electrical conductivity of our thin-film TCEs, the ZnO matrix embeds and strengthens the CuNW network in its adhesion to the substrate, while the rGO platelets provide a protective overcoat for the composite electrode, thereby improving its stability in hot and humid environments. Our CuNW/ZnO/rGO hybrid electrodes deposited on glass substrates have low sheet resistance (Rs ˜ 20 Ω/sq) and fairly high optical transmittance (T550 ˜ 79%). In addition, our hybrid TCEs are mechanically strong and able to withstand multiple scotch-tape peel tests. Finally, these TCEs can be fabricated on rigid glass as well as flexible plastic substrates.

  14. Direct Imaging of the Onset of Electrical Conduction in Silver Nanowire Networks by Infrared Thermography: Evidence of Geometrical Quantized Percolation.

    PubMed

    Sannicolo, Thomas; Muñoz-Rojas, David; Nguyen, Ngoc Duy; Moreau, Stéphane; Celle, Caroline; Simonato, Jean-Pierre; Bréchet, Yves; Bellet, Daniel

    2016-11-09

    Advancement in the science and technology of random metallic nanowire (MNW) networks is crucial for their appropriate integration in many applications including transparent electrodes for optoelectronics and transparent film heaters. We have recently highlighted the discontinuous activation of efficient percolating pathways (EPPs) for networks having densities slightly above the percolation threshold. Such networks exhibit abrupt drops of electrical resistance when thermal or electrical annealing is performed, which gives rise to a "geometrically quantized percolation". In this Letter, lock-in thermography (LiT) is used to provide visual evidence of geometrical quantized percolation: when low voltage is applied to the network, individual "illuminated pathways" can be detected, and new branches get highlighted as the voltage is incrementally increased. This experimental approach has allowed us to validate our original model and map the electrical and thermal distributions in silver nanowire (AgNW) networks. We also study the effects of electrode morphology and wire dimensions on quantized percolation. Furthermore, we demonstrate that the network failure at high temperature can also be governed by a quantized increase of the electrical resistance, which corresponds to the discontinuous destruction of individual pathways (antipercolation). More generally, we demonstrate that LiT is a promising tool for the detection of conductive subclusters as well as hot spots in AgNW networks.

  15. Silver nanowire based flexible electrodes with improved properties: High conductivity, transparency, adhesion and low haze

    SciTech Connect

    Kiran Kumar, A.B.V.; Wan Bae, Chang; Piao, Longhai Kim, Sang-Ho

    2013-08-01

    Graphical abstract: This graphical abstract illustrates the schematic representation of the main drawbacks and rectifications for AgNWs based transparent electrodes. - Highlights: • Films exhibited low sheet resistance and optical properties with R{sub s} ≤ 30 Ω/□ and T ≥ 90%. • We decreased haze to 2% by controlling AgNWs length, diameter, and concentration. • We achieved good adhesion for AgNWs on PET film. • There is no significant change in resistance in the bending angle from 0° to 180°, and on twisting. - Abstract: Recent work has been focusing on solution processable transparent electrodes for various applications including solar cells and displays. As well as, the research aims majorly at silver nanowires (AgNWs) to replace ITO. We enhance the transparent electrode performance as a function of optical and mechanical properties with low sheet resistance, by controlling the AgNWs accept ratios, ink composition, and processing conditions. The nanowire network of transparent films agrees with the 2D percolation law. The film transmittance values at 550 nm are coping with a reference ITO film. Sheet resistance and haze values are suitable for flexible electronic applications. We fabricate transparent flexible film using a low-cost processing technique.

  16. Nanoscale current spreading analysis in solution-processed graphene oxide/silver nanowire transparent electrodes via conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Shaw, Joseph E.; Perumal, Ajay; Bradley, Donal D. C.; Stavrinou, Paul N.; Anthopoulos, Thomas D.

    2016-05-01

    We use conductive atomic force microscopy (CAFM) to study the origin of long-range conductivity in model transparent conductive electrodes composed of networks of reduced graphene oxide (rGOX) and silver nanowires (AgNWs), with nanoscale spatial resolution. Pristine networks of rGOX (1-3 monolayers-thick) and AgNWs exhibit sheet resistances of ˜100-1000 kΩ/□ and 100-900 Ω/□, respectively. When the materials are deposited sequentially to form bilayer rGOX/AgNW electrodes and thermally annealed at 200 °C, the sheet resistance reduces by up to 36% as compared to pristine AgNW networks. CAFM was used to analyze the current spreading in both systems in order to identify the nanoscale phenomena responsible for this effect. For rGOX networks, the low intra-flake conductivity and the inter-flake contact resistance is found to dominate the macroscopic sheet resistance, while for AgNW networks the latter is determined by the density of the inter-AgNW junctions and their associated resistance. In the case of the bilayer rGOX/AgNWs' networks, rGOX flakes are found to form conductive "bridges" between AgNWs. We show that these additional nanoscopic electrical connections are responsible for the enhanced macroscopic conductivity of the bilayer rGOX/AgNW electrodes. Finally, the critical role of thermal annealing on the formation of these nanoscopic connections is discussed.

  17. Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device

    PubMed Central

    Deng, M. T.; Yu, C. L.; Huang, G. Y.; Larsson, M.; Caroff, P.; Xu, H. Q.

    2014-01-01

    We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. At zero magnetic field, well-defined Coulomb diamonds and the Kondo effect are observed. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with Majorana fermion physics in such a hybrid topological system. PMID:25434375

  18. Parity independence of the zero-bias conductance peak in a nanowire based topological superconductor-quantum dot hybrid device.

    PubMed

    Deng, M T; Yu, C L; Huang, G Y; Larsson, M; Caroff, P; Xu, H Q

    2014-12-01

    We explore the signatures of Majorana fermions in a nanowire based topological superconductor-quantum dot-topological superconductor hybrid device by charge transport measurements. At zero magnetic field, well-defined Coulomb diamonds and the Kondo effect are observed. Under the application of a finite, sufficiently strong magnetic field, a zero-bias conductance peak structure is observed. It is found that the zero-bias conductance peak is present in many consecutive Coulomb diamonds, irrespective of the even-odd parity of the quasi-particle occupation number in the quantum dot. In addition, we find that the zero-bias conductance peak is in most cases accompanied by two differential conductance peaks, forming a triple-peak structure, and the separation between the two side peaks in bias voltage shows oscillations closely correlated to the background Coulomb conductance oscillations of the device. The observed zero-bias conductance peak and the associated triple-peak structure are in line with Majorana fermion physics in such a hybrid topological system.

  19. Nanowire-based detector

    DOEpatents

    Berggren, Karl K; Hu, Xiaolong; Masciarelli, Daniele

    2014-06-24

    Systems, articles, and methods are provided related to nanowire-based detectors, which can be used for light detection in, for example, single-photon detectors. In one aspect, a variety of detectors are provided, for example one including an electrically superconductive nanowire or nanowires constructed and arranged to interact with photons to produce a detectable signal. In another aspect, fabrication methods are provided, including techniques to precisely reproduce patterns in subsequently formed layers of material using a relatively small number of fabrication steps. By precisely reproducing patterns in multiple material layers, one can form electrically insulating materials and electrically conductive materials in shapes such that incoming photons are redirected toward a nearby electrically superconductive materials (e.g., electrically superconductive nanowire(s)). For example, one or more resonance structures (e.g., comprising an electrically insulating material), which can trap electromagnetic radiation within its boundaries, can be positioned proximate the nanowire(s). The resonance structure can include, at its boundaries, electrically conductive material positioned proximate the electrically superconductive nanowire such that light that would otherwise be transmitted through the sensor is redirected toward the nanowire(s) and detected. In addition, electrically conductive material can be positioned proximate the electrically superconductive nanowire (e.g. at the aperture of the resonant structure), such that light is directed by scattering from this structure into the nanowire.

  20. Highly conductive and stretchable Ag nanowire/carbon nanotube hybrid conductors

    NASA Astrophysics Data System (ADS)

    Woo, Ju Yeon; Kim, Kyun Kyu; Lee, Jongsoo; Kim, Ju Tae; Han, Chang-Soo

    2014-07-01

    Fabricating stretchable conductors through simple, cost-effective and scalable methods is a challenge. Here, we report on an approach used to develop nanowelded Ag nanowire/single-walled carbon nanotube (AgNW/SWCNT) hybrid films to be used as high-performance stretchable conductors. Plasmonic welding, which was done at the junctions of AgNWs in order to form hybrid AgNW/SWCNT conductors on an Ecoflex substrate, enabled excellent electrical and mechanical stability under large tensile strains of over 480% without the need to pre-strain. Furthermore, we demonstrate highly stretchable circuits that are used to power LED arrays. The LED arrays are formed using the plasmonic-welded AgNW/SWCNT/Ecoflex hybrid material, which demonstrates suitability for interconnector applications in flexible electronics.

  1. Correlation Between Heterogeneous Bacterial Attachment Rate Coefficients and Hydraulic Conductivity and Impacts on Field-Scale Bacterial Transport

    SciTech Connect

    Scheibe, Timothy D.

    2002-10-28

    In granular porous media, bacterial transport is often modeled using the advection-dispersion transport equation, modified to account for interactions between the bacteria and grain surfaces (attachment and detachment) using a linear kinetic reaction model. In this paper we examine the relationships among the parameters of the above model in the context of bacterial transport for bioaugmentation. In this context, we wish to quantify the distance to which significant concentrations of bacteria can be transported, as well as the uniformity with which they can be distributed within the subsurface. Because kinetic detachment rates (Kr) are typically much smaller than corresponding attachment rates (Kf), the attachment rate exerts primary control on the distance of bacterial transport. Hydraulic conductivity (K) also plays a significant role because of its direct relationship to the advective velocity and its typically high degree of spatial variability at field scales. Because Kf is related to the velocity, grain size, and porosity of the medium, as is K, we expect that there exists correlation between these two parameters. Previous investigators have assumed a form of correlation between Kf and ln(K) based in part on reparameterization of clean-bed filtration equations in terms of published relations between grain size, effective porosity, and ln(K). The hypotheses examined here are that (1) field-scale relationships between K and Kf can be developed by combining a number of theoretical and empirical results in the context of a heterogeneous aquifer flow model (following a similar approach to previous investigators with some extensions), and (2) correlation between K and Kf will enhance the distance of field-scale bacterial transport in granular aquifers. We test these hypotheses using detailed numerical models and observations of field-scale bacterial transport in a shallow sandy aquifer within the South Oyster Site near Oyster, Virginia, USA.

  2. High-reproducibility, flexible conductive patterns fabricated with silver nanowire by drop or fit-to-flow method

    NASA Astrophysics Data System (ADS)

    Tao, Yu; Tao, Yuxiao; Wang, Liuyang; Wang, Biaobing; Yang, Zhenguo; Tai, Yanlong

    2013-03-01

    An unusual strategy was designed to fabricate conductive patterns with high reproducibility for flexible electronics by drop or fit-to-flow method. Silver nanowire (SNW) ink with surface tension of 36.9 mN/m and viscosity of 13.8 mPa s at 20°C was prepared and characterized using a field emission transmission electron microscope, X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, and four-point probe. Polydimethylsiloxane (PDMS) pattern as template was fabricated by spin coating (500 rpm), baking at 80°C for 3 h, and laser cutting. The prepared SNW ink can flow along the trench of the PDMS pattern spontaneously, especially after plasma treatment with oxygen, and show a low resistivity of 12.9 μΩ cm after sintering at 125°C for 30 min. In addition, an antenna pattern was also prepared to prove the feasibility of the approach.

  3. High-reproducibility, flexible conductive patterns fabricated with silver nanowire by drop or fit-to-flow method

    PubMed Central

    2013-01-01

    An unusual strategy was designed to fabricate conductive patterns with high reproducibility for flexible electronics by drop or fit-to-flow method. Silver nanowire (SNW) ink with surface tension of 36.9 mN/m and viscosity of 13.8 mPa s at 20°C was prepared and characterized using a field emission transmission electron microscope, X-ray diffractometer, thermogravimetric analyzer, scanning electron microscope, and four-point probe. Polydimethylsiloxane (PDMS) pattern as template was fabricated by spin coating (500 rpm), baking at 80°C for 3 h, and laser cutting. The prepared SNW ink can flow along the trench of the PDMS pattern spontaneously, especially after plasma treatment with oxygen, and show a low resistivity of 12.9 μΩ cm after sintering at 125°C for 30 min. In addition, an antenna pattern was also prepared to prove the feasibility of the approach. PMID:23537333

  4. AlGaInP LED with low-speed spin-coating silver nanowires as transparent conductive layer.

    PubMed

    Guo, Xia; Guo, Chun Wei; Wang, Cheng; Li, Chong; Sun, Xiao Ming

    2014-12-01

    The low-speed spin-coating method was developed to prepare uniform and interconnected silver nanowires (AgNWs) film with the transmittance of 95% and sheet resistance of 20Ω/sq on glass, which was comparable to ITO. The fitting value of σ dc/σ op of 299.3 was attributed to the spin-coating process. Advantages of this solution-processed AgNW film on AlGaInP light-emitting diodes (LEDs) as transparent conductive layer were explored. The optical output power enhanced 100%, and the wavelength redshift decreased from 12 to 3 nm, which indicated the AgNW films prepared by low-speed spin-coating possessed attractive features for large-scale TCL applications in optoelectronic devices.

  5. Fully solution-processed semitransparent organic solar cells with a silver nanowire cathode and a conducting polymer anode.

    PubMed

    Yim, Jong Hyuk; Joe, Sung-yoon; Pang, Christina; Lee, Kyung Moon; Jeong, Huiseong; Park, Ji-Yong; Ahn, Yeong Hwan; de Mello, John C; Lee, Soonil

    2014-03-25

    We report the fabrication of efficient indium-tin-oxide-free organic solar cells based on poly(3-hexylthiophene-2,5-diyl):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM). All layers of the devices from the lowermost silver nanowire cathode to the uppermost conducting polymer anode are deposited from solution and processed at plastic-compatible temperatures<200 °C. Owing to the absence of an opaque metal electrode, the devices are semitransparent with potential applications in power-generating windows and tandem-cells. The measured power conversion efficiencies (PCEs) of 2.3 and 2.0% under cathode- and anode-side illumination, respectively, match previously reported PCE values for equivalent semitransparent organic solar cells using indium tin oxide.

  6. Correction: Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials

    NASA Astrophysics Data System (ADS)

    Rojo, Miguel Muñoz; Martín, Jaime; Grauby, Stéphane; Borca-Tasciuc, Theodorian; Dilhaire, Stefan; Martin-Gonzalez, Marisol

    2015-02-01

    Correction for `Decrease in thermal conductivity in polymeric P3HT nanowires by size-reduction induced by crystal orientation: new approaches towards thermal transport engineering of organic materials' by Miguel Muñoz Rojo et al., Nanoscale, 2014, 6, 7858-7865.

  7. Nanowire structures and electrical devices

    DOEpatents

    Bezryadin, Alexey; Remeika, Mikas

    2010-07-06

    The present invention provides structures and devices comprising conductive segments and conductance constricting segments of a nanowire, such as metallic, superconducting or semiconducting nanowire. The present invention provides structures and devices comprising conductive nanowire segments and conductance constricting nanowire segments having accurately selected phases including crystalline and amorphous states, compositions, morphologies and physical dimensions, including selected cross sectional dimensions, shapes and lengths along the length of a nanowire. Further, the present invention provides methods of processing nanowires capable of patterning a nanowire to form a plurality of conductance constricting segments having selected positions along the length of a nanowire, including conductance constricting segments having reduced cross sectional dimensions and conductance constricting segments comprising one or more insulating materials such as metal oxides.

  8. A solution-processed molybdenum oxide treated silver nanowire network: a highly conductive transparent conducting electrode with superior mechanical and hole injection properties

    NASA Astrophysics Data System (ADS)

    Chang, Jung-Hao; Chiang, Kai-Ming; Kang, Hao-Wei; Chi, Wei-Jung; Chang, Jung-Hung; Wu, Chih-I.; Lin, Hao-Wu

    2015-02-01

    We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq-1, a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole injection in optoelectronic applications. By utilizing these s-MoOx-treated AgNW TCEs as the anode in ITO-free organic light emitting diodes, promising performance of 29.2 lm W-1 and 10.3% external quantum efficiency are demonstrated. The versatile, multi-functional s-MoOx treatment presented here paves the way for the use of low-temperature, solution-processed MoOx as both a nanowire linker and a hole injection interfacial layer for future flexible optoelectronic devices.We demonstrate the fabrication of solution-processed MoOx-treated (s-MoOx) silver nanowire (AgNW) transparent conductive electrodes (TCEs) utilizing low-temperature (sub-100 °C) processes. The s-MoOx aggregates around the AgNW and forms gauze-like MoOx thin films between the mesh, which can effectively lower the sheet resistance by more than two orders of magnitude. Notably, these s-MoOx-treated AgNW TCEs exhibit a combination of several promising characteristics, such as a high and broad transmittance across a wavelength range of 400 to 1000 nm, transmission of up to 96.8%, a low sheet resistance of 29.8 ohm sq-1, a low haze value of 0.90%, better mechanical properties against bending and adhesion tests, and preferable gap states for efficient hole

  9. Hydrothermal Fabrication of Silver Nanowires-Silver Nanoparticles-Graphene Nanosheets Composites in Enhancing Electrical Conductive Performance of Electrically Conductive Adhesives

    PubMed Central

    Ma, Hongru; Zeng, Jinfeng; Harrington, Steven; Ma, Lei; Ma, Mingze; Guo, Xuhong; Ma, Yanqing

    2016-01-01

    Silver nanowires-silver nanoparticles-graphene nanosheets (AgNWs-AgNPs-GN) hybrid nanomaterials were fabricated through a hydrothermal method by using glucose as a green reducing agent. The charge carriers of AgNWs-AgNPs-GN passed through defect regions in the GNs rapidly with the aid of the AgNW and AgNP building blocks, leading to high electrical conductivity of electrically conductive adhesives (ECA) filled with AgNWs-AgNPs-GN. The morphologies of synthesized AgNWs-AgNPs-GN hybrid nanomaterials were characterized by field emission scanning electron microscope (FESEM), and high resolution transmission electron microscopy (HRTEM). X-ray diffraction (XRD) and laser confocal micro-Raman spectroscopy were used to investigate the structure of AgNWs-AgNPs-GN. The resistance of cured ECAs was investigated by the four-probe method. The results indicated AgNWs-AgNPs-GN hybrid nanomaterials exhibited excellent electrical properties for decreasing the resistivity of electrically conductive adhesives (ECA). The resistivity of ECA was 3.01 × 10−4 Ω·cm when the content of the AgNWs-AgNPs-GN hybrid nanomaterial was 0.8 wt %. PMID:28335247

  10. Nano-Welding of Ag Nanowires Using Rapid Thermal Annealing for Transparent Conductive Films.

    PubMed

    Oh, Jong Sik; Oh, Ji Soo; Shin, Jae Hee; Yeom, Geun Young; Kim, Kyong Nam

    2015-11-01

    Ag nanowire (NW) films obtained by the spraying the Ag NWs on the substrates were nano-welded by rapid thermal annealing (RTA) process and the effect of RTA process on the change of sheet resistance and optical transmittance of the Ag NW films was investigated. The increased number of Ag NW sprays on the substrate decreased the sheet resistance but also decreased the optical transmittance. By the annealing for 60 sec in a nitrogen environment to 225-250 degrees C, the sheet resistance of Ag NW film could be decreased to about 50%, even though it was accompanied by the slight decrease of optical transmittance less than 5%. The decrease of sheet resistance was related to the nano-welding of the Ag NW junctions and the slight decrease of optical transmittance was related local melting of the Ag NWs and spreading on the substrate surface. Through the nano-welding by RTA process, the Ag NW film with the sheet resistance of -20 Ω/sq. and the optical transmittance of 93% could be obtained.

  11. Tunable emission and conductivity enhancement by tellurium doping in CdS nanowires for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Kamran, Muhammad Arshad; Nabi, Ghulam; Majid, Abdul; Iqbal, Muhammad Waqas; Alharbi, Thamer; Zhang, Yongyou; Zou, Bingsuo

    2017-02-01

    Improvement of the optical and electrical characteristics is essential to get advanced performance from one dimensional (1D) material. Here, we report the first synthesis of a single crystalline Te-doped CdS nanowires (NWs) by a chemical-vapor-deposition (CVD) method. Room temperature photoluminescence (PL) spectra showed that Te concentration plays an important role in tuning emission color from orange to infrared (IR). Decrease in bandgap and PL intensity with increase in Te concentration was observed as compared to undoped CdS NWs. Red and IR emissions were found at 736.5 and 881 nm for doping concentration >6.06%. To our best knowledge, IR emission band has been observed for the first time in CdS NWs. Red-shift of LO phonon mode and its overtone in Raman spectra, and lifetime of red and IR emissions are longer than bandgap of host indicating the doping effect of CdS NWs. Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) of the Te-doped CdS NWs further confirms the presence of Te in the CdS NWs. Output characteristics confirm enhanced output current Ids with the increase in doping concentration. A possible growth mechanism was proposed. Doping technique offers to develop high-quality, a very stable, effective, and easily-applicable way to enhance the performance of one dimensional optoelectronic devices and solar cell applications.

  12. Correlation Between Bacterial Attachment Rate Coefficients and Hydraulic Conductivity and its Effect on Field-Scale Bacterial Transport

    SciTech Connect

    Scheibe, Timothy D.; Dong, Hailiang; Xie, YuLong

    2007-06-01

    It has been widely observed in field experiments that the apparent rate of bacterial attachment, particularly as parameterized by the collision efficiency in filtration-based models, decreases with transport distance (i.e., exhibits scale-dependency). This effect has previously been attributed to microbial heterogeneity; that is, variability in cell-surface properties within a single monoclonal population. We demonstrate that this effect could also be interpreted as a field-scale manifestation of local-scale correlation between physical heterogeneity (hydraulic conductivity variability) and reaction heterogeneity (attachment rate coefficient variability). A field-scale model of bacterial transport developed for the South Oyster field research site located near Oyster, Virginia, and observations from field experiments performed at that site, are used as the basis for this study. Three-dimensional Monte Carlo simulations of bacterial transport were performed under four alternative scenarios: 1) homogeneous hydraulic conductivity (K) and attachment rate coefficient (Kf), 2) heterogeneous K, homogeneous Kf, 3) heterogeneous K and Kf with local correlation based on empirical and theoretical relationships, and 4) heterogeneous K and Kf without local correlation. The results of the 3D simulations were analyzed using 1D model approximations following conventional methods of field data analysis. An apparent decrease with transport distance of effective collision efficiency was observed only in the case where the local properties were both heterogeneous and correlated. This effect was observed despite the fact that the local collision efficiency was specified as a constant in the 3D model, and can therefore be interpreted as a scale effect associated with the local correlated heterogeneity as manifested at the field scale.

  13. Silver nanosheet-coated copper nanowire/epoxy resin nanocomposites with enhanced electrical conductivity and wear resistance

    NASA Astrophysics Data System (ADS)

    Zeng, Ningning; Ma, Jingyi; Zhang, Yujuan; Yang, Guangbin; Zhang, Shengmao; Zhang, Pingyu

    2017-03-01

    Silver (Ag) nanosheet-coated Cu nanowires (denoted as Cu@AgNWs) were prepared with a facile transmetalation reaction method. The effect of reaction conditions on the morphology and microstructure of the as-prepared Cu@AgNWs was investigated, and the thermal stability of Cu@AgNWs was evaluated by thermogravimetric analysis. In the meantime, the as-prepared Cu@AgNWs were used as the nanofillers of epoxy resin (EP), and their effect on the electrical conductivity and wear resistance of the EP-matrix composites was examined. Results indicate that the as-prepared Cu@AgNWs consist of CuNW core and Ag nanosheet shell. The Ag nanosheet shell can well inhibit the oxidation of the CuNW core, thereby providing the as-prepared Cu@AgNWs with good thermal stability even at an elevated temperature of 230 °C. The reaction temperature, Cu/Ag molar ratio, Cu dispersion concentration, and the dropping speed of silver ammonia reagent are suggested to be 40 °C, 5:1, 1% (mass fraction), and poured directly, respectively. Resultant Cu@AgNWs exhibit desired morphology and performance and can effectively increase the electrical conductivity and wear resistance of EP. This could make it feasible for the Cu@AgNW-EP composite to be applied as an electrostatic conductive material.

  14. Quadrature conductivity: A quantitative indicator of bacterial abundance in porous media

    SciTech Connect

    Chi Zhang; Andre Revil; Yoshiko Fujita; Junko Munakata-Marr; George Redden

    2014-09-01

    ABSTRACT The abundance and growth stages of bacteria in subsurface porous media affect the concentrations and distributions of charged species within the solid-solution interfaces. Therefore, spectral induced polarization (SIP) measurements can be used to monitor changes in bacterial biomass and growth stage. Our goal was to gain a better understanding of the SIP response of bacteria present in a porous material. Bacterial cell surfaces possess an electric double layer and therefore become polarized in an electric field. We performed SIP measurements over the frequency range of 0.1–1 kHz on cell suspensions alone and cell suspensions mixed with sand at four pore water conductivities. We used Zymomonas mobilis at four different cell densities (in- cluding the background). The quadrature conductivity spectra exhibited two peaks, one around 0.05–0.10 Hz and the other around 1–10 Hz. Because SIP measurements on bacterial suspensions are typically made at frequencies greater than 1 Hz, these peaks have not been previously reported. In the bac-terial suspensions in growth medium, the quadrature conduc-tivity at peak I was linearly proportional to the density of the bacteria. For the case of the suspensions mixed with sands, we observed that peak II presented a smaller increase in the quadrature conductivity with the cell density. A comparison of the experiments with and without sand grains illustrated the effect of the porous medium on the overall quadrature con- ductivity response (decrease in the amplitude and shift of the peaks to the lower frequencies). Our results indicate that for a given porous medium, time-lapse SIP has potential for mon- itoring changes in bacterial abundance within porous media.

  15. Tuning Thermal and Electrical Conductivities in Structure-engineered Nanowires for High-efficiency Thermoelectric Devices

    DTIC Science & Technology

    2011-09-30

    materials, which determines the efficiency of thermoelectric devices, because the three parameters such as Seebeck coefficient (S), electrical conductivity...predicted to be enhanced by size effects and quantum confinement effects providing the opportunities to control S, σ and κ independently. In...efficiency of thermoelectric devices, because the three parameters such as Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity

  16. Ammonia plasma modification towards a rapid and low temperature approach for tuning electrical conductivity of ZnO nanowires on flexible substrates.

    PubMed

    Ong, Wei Li; Zhang, Chun; Ho, Ghim Wei

    2011-10-05

    Though the fabrication of ZnO nanostructures is economical and low temperature, the lack of a facile, reliable and low temperature methodology to tune its electrical conductivity has prevented it from competing with other semiconductors. Here, we carried out surface modification of ZnO nanowires using ammonia plasma with no heat treatment, and studied their electrical properties over an extended time frame of more than a year. The fabrication of flexible devices was demonstrated via various methods of transferring and aligning as-synthesized ZnO nanowires onto plastic substrates. Hall measurements of the plasma modified ZnO nanowires revealed p-type conductivity. The N1s peak was present in the X-ray photoelectron spectrum of the surface modified ZnO, showing the presence of ammonia complexes. Low temperature photoluminescence showed evidence of acceptor-bound exciton emission. The resulting electrical devices, a chemical sensor and p-n homojunction, show the tunable electrical response of the surface modified ZnO nanowires.

  17. Non-contact measurement of the electrical conductivity and coverage density of silver nanowires for transparent electrodes using Terahertz spectroscopy

    NASA Astrophysics Data System (ADS)

    Park, Sung-Hyeon; Chung, Wan-Ho; Kim, Hak-Sung

    2017-02-01

    In this work, a terahertz time-domain spectroscopy (THz-TDS) imaging technique was used for non-contact measurement of the conductivity and coverage density (D C) of silver nanowires (SNWs) as transparent electrodes. The reflection mode of THz-TDS with an incident angle of 30° was used, and the sheet resistance (R sh) of SNW films was measured using the four-point probe method. The correlations between the THz reflection ratio and R sh were studied by comparing the results of the four-point probe method and the measured THz reflection ratios. Also, the D C of SNWs was evaluated using THz waveforms with a general refractivity formula. This result matched well with a conventional approximation method using a scanning electron microscope image. Furthermore, defects in the SNWs could be easily detected using the THz-TDS imaging technique. The non-contact THz-TDS measurement method that we developed is expected to be a promising technique for non-contact measurement of the R sh and D C for transparent conductive electrodes.

  18. Nonmonotonic Diameter Dependence of Thermal Conductivity of Extremely Thin Si Nanowires: Competition between Hydrodynamic Phonon Flow and Boundary Scattering.

    PubMed

    Zhou, Yanguang; Zhang, Xiaoliang; Hu, Ming

    2017-02-08

    By carefully and systematically performing Green-Kubo equilibrium molecular dynamics simulations, we report that the thermal conductivity (κ) of Si nanowires (NWs) does not diverge but converges and increases steeply when NW diameter (D) becomes extremely small (dκ/dD < 0), a long debate of one-dimensional heat conduction in history. The κ of the thinnest possible Si NWs reaches a superhigh level that is as large as more than 1 order of magnitude higher than its bulk counterpart. The abnormality is explained in terms of the dominant normal (N) process (energy and momentum conservation) of low frequency acoustic phonons that induces hydrodynamic phonon flow in the Si NWs without being scattered. With D increasing, the downward shift of optical phonons triggers strong Umklapp (U) scattering with acoustic phonons and attenuates the N process, leading to the regime of phonon boundary scattering (dκ/dD < 0). The two competing mechanisms result in nonmonotonic diameter dependence of κ with minima at critical diameter of 2-3 nm. Our results unambiguously demonstrate the converged κ and the clear trend of κ ∼ D for extremely thin Si NWs by fully elucidating the competition between the hydrodynamic phonon flow and phonon boundary scattering.

  19. Cl-doped ZnO nanowires with metallic conductivity and their application for high-performance photoelectrochemical electrodes.

    PubMed

    Wang, Fei; Seo, Jung-Hun; Li, Zhaodong; Kvit, Alexander V; Ma, Zhenqiang; Wang, Xudong

    2014-01-22

    Doping semiconductor nanowires (NWs) for altering their electrical and optical properties is a critical strategy for tailoring the performance of nanodevices. ZnO NWs grown by hydrothermal method are pervasively used in optoelectronic, photovoltaic, and piezoelectric energy-harvesting devices. We synthesized in situ Cl-doped ZnO NWs with metallic conductivity that would fit seamlessly with these devices and improve their performance. Possible Cl doping mechanisms were discussed. UV-visible absorption spectroscopy confirmed the visible light transparency of Cl-doped ZnO NWs. Cl-doped ZnO NW/TiO2 core/shell-structured photoelectrochemical (PEC) anode was fabricated to demonstrate the application potential of highly conductive ZnO NWs. Higher photocurrent density and overall PEC efficiency compared with the undoped ZnO NW-based device were achieved. The successful doping and low resistivity of ZnO could unlock the potential of ZnO NWs for applications in low-cost flexible transparent electrodes.

  20. Improved Performance by SiO2 Hollow Nanospheres for Silver Nanowire-Based Flexible Transparent Conductive Films.

    PubMed

    Zhang, Liwen; Zhang, Longjiang; Qiu, Yejun; Ji, Yang; Liu, Ya; Liu, Hong; Li, Guangji; Guo, Qiuquan

    2016-10-12

    Flexible transparent conductive films (TCFs) have attracted tremendous interest thanks to the rapid development of portable/flexible/wearable electronics. TCFs on the basis of silver nanowires (AgNWs) with excellent performance are becoming an efficient alternative to replace the brittle transparent metal oxide. In this study, a promising method was developed by introducing SiO2 hollow nanospheres (SiO2-HNSs) into the film to significantly improve the performance of AgNW-based TCFs. Since SiO2-HNSs have opposite charges to AgNWs, the strong attraction had promoted a uniform distribution of AgNWs and made the distance between AgNWs closer, which could decrease the contact resistance greatly. The introduction of SiO2 layer remarkably enhanced the transmission of visible light and the conductivity. In addition, the TCFs constructed by AgNWs and SiO2-HNSs showed much higher thermal stability and adhesive force than those by only AgNWs. As an example, the transmission of AgNW/SiO2-HNS-coated poly(ethylene terephthalate) (PET) could increase about 14.3% in comparison to AgNW-coated PET. Typically, a AgNW/SiO2-HNS-based TCF with a sheet resistance of about 33 Ω/sq and transmittance of about 98.0% (excluding substrate) could be obtained with excellent flexibility, adhesion, and thermal stability. At last some devices were fabricated.

  1. Electrical Characterization of Zn and ZnO Nanowires Grown on PEDOT:PSS Conductive Polymer Thin Films by Physical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Chamberlin, Matthew; Constantin, Costel

    2011-10-01

    Physical vapor deposition (PVD) techniques offer tremendous possibilities for easy fabrication of nanostructure arrays for use in thin film electronics. In this study we examine inorganic/organic heterojunctions produced by growing conductive Zn and semiconductive ZnO nanowire arrays on organic conductive PEDOT:PSS polymer thin films using simple and cost-effective PVD methods. Understanding the electrical properties of these hybrid films are of particular interest for applications in organic electronics. However, traditional systems for measuring conductivity and resistivity of thin films by the Van Der Pauw method prove problematic when dealing with soft polymeric surfaces. We present here electrical studies of ZnO- and Zn-nanowire/PEDOT:PSS heterojunctions using a modified 2-point probe method constructed from inexpensive and easily available materials.

  2. Effects of carbon dioxide on bacterial growth parameters in milk as measured by conductivity.

    PubMed

    Martin, J D; Werner, B G; Hotchkiss, J H

    2003-06-01

    Inhibition of bacterial growth by dissolved carbon dioxide (CO2) has been well established in many foods including dairy foods. However, the effects of dissolved CO2 on specific growth parameters such as length of lag phase, time to maximum growth rate, and numbers of organisms at the stationary phase have not been quantified for organisms of concern in milk. The effect of dissolved CO2 concentrations of 0.6 to 61.4 mM on specific bacterial growth parameters in raw or single organism inoculated sterile milk was determined at 15 degrees C by conductance. Commingled raw or sterile milks were amended to a final concentration of 0.5 mg/ml each of urea and arginine HCl. Sterile milks were inoculated singly with one of six different microorganisms to a final concentration of approximately 10(2) to 10(3) cfu/ml; raw milk was adjusted to a final indigenous bacterial population of approximately 10(3) cfu/ml. Conductivity of the milk was recorded every 60 s over 4 to 5 d in a circulating apparatus at 15 degrees C. Conductivity values were fit to Gompertz equations and growth parameters calculated. Conductance correlated with plate counts and was satisfactory for monitoring microbial growth. Data fit the Gompertz equation with high correlation (R2 = 0.96 to 1.00). In all cases, dissolved CO2 significantly inhibited growth of raw milk bacteria, influencing lag, exponential, and stationary growth phases as well as all tested monocultures.

  3. Thermal conductivity of bulk and nanowire Mg₂SixSn1–x alloys from first principles

    SciTech Connect

    Li, Wu; Lindsay, L.; Broido, D. A.; Stewart, Derek A.; Mingo, Natalio

    2012-11-29

    The lattice thermal conductivity (κ) of the thermoelectric materials, Mg₂Si, Mg₂Sn, and their alloys, are calculated for bulk and nanowires, without adjustable parameters. We find good agreement with bulk experimental results. For large nanowire diameters, size effects are stronger for the alloy than for the pure compounds. For example, in 200 nm diameter nanowires κ is lower than its bulk value by 30%, 20%, and 20% for Mg₂Si₀.₆Sn₀.₄, Mg₂Si, and Mg₂Sn, respectively. For nanowires less than 20 nm thick, the relative decrease surpasses 50%, and it becomes larger in the pure compounds than in the alloy. At room temperature, κ of Mg₂SixSn1–x is less sensitive to nanostructuring size effects than SixGe1–x, but more sensitive than PbTexSe1–x. This suggests that further improvement of Mg₂SixSn1–x as a nontoxic thermoelectric may be possible.

  4. Universal conductance of nanowires near the superconductor-metal quantum transition.

    PubMed

    Sachdev, Subir; Werner, Philipp; Troyer, Matthias

    2004-06-11

    We consider wires near a zero temperature transition between superconducting and metallic states. The critical theory obeys hyperscaling, which leads to a universal frequency, temperature, and length dependence of the conductance; quantum and thermal phase slips are contained within this critical theory. Normal, superconducting, and mixed (SN) leads on the wire determine distinct universality classes. For the SN case, wires near the critical point have a universal dc conductance which is independent of the length of the wire at low temperatures.

  5. The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes

    PubMed Central

    Seo, Tae Hoon; Lee, Seula; Min, Kyung Hyun; Chandramohan, S.; Park, Ah Hyun; Lee, Gun Hee; Park, Min; Suh, Eun-Kyung; Kim, Myung Jong

    2016-01-01

    This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs. PMID:27387274

  6. The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes

    NASA Astrophysics Data System (ADS)

    Seo, Tae Hoon; Lee, Seula; Min, Kyung Hyun; Chandramohan, S.; Park, Ah Hyun; Lee, Gun Hee; Park, Min; Suh, Eun-Kyung; Kim, Myung Jong

    2016-07-01

    This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs.

  7. The role of graphene formed on silver nanowire transparent conductive electrode in ultra-violet light emitting diodes.

    PubMed

    Seo, Tae Hoon; Lee, Seula; Min, Kyung Hyun; Chandramohan, S; Park, Ah Hyun; Lee, Gun Hee; Park, Min; Suh, Eun-Kyung; Kim, Myung Jong

    2016-07-08

    This paper reports a highly reliable transparent conductive electrode (TCE) that integrates silver nanowires (AgNWs) and high-quality graphene as a protecting layer. Graphene with minimized defects and large graphene domains has been successfully obtained through a facile two-step growth approach. Ultraviolet light emitting diodes (UV-LEDs) were fabricated with AgNWs or hybrid electrodes where AgNWs were combined with two-step grown graphene (A-2GE) or conventional one-step grown graphene (A-1GE). The device performance and reliability of the UV-LEDs with three different electrodes were compared. The A-2GE offered high figure of merit owing to the excellent UV transmittance and reduced sheet resistance. As a consequence, the UV-LEDs made with A-2GE demonstrated reduced forward voltage, enhanced electroluminescence (EL) intensity, and alleviated efficiency droop. The effects of joule heating and UV light illumination on the electrode stability were also studied. The present findings prove superior performance of the A-2GE under high current injection and continuous operation of UV LED, compared to other electrodes. From our observation, the A-2GE would be a reliable TCE for high power UV-LEDs.

  8. The effect of driven electron-phonon coupling on the electronic conductance of a polar nanowire

    SciTech Connect

    Mardaani, Mohammad Rabani, Hassan; Esmaili, Esmat; Shariati, Ashrafalsadat

    2015-08-07

    A semi-classical model is proposed to explore the effect of electron-phonon coupling on the coherent electronic transport of a polar chain which is confined between two rigid leads in the presence of an external electric field. To this end, we construct the model by means of Green's function technique within the nearest neighbor tight-binding and harmonic approximations. For a time-periodic electric field, the atomic displacements from the equilibrium positions are obtained precisely. The result is then used to compute the electronic transport properties of the chain within the Peierls-type model. The numerical results indicate that the conductance of the system shows interesting behavior in some special frequencies. For each special frequency, there is an electronic quasi-state in which the scattering of electrons by vibrating atoms reaches maximum. The system electronic conductance decreases dramatically at the strong electron-phonon couplings and low electron energies. In the presence of damping forces, the electron-phonon interaction has a less significant effect on the conductance.

  9. Highly conductive and ultrastretchable electric circuits from covered yarns and silver nanowires.

    PubMed

    Cheng, Yin; Wang, Ranran; Sun, Jing; Gao, Lian

    2015-04-28

    Stretchable electronics, as a promising research frontier, has achieved progress in a variety of sophisticated applications. The realization of stretchable electronics frequently involves the demand for a stretchable conductor as an electrical circuit. However, it still remains a challenge to fabricate high-performance (working strain exceeding 200%) stretchable conductors. Here, we present for the first time a facile, cost-effective, and scalable method for manufacturing ultrastretchable composite fibers with a "twining spring" configuration: cotton fibers twining spirally around a polyurethane fiber. The composite fiber possesses a high conductivity up to 4018 S/cm, which remains as high as 688 S/cm at 500% tensile strain. In addition, the conductivity of the composite fiber (initial conductivity of 4018 S/cm) remains perfectly stable after 1000 bending events and levels off at 183 S/cm after 1000 cyclic stretching events of 200% strain. Stretchable LED arrays are integrated efficiently utilizing the composite fibers as a stretchable electric wiring system, demonstrating the potential applications in large-area stretchable electronics. The biocompatibility of the composite fiber is verified, opening up its prospects in the field of implantable devices. Our fabrication strategy is also versatile for the preparation of other specially functionalized composite fibers with superb stretchability.

  10. Highly stable and flexible silver nanowire-graphene hybrid transparent conducting electrodes for emerging optoelectronic devices.

    PubMed

    Lee, Donghwa; Lee, Hyungjin; Ahn, Yumi; Jeong, Youngjun; Lee, Dae-Young; Lee, Youngu

    2013-09-07

    A new AgNW-graphene hybrid transparent conducting electrode (TCE) was prepared by dry-transferring a chemical vapor deposition (CVD)-grown monolayer graphene onto a pristine AgNW TCE. The AgNW-graphene hybrid TCE exhibited excellent optical and electrical properties as well as mechanical flexibility. The AgNW-graphene hybrid TCE showed highly enhanced thermal oxidation and chemical stabilities because of the superior gas-barrier property of the graphene protection layer. Furthermore, the organic solar cells with the AgNW-graphene hybrid TCE showed excellent photovoltaic performance as well as superior long-term stability under ambient conditions.

  11. Record Low Thermal Conductivity of Polycrystalline Si Nanowire: Breaking the Casimir Limit by Severe Suppression of Propagons.

    PubMed

    Zhou, Yanguang; Hu, Ming

    2016-10-12

    Thermoelectrics offer an attractive pathway for addressing an important niche in the globally growing landscape of energy demand. Nanoengineering existing low-dimensional thermoelectric materials pertaining to realizing fundamentally low thermal conductivity has emerged as an efficient route to achieve high energy conversion performance for advanced thermoelectrics. In this paper, by performing nonequilibrium and Green-Kubo equilibrium molecular dynamics simulations we report that the thermal conductivity of Si nanowires (NWs) in polycrystalline form can reach a record low value substantially below the Casimir limit, a theory of diffusive boundary limit that regards the direction-averaged mean free path is limited by the characteristic size of the nanostructures. The astonishingly low thermal conductivity of polycrystalline Si NW is 269 and 77 times lower with respect to that of bulk Si and pristine Si NW, respectively, and is even only about one-third of the value of the purely amorphous Si NW at room temperature. By examining the mode level phonon behaviors including phonon group velocities, lifetime, and so forth, we identify the mechanism of breaking the Casimir limit as the strong localization of the middle and high frequency phonon modes, which leads to a prominent decrease of effective mean free path of the heat carriers including both propagons and diffusons. The contribution of the propagons to the overall thermal transport is further quantitatively characterized and is found to be dramatically suppressed in polycrystalline Si NW form as compared with bulk Si, perfect Si NW, and pure amorphous Si NW. Consequently, the diffusons, which transport the heat through overlap with other vibrations, carry the majority of the heat in polycrystalline Si NWs. We also proposed approach of introducing "disorder" in the polycrystalline Si NWs that could eradicate the contribution of propagons to achieve an even lower thermal conductivity than that ever thought possible

  12. Development of Hierarchical Polymer@Pd Nanowire-Network: Synthesis and Application as Highly Active Recyclable Catalyst and Printable Conductive Ink.

    PubMed

    Mir, Sajjad Husain; Ochiai, Bungo

    2016-06-01

    A facile one-pot approach for preparing hierarchical nanowire-networks of hollow polymer@Pd nanospheres is reported. First, polymer@Pd hollow nanospheres were produced through metal-complexation-induced phase separation with functionalized graft copolymers and subsequent self-assembly of PdNPs. The nanospheres hierarchically assembled into the nanowire-network upon drying. The Pd nanowire-network served as an active catalyst for Mizoroki-Heck and Suzuki-Miyaura coupling reactions. As low as 500 μmol % Pd was sufficient for quantitative reactions, and the origin of the high activity is ascribed to the highly active sites originating from high-index facets, kinks, and coalesced structures. The catalyst can be recycled via simple filtration and washing, maintaining its high activity owing to the micrometer-sized hierarchical structure of the nanomaterial. The polymer@Pd nanosphere also served as a printable conductive ink for a translucent grid pattern with excellent horizontal conductivity (7.5×10(5) S m(-1)).

  13. Highly flexible, transparent, conductive and antibacterial films made of spin-coated silver nanowires and a protective ZnO layer

    NASA Astrophysics Data System (ADS)

    Chen, Youxin; Lan, Wei; Wang, Junya; Zhu, Ranran; Yang, Zhiwei; Ding, Delei; Tang, Guomei; Wang, Kairong; Su, Qing; Xie, Erqing

    2016-02-01

    We prepared highly flexible, transparent, conductive and antibacterial film by spin coating a silver nanowire suspension on a poly (ethylene terephthalate) (PET) substrate. The ZnO layer covered the conductive silver nanowire (AgNW) network to protect the metal nanowires from oxidization and enhance both wire-to-wire adhesion and wire-to-substrate adhesion. It is found that the number of AgNW coatings correlates with both the sheet resistance (Rs) and the transmittance of the AgNW/ZnO composite films. An excellent 92% optical transmittance in the visible range and a surface sheet resistance of only 9 Ω sq-1 has been achieved, respectively. Even after bending 1000 times (5 mm bending radius), we found no significant change in the sheet resistance or optical transmittance. The real-time sheet resistance measured as a function of bending radius also remains stable even at the smallest measured bending radius (1 mm). The AgNW/ZnO composite films also show antibacterial effects which could be useful for the fabrication of wearable electronic devices.

  14. Composites of Polyindole nanowires within Silicate and Aluminosilicate hosts with distinct conductive properties

    NASA Astrophysics Data System (ADS)

    Juárez, J. M.; Gómez Costa, M. B.; Anunziata, O. A.

    2016-07-01

    Nanostructured silicate SBA-15 and aluminosilicate AlSBA-15 were synthesized in order to prepare polyindole composites. The Silica mesoporous materials were prepared by sol- gel method and alumination using post-synthesis technique and analysed by different methods (XRD, BET, TEM, and FTIR). Polyindole/host composites were prepared by in situ oxidative polymerization of pre-adsorbed indole, employing Cl3Fe as oxidant. TG, FTIR, BET, XRD, SEM and TEM were used to characterize the resulting composites. These studies show that the porous structures of the materials are preserved after polymerization, and polyindole is found within the porous channels. The composites have an electrical conductivity range between values higher than those of the pure chemically synthesized polyindole, close to those of the pure electrochemically synthesized polymer and lower than those of the pure chemically synthesized polymer, in the order of 10-8 S/cm.

  15. Modeling the electrical conduction in DNA nanowires: charge transfer and lattice fluctuation theories.

    PubMed

    Behnia, S; Fathizadeh, S

    2015-02-01

    An analytical approach is proposed for the investigation of the conductivity properties of DNA. The charge mobility of DNA is studied based on an extended Peyrard-Bishop-Holstein model when the charge carrier is also subjected to an external electrical field. We have obtained the values of some of the system parameters, such as the electron-lattice coupling constant, by using the mean Lyapunov exponent method. On the other hand, the electrical current operator is calculated directly from the lattice operators. Also, we have studied Landauer resistance behavior with respect to the external field, which could serve as the interface between chaos theory tools and electronic concepts. We have examined the effect of two types of electrical fields (dc and ac) and variation of the field frequency on the current flowing through DNA. A study of the current-voltage (I-V) characteristic diagram reveals regions with a (quasi-)Ohmic property and other regions with negative differential resistance (NDR). NDR is a phenomenon that has been observed experimentally in DNA at room temperature. We have tried to study the affected agents in charge transfer phenomena in DNA to better design nanostructures.

  16. Large-scale synthesis of well-dispersed copper nanowires in an electric pressure cooker and their application in transparent and conductive networks.

    PubMed

    Li, Shenjie; Chen, Yanyan; Huang, Lijian; Pan, Daocheng

    2014-05-05

    We present a novel large-scale synthetic method for well-separated copper nanowires (CuNWs) in a commercial electric pressure cooker under mild reaction conditions. CuNWs (∼2.1 g) can be prepared in a batch with the cost of $4.20/g. Well-dispersed polyvinylpyrrolidone-capped CuNWs were obtained via a ligand-exchange method. The transparent and conductive CuNW networks with excellent electrical conductivity and high optical transmittance (30 Ω/□ at 86% transmittance, respectively) were fabricated by a spin-coating process.

  17. Controlled electrodeposition of bismuth nanocatalysts for the solution-liquid-solid synthesis of CdSe nanowires on transparent conductive substrates.

    PubMed

    Reim, Natalia; Littig, Alexander; Behn, Dino; Mews, Alf

    2013-12-11

    Semiconductor nanowires (NWs) composed of cadmium selenide (CdSe) have been directly grown on transparent conductive substrates via the solution-liquid-solid (SLS) approach using electrodeposited bismuth nanoparticles (Bi NPs) as catalyst. Bi NPs were fabricated on indium tin oxide (ITO) surfaces from a bismuth trichloride solution using potentiostatic double-pulse techniques. The size and density of electrodeposited Bi NPs were controlled by the pulse parameters. Since the NW diameter is governed by the dimension of the Bi catalyst, the electrodeposition is a reliable method to synthesize nanowires directly on substrates with a desired size and density. We show that the density can be adjusted from individual NWs on several square micrometer to very dense NW networks. The diameter can be controlled between thick nanowires above 100 nm to very thin NW of 7 nm in diameter, which is well below the respective exciton dimension. Hence, especially the thinnest NWs exhibit diameter-dependent photoluminescence energies as a result of quantum confinement effects in the radial dimension.

  18. Observation of Aharonov-Bohm and Al'tshuler-Aronov-Spivak oscillations in the background of universal conductance fluctuations in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Mtsuko, Davie; Aslan, Tahir; Ncube, Siphephile; Coleman, Christopher; Wamwangi, Daniel; Bhattacharyya, Somnath

    2016-02-01

    Magnetoresistance (MR) oscillations of multiple periodicities are recorded in singly connected silicon nanowires of diameter ≈50 \\text{nm} . At 100 K we observe oscillations of periodicity ≈1.78 \\text{T} and 0.444 T corresponding to h/e and h/4e Aharonov-Bohm (AB) oscillations, whereas at 10 K we record periodicities of 0.98 T, 0.49 T and 0.25 T corresponding to h/e, h/2e (Al'tshuler-Aronov-Spivak (AAS)) and h/4e oscillations. At 2.5 K we find magnetoresistance oscillations with multiple periodicities of 1.3 T, 0.52 T, and 0.325 T corresponding to AB and AAS oscillations. The h/2e and h/4e peaks can be attributed to the interference of time-reversed paths originating from the core orbits that scatter coherently on the surface of the nanowires multiple times. We also observed 20 mT and 60 mT oscillations of small amplitude superimposed on a quasi-periodic background which we attribute to the quantum interference of special surface states associated with skipping orbits that propagate quasi-ballistically. The aperiodic fluctuations in the MR at all temperatures are universal conductance fluctuations (UCF) originating from randomly spaced impurity scattering in the core of the nanowire.

  19. Conduction mechanisms in P(VDF-TrFE)/gold nanowire composites: tunnelling and thermally-activated hopping process near the percolation threshold

    NASA Astrophysics Data System (ADS)

    Ramachandran, Laavanya; Lonjon, Antoine; Demont, Philippe; Dantras, Eric; Lacabanne, Colette

    2016-08-01

    High-aspect ratio gold nanowires were dispersed in a P(VDF-TrFE) matrix to form conducting polymer composites. The composites were found to follow a percolation law, with a low percolation threshold of 2.2%vol and attaining a conductivity value of 100 S m-1. The temperature and frequency dependence of the composites were studied using broadband dielectric spectroscopy. Tunnelling was found to be the main charge transport mechanism at temperatures below -100 °C and a thermally-activated hopping mechanism was determined to be responsible for conduction at temperatures above -100 °C. The correlated barrier hopping model was found to be the best fit to explain the conduction mechanisms in the composites.

  20. Selective formation of tungsten nanowires

    PubMed Central

    2011-01-01

    We report on a process for fabricating self-aligned tungsten (W) nanowires with polycrystalline silicon core. Tungsten nanowires as thin as 10 nm were formed by utilizing polysilicon sidewall transfer technology followed by selective deposition of tungsten by chemical vapor deposition (CVD) using WF6 as the precursor. With selective CVD, the process is self-limiting whereby the tungsten formation is confined to the polysilicon regions; hence, the nanowires are formed without the need for lithography or for additional processing. The fabricated tungsten nanowires were observed to be perfectly aligned, showing 100% selectivity to polysilicon and can be made to be electrically isolated from one another. The electrical conductivity of the nanowires was characterized to determine the effect of its physical dimensions. The conductivity for the tungsten nanowires were found to be 40% higher when compared to doped polysilicon nanowires of similar dimensions. PMID:21970543

  1. Silver Nanowires Binding with Sputtered ZnO to Fabricate Highly Conductive and Thermally Stable Transparent Electrode for Solar Cell Applications.

    PubMed

    Singh, Manjeet; Rana, Tanka R; Kim, SeongYeon; Kim, Kihwan; Yun, Jae Ho; Kim, JunHo

    2016-05-25

    Silver nanowire (AgNW) film has been demonstrated as excellent and low cost transparent electrode in organic solar cells as an alternative to replace scarce and expensive indium tin oxide (ITO). However, the low contact area and weak adhesion with low-lying surface as well as junction resistance between nanowires have limited the applications of AgNW film to thin film solar cells. To resolve this problem, we fabricated AgNW film as transparent conductive electrode (TCE) by binding with a thin layer of sputtered ZnO (40 nm) which not only increased contact area with low-lying surface in thin film solar cell but also improved conductivity by connecting AgNWs at the junction. The TCE thus fabricated exhibited transparency and sheet resistance of 92% and 20Ω/□, respectively. Conductive atomic force microscopy (C-AFM) study revealed the enhancement of current collection vertically and laterally through AgNWs after coating with ZnO thin film. The CuInGaSe2 solar cell with TCE of our AgNW(ZnO) demonstrated the maximum power conversion efficiency of 13.5% with improved parameters in comparison to solar cell fabricated with conventional ITO as TCE.

  2. Nanowire mesh solar fuels generator

    DOEpatents

    Yang, Peidong; Chan, Candace; Sun, Jianwei; Liu, Bin

    2016-05-24

    This disclosure provides systems, methods, and apparatus related to a nanowire mesh solar fuels generator. In one aspect, a nanowire mesh solar fuels generator includes (1) a photoanode configured to perform water oxidation and (2) a photocathode configured to perform water reduction. The photocathode is in electrical contact with the photoanode. The photoanode may include a high surface area network of photoanode nanowires. The photocathode may include a high surface area network of photocathode nanowires. In some embodiments, the nanowire mesh solar fuels generator may include an ion conductive polymer infiltrating the photoanode and the photocathode in the region where the photocathode is in electrical contact with the photoanode.

  3. Using Reactive Transport Modeling to Understand Changes in Electrical Conductivity Associated with Bacterial Growth and Respiration

    NASA Astrophysics Data System (ADS)

    Regberg, A. B.; Singha, K.; Picardal, F.; Brantley, S. L.

    2011-12-01

    Previous research has linked measured changes in the bulk electrical conductivity (σb) of water-saturated sediments to the respiration and growth of anaerobic bacteria. If the mechanism causing this signal is understood and characterized it could be used to identify and monitor zones of bacterial activity in the subsurface. The 1-D reactive transport model PHREEQC was used to understand σb signals by modeling chemical gradients within two column reactors and corresponding changes in effluent chemistry. The flow-through column reactors were packed with Fe(III)-bearing sediment from Oyster, VA and inoculated with an environmental consortia of microorganisms. Influent in the first reactor was amended with 1mM Na-acetate to encourage the growth of iron-reducing bacteria. Influent in the second reactor was amended with 0.1mM Na-Acetate and 2mM NaNO3 to encourage the growth of nitrate-reducing bacteria. While effluent concentrations of acetate, Fe(II), NO3-, NO2-, and NH4+ remained at steady state, we measured a 3-fold increase (0.055 S/m - 0.2 S/m) in σb in the iron-reducing column and a 10-fold increase in σb (0.07 S/m - 0.8 S/m) in the nitrate-reducing column over 198 days. The ionic strength in both reactors remained constant through time indicating that the measured increases in σb were not caused by changing effluent concentrations. PHREEQC successfully matched the measured changes in effluent concentrations for both columns when the reaction database was modified in the following manner. For the iron-reducing column, kinetic expressions governing the rate of iron reduction, the rate of bacterial growth, and the production of methane were added to the reaction database. Additionally, surface adsorption and cation exchange reactions were added so that the model was consistent with measured effluent chemistry. For the nitrate-reducing column, kinetic expressions governing nitrate reduction and bacterial growth were added to the reaction database. Additionally

  4. Switchable photoluminescence liquid crystal coated bacterial cellulose films with conductive response.

    PubMed

    Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Ribeiro, Sidney J L

    2016-06-05

    Three different low molecular weight nematic liquid crystals (LCs) were used to impregnate bacterial cellulose (BC) film. This simple fabrication pathway allows to obtain highly transparent BC based films. The coating of BC film with different liquid crystals changed transmittance spectra in ultraviolet-visible region and allows to design UVC and UVB shielding materials. Atomic force microscopy results confirmed that liquid crystals coated BC films maintain highly interconnected three-dimensional network characteristic of BC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the three-dimensional network of BC nanofibers. Investigated BC films maintain nematic liquid crystal properties being switchable photoluminiscence as a function of temperature during repeatable heating/cooling cycles. Conductive response of the liquid crystal coated BC films was proved by tunneling atomic force microscopy measurement. Moreover, liquid crystal coated BC films maintain thermal stability and mechanical properties of the BC film. Designed thermoresponsive materials possessed interesting optical and conductive properties opening a novel simple pathway of fabrication liquid crystal coated BC films with tuneable properties.

  5. Excess conductivity analysis in YBa2Cu3O7-d added with SiO2 nanoparticles and nanowires: Comparative study

    NASA Astrophysics Data System (ADS)

    Al-Otaibi, A. L.; Almessiere, M. A.; Salem, M. Ben; Azzouz, F. Ben

    2016-07-01

    The effect of nanosized silicon oxide nanoparticles (denoted NP-SiO2) and nanowires (denoted NW-SiO2) additions during the final processing stage on electrical fluctuation conductivity of polycrystalline YBa2Cu3Oy (Y-123 for brevity) in the mean field region has been reported. Series of samples were synthesized in air using a standard solid-state reaction technique by adding nanosized entities up to 0.5 wt.%. Phases, microstructure and superconductivity properties have been systematically investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrical measurements. TEM investigations show the presence of inhomogeneities embedded in the superconducting matrix along with the presence of columnar defects in the case of SiO2 nanoparticles added samples, however nanowires tend to agglomerate by entangling with each other in the intergrain regions. The fluctuation conductivity was analyzed as a function of reduced temperature using the Aslamazov-Larkin model. Using the Lawrence-Doniach equations, the Ginzburg-Landau (GL) number (NG) and equations, the coherence length, the effective layer thickness, the lower critical field Bc1(0), the upper critical field Bc2(0) and the critical current density Jc(0) were estimated. It was found that the addition of an optimum concentration of SiO2 nanomaterials, that depends on the shape, effectively controlled the microstructure, the grains coupling and hence improved the physical properties of Y-123 compound.

  6. Cr0.5Nb24.5O62 Nanowires with High Electronic Conductivity for High-Rate and Long-Life Lithium-Ion Storage.

    PubMed

    Yang, Chao; Yu, Shu; Lin, Chunfu; Lv, Fan; Wu, Shunqing; Yang, Yong; Wang, Wei; Zhu, Zi-Zhong; Li, Jianbao; Wang, Ning; Guo, Shaojun

    2017-04-03

    Intercalation-type TiNbxO2+2.5x (x = 2, 5, and 24) anode materials have recently become more interesting for lithium-ion batteries (LIBs) due to their large theoretical capacities of 388-402 mAh g(-1). However, the Ti(4+)/Nb(5+) ions in TiNbxO2+2.5x with empty 3d/4d orbitals usually lead to extremely low electronic conductivity of <10(-9) S cm(-1), greatly restricting their practical capacity and rate capability. Herein, we report a class of highly conductive Cr0.5Nb24.5O62 nanowires as an intercalation-type anode material for high-performance LIBs. The as-made Cr0.5Nb24.5O62 nanowires show an open shear ReO3 crystal structure (C2 space group) with 4% tetrahedra and a conducting characteristic with ultrahigh electronic conductivity of 3.6 × 10(-2) S cm(-1) and a large Li(+)-ion diffusion coefficient of 2.19 × 10(-13) cm(2) s(-1). These important characteristics make them deliver outstanding electrochemical properties in term of the largest reversible capacity (344 mAh g(-1) at 0.1 C) in all the known niobium- and titanium-based anode materials, safe working potential (∼1.65 V vs Li/Li(+)), high first-cycle Coulombic efficiency (90.8%), superior rate capability (209 mAh g(-1) at 30 C), and excellent cycling stability, making them among the best for LIBs in niobium- and titanium-based anode materials.

  7. Composition, Reactivity and Regulation of Extracellular Metal-Reducing Structures (Bacterial Nanowires) Produced by Dissimilatory Metal - Reducing Bacteria

    SciTech Connect

    Beveridge, Terrance J.

    2004-06-01

    Approach. Previously, using conventional and cryoTEM techniques, surface physicochemistry assays, NMR structural analysis, etc., we showed that the structure and composition of Shewanella's lipopolysaccharide (LPS) and capsular polysaccharide (PS) significantly determined overall cell surface physicochemistry. In our study a strong correlation between such macroscopic parameters as surface electronegativity, hydrophobicity or hydrophilicity, and bacterial adhesion to hematite was observed. Rough LPS strains exhibited more than an order higher affinity and maximal sorption capacity to hematite when compared to encapsulated strains. These general trends, however, characterize bacterial adhesion only as a bulk process, being unable to reveal finer mechanisms taking place at the level of an individual cell. Cell surface physicochemical and structural heterogeneity suggests much more complex interactions at the bacterial-mineral interface than predicted by such approaches operating within macroscopic parameters.

  8. Surface passivation of tellurium-doped GaAs nanowires by GaP: Effect on electrical conduction

    SciTech Connect

    Darbandi, A.; Salehzadeh, O.; Watkins, S. P.; Kuyanov, P.; LaPierre, R. R.

    2014-06-21

    We report on the surface passivation of Au-assisted Te-doped GaAs nanowires (NWs) grown by metalorganic vapor phase epitaxy. The electrical properties of individual free standing NWs were assessed using a tungsten nano-probe inside a scanning electron microscope. The diameter independent apparent resistivity of both strained and relaxed passivated NWs suggests the unpinning of the Fermi level and reduction of sidewalls surface states density. Similar current-voltage properties were observed for partially axially relaxed GaAs/GaP NWs. This indicates a negligible contribution of misfit dislocations in the charge transport properties of the NWs. Low temperature micro-photoluminescence (μ-PL) measurements were also carried out for both uncapped and passivated GaAs NWs. The improvement of the integrated (μ-PL) intensity for GaAs/GaP NWs further confirms the effect of passivation.

  9. Are Microbial Nanowires Responsible for Geoelectrical Changes at Hydrocarbon Contaminated Sites?

    NASA Astrophysics Data System (ADS)

    Hager, C.; Atekwana, E. A.; Gorby, Y. A.; Duris, J. W.; Allen, J. P.; Atekwana, E. A.; Ownby, C.; Rossbach, S.

    2007-05-01

    Significant advances in near-surface geophysics and biogeophysics in particular, have clearly established a link between geoelectrical response and the growth and enzymatic activities of microbes in geologic media. Recent studies from hydrocarbon contaminated sites suggest that the activities of distinct microbial populations, specifically syntrophic, sulfate reducing, and dissimilatory iron reducing microbial populations are a contributing factor to elevated sediment conductivity. However, a fundamental mechanistic understanding of the processes and sources resulting in the measured electrical response remains uncertain. The recent discovery of bacterial nanowires and their electron transport capabilities suggest that if bacterial nanowires permeate the subsurface, they may in part be responsible for the anomalous conductivity response. In this study we investigated the microbial population structure, the presence of nanowires, and microbial-induced alterations of a hydrocarbon contaminated environment and relate them to the sediments' geoelectrical response. Our results show that microbial communities varied substantially along the vertical gradient and at depths where hydrocarbons saturated the sediments, ribosomal intergenic spacer analysis (RISA) revealed signatures of microbial communities adapted to hydrocarbon impact. In contrast, RISA profiles from a background location showed little community variations with depth. While all sites showed evidence of microbial activity, a scanning electron microscope (SEM) study of sediment from the contaminated location showed pervasive development of "nanowire-like structures" with morphologies consistent with nanowires from laboratory experiments. SEM analysis suggests extensive alteration of the sediments by microbial Activity. We conclude that, excess organic carbon (electron donor) but limited electron acceptors in these environments cause microorganisms to produce nanowires to shuttle the electrons as they seek for

  10. High performance of carbon nanotubes/silver nanowires-PET hybrid flexible transparent conductive films via facile pressing-transfer technique.

    PubMed

    Jing, Mao-Xiang; Han, Chong; Li, Min; Shen, Xiang-Qian

    2014-01-01

    To obtain low sheet resistance, high optical transmittance, small open spaces in conductive networks, and enhanced adhesion of flexible transparent conductive films, a carbon nanotube (CNT)/silver nanowire (AgNW)-PET hybrid film was fabricated by mechanical pressing-transfer process at room temperature. The morphology and structure were characterized by scanning electron microscope (SEM) and atomic force microscope (AFM), the optical transmittance and sheet resistance were tested by ultraviolet-visible spectroscopy (UV-vis) spectrophotometer and four-point probe technique, and the adhesion was also measured by 3M sticky tape. The results indicate that in this hybrid nanostructure, AgNWs form the main conductive networks and CNTs as assistant conductive networks are filled in the open spaces of AgNWs networks. The sheet resistance of the hybrid films can reach approximately 20.9 to 53.9 Ω/□ with the optical transmittance of approximately 84% to 91%. The second mechanical pressing step can greatly reduce the surface roughness of the hybrid film and enhance the adhesion force between CNTs, AgNWs, and PET substrate. This process is hopeful for large-scale production of high-end flexible transparent conductive films.

  11. Superstable transparent conductive Cu@Cu4Ni nanowire elastomer composites against oxidation, bending, stretching, and twisting for flexible and stretchable optoelectronics.

    PubMed

    Song, Jizhong; Li, Jianhai; Xu, Jiayue; Zeng, Haibo

    2014-11-12

    Low cost and high conductivity make copper (Cu) nanowire (NW) electrodes an attractive material to construct flexible and stretchable electronic skins, displays, organic light-emitting diodes (OLEDs), solar cells, and electrochromic windows. However, the vulnerabilities that Cu NW electrodes have to oxidation, bending, and stretching still present great challenges. This work demonstrates a new Cu@Cu4Ni NW conductive elastomer composite with ultrahigh stability for the first time. Cu@Cu4Ni NWs, facilely synthesized through a one-pot method, have highly crystalline alloyed shells, clear and abrupt interfaces, lengths more than 50 μm, and smooth surfaces. These virtues provide the NW-elastomer composites with a low resistance of 62.4 ohm/sq at 80% transparency, which is even better than the commercial ITO/PET flexible electrodes. In addition, the fluctuation amplitude of resistance is within 2 ohm/sq within 30 days, meaning that at ΔR/R0 = 1, the actual lifetime is estimated to be more than 1200 days. Neither the conductivity nor the performances of OLED with elastomers as conductive circuits show evident degradation during 600 cycles of bending, stretching, and twisting tests. These high-performance and extremely stable NW elastomeric electrodes could endow great chances for transparent, flexible, stretchable, and wearable electronic and optoelectronic devices.

  12. Reduced Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Léonard, François

    2011-03-01

    The temperature distribution in nanowires due to Joule heating is studied analytically using a continuum model and a Green's function approach. We show that the temperatures reached in nanowires can be much lower than that predicted by bulk models of Joule heating, due to heat loss at the nanowire surface that is important at nanoscopic dimensions, even when the thermal conductivity of the environment is relatively low. In addition, we find that the maximum temperature in the nanowire scales weakly with length, in contrast to the bulk system. A simple criterion is presented to assess the importance of these effects. The results have implications for the experimental measurements of nanowire thermal properties, for thermoelectric applications, and for controlling thermal effects in nanowire electronic devices.

  13. Enhanced photoelectrochemical biosensing performances for graphene (2D) - Titanium dioxide nanowire (1D) heterojunction polymer conductive nanosponges.

    PubMed

    Muthuchamy, N; Lee, K-P; Gopalan, A-I

    2017-03-15

    In this work, an efficient photoelectrochemical (PEC) biosensing platform has been designed and developed based on graphene (G) through modifying it into an electroconductive polymer nanosponge (EPNS) and with the incorporation of titanium dioxide nanowires (TiO2 NW) (designated as TiO2 (G) NW@EPNS). Functioning as an efficient immobilization matrix for immobilization of the enzyme Cytochrome C (Cyt C), TiO2 (G) NW@EPNS delivers features for an efficient PEC biosensor, such as fast kinetics of direct electron transfer (DET) to the electrode and effective separation of photogenerated holes and electrons. TiO2 (G) NW@EPNS exhibited DET to the electrode with a highly heterogeneous electron transfer rate constant of 6.29±0.002s(-1). The existence of TiO2, G and EPNS in conjunction facilitates DET between the electrode surface and the protein. The fabricated PEC nitrite ion (NO2(-)) biosensor showed superior analytical performances such as wide linear range (0.5-9000µM), lowest detection limit (0.225mM) and excellent specificity for NO2(-) in the presence other interferences at a very low bias potential (-0.11V). This study opens up the feasibility of fabricating a PEC biosensor for any analyte using a matrix comprising of G and a photoactive material and EPNS, because these components synergistically contribute to effective immobilization of on enzyme, DET to the electrode and simple read-out under the light.

  14. Two-beam laser fabrication technique and the application for fabricating conductive silver nanowire on flexible substrate

    NASA Astrophysics Data System (ADS)

    He, Gui-Cang; Zheng, Mei-Ling; Dong, Xian-Zi; Liu, Jie; Duan, Xuan-Ming; Zhao, Zhen-Sheng

    2017-03-01

    In this study, a two-beam laser fabrication technique is proposed to fabricate silver nanowire (AgNW) on the polyethylene terephthalate (PET) substrate. The femtosecond pulse laser in the technique plays a role in generating Ag nanoparticles from the silver aqueous solution by multiphoton photoreduction. The continuous wave (CW) laser of the technique works as optical tweezers, and make the Ag nanoparticles gather to a continuous AgNW by the optical trapping force. The optical trapping force of the CW laser was calculated under our experimental condition. The flexibility and the resistance stability of the AgNW that fabricated by this technique are very excellent. Compared to the resistance of the AgNW without bending, the decreasing rate of the AgNW resistance is about 16% under compressed bending condition at the radius of 1 mm, and the increasing rate of the AgNW resistance is only 1.3% after the AgNW bended about 3500 times at the bending radius of 1 mm. The study indicates that the AgNW is promising for achieving flexible device and would promote the development of the flexible electronics.

  15. Rapid synthesis of ultra-long silver nanowires for tailor-made transparent conductive electrodes: proof of concept in organic solar cells.

    PubMed

    José Andrés, Luis; Fe Menéndez, María; Gómez, David; Luisa Martínez, Ana; Bristow, Noel; Paul Kettle, Jeffrey; Menéndez, Armando; Ruiz, Bernardino

    2015-07-03

    Rapid synthesis of ultralong silver nanowires (AgNWs) has been obtained using a one-pot polyol-mediated synthetic procedure. The AgNWs have been prepared from the base materials in less than one hour with nanowire lengths reaching 195 μm, which represents the quickest synthesis and one of the highest reported aspect ratios to date. These results have been achieved through a joint analysis of all reaction parameters, which represents a clear progress beyond the state of the art. Dispersions of the AgNWs have been used to prepare thin, flexible, transparent and conducting films using spray coating. Due to the higher aspect ratio, an improved electrical percolation network is observed. This allows a low sheet resistance (RS = 20.2 Ω/sq), whilst maintaining high optical film transparency (T = 94.7%), driving to the highest reported figure-of-merit (FoM = 338). Owing to the light-scattering influence of the AgNWs, the density of the AgNW network can also be varied to enable controllability of the optical haze through the sample. Based on the identification of the optimal haze value, organic photovoltaics (OPVs) have been fabricated using the AgNWs as the transparent electrode and have been benchmarked against indium tin oxide (ITO) electrodes. Overall, the performance of OPVs made using AgNWs sees a small decrease in power conversion efficiency (PCE), primarily due to a fall in open-circuit voltage (50 mV). This work indicates that AgNWs can provide a low cost, rapid and roll-to-roll compatible alternative to ITO in OPVs, with only a small compromise in PCE needed.

  16. Highly Conductive and Uniform Alginate/Silver Nanowire Composite Transparent Electrode by Room Temperature Solution Processing for Organic Light Emitting Diode.

    PubMed

    Lian, Lu; Dong, Dan; Yang, Shuai; Wei, Bingwu; He, Gufeng

    2017-04-05

    A novel transparent electrode composed of alginate/silver nanowire (AgNW) with high conductivity and low roughness is fabricated via a solution process at room temperature. The sol-gel transition of the alginate triggered by CaCl2 solution bonds the AgNWs to the substrate tightly. Meanwhile, Cl(-) in the solution can renovate the cracks on the AgNW surfaces created during the mechanical pressing, resulting in a great increase of the electrical conductivity. The alginate/AgNW composite film can reach a sheet resistance of 2.3 Ω/sq with a transmittance of 83% at 550 nm. The conductivity of the composite film remains stable after bending and tape tests, demonstrating excellent flexibility and great adhesion of AgNWs to the substrate. Moreover, the composite film shows better stability to resist longtime storage than conventional annealed-AgNW film. The organic light emitting diode using such alginate/AgNW composite film as anode presents current densities and luminances comparable to those of indium tin oxide (ITO) anode, and higher efficiencies are obtained due to the better charge balance.

  17. Bacterial Etiologies of Five Core Syndromes: Laboratory-Based Syndromic Surveillance Conducted in Guangxi, China

    PubMed Central

    Dong, Baiqing; Liang, Dabin; Lin, Mei; Wang, Mingliu; Zeng, Jun; Liao, Hezhuang; Zhou, Lingyun; Huang, Jun; Wei, Xiaolin; Zou, Guanyang; Jing, Huaiqi

    2014-01-01

    Background Under the existing national surveillance system in China for selected infectious diseases, bacterial cultures are performed for only a small percentage of reported cases. We set up a laboratory-based syndromic surveillance system to elucidate bacterial etiologic spectrum and detect infection by rare etiologies (or serogroups) for five core syndromes in the given study area. Methods Patients presenting with one of five core syndromes at nine sentinel hospitals in Guagnxi, China were evaluated using laboratory-based syndrome surveillance to elucidate bacterial etiologies. We collected respiratory and stool specimens, as well as CSF, blood and other related samples for bacterial cultures and pulse field gel electrophoresis (PFGE) assays. Results From February 2009 to December 2011, 2,964 patients were enrolled in the study. Etiologies were identified in 320 (10.08%) patients. Streptococcus pneumonia (37 strains, 24.18%), Klebsiella pneumonia (34, 22.22%), Pseudomonas aeruginosa (19, 12.42%) and Haemophilus influenza (18, 11.76%) were the most frequent pathogens for fever and respiratory syndrome, while Salmonella (77, 81.05%) was most often seen in diarrhea syndrome cases. Salmonella paratyphi A (38, 86.36%) occurred in fever and rash syndrome, with Cryptococcus neoformans (20, 35.09%), Streptococcus pneumonia (5, 8.77%), Klebsiella pneumonia (5, 8.77%),streptococcus suis (3, 5.26%) and Neisseria meningitides group B (2, 3.51%) being the most frequently detected in encephalitis-meningitis syndrome. To date no pathogen was isolated from the specimens from fever and hemorrhage patients. Conclusions In addition to common bacterial pathogens, opportunistic pathogens and fungal infections require more attention. Our study contributes to the strengthening of the existing national surveillance system and provides references for other regions that are similar to the study area. PMID:25360596

  18. Thermal conductivity measurements of single-crystalline bismuth nanowires by the four-point-probe 3-ω technique at low temperatures.

    PubMed

    Lee, Seung-Yong; Kim, Gil-Sung; Lee, Mi-Ri; Lim, Hyuneui; Kim, Wan-Doo; Lee, Sang-Kwon

    2013-05-10

    We have successfully investigated the thermal conductivity (κ) of single-crystalline bismuth nanowires (BiNWs) with [110] growth direction, via a straightforward and powerful four-point-probe 3-ω technique in the temperature range 10-280 K. The BiNWs, which are well known as the most effective material for thermoelectric (TE) device applications, were synthesized by compressive thermal stress on a SiO2/Si substrate at 250-270 °C for 10 h. To understand the thermal transport mechanism of BiNWs, we present three kinds of experimental technique as follows, (i) a manipulation of a single BiNW by an Omni-probe in a focused ion beam (FIB), (ii) a suspended bridge structure integrating a four-point-probe chip by micro-fabrication to minimize the thermal loss to the substrate, and (iii) a simple 3-ω technique system setup. We found that the thermal transport of BiNWs is highly affected by boundary scattering of both phonons and electrons as the dominant heat carriers. The thermal conductivity of a single BiNW (d ~ 123 nm) was estimated to be ~2.9 W m(-1) K(-1) at 280 K, implying lower values compared to the thermal conductivity of the bulk (~11 W m(-1) K(-1) at 280 K). It was noted that this reduction in the thermal conductivity of the BiNWs could be due to strongly enhanced phonon-boundary scattering at the surface of the BiNWs. Furthermore, we present temperature-dependent (10-280 K) thermal conductivity of the BiNWs using the 3-ω technique.

  19. One-Step Process for High-Performance, Adhesive, Flexible Transparent Conductive Films Based on p-Type Reduced Graphene Oxides and Silver Nanowires.

    PubMed

    Lai, Yi-Ting; Tai, Nyan-Hwa

    2015-08-26

    This work demonstrates a one-step process to synthesize uniformly dispersed hybrid nanomaterial containing silver nanowires (AgNWs) and p-type reduced graphene (p-rGO). The hybrid nanomaterial was coated onto a polyethylene terephthalate (PET) substrate for preparing high-performance flexible transparent conductive films (TCFs). The p-rGO plays the role of bridging discrete AgNWs, providing more electron holes and lowering the resistance of the contacted AgNWs; therefore, enhancing the electrical conductivity without sacrificing too much transparence of the TCFs. Additionally, the p-rGO also improves the adhesion between AgNWs and substrate by covering the AgNWs on the substrate tightly. The study shows that coating of the hybrid nanomaterials on the PET substrate demonstrates exceptional optoelectronic properties with a transmittance of 94.68% (at a wavelength of 550 nm) and a sheet resistance of 25.0 ± 0.8 Ω/sq. No significant variation in electric resistance can be detected even when the film was subjected to a bend loading with a radius of curvature of 5.0 mm or the film was loaded with a reciprocal tension or compression for 1000 cycles. Furthermore, both chemical corrosion resistance and haze effect were improved when p-rGO was introduced. The study shows that the fabricated flexible TCFs have the potential to replace indium tin oxide film in the optoelectronic industry.

  20. Plasticized Polymer Interlayer for Low Temperature Fabrication of a High-Quality Silver Nanowire-Based Flexible Transparent and Conductive Film.

    PubMed

    Jo, Wonhee; Kang, Hong Suk; Choi, Jaeho; Lee, Hongkyung; Kim, Hee-Tak

    2017-04-04

    Silver nanowires (AgNWs) are one of the most promising materials for flexible transparent conductive films (TCFs) to replace commercially available indium tin oxide (ITO); however, there are still numerous problems originating from poor AgNW junction formation and improper AgNW embedment into transparent substrates. To mitigate these problems, high temperature processes have been adopted; however, unwanted substrate deformation prevents the use of these processes for flexible TCFs. In this work, we present a novel poly(methyl methacrylate) (PMMA) interlayer plasticized by dibutyl phthalate (DBP) to achieve a low temperature fabrication of AgNW-based TCF, which does not cause any substrate deformation. By exploiting the viscoelastic property of the plasticized interlayer near the lowered glass transition temperature, the monolithic junction of the AgNWs on the interlayer and embedment of the inter-connected AgNWs into the interlayer are achieved in a single-step pressing. The resulting AgNW TCFs are highly transparent (~92% at a wavelength of 550 nm), highly conductive (< 90 Ω/sq), and environmentally and mechanically robust. Therefore, the plasticized interlayer provides a simple and effective route to fabricate high quality AgNW-based TCFs.

  1. Nanowire sensors and arrays for chemical/biomolecule detection

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Ramanathan, K.; Bangar, M. A.; Chen, W.; Mulchandan, A.; Myung, N. V.

    2005-01-01

    We report electrochemical growth of single nanowire based sensors using e-beam patterned electrolyte channels, potentially enabling the controlled fabrication of individually addressable high density arrays. The electrodeposition technique results in nanowires with controlled dimensions, positions, alignments, and chemical compositions. Using this technique, we have fabricated single palladium nanowires with diameters ranging between 75 nm and 300 nm and conducting polymer nanowires (polypyrrole and polyaniline) with diameters between 100 nm and 200 nm. Using these single nanowires, we have successfully demonstrated gas sensing with Pd nanowires and pH sensing with polypirrole nanowires.

  2. Soil pH and electrical conductivity are key edaphic factors shaping bacterial communities of greenhouse soils in Korea.

    PubMed

    Kim, Jeong Myeong; Roh, An-Sung; Choi, Seung-Chul; Kim, Eun-Jeong; Choi, Moon-Tae; Ahn, Byung-Koo; Kim, Sun-Kuk; Lee, Young-Han; Joa, Jae-Ho; Kang, Seong-Soo; Lee, Shin Ae; Ahn, Jae-Hyung; Song, Jaekyeong; Weon, Hang-Yeon

    2016-12-01

    Soil microorganisms play an essential role in soil ecosystem processes such as organic matter decomposition, nutrient cycling, and plant nutrient availability. The land use for greenhouse cultivation has been increasing continuously, which involves an intensive input of agricultural materials to enhance productivity; however, relatively little is known about bacterial communities in greenhouse soils. To assess the effects of environmental factors on the soil bacterial diversity and community composition, a total of 187 greenhouse soil samples collected across Korea were subjected to bacterial 16S rRNA gene pyrosequencing analysis. A total of 11,865 operational taxonomic units at a 97% similarity cutoff level were detected from 847,560 sequences. Among nine soil factors evaluated; pH, electrical conductivity (EC), exchangeable cations (Ca(2+), Mg(2+), Na(+), and K(+)), available P2O5, organic matter, and NO3-N, soil pH was most strongly correlated with bacterial richness (polynomial regression, pH: R(2) = 0.1683, P < 0.001) and diversity (pH: R(2) = 0.1765, P < 0.001). Community dissimilarities (Bray-Curtis distance) were positively correlated with Euclidean distance for pH and EC (Mantel test, pH: r = 0.2672, P < 0.001; EC: r = 0.1473, P < 0.001). Among dominant phyla (> 1%), the relative abundances of Proteobacteria, Gemmatimonadetes, Acidobacteria, Bacteroidetes, Chloroflexi, and Planctomycetes were also more strongly correlated with pH and EC values, compared with other soil cation contents, such as Ca(2+), Mg(2+), Na(+), and K(+). Our results suggest that, despite the heterogeneity of various environmental variables, the bacterial communities of the intensively cultivated greenhouse soils were particularly influenced by soil pH and EC. These findings therefore shed light on the soil microbial ecology of greenhouse cultivation, which should be helpful for devising effective management strategies to enhance soil microbial diversity and improving crop productivity.

  3. Sources of conductance changes during bacterial reduction of trimethylamine oxide to trimethylammonium in phosphate buffer.

    PubMed

    Owens, J D; Miskin, D R; Wacher-Viveros, M C; Benge, L C

    1985-06-01

    The sources of conductance changes during reduction of trimethylamine oxide to trimethylamine by Escherichia coli with formate as electron donor and in the presence of phosphate buffer were investigated. Theoretical considerations and experimental results suggest that the major source of conductance change is the conversion of dihydrogen phosphate to hydrogen phosphate. This transformation contributes almost twice as much to the total conductance change as does the conversion of uncharged trimethylamine oxide to charged trimethylammonium.

  4. Microtubule-based gold nanowires and nanowire arrays.

    PubMed

    Zhou, Jing C; Gao, Yao; Martinez-Molares, Alfredo A; Jing, Xiaoye; Yan, Dong; Lau, Joseph; Hamasaki, Toshikazu; Ozkan, Cengiz S; Ozkan, Mihrimah; Hu, Evelyn; Dunn, Bruce

    2008-09-01

    Biological structures are attractive as templates to form nanoscale architectures for electronics because of their dimensions and the ability to interact with inorganic materials. In this study, we report the fabrication and electrical properties of microtubule (MT)-templated Au nanowires, and methods for assembling Au nanowire arrays based on these templates. The adsorption of MTs on silicon substrates is an effective means for preserving the conformation of the MT and provides a convenient platform for electrical measurements. To improve the metallization of MTs, a photochemical route for gold reduction is adapted, which leads to continuous coverage. The conductivity values measured on micrometer-long nanowires are similar to those reported for other biotemplated gold nanowires. A protocol for fabricating arrays of MT-templated gold nanowires is demonstrated.

  5. Investigation of Ag-TiO2 Interfacial Reaction of Highly Stable Ag Nanowire Transparent Conductive Film with Conformal TiO2 Coating by Atomic Layer Deposition.

    PubMed

    Yeh, Ming-Hua; Chen, Po-Hsun; Yang, Yi-Ching; Chen, Guan-Hong; Chen, Hsueh-Shih

    2017-03-29

    The atomic layer deposition (ALD) technique is applied to coat Ag nanowires (NWs) with a highly uniform and conformal TiO2 layer to improve the stability and sustainability of Ag NW transparent conductive films (TCFs) at high temperatures. The TiO2 layer can be directly deposited on Ag NWs with a surface polyvinylpyrrolidone (PVP) coat that acts a bed for TiO2 seeding in the ALD process. The ALD TiO2 layer significantly enhances the thermal stability at least 100 fold when aged between 200-400 °C and also provides an extra function of violet-blue light filtration for Ag NW TCFs. Investigation into the interaction between TiO2 and Ag reveals that the conformal TiO2 shell could effectively prevent Ag from 1D-to-3D ripening. However, Ag could penetrate the conformal TiO2 shell and form nanocrystals on the TiO2 shell surface when it is aged at 400 °C. According to experimental data and thermodynamic evaluation, the Ag penetration leads to an interlayer composed of mixed Ag-Ag2O-amorphous carbon phases and TiO2-x at the Ag-TiO2 interface, which is thought to be caused by extremely high vapor pressure of Ag at the Ag-TiO2 interface at a higher temperature (e.g., 400 °C).

  6. Coaxial three-dimensional CoMoO4 nanowire arrays with conductive coating on carbon cloth for high-performance lithium ion battery anode

    NASA Astrophysics Data System (ADS)

    Chen, Yaping; Liu, Borui; Jiang, Wei; Liu, Qi; Liu, Jingyuan; Wang, Jun; Zhang, Hongsen; Jing, Xiaoyan

    2015-12-01

    Nanostructured transition metal oxides have attracted considerable attentions for both high-capacity and high-rate, but great challenges remain to utilize them. In order to overcome these challenges, hierarchical three-dimensional CoMoO4/polypyrrole core-shell nanowire (NW) arrays on flexible and conductive carbon cloth (CC) have been successfully constructed through a facile two-step solution-based approach. The hybrid NWs electrode as a binder-free lithium ion batteries (LIBs) anode material exhibits a reversible capacity of around 1400-1450 mAh g-1 at a low current density of 100 mA g-1. The specific capacity retains at 753 mAh g-1 while featuring an excellent cycling properties with a capacity of 764 mAh g-1 after 1000 cycles under the current rate of 1200 mA g-1. Furthermore, full batteries have been fabricated and demonstrated characteristics of outstanding electrical stability and superior power output characteristics, which represents an efficient way for practical implementation.

  7. Nanowire Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Borshchevsky, Alexander; Fleurial, Jean-Pierre; Herman, Jennifer; Ryan, Margaret

    2005-01-01

    Nanowire thermoelectric devices, now under development, are intended to take miniaturization a step beyond the prior state of the art to exploit the potential advantages afforded by shrinking some device features to approximately molecular dimensions (of the order of 10 nm). The development of nanowire-based thermoelectric devices could lead to novel power-generating, cooling, and sensing devices that operate at relatively low currents and high voltages. Recent work on the theory of thermoelectric devices has led to the expectation that the performance of such a device could be enhanced if the diameter of the wires could be reduced to a point where quantum confinement effects increase charge-carrier mobility (thereby increasing the Seebeck coefficient) and reduce thermal conductivity. In addition, even in the absence of these effects, the large aspect ratios (length of the order of tens of microns diameter of the order of tens of nanometers) of nanowires would be conducive to the maintenance of large temperature differences at small heat fluxes. The predicted net effect of reducing diameters to the order of tens of nanometers would be to increase its efficiency by a factor of .3. Nanowires made of thermoelectric materials and devices that comprise arrays of such nanowires can be fabricated by electrochemical growth of the thermoelectric materials in templates that contain suitably dimensioned pores (10 to 100 nm in diameter and 1 to 100 microns long). The nanowires can then be contacted in bundles to form devices that look similar to conventional thermoelectric devices, except that a production version may contain nearly a billion elements (wires) per square centimeter, instead of fewer than a hundred as in a conventional bulk thermoelectric device or fewer than 100,000 as in a microdevice. It is not yet possible to form contacts with individual nanowires. Therefore, in fabricating a nanowire thermoelectric device, one forms contacts on nanowires in bundles of the

  8. Microbial nanowires and methods of making and using

    DOEpatents

    Reguera, Gemma; Cologgi, Dena; Worden, Robert Mark; Castro-Forero, Angelines A.; Steidl, Rebecca

    2017-03-21

    Electrically conductive nanowires, and genetically or chemically modified production and use of such nanowires with altered conductive, adhesive, coupling or other properties are described. The disclosed nanowires are used as device or device components or may be adapted for soluble metal remediation.

  9. Molecular Dynamic Study to Determine the Ammonia Conduction Mechanisms in Human RhCG and Bacterial Homoloques

    NASA Astrophysics Data System (ADS)

    Akgun, Ugur

    2014-03-01

    The transport of Ammonia is provided by Amt/MEP/Rh protein superfamily. The x-ray structures of AmtB from Escherichia coli, Rh50 from Nitrosomonas europaea, and human RhCG show only few differences on periplasmic vestibules. After more than microsecond simulation on three models, we determined the striking difference on conduction mechanism between bacterial AmtB and Human RhCG proteins. In AmtB the backbone carbonyl groups at the periplasmic vestibule direct charged ammonia to the conserved aromatic cage at the bottom of the vestibule. Furthermore, two partially stacked phenyl rings of F107 and F215, separating the periplasmic vestibule from the hydrophobic lumen, flip open and closed simultaneouslywith a frequency of approximately 108 flipping events per second. During the passage from the phenyl gates charged ammonia releases its proton and becomes gas. However, the absence of an aromatic cage on Rh proteins and a strongly conserved E166 residue in the vicinity hints different conduction mechanism. Our studies confirm the conserved E166 emerges as a strong charged ammonia recruitment site for Human RhCG. The conserved phenyl gate behaves different for Rh proteins and the synchronized motion is not observed. These findings suggest a different deprotonation mechanism than bacterial AmtB.

  10. Energetic and Spatial Parameters for Gating of the Bacterial Large Conductance Mechanosensitive Channel, MscL

    PubMed Central

    Sukharev, Sergei I.; Sigurdson, Wade J.; Kung, Ching; Sachs, Frederick

    1999-01-01

    MscL is multimeric protein that forms a large conductance mechanosensitive channel in the inner membrane of Escherichia coli. Since MscL is gated by tension transmitted through the lipid bilayer, we have been able to measure its gating parameters as a function of absolute tension. Using purified MscL reconstituted in liposomes, we recorded single channel currents and varied the pressure gradient (P) to vary the tension (T). The tension was calculated from P and the radius of curvature was obtained using video microscopy of the patch. The probability of being open (Po) has a steep sigmoidal dependence on T, with a midpoint (T1/2) of 11.8 dyn/cm. The maximal slope sensitivity of Po/Pc was 0.63 dyn/cm per e-fold. Assuming a Boltzmann distribution, the energy difference between the closed and fully open states in the unstressed membrane was ΔE = 18.6 kBT. If the mechanosensitivity arises from tension acting on a change of in-plane area (ΔA), the free energy, TΔA, would correspond to ΔA = 6.5 nm2. MscL is not a binary channel, but has four conducting states and a closed state. Most transition rates are independent of tension, but the rate-limiting step to opening is the transition between the closed state and the lowest conductance substate. This transition thus involves the greatest ΔA. When summed over all transitions, the in-plane area change from closed to fully open was 6 nm2, agreeing with the value obtained in the two-state analysis. Assuming a cylindrical channel, the dimensions of the (fully open) pore were comparable to ΔA. Thus, the tension dependence of channel gating is primarily one of increasing the external channel area to accommodate the pore of the smallest conducting state. The higher conducting states appear to involve conformational changes internal to the channel that don't involve changes in area. PMID:10102934

  11. Energetic and spatial parameters for gating of the bacterial large conductance mechanosensitive channel, MscL

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Sigurdson, W. J.; Kung, C.; Sachs, F.

    1999-01-01

    MscL is multimeric protein that forms a large conductance mechanosensitive channel in the inner membrane of Escherichia coli. Since MscL is gated by tension transmitted through the lipid bilayer, we have been able to measure its gating parameters as a function of absolute tension. Using purified MscL reconstituted in liposomes, we recorded single channel currents and varied the pressure gradient (P) to vary the tension (T). The tension was calculated from P and the radius of curvature was obtained using video microscopy of the patch. The probability of being open (Po) has a steep sigmoidal dependence on T, with a midpoint (T1/2) of 11.8 dyn/cm. The maximal slope sensitivity of Po/Pc was 0.63 dyn/cm per e-fold. Assuming a Boltzmann distribution, the energy difference between the closed and fully open states in the unstressed membrane was DeltaE = 18.6 kBT. If the mechanosensitivity arises from tension acting on a change of in-plane area (DeltaA), the free energy, TDeltaA, would correspond to DeltaA = 6.5 nm2. MscL is not a binary channel, but has four conducting states and a closed state. Most transition rates are independent of tension, but the rate-limiting step to opening is the transition between the closed state and the lowest conductance substate. This transition thus involves the greatest DeltaA. When summed over all transitions, the in-plane area change from closed to fully open was 6 nm2, agreeing with the value obtained in the two-state analysis. Assuming a cylindrical channel, the dimensions of the (fully open) pore were comparable to DeltaA. Thus, the tension dependence of channel gating is primarily one of increasing the external channel area to accommodate the pore of the smallest conducting state. The higher conducting states appear to involve conformational changes internal to the channel that don't involve changes in area.

  12. Faradic redox active material of Cu7S4 nanowires with a high conductance for flexible solid state supercapacitors

    NASA Astrophysics Data System (ADS)

    Javed, Muhammad Sufyan; Dai, Shuge; Wang, Mingjun; Xi, Yi; Lang, Qiang; Guo, Donglin; Hu, Chenguo

    2015-08-01

    The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in a high pseudocapacitive performance with a relatively high specific energy and specific power. Such a new type of pseudocapacitive material of Cu7S4-NWs with its low cost is very promising for actual application in supercapacitors.The exploration of high Faradic redox active materials with the advantages of low cost and low toxicity has been attracting great attention for producing high energy storage supercapacitors. Here, the high Faradic redox active material of Cu7S4-NWs coated on a carbon fiber fabric (CFF) is directly used as a binder-free electrode for a high performance flexible solid state supercapacitor. The Cu7S4-NW-CFF supercapacitor exhibits excellent electrochemical performance such as a high specific capacitance of 400 F g-1 at the scan rate of 10 mV s-1 and a high energy density of 35 Wh kg-1 at a power density of 200 W kg-1, with the advantages of a light weight, high flexibility and long term cycling stability by retaining 95% after 5000 charge-discharge cycles at a constant current of 10 mA. The high Faradic redox activity and high conductance behavior of the Cu7S4-NWs result in

  13. Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles

    NASA Astrophysics Data System (ADS)

    Ko, Ting-Yu; Shellaiah, Muthaiah; Sun, Kien Wen

    2016-10-01

    In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10‑4 S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (kNW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 104 S/m) Sb2Se3 single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb2Se3 single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.

  14. Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles.

    PubMed

    Ko, Ting-Yu; Shellaiah, Muthaiah; Sun, Kien Wen

    2016-10-07

    In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10(-4) S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (kNW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36-1.9 W/m·K) and highly conductive (σ ~ 3 × 10(4) S/m) Sb2Se3 single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb2Se3 single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed.

  15. Thermal and Thermoelectric Transport in Highly Resistive Single Sb2Se3 Nanowires and Nanowire Bundles

    PubMed Central

    Ko, Ting-Yu; Shellaiah, Muthaiah; Sun, Kien Wen

    2016-01-01

    In this study, we measured the thermal conductivity and Seebeck coefficient of single Sb2Se3 nanowires and nanowire bundles with a high resistivity (σ ~ 4.37 × 10−4 S/m). Microdevices consisting of two adjacent suspended silicon nitride membranes were fabricated to measure the thermal transport properties of the nanowires in vacuum. Single Sb2Se3 nanowires with different diameters and nanowire bundles were carefully placed on the device to bridge the two membranes. The relationship of temperature difference on each heating/sensing suspension membranes with joule heating was accurately determined. A single Sb2Se3 nanowire with a diameter of ~ 680 nm was found to have a thermal conductivity (kNW) of 0.037 ± 0.002 W/m·K. The thermal conductivity of the nanowires is more than an order of magnitude lower than that of bulk materials (k ~ 0.36–1.9 W/m·K) and highly conductive (σ ~ 3 × 104 S/m) Sb2Se3 single nanowires (k ~ 1 W/m·K). The measured Seebeck coefficient with a positive value of ~ 661 μV/K is comparable to that of highly conductive Sb2Se3 single nanowires (~ 750 μV/K). The thermal transport between wires with different diameters and nanowire bundles was compared and discussed. PMID:27713527

  16. Semiconductor nanowires: Controlled growth and thermal properties

    NASA Astrophysics Data System (ADS)

    Wu, Yiying

    This dissertation presents an experimental study of the controlled growth of semiconductor nanowires and their thermophysical properties. The synthesis of nanowires was based on the well-known Vapor-Liquid-Solid (VLS) mechanism in which the growth of nanowire is initiated by a nanosized liquid droplet. The prepared nanowires are single-crystalline with certain preferred growth direction. Nanowires with different compositions have been synthesized, including Si, Ge, boron and MgB2. The control of nanowire composition, diameter and orientation has also been achieved. In addition, a Pulsed Laser Ablation-Chemical Vapor Deposition (PLA-CVD) hybrid process was developed to synthesize Si/SiGe longitudinally superlattice nanowires. The thermal conductivity of individual pure Si nanowire and Si/SiGe nanowire was measured using a microfabricated suspended device over a temperature range of 20--320 K. The thermal conductivities of individual 22, 37, 56, and 115 nm diameter single crystalline intrinsic Si nanowires were much lower than the bulk value due to the strong phonon boundary scattering. Except for the 22 nm diameter nanowire, theoretical predictions using a modified Callaway model fit the experimental data very well. The data for the 22 nm diameter wire suggest that changes in phonon dispersion due to confinement can cause additional thermal conductivity reduction. The Si/SiGe superlattice nanowires with diameters of 83 run and 58 nm were also measured. Their thermal conductivities are smaller than pure Si nanowire with similar diameter, as well as Si/SiGe superlattice thin film with comparable period. Both the alloying scattering and the boundary scattering are believed to contribute to this reduction. Size dependent melting-recrystallization study of the carbon-sheathed semiconductor Ge nanowires was carried out in in-situ high temperature transmission electron microscope (TEM). Significant depression in melting temperature with decreasing size of the nanowires as

  17. Stoichiometry of the large conductance bacterial mechanosensitive channel of E. coli. A biochemical study

    NASA Technical Reports Server (NTRS)

    Sukharev, S. I.; Schroeder, M. J.; McCaslin, D. R.

    1999-01-01

    both double and triple tandems form channels of normal conductance implies that the pentameric assembly is to some degree independent of the number of subunit repeats in the polypeptide precursor. The channel is thus a pentameric core with the 'extra' subunits left out of the functional complex. From sedimentation equilibrium and size-exclusion chromatography, we also conclude that MscL complexes are not in a dynamic equilibrium with monomers, but are pre-assembled; and thus, their gating properties must result from changes in the conformation of the entire complex induced by the mechanical stress.

  18. Synthesis of silver nanowires using hydrothermal technique for flexible transparent electrode application

    NASA Astrophysics Data System (ADS)

    Vijila, C. V. Mary; Rahman, K. K. Arsina; Parvathy, N. S.; Jayaraj, M. K.

    2016-05-01

    Transparent conducting films are becoming increasingly interesting because of their applications in electronics industry such as their use in solar energy applications. In this work silver nanowires were synthesized using solvothermal method by reducing silver nitrate and adding sodium chloride for assembling silver into nanowires. Absorption spectra of nanowires in the form of a dispersion in deionized water, AFM and SEM images confirm the nanowire formation. Solution of nanowire was coated over PET films to obtain transparent conducting films.

  19. Nanostructured bacterial cellulose-poly(4-styrene sulfonic acid) composite membranes with high storage modulus and protonic conductivity.

    PubMed

    Gadim, Tiago D O; Figueiredo, Andrea G P R; Rosero-Navarro, Nataly C; Vilela, Carla; Gamelas, José A F; Barros-Timmons, Ana; Neto, Carlos Pascoal; Silvestre, Armando J D; Freire, Carmen S R; Figueiredo, Filipe M L

    2014-05-28

    The present study reports the development of a new generation of bio-based nanocomposite proton exchange membranes based on bacterial cellulose (BC) and poly(4-styrene sulfonic acid) (PSSA), produced by in situ free radical polymerization of sodium 4-styrenesulfonate using poly(ethylene glycol) diacrylate (PEGDA) as cross-linker, followed by conversion of the ensuing polymer into the acidic form. The BC nanofibrilar network endows the composite membranes with excellent mechanical properties at least up to 140 °C, a temperature where either pure PSSA or Nafion are soft, as shown by dynamic mechanical analysis. The large concentration of sulfonic acid groups in PSSA is responsible for the high ionic exchange capacity of the composite membranes, reaching 2.25 mmol g(-1) for a composite with 83 wt % PSSA/PEGDA. The through-plane protonic conductivity of the best membrane is in excess of 0.1 S cm(-1) at 94 °C and 98% relative humidity (RH), decreasing to 0.042 S cm(-1) at 60% RH. These values are comparable or even higher than those of ionomers such as Nafion or polyelectrolytes such as PSSA. This combination of electric and viscoelastic properties with low cost underlines the potential of these nanocomposites as a bio-based alternative to other polymer membranes for application in fuel cells, redox flow batteries, or other devices requiring functional proton conducting elements, such as sensors and actuators.

  20. Bacterial cellulose composites: Synthetic strategies and multiple applications in bio-medical and electro-conductive fields.

    PubMed

    Ul-Islam, Mazhar; Khan, Shaukat; Ullah, Muhammad Wajid; Park, Joong Kon

    2015-12-01

    Bacterial cellulose (BC), owing to its pure nature and impressive physicochemical properties, including high mechanical strength, crystallinity, porous fibrous structure, and liquid absorbing capabilities, has emerged as an advanced biomaterial. To match the market demand and economic values, BC has been produced through a number of synthetic routes, leading to slightly different structural features and physical appearance. Chemical nature, porous geometry, and 3D fibrous structure of BC make it an ideal material for composites synthesis that successfully overcome certain deficiencies of pure BC. In this review, we have focused various strategies developed for synthesizing BC and BC composites. Reinforcement materials including nanoparticles and polymers have enhanced the antimicrobial, conducting, magnetic, biocompatible, and mechanical properties of BC. Both pure BC and its composites have shown impressive applications in medical fields and in the development of optoelectronic devices. Herein, we have given a special attention to discuss its applications in the medical and electronic fields. In conclusion, BC and BC composites have realistic potential to be used in future development of medical devices, artificial organs and electronic and conducting materials. The contents discussed herein will provide an eye-catching theme to the researchers concerned with practical applications of BC and BC composites.

  1. Effects of the interfacial charge injection properties of silver nanowire transparent conductive electrodes on the performance of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Jin-Hoon; Triambulo, Ross E.; Park, Jin-Woo

    2017-03-01

    We investigated the charge injection properties of silver nanowire networks (AgNWs) in a composite-like structure with poly(2,3-dihydrothieno-1,4-dioxin)-poly(styrenesulfonate) (PEDOT:PSS). The composite films acted as the anodes and hole transport layers (HTLs) in organic light-emitting diodes (OLEDs). The current density (J)-voltage (V)-luminance (L) characteristics and power efficiency (ɛ) of the OLEDs were measured to determine their electrical and optical properties. The charge injection properties of the AgNWs in the OLEDs during operation were characterized via impedance spectroscopy (IS) by determining the variations in the capacitances (C) of the devices with respect to the applied V and the corresponding frequency (f). All measured results were compared with results for OLEDs fabricated on indium tin oxide (ITO) anodes. The OLEDs on AgNWs showed lower L and ɛ values than the OLEDs on ITO. It was also observed that AgNWs exhibit excellent charge injection properties and that the interfaces between the AgNWs and the HTL have very small charge injection barriers, resulting in an absence of charge carrier traps when charges move across these interfaces. However, in the AgNW-based OLED, there was a large mismatch in the number of injected holes and electrons. Furthermore, the highly conductive electrical paths of the AgNWs in the composite-like AgNW and PEDOT:PSS structure allowed a large leakage current of holes that did not participate in radiative recombination with the electrons; consequently, a lower ɛ was observed for the AgNW-based OLEDs than for the ITO-based OLEDs. To match the injection of electrons by the electron transport layer (ETL) in the AgNW-based OLED with that of holes by the AgNW/PEDOT:PSS composite anode, the electron injection barrier of the ETL was decreased by using the low work function polyethylenimine ethoxylated (PEIE) doped with n-type cesium carbonate (Cs2CO3). With the doped-PEIE, the performance of the AgNW-based OLED was

  2. Improving Thermoelectric Properties of Nanowires Through Inhomogeneity

    NASA Astrophysics Data System (ADS)

    González, J. Eduardo; Sánchez, Vicenta; Wang, Chumin

    2016-10-01

    Inhomogeneity in nanowires can be present in the cross-section and/or by breaking the translational symmetry along the nanowire. In particular, the quasiperiodicity introduces an unusual class of electronic and phononic transport with a singular continuous eigenvalue spectrum and critically localized wave functions. In this work, the thermoelectricity in periodic and quasiperiodically segmented nanobelts and nanowires is addressed within the Boltzmann formalism by using a real-space renormalization plus convolution method developed for the Kubo-Greenwood formula, in which tight-binding and Born models are, respectively, used for the calculation of electric and lattice thermal conductivities. For periodic nanowires, we observe a maximum of the thermoelectric figure-of-merit (ZT) in the temperature space, as occurred in the carrier concentration space. This maximum ZT can be improved by introducing into nanowires periodically arranged segments and an inhomogeneous cross-section. Finally, the quasiperiodically segmented nanowires reveal an even larger ZT in comparison with the periodic ones.

  3. Nanowire transformation and annealing by Joule heating.

    PubMed

    Hummelgård, Magnus; Zhang, Renyun; Carlberg, Torbjörn; Vengust, Damjan; Dvorsek, Damjan; Mihailovic, Dragan; Olin, Håkan

    2010-04-23

    Joule heating of bundles of Mo(6)S(3)I(6) nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo(6)S(3)I(6) into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m( - 1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

  4. DNA-templated gold nanowires

    NASA Astrophysics Data System (ADS)

    Mohammadzadegan, Reza; Mohabatkar, Hassan; Sheikhi, Mohammad Hossein; Safavi, Afsaneh; Khajouee, Mahmood Barati

    2008-10-01

    We have developed simple methods of reproducibly creating deoxyribonucleic acid (DNA)-templated gold nanowires on silicon. First DNA nanowires were aligned on silicon surfaces. Briefly, modified silicon wafer was soaked in the DNA solution, and then the solution was removed using micropipettes; the surface tension at the moving air-solution interface is sufficient to align the DNA nanowires on the silicon wafer. In another attempt, an aqueous dispersion of sodium azide-stabilized gold nanoparticles was prepared. The nanoparticles aligned double-stranded λ-DNA to form a linear nanoparticle array. Continuous gold nanowires were obtained. The above nanowires were structurally characterized using scanning electron microscopy. The results of the characterizations show the wires to be 57-323 nm wide, to be continuous with a length of 2.8-9.5 μm. The use of DNA as a template for the self-assembly of conducting nanowires represents a potentially important approach in the fabrication of nanoscale interconnects.

  5. Solution-processed copper-nickel nanowire anodes for organic solar cells.

    PubMed

    Stewart, Ian E; Rathmell, Aaron R; Yan, Liang; Ye, Shengrong; Flowers, Patrick F; You, Wei; Wiley, Benjamin J

    2014-06-07

    This work describes a process to make anodes for organic solar cells from copper-nickel nanowires with solution-phase processing. Copper nanowire films were coated from solution onto glass and made conductive by dipping them in acetic acid. Acetic acid removes the passivating oxide from the surface of copper nanowires, thereby reducing the contact resistance between nanowires to nearly the same extent as hydrogen annealing. Films of copper nanowires were made as oxidation resistant as silver nanowires under dry and humid conditions by dipping them in an electroless nickel plating solution. Organic solar cells utilizing these completely solution-processed copper-nickel nanowire films exhibited efficiencies of 4.9%.

  6. Determination of transport properties in chromium disilicide nanowires via combined thermoelectric and structural characterizations.

    PubMed

    Zhou, Feng; Szczech, Jeannine; Pettes, Michael T; Moore, Arden L; Jin, Song; Shi, Li

    2007-06-01

    The Seebeck coefficient, electrical conductivity, and thermal conductivity of individual chromium disilicide nanowires were characterized using a suspended microdevice and correlated with the crystal structure and growth direction obtained by transmission electron microscopy on the same nanowires. The obtained thermoelectric figure of merit of the nanowires was comparable to the bulk values. We show that combined Seebeck coefficient and electrical conductivity measurements provide an effective approach to probing the Fermi Level, carrier concentration and mobility in nanowires.

  7. Multilevel correlations in the biological phosphorus removal process: From bacterial enrichment to conductivity-based metabolic batch tests and polyphosphatase assays.

    PubMed

    Weissbrodt, David G; Maillard, Julien; Brovelli, Alessandro; Chabrelie, Alexandre; May, Jonathan; Holliger, Christof

    2014-12-01

    Enhanced biological phosphorus removal (EBPR) from wastewater relies on the preferential selection of active polyphosphate-accumulating organisms (PAO) in the underlying bacterial community continuum. Efficient management of the bacterial resource requires understanding of population dynamics as well as availability of bioanalytical methods for rapid and regular assessment of relative abundances of active PAOs and their glycogen-accumulating competitors (GAO). A systems approach was adopted here toward the investigation of multilevel correlations from the EBPR bioprocess to the bacterial community, metabolic, and enzymatic levels. Two anaerobic-aerobic sequencing-batch reactors were operated to enrich activated sludge in PAOs and GAOs affiliating with "Candidati Accumulibacter and Competibacter phosphates", respectively. Bacterial selection was optimized by dynamic control of the organic loading rate and the anaerobic contact time. The distinct core bacteriomes mainly comprised populations related to the classes Betaproteobacteria, Cytophagia, and Chloroflexi in the PAO enrichment and of Gammaproteobacteria, Alphaproteobacteria, Acidobacteria, and Sphingobacteria in the GAO enrichment. An anaerobic metabolic batch test based on electrical conductivity evolution and a polyphosphatase enzymatic assay were developed for rapid and low-cost assessment of the active PAO fraction and dephosphatation potential of activated sludge. Linear correlations were obtained between the PAO fraction, biomass specific rate of conductivity increase under anaerobic conditions, and polyphosphate-hydrolyzing activity of PAO/GAO mixtures. The correlations between PAO/GAO ratios, metabolic activities, and conductivity profiles were confirmed by simulations with a mathematical model developed in the aqueous geochemistry software PHREEQC.

  8. Enhanced photogenerated carrier collection in hybrid films of bio-templated gold nanowires and nanocrystalline CdSe.

    PubMed

    Haberer, Elaine D; Joo, John H; Hodelin, Juan F; Hu, Evelyn L

    2009-10-14

    Hybrid films of bio-templated gold nanowires and chemical bath deposited nanocrystalline CdSe were fabricated. The conductivity of the gold nanowires within the hybrid material was controlled by gold electroless deposition. Photocurrent measurements were taken on gold nanowire films, CdSe chemical bath deposited films, and hybrid films. The incorporation of gold nanowires within the hybrid material clearly increased the extraction of photogenerated carriers within the CdSe. Photocurrent showed a direct correlation with gold nanowire conductivity.

  9. Enhanced photogenerated carrier collection in hybrid films of bio-templated gold nanowires and nanocrystalline CdSe

    NASA Astrophysics Data System (ADS)

    Haberer, Elaine D.; Joo, John H.; Hodelin, Juan F.; Hu, Evelyn L.

    2009-10-01

    Hybrid films of bio-templated gold nanowires and chemical bath deposited nanocrystalline CdSe were fabricated. The conductivity of the gold nanowires within the hybrid material was controlled by gold electroless deposition. Photocurrent measurements were taken on gold nanowire films, CdSe chemical bath deposited films, and hybrid films. The incorporation of gold nanowires within the hybrid material clearly increased the extraction of photogenerated carriers within the CdSe. Photocurrent showed a direct correlation with gold nanowire conductivity.

  10. Superconductive silicon nanowires using gallium beam lithography.

    SciTech Connect

    Henry, Michael David; Jarecki, Robert Leo,

    2014-01-01

    This work was an early career LDRD investigating the idea of using a focused ion beam (FIB) to implant Ga into silicon to create embedded nanowires and/or fully suspended nanowires. The embedded Ga nanowires demonstrated electrical resistivity of 5 m-cm, conductivity down to 4 K, and acts as an Ohmic silicon contact. The suspended nanowires achieved dimensions down to 20 nm x 30 nm x 10 m with large sensitivity to pressure. These structures then performed well as Pirani gauges. Sputtered niobium was also developed in this research for use as a superconductive coating on the nanowire. Oxidation characteristics of Nb were detailed and a technique to place the Nb under tensile stress resulted in the Nb resisting bulk atmospheric oxidation for up to years.

  11. Electrical properties of nominally undoped silicon nanowires grown by molecular-beam epitaxy

    NASA Astrophysics Data System (ADS)

    Bauer, Jan; Fleischer, Frank; Breitenstein, Otwin; Schubert, Luise; Werner, Peter; Gösele, Ulrich; Zacharias, Margit

    2007-01-01

    Single undoped Si nanowires were electrically characterized. The nanowires were grown by molecular-beam epitaxy on n+ silicon substrates and were contacted by platinum/iridium tips. I-V curves were measured and electron beam induced current investigations were performed on single nanowires. It was found that the nanowires have an apparent resistivity of 0.85Ωcm, which is much smaller than expected for undoped Si nanowires. The conductance is explained by hopping conductivity at the Si -SiO2 interface of the nanowire surface.

  12. EDITORIAL: Nanowires for energy Nanowires for energy

    NASA Astrophysics Data System (ADS)

    LaPierre, Ray; Sunkara, Mahendra

    2012-05-01

    This special issue of Nanotechnology focuses on studies illustrating the application of nanowires for energy including solar cells, efficient lighting and water splitting. Over the next three decades, nanotechnology will make significant contributions towards meeting the increased energy needs of the planet, now known as the TeraWatt challenge. Nanowires in particular are poised to contribute significantly in this development as presented in the review by Hiralal et al [1]. Nanowires exhibit light trapping properties that can act as a broadband anti-reflection coating to enhance the efficiency of solar cells. In this issue, Li et al [2] and Wang et al [3] present the optical properties of silicon nanowire and nanocone arrays. In addition to enhanced optical properties, core-shell nanowires also have the potential for efficient charge carrier collection across the nanowire diameter as presented in the contribution by Yu et al [4] for radial junction a-Si solar cells. Hybrid approaches that combine organic and inorganic materials also have potential for high efficiency photovoltaics. A Si-based hybrid solar cell is presented by Zhang et al [5] with a photoconversion efficiency of over 7%. The quintessential example of hybrid solar cells is the dye-sensitized solar cell (DSSC) where an organic absorber (dye) coats an inorganic material (typically a ZnO nanostructure). Herman et al [6] present a method of enhancing the efficiency of a DSSC by increasing the hetero-interfacial area with a unique hierarchical weeping willow ZnO structure. The increased surface area allows for higher dye loading, light harvesting, and reduced charge recombination through direct conduction along the ZnO branches. Another unique ZnO growth method is presented by Calestani et al [7] using a solution-free and catalyst-free approach by pulsed electron deposition (PED). Nanowires can also make more efficient use of electrical power. Light emitting diodes, for example, will eventually become the

  13. Nanowire Optoelectronics

    NASA Astrophysics Data System (ADS)

    Wang, Zhihuan; Nabet, Bahram

    2015-12-01

    Semiconductor nanowires have been used in a variety of passive and active optoelectronic devices including waveguides, photodetectors, solar cells, light-emitting diodes (LEDs), lasers, sensors, and optical antennas. We review the optical properties of these nanowires in terms of absorption, guiding, and radiation of light, which may be termed light management. Analysis of the interaction of light with long cylindrical/hexagonal structures with subwavelength diameters identifies radial resonant modes, such as Leaky Mode Resonances, or Whispering Gallery modes. The two-dimensional treatment should incorporate axial variations in "volumetric modes,"which have so far been presented in terms of Fabry-Perot (FP), and helical resonance modes. We report on finite-difference timedomain (FDTD) simulations with the aim of identifying the dependence of these modes on geometry (length, width), tapering, shape (cylindrical, hexagonal), core-shell versus core-only, and dielectric cores with semiconductor shells. This demonstrates how nanowires (NWs) form excellent optical cavities without the need for top and bottommirrors. However, optically equivalent structures such as hexagonal and cylindrical wires can have very different optoelectronic properties meaning that light management alone does not sufficiently describe the observed enhancement in upward (absorption) and downward transitions (emission) of light inNWs; rather, the electronic transition rates should be considered. We discuss this "rate management" scheme showing its strong dimensional dependence, making a case for photonic integrated circuits (PICs) that can take advantage of the confluence of the desirable optical and electronic properties of these nanostructures.

  14. Tunneling magnetoresistance in Si nanowires

    NASA Astrophysics Data System (ADS)

    Montes, E.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

    2016-11-01

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green’s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  15. Reporting buckling strength and elastic properties of nanowires

    NASA Astrophysics Data System (ADS)

    Shaat, M.; Abdelkefi, A.

    2016-12-01

    Nanocrystalline-nanowires have been incorporated in many micro-/nano-scale applications. To design nanowires-based nano-devices, studies should be conducted on the characterization of the elastic properties and the buckling strengths of nanowires. The challenge associated with detecting the properties of nanowires is that their properties are size-dependent. This motivated us to propose a model for the mechanics of nanocrystalline nanowires. In the context of this model, new measures are incorportated to account for the nanowire material structure and size effects and to reflect the experimental observations of nanomaterials-nanowires. This model is then harnessed to report the ranges of the buckling strength and the elastic properties of nanowires made of nanocrystalline diamond, Si, Al, Cu, Ag, Au, and Pt, for the first time. First, we report the range of the grain boundary Young's modulus for the various nanocrystalline materials. Depending on the contents of the grain boundary and the amount of impurities, the grain boundary Young's modulus is likely to be within the reported ranges. Second, for each grain size (from 200 nm to 2 nm), we report the range of Young's modulus, shear modulus, bulk modulus, and mass density of the aforementioned nanocrystalline nanomaterials. Third, we report the buckling strength and the equivalent Young's modulus of nanowires with different sizes accounting for the nanowire surface effects. The reported ranges of the buckling strength and the elastic properties of nanowires are experimentally validated.

  16. How Copper Nanowires Grow and How To Control Their Properties.

    PubMed

    Ye, Shengrong; Stewart, Ian E; Chen, Zuofeng; Li, Bo; Rathmell, Aaron R; Wiley, Benjamin J

    2016-03-15

    Scalable, solution-phase nanostructure synthesis has the promise to produce a wide variety of nanomaterials with novel properties at a cost that is low enough for these materials to be used to solve problems. For example, solution-synthesized metal nanowires are now being used to make low cost, flexible transparent electrodes in touch screens, organic light-emitting diodes (OLEDs), and solar cells. There has been a tremendous increase in the number of solution-phase syntheses that enable control over the assembly of atoms into nanowires in the last 15 years, but proposed mechanisms for nanowire formation are usually qualitative, and for many syntheses there is little consensus as to how nanowires form. It is often not clear what species is adding to a nanowire growing in solution or what mechanistic step limits its rate of growth. A deeper understanding of nanowire growth is important for efficiently directing the development of nanowire synthesis toward producing a wide variety of nanostructure morphologies for structure-property studies or producing precisely defined nanostructures for a specific application. This Account reviews our progress over the last five years toward understanding how copper nanowires form in solution, how to direct their growth into nanowires with dimensions ideally suited for use in transparent conducting films, and how to use copper nanowires as a template to grow core-shell nanowires. The key advance enabling a better understanding of copper nanowire growth is the first real-time visualization of nanowire growth in solution, enabling the acquisition of nanowire growth kinetics. By measuring the growth rate of individual nanowires as a function of concentration of the reactants and temperature, we show that a growing copper nanowire can be thought of as a microelectrode that is charged with electrons by hydrazine and grows through the diffusion-limited addition of Cu(OH)2(-). This deeper mechanistic understanding, coupled to an

  17. Electrochromic nanostructures grown on a silicon nanowire template.

    PubMed

    Kim, Yuna; Baek, Jehoon; Kim, Myoung-Ha; Choi, Heon-Jin; Kim, Eunkyoung

    2008-09-01

    Vertically grown Si nanowires were prepared as a nanotemplate for conducting polymers. Electrochromic (EC) PEDOT (poly(3,4-ethylenedioxythiophene)) layer was successfully grown on Si nanowires by electrochemical polymerization method to form PEDOT nanowires having average wall thickness of approximately 60 nm. As-prepared conductive nanowire electrode was applied to a low voltage working EC device by fabricating an all solid state EC device. The EC properties of the device were enhanced in the nanowire structure, showing reversible fast optical transition by applying +/-2 V. The response time (t(R)) of the EC device from the PEDOT grown on Si nanowires was approximately 0.7 s, which was much faster than that from PEDOT film coated on ITO glass electrochemically (t(R)=1.9 s).

  18. Synthesis and Characterization of Nanowires

    SciTech Connect

    Musket, R.G.; Felter, T.; Quong, A.

    2000-03-01

    With the dimensions of components in microelectronic circuits shrinking, the phenomena associated with electronic conduction through wires and with device operation can be expected to change. For example, as the length of electrical conductors is reduced, ballistic transport will become the main mode of conduction. Sufficient reduction in the cross sectional area of conductors can lead to quantum confinement effects. Prior knowledge of the phenomena associated with decreasing size should help guide the designers of future, smaller devices in terms of geometry and materials. However, prior knowledge requires the availability of sufficiently small nanowires for experiments. To date, the smallest nanowires that have been fabricated and investigated had diameters of 8 nm. We propose to extend the investigation of these size-related phenomena by synthesizing, using a novel version of nuclear, or ion, track lithography and characterizing, physically and electrically, nanowires with diameters D of 1 to 5 nm and lengths L of 2 to 250 nm. Thus, by varying the dimensions of the nanowires, we will be able to determine experimentally when the ideas of macroscopic conductance break down and the conductance becomes dominated by quantum and ballistic effects. In our approach the nature of the small-diameter nanostructure formed can be controlled: Nanowires are formed when L/D is large, and quantum dots are formed when both L and D are small. Theoretical calculations will be performed to both guide and understand the experimental studies. We have examined several aspects of this challenging problem and generated some promising results, but the project was not extended for the second year as planned. Thus, we did not have sufficient resources to complete the proof of concept.

  19. Hybrid superconductor-quantum point contact devices using InSb nanowires

    NASA Astrophysics Data System (ADS)

    Gill, S. T.; Damasco, J.; Car, D.; Bakkers, E. P. A. M.; Mason, N.

    2016-12-01

    Proposals for studying topological superconductivity and Majorana bound states in a nanowire proximity coupled to superconductors require that transport in the nanowire is ballistic. Previous works on hybrid nanowire-superconductor systems have shown evidence for Majorana bound states, but these experiments were also marked by disorder, which disrupts ballistic transport. In this paper, we demonstrate ballistic transport in the InSb nanowires interfaced directly with superconducting Al by observing quantized conductance at zero-magnetic field. Additionally, we demonstrate that the nanowire is proximity coupled to the superconducting contacts by observing Andreev reflection. These results are important steps for robustly establishing topological superconductivity in the InSb nanowires.

  20. Solar heating of GaAs nanowire solar cells.

    PubMed

    Wu, Shao-Hua; Povinelli, Michelle L

    2015-11-30

    We use a coupled thermal-optical approach to model the operating temperature rise in GaAs nanowire solar cells. We find that despite more highly concentrated light absorption and lower thermal conductivity, the overall temperature rise in a nanowire structure is no higher than in a planar structure. Moreover, coating the nanowires with a transparent polymer can increase the radiative cooling power by 2.2 times, lowering the operating temperature by nearly 7 K.

  1. Tunneling and Transport in Nanowires

    SciTech Connect

    Goldman, Allen M.

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  2. A spray-coating process for highly conductive silver nanowire networks as the transparent top-electrode for small molecule organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Selzer, Franz; Weiß, Nelli; Kneppe, David; Bormann, Ludwig; Sachse, Christoph; Gaponik, Nikolai; Eychmüller, Alexander; Leo, Karl; Müller-Meskamp, Lars

    2015-01-01

    We present a novel top-electrode spray-coating process for the solution-based deposition of silver nanowires (AgNWs) onto vacuum-processed small molecule organic electronic solar cells. The process is compatible with organic light emitting diodes (OLEDs) and organic light emitting thin film transistors (OLETs) as well. By modifying commonly synthesized AgNWs with a perfluorinated methacrylate, we are able to disperse these wires in a highly fluorinated solvent. This solvent does not dissolve most organic materials, enabling a top spray-coating process for sensitive small molecule and polymer-based devices. The optimized preparation of the novel AgNW dispersion and spray-coating at only 30 °C leads to high performance electrodes directly after the deposition, exhibiting a sheet resistance of 10.0 Ω □-1 at 87.4% transparency (80.0% with substrate). By spraying our novel AgNW dispersion in air onto the vacuum-processed organic p-i-n type solar cells, we obtain working solar cells with a power conversion efficiency (PCE) of 1.23%, compared to the air exposed reference devices employing thermally evaporated thin metal layers as the top-electrode.We present a novel top-electrode spray-coating process for the solution-based deposition of silver nanowires (AgNWs) onto vacuum-processed small molecule organic electronic solar cells. The process is compatible with organic light emitting diodes (OLEDs) and organic light emitting thin film transistors (OLETs) as well. By modifying commonly synthesized AgNWs with a perfluorinated methacrylate, we are able to disperse these wires in a highly fluorinated solvent. This solvent does not dissolve most organic materials, enabling a top spray-coating process for sensitive small molecule and polymer-based devices. The optimized preparation of the novel AgNW dispersion and spray-coating at only 30 °C leads to high performance electrodes directly after the deposition, exhibiting a sheet resistance of 10.0 Ω □-1 at 87

  3. Percolating silicon nanowire networks with highly reproducible electrical properties.

    PubMed

    Serre, Pauline; Mongillo, Massimo; Periwal, Priyanka; Baron, Thierry; Ternon, Céline

    2015-01-09

    Here, we report the morphological and electrical properties of self-assembled silicon nanowires networks, also called Si nanonets. At the macroscopic scale, the nanonets involve several millions of nanowires. So, the observed properties should result from large scale statistical averaging, minimizing thus the discrepancies that occur from one nanowire to another. Using a standard filtration procedure, the so-obtained Si nanonets are highly reproducible in terms of their morphology, with a Si nanowire density precisely controlled during the nanonet elaboration. In contrast to individual Si nanowires, the electrical properties of Si nanonets are highly consistent, as demonstrated here by the similar electrical properties obtained in hundreds of Si nanonet-based devices. The evolution of the Si nanonet conductance with Si nanowire density demonstrates that Si nanonets behave like standard percolating media despite the presence of numerous nanowire-nanowire intersecting junctions into the nanonets and the native oxide shell surrounding the Si nanowires. Moreover, when silicon oxidation is prevented or controlled, the electrical properties of Si nanonets are stable over many months. As a consequence, Si nanowire-based nanonets constitute a promising flexible material with stable and reproducible electrical properties at the macroscopic scale while being composed of nanoscale components, which confirms the Si nanonet potential for a wide range of applications including flexible electronic, sensing and photovoltaic applications.

  4. Laterally assembled nanowires for ultrathin broadband solar absorbers.

    PubMed

    Song, Kyung-Deok; Kempa, Thomas J; Park, Hong-Gyu; Kim, Sun-Kyung

    2014-05-05

    We studied optical resonances in laterally oriented Si nanowire arrays by conducting finite-difference time-domain simulations. Localized Fabry-Perot and whispering-gallery modes are supported within the cross section of each nanowire in the array and result in broadband light absorption. Comparison of a nanowire array with a single nanowire shows that the current density (J(SC)) is preserved for a range of nanowire morphologies. The J(SC) of a nanowire array depends on the spacing of its constituent nanowires, which indicates that both diffraction and optical antenna effects contribute to light absorption. Furthermore, a vertically stacked nanowire array exhibits significantly enhanced light absorption because of the emergence of coupled cavity-waveguide modes and the mitigation of a screening effect. With the assumption of unity internal quantum efficiency, the J(SC) of an 800-nm-thick cross-stacked nanowire array is 14.0 mA/cm², which yields a ~60% enhancement compared with an equivalent bulk film absorber. These numerical results underpin a rational design strategy for ultrathin solar absorbers based on assembled nanowire cavities.

  5. Growth and optical properties of phosphorus-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Kim, D. S.; Fallert, J.; Lotnyk, A.; Scholz, R.; Pippel, E.; Senz, S.; Kalt, H.; Gösele, U.; Zacharias, M.

    2007-09-01

    Single-crystal phosphorus-doped ZnO nanowires were synthesized by using a single-source precursor-based vapor transport method. The photoluminescence spectra of phosphorus-doped ZnO nanowires and undoped nanowires are compared. While both show several shallow bound exciton complexes, the phosphorus-doped nanowires reveal an additional distinct emission feature at 3.316 eV. Additionally, the time-resolved PL measurements were conducted to characterize the recombination dynamics.

  6. Electrospun metallic nanowires: Synthesis, characterization, and applications

    NASA Astrophysics Data System (ADS)

    Khalil, Abdullah; Singh Lalia, Boor; Hashaikeh, Raed; Khraisheh, Marwan

    2013-11-01

    Metals are known to have unique thermal, mechanical, electrical, and catalytic properties. On the other hand, metallic nanowires are promising materials for variety of applications such as transparent conductive film for photovoltaic devices, electrodes for batteries, as well as nano-reinforcement for composite materials. Whereas varieties of methods have been explored to synthesize metal nanowires with different characteristics, electrospinning has also been found to be successful for that purpose. Even though electrospinning of polymeric nanofibers is a well-established field, there are several challenges that need to be overcome to use the electrospinning technique for the fabrication of metallic nanowires. These challenges are mainly related to the multi-steps fabrication process and its relation to the structure evolution of the nanowires. In addition to reviewing the literature, this article identifies promising avenues for further research in this area with particular emphasis on the applications that nonwoven metal wires confined in a nano-scale can open.

  7. Role of dissipation in realistic Majorana nanowires

    NASA Astrophysics Data System (ADS)

    Liu, Chun-Xiao; Sau, Jay D.; Das Sarma, S.

    2017-02-01

    We carry out a realistic simulation of Majorana nanowires in order to understand the latest high-quality experimental data [H. Zhang et al., arXiv:1603.04069 (2016)] and, in the process, develop a comprehensive picture for what physical mechanisms may be operational in realistic nanowires leading to discrepancies between minimal theory and experimental observations (e.g., weakness and broadening of the zero-bias peak and breaking of particle-hole symmetry). Our focus is on understanding specific intriguing features in the data, and our goal is to establish matters of principle controlling the physics of the best possible nanowires available in current experiments. We identify dissipation, finite temperature, multi-sub-band effects, and the finite tunnel barrier as the four most important physical mechanisms controlling the zero-bias conductance peak. Our theoretical results including these realistic effects agree well with the best available experimental data in ballistic nanowires.

  8. Periodic nanowire array at the crystal interface.

    PubMed

    Nakamura, Atsutomo; Mizoguchi, Teruyasu; Matsunaga, Katsuyuki; Yamamoto, Takahisa; Shibata, Naoya; Ikuhara, Yuichi

    2013-07-23

    A dislocation in a crystalline material has dangling bonds at its core and a strong strain field in its vicinity. Consequently, the dislocation attracts solute atoms and forms a so-called Cottrell atmosphere along the dislocation. A crystalline dislocation can be used as a template to produce nanowires by selectively doping foreign atoms along the dislocation. However, control of the configuration, spacing, and density of the formed periodic nanowire array has heretofore been extremely difficult. Here we show a method for fabricating ordered, electrically conductive nanowire arrays using periodic dislocations at crystal interfaces. As a demonstration, we fabricated arrays of titanium nanowires arranged at intervals of either 13 or 90 nm and then confirmed by scanning probe microscopy that they exhibit electrical conductivity inside an insulating aluminum oxide. Significantly, we were able to precisely control nanowire periodicity by the choice of crystal orientation and/or crystal planes at the crystal interface. This simple method for the fabrication of periodic nanowire arrays of highly controlled density should be widely applicable to electrical, magnetic, and optical devices.

  9. On-surface formation of metal nanowire transparent top electrodes on CdSe nanowire array-based photoconductive devices.

    PubMed

    Azulai, Daniel; Givan, Uri; Shpaisman, Nava; Belenkova, Tatyana Levi; Gilon, Hagit; Patolsky, Fernando; Markovich, Gil

    2012-06-27

    A simple wet chemical approach was developed for a unique on-surface synthesis of transparent conductive films consisting of ultrathin gold/silver nanowires directly grown on top of CdSe nanowire array photoconductive devices enclosed in polycarbonate membranes. The metal nanowire film formed an ohmic contact to the semiconductor nanowires without additional treatment. The sheet resistance and transparency of the metal nanowire arrays could be controlled by the number of metal nanowire layers deposited, ranging from ∼98-99% transmission through the visible range and several kOhm/sq sheet resistance for a single layer, to 80-85% transmission and ∼100 Ohm/sq sheet resistance for 4 layers.

  10. Phonon Trapping in Pearl-Necklace-Shaped Silicon Nanowires.

    PubMed

    Miao, Chunyang; Tai, Guoan; Zhou, Jianxin; Guo, Wanlin

    2015-12-22

    A pearl-necklace-shaped silicon nanowire, in contrast to a smooth nanowire, presents a much lower thermal conductivity due to the phonon trapping effect. By precisely controlling the pearl size and density, this reduction can be more than 70% for the structures designed in the study, which provides a unique approach for designing high-performance nanoscale thermoelectric devices.

  11. Boron carbide nanowires: Synthesis and characterization

    NASA Astrophysics Data System (ADS)

    Guan, Zhe

    Bulk boron carbide has been widely used in ballistic armored vest and the property characterization has been heavily focused on mechanical properties. Even though boron carbides have also been projected as a promising class of high temperature thermoelectric materials for energy harvesting, the research has been limited in this field. Since the thermal conductivity of bulk boron carbide is still relatively high, there is a great opportunity to take advantage of the nano effect to further reduce it for better thermoelectric performance. This dissertation work aims to explore whether improved thermoelectric performance can be found in boron carbide nanowires compared with their bulk counterparts. This dissertation work consists of four main parts. (1) Synthesis of boron carbide nanowires. Boron carbide nanowires were synthesized by co-pyrolysis of diborane and methane at low temperatures (with 879 °C as the lowest) in a home-built low pressure chemical vapor deposition (LPCVD) system. The CVD-based method is energy efficient and cost effective. The as-synthesized nanowires were characterized by electron microscopy extensively. The transmission electron microscopy (TEM) results show the nanowires are single crystalline with planar defects. Depending on the geometrical relationship between the preferred growth direction of the nanowire and the orientation of the defects, the as-synthesized nanowires could be further divided into two categories: transverse fault (TF) nanowires grow normal to the defect plane, while axial fault (AF) ones grow within the defect plane. (2) Understanding the growth mechanism of as-synthesized boron carbide nanowires. The growth mechanism can be generally considered as the famous vapor-liquid-solid (VLS) mechanism. TF and AF nanowires were found to be guided by Ni-B catalysts of two phases. A TF nanowire is lead by a hexagonal phase catalyst, which was proved to be in a liquid state during reaction. While an AF nanowires is catalyzed by a

  12. TOPICAL REVIEW: DNA nanowire fabrication

    NASA Astrophysics Data System (ADS)

    Gu, Qun; Cheng, Chuanding; Gonela, Ravikanth; Suryanarayanan, Shivashankar; Anabathula, Sathish; Dai, Kun; Haynie, Donald T.

    2006-01-01

    Deoxyribonucleic acid (DNA) has been a key building block in nanotechnology since the earliest work on what is now called DNA-templated self-assembly (Alivisatos et al 1996 Nature 382 609; Mirkin et al 1996 Nature 382 607; Braun et al 1998 Nature 391 775). A range of different nanoparticles and nanoclusters have been assembled on single DNA molecules for a variety of purposes (Braun et al 1998 Nature 391 775; Richter et al 2001 Appl. Phys. Lett. 78 536; Park et al 2002 Science 295 1503; Mirkin 2000 Inorg. Chem. 39 2258; Keren et al 2003 Science 302 1380). Electrically conductive silver (Braun et al 1998 Nature 391 775) and palladium (Richter et al 2001 Appl. Phys. Lett. 78 536) nanowires, for example, have been fabricated by DNA templating for the development of interconnection of nanoelectric elements, and field effect transistors have been built by assembly of a single carbon nanotube and DNA-templated nanowires (Keren et al 2003 Science 302 1380). DNA is well suited for nanowire assembly because of its size, well organized structure, and exquisite molecular-recognition-ability-specific base pairing. This property has been used to detect nucleic acids (Park et al 2002 Science 295 1503) and anthrax (Mirkin 2000 Inorg. Chem. 39 2258) with high sensitivity and specificity. Molecular recognition can also be used to localize nanowires in electronics. Various methods, for example molecular combing, electrophoretic stretching, and hydrodynamic stretching, have been developed to orient DNA molecules on a solid support. This review focuses on methods used to manipulate and metallize DNA in nanowire fabrication. A novel approach based on a single-stranded DNA template and molecular recognition is also discussed.

  13. Electron beam tuning of carrier concentrations in oxide nanowires

    NASA Astrophysics Data System (ADS)

    Ji, Hyunjin; Choi, Jaewan; Cho, Youngseung; Hwang, In-Sung; Kim, Sun-Jung; Lee, Jong-Heun; Roth, Siegmar; Kim, Gyu-Tae

    2011-07-01

    In spite of the attractive electrical properties of metal oxide nanowires, it is difficult to tune their surface states, notably the ionic adsorbents and oxygen vacancies, both of which can cause instability, degradation, and the irreproducibility or unrepeatable changes of the electrical characteristics. In order to control the surface states of the nanowires, electron beams were locally irradiated onto the channels of metal oxide nanowire field effect transistors. This high energy electron beam irradiation changed the electrical properties of the individual metal oxide nanowires, due to the removal of the negative adsorbents (O2-, O-). The detachment of the ionic adsorbents changes the charge states of the nanowires, resulting in the enhancement of the electrical conductance in n-type nanowires (ZnO, SnO2) and the degradation of the conductance in p-type nanowires (CuO). By investigating the changes in the electrical properties of nanowire devices in air or vacuum, with or without exposure to electron beams, the roles of the physisorbed water molecules or chemisorbed oxygen molecules can be independently understood. Unlike the electron beam irradiation, the vacuum enhanced the conductance of both n-type (ZnO, SnO2) and p-type (CuO) nanowires, due to the release of charges caused by the detachment of the polarized water molecules that were screening them from the surface of the nanowires, irrespective of the major carrier type. The electron beam irradiation technique has the potential to locally modulate the charge carriers in electronic nanowire devices, and the changes could be maintained with proper passivation for the long-term preservation of the device characteristics.

  14. Stoichiometry dependent electron transport and gas sensing properties of indium oxide nanowires.

    PubMed

    Gali, Pradeep; Sapkota, Gopal; Syllaios, A J; Littler, Chris; Philipose, U

    2013-06-07

    The effect of stoichiometry of single crystalline In2O3 nanowires on electrical transport and gas sensing was investigated. The nanowires were synthesized by vapor phase transport and had diameters ranging from 80 to 100 nm and lengths between 10 and 20 μm, with a growth direction of [001]. Transport measurements revealed n-type conduction, attributed to the presence of oxygen vacancies in the crystal lattice. As-grown In2O3 nanowires were shown to have a carrier concentration of ≈5 × 10(17) cm(-3), while nanowires that were annealed in wet O2 showed a reduced carrier concentration of less than 10(16) cm(-3). Temperature dependent conductivity measurements on the as-grown nanowires and analysis of the thermally activated Arrhenius conduction for the temperature range of 77-350 K yielded an activation energy of 0.12 eV. This is explained on the basis of carrier exchange that occurs between the surface states and the bulk of the nanowire, resulting in a depleted surface layer of thickness of the order of the Debye length (LD), estimated to be about 3-4 nm for the as-grown nanowires and about 10 times higher for the more stoichiometric nanowires. Significant changes in the electrical conductance of individual In2O3 nanowires were also observed within several seconds of exposure to NH3 and O2 gas molecules at room temperature, thus demonstrating the potential use of In2O3 nanowires as efficient miniaturized chemical sensors. The sensing mechanism is dominated by the nanowire channel conductance, and a simple energy band diagram is used to explain the change in conductivity when gas molecules adsorbed on the nanowire surface influence its electrical properties. Less stoichiometric nanowires were found to be more sensitive to oxidizing gases while more stoichiometric nanowires showed significantly enhanced response to reducing gases.

  15. Nonlocal optical response of plasmonic nanowire metamaterials

    NASA Astrophysics Data System (ADS)

    Wells, Brian Michael

    Nanowire metamaterials are a class of composite photonic media formed by an array of aligned plasmonic nanowires embedded in a dielectric matrix. Depending on exact composition, geometry, and excitation wavelength, nanowire structures are known to exhibit elliptical, hyperbolic, or epsilon-near-zero (ENZ) responses. In the ENZ regime, optical response of the composite becomes strongly nonlocal. Excitation of an additional wave, caused by nonlocality, has been experimentally demonstrated in nanowire-based metamaterials. In this thesis, a computational study of the nonlocal optical response in plasmonic nanowire arrays has been conducted to better understand such materials. The results of this computational study were used to develop an analytical technique that provides an adequate description of the optical response of wire based metamaterials. This formalism combines the local and nonlocal effective-medium theories often used to describe the optics of nanowire composites. It provides insight into the origin of the additional wave and allows implementation of additional boundary conditions. This approach can be straightforwardly extended to describe the optics for numerious plasmonic structures.

  16. Electrical and Optical Characterization of Nanowire based Semiconductor Devices

    NASA Astrophysics Data System (ADS)

    Ayvazian, Talin

    (KPFM) was utilized to understand mechanism of light emission in CdSe nanowires. Arrays of CdTe nanowires were electrodeposited using LPNE process where the elec- trodeposition of pc-CdTe was carried out at two temperatures: 20 °C (cold) and 55 °C (hot). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) re- sults revealed higher crystallinity, larger grain size and presence of Te for nanowires prepared at 55°C compared to nanowires deposited at 20°C. Nanowires prepared at 55°C showed higher electrical conductivity and enhanced electroluminescence proper- ties, including higher light emission intensity and improved External Quantum Efficiency (EQE). Electrical conduction mechanism also investigated for CdTe nanowires. Thermionic emission over schottky barrier height was identified as the dominant charge transport mechanism in pc-CdTe nanowires.°C x 1h enhanced grain growth confirmed by structural characterization including X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Raman Spectroscopy. Correspondingly the light emission intensity and EQE improved due to this grain growth. Kelvin probe force microscopy (KPFM) was utilized to understand mechanism of light emission in CdSe nanowires. Arrays of CdTe nanowires were electrodeposited using LPNE process where the electrodeposition of pc-CdTe was carried out at two temperatures: 20 °C (cold) and 55 °C (hot). Transmission electron microscopy (TEM) and X-ray diffraction (XRD) re- sults revealed higher crystallinity, larger grain size and presence of Te for nanowires prepared at 55°C compared to nanowires deposited at 20°C. Nanowires prepared at 55°C showed higher electrical conductivity and enhanced electroluminescence properties, including higher light emission intensity and improved External Quantum Efficiency (EQE). Electrical conduction mechanism also investigated for CdTe nanowires. Thermionic emission over schottky barrier height was identified as the dominant charge transport

  17. Growth of silver nanowires on GaAs wafers.

    PubMed

    Sun, Yugang

    2011-05-01

    Silver (Ag) nanowires with chemically clean surfaces have been directly grown on semi-insulating gallium arsenide (GaAs) wafers through a simple solution/solid interfacial reaction (SSIR) between the GaAs wafers themselves and aqueous solutions of silver nitrate (AgNO(3)) at room temperature. The success in synthesis of Ag nanowires mainly benefits from the low concentration of surface electrons in the semi-insulating GaAs wafers that can lead to the formation of a low-density of nuclei that facilitate their anisotropic growth into nanowires. The resulting Ag nanowires exhibit rough surfaces and reasonably good electric conductivity. These characteristics are beneficial to sensing applications based on single-nanowire surface-enhanced Raman scattering (SERS) and possible surface-adsorption-induced conductivity variation.

  18. Thermoelectric properties of large-scale Zn3P2 nanowire assemblies.

    PubMed

    Brockway, Lance; Vasiraju, Venkata; Asayesh-Ardakani, Hasti; Shahbazian-Yassar, Reza; Vaddiraju, Sreeram

    2014-04-11

    Gram quantities of both unfunctionalized and 1,4-benzenedithiol (BDT) functionalized zinc phosphide (Zn3P2) nanowire powders, synthesized using direct reaction of zinc and phosphorus, were hot-pressed into highly dense pellets (≥98% of the theoretical density) for the determination of their thermoelectric performance. It was deduced that mechanical flexibility of the nanowires is essential for consolidating them in randomly oriented fashion into dense pellets, without making any major changes to their morphologies. Electrical and thermal transport measurements indicated that the enhanced thermoelectric performance expected of individual Zn3P2 nanowires is still retained within large-scale nanowire assemblies. A maximum reduction of 28% in the thermal conductivity of Zn3P2 resulted from nanostructuring. Use of nanowire morphology also led to enhanced electrical conductivity in Zn3P2. Interface engineering of the nanowires in the pellets, accomplished by hot-pressing BDT functionalized nanowires, resulted in an increase on both the Seebeck coefficient and the electrical conductivity of the nanowire pellets. It is believed that filtering of low energy carriers resulting from the variation of the chemical compositions at the nanowire interfaces is responsible for this phenomenon. Overall, this study indicated that mechanical properties of the nanowires along with the chemical compositions of their surfaces play a hitherto unknown, but vital, role in realizing highly efficient bulk thermoelectric modules based on nanowires.

  19. Thermoelectric properties of large-scale Zn3 P2 nanowire assemblies

    NASA Astrophysics Data System (ADS)

    Brockway, Lance; Vasiraju, Venkata; Asayesh-Ardakani, Hasti; Shahbazian-Yassar, Reza; Vaddiraju, Sreeram

    2014-04-01

    Gram quantities of both unfunctionalized and 1,4-benzenedithiol (BDT) functionalized zinc phosphide (Zn3P2) nanowire powders, synthesized using direct reaction of zinc and phosphorus, were hot-pressed into highly dense pellets (≥98% of the theoretical density) for the determination of their thermoelectric performance. It was deduced that mechanical flexibility of the nanowires is essential for consolidating them in randomly oriented fashion into dense pellets, without making any major changes to their morphologies. Electrical and thermal transport measurements indicated that the enhanced thermoelectric performance expected of individual Zn3P2 nanowires is still retained within large-scale nanowire assemblies. A maximum reduction of 28% in the thermal conductivity of Zn3P2 resulted from nanostructuring. Use of nanowire morphology also led to enhanced electrical conductivity in Zn3P2. Interface engineering of the nanowires in the pellets, accomplished by hot-pressing BDT functionalized nanowires, resulted in an increase on both the Seebeck coefficient and the electrical conductivity of the nanowire pellets. It is believed that filtering of low energy carriers resulting from the variation of the chemical compositions at the nanowire interfaces is responsible for this phenomenon. Overall, this study indicated that mechanical properties of the nanowires along with the chemical compositions of their surfaces play a hitherto unknown, but vital, role in realizing highly efficient bulk thermoelectric modules based on nanowires.

  20. The protective effect of osmoprotectant TMAO on bacterial mechanosensitive channels of small conductance MscS/MscK under high hydrostatic pressure.

    PubMed

    Petrov, Evgeny; Rohde, Paul R; Cornell, Bruce; Martinac, Boris

    2012-01-01

    Activity of the bacterial mechanosensitive channels of small conductance MscS/MscK of E. coli was investigated under high hydrostatic pressure (HHP) using the "flying-patch" patch-clamp technique. The channels were gated by negative pipette voltage and their open probability was measured at HHP of 0.1 to 80 MPa. The channel open probability decreased with increasing HHP. When the osmolyte methylamine N-oxide (TMAO) was applied to the cytoplasmic side of the inside-out excised membrane patches of E. coli giant spheroplasts the inhibitory effect of HHP on the channel activity was suppressed at pressures of up to 40 MPa. At 40 MPa and above the channel open probability decreased in a similar fashion with or without TMAO. Our study suggests that TMAO helps to counteract the effect of HHP up to 40 MPa on the MscS/MscK open state by "shielding" the cytoplasmic domain of the channels.

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

    PubMed

    Ben Khedim, Meriam; Cagnon, Laurent; Garagnon, Christophe; Serradeil, Valerie; Bourgault, Daniel

    2016-04-28

    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.

  2. Advances in nanowire bioelectronics

    NASA Astrophysics Data System (ADS)

    Zhou, Wei; Dai, Xiaochuan; Lieber, Charles M.

    2017-01-01

    Semiconductor nanowires represent powerful building blocks for next generation bioelectronics given their attractive properties, including nanometer-scale footprint comparable to subcellular structures and bio-molecules, configurable in nonstandard device geometries readily interfaced with biological systems, high surface-to-volume ratios, fast signal responses, and minimum consumption of energy. In this review article, we summarize recent progress in the field of nanowire bioelectronics with a focus primarily on silicon nanowire field-effect transistor biosensors. First, the synthesis and assembly of semiconductor nanowires will be described, including the basics of nanowire FETs crucial to their configuration as biosensors. Second, we will introduce and review recent results in nanowire bioelectronics for biomedical applications ranging from label-free sensing of biomolecules, to extracellular and intracellular electrophysiological recording.

  3. Multicolored Vertical Silicon Nanowires

    SciTech Connect

    Seo, Kwanyong; Wober, Munib; Steinvurzel, P.; Schonbrun, E.; Dan, Yaping; Ellenbogen, T.; Crozier, K. B.

    2011-04-13

    We demonstrate that vertical silicon nanowires take on a surprising variety of colors covering the entire visible spectrum, in marked contrast to the gray color of bulk silicon. This effect is readily observable by bright-field microscopy, or even to the naked eye. The reflection spectra of the nanowires each show a dip whose position depends on the nanowire radii. We compare the experimental data to the results of finite difference time domain simulations to elucidate the physical mechanisms behind the phenomena we observe. The nanowires are fabricated as arrays, but the vivid colors arise not from scattering or diffractive effects of the array, but from the guided mode properties of the individual nanowires. Each nanowire can thus define its own color, allowing for complex spatial patterning. We anticipate that the color filter effect we demonstrate could be employed in nanoscale image sensor devices.

  4. Phonons in Ge nanowires

    NASA Astrophysics Data System (ADS)

    Peelaers, H.; Partoens, B.; Peeters, F. M.

    2009-09-01

    The phonon spectra of thin freestanding, hydrogen passivated, Ge nanowires are calculated by ab initio techniques. The effect of confinement on the phonon modes as caused by the small diameters of the wires is investigated. Confinement causes a hardening of the optical modes and a softening of the longitudinal acoustic modes. The stability of the nanowires, undoped or doped with B or P atoms, is investigated using the obtained phonon spectra. All considered wires were stable, except for highly doped, very thin nanowires.

  5. Joule heating in nanowires

    NASA Astrophysics Data System (ADS)

    Fangohr, Hans; Chernyshenko, Dmitri S.; Franchin, Matteo; Fischbacher, Thomas; Meier, Guido

    2011-08-01

    We study the effect of Joule heating from electric currents flowing through ferromagnetic nanowires on the temperature of the nanowires and on the temperature of the substrate on which the nanowires are grown. The spatial current density distribution, the associated heat generation, and diffusion of heat are simulated within the nanowire and the substrate. We study several different nanowire and constriction geometries as well as different substrates: (thin) silicon nitride membranes, (thick) silicon wafers, and (thick) diamond wafers. The spatially resolved increase in temperature as a function of time is computed. For effectively three-dimensional substrates (where the substrate thickness greatly exceeds the nanowire length), we identify three different regimes of heat propagation through the substrate: regime (i), where the nanowire temperature increases approximately logarithmically as a function of time. In this regime, the nanowire temperature is well described analytically by You [Appl. Phys. Lett.APPLAB0003-695110.1063/1.2399441 89, 222513 (2006)]. We provide an analytical expression for the time tc that marks the upper applicability limit of the You model. After tc, the heat flow enters regime (ii), where the nanowire temperature stays constant while a hemispherical heat front carries the heat away from the wire and into the substrate. As the heat front reaches the boundary of the substrate, regime (iii) is entered, where the nanowire and substrate temperature start to increase rapidly. For effectively two-dimensional substrates (where the nanowire length greatly exceeds the substrate thickness), there is only one regime in which the temperature increases logarithmically with time for large times, before the heat front reaches the substrate boundary. We provide an analytical expression, valid for all pulse durations, that allows one to accurately compute this temperature increase in the nanowire on thin substrates.

  6. Efficient Capture and Isolation of Tumor-Related Circulating Cell-Free DNA from Cancer Patients Using Electroactive Conducting Polymer Nanowire Platforms

    PubMed Central

    Jeon, SeungHyun; Lee, HyungJae; Bae, Kieun; Yoon, Kyong-Ah; Lee, Eun Sook; Cho, Youngnam

    2016-01-01

    Circulating cell-free DNA (cfDNA) is currently recognized as a key non-invasive biomarker for cancer diagnosis and progression and therapeutic efficacy monitoring. Because cfDNA has been detected in patients with diverse types of cancers, the use of efficient strategies to isolate cfDNA not only provides valuable insights into tumour biology, but also offers the potential for developing new cancer-specific targets. However, the challenges associated with conventional cfDNA extraction methods prevent their further clinical applications. Here, we developed a nanostructured conductive polymer platform for the efficient capture and release of circulating cfDNA and demonstrated its potential clinical utility using unprocessed plasma samples from patients with breast and lung cancers. Our results confirmed that the platform's enhanced efficiency allows tumor-specific circulating cfDNA to be recovered at high yield and purity. PMID:27162553

  7. Superconducting qubits with semiconductor nanowire Josephson junctions

    NASA Astrophysics Data System (ADS)

    Petersson, K. D.; Larsen, T. W.; Kuemmeth, F.; Jespersen, T. S.; Krogstrup, P.; Nygård, J.; Marcus, C. M.

    2015-03-01

    Superconducting transmon qubits are a promising basis for a scalable quantum information processor. The recent development of semiconducting InAs nanowires with in situ molecular beam epitaxy-grown Al contacts presents new possibilities for building hybrid superconductor/semiconductor devices using precise bottom up fabrication techniques. Here, we take advantage of these high quality materials to develop superconducting qubits with superconductor-normal-superconductor Josephson junctions (JJs) where the normal element is an InAs semiconductor nanowire. We have fabricated transmon qubits in which the conventional Al-Al2O3-Al JJs are replaced by a single gate-tunable nanowire JJ. Using spectroscopy to probe the qubit we observe fluctuations in its level splitting with gate voltage that are consistent with universal conductance fluctuations in the nanowire's normal state conductance. Our gate-tunable nanowire transmons may enable new means of control for large scale qubit architectures and hybrid topological quantum computing schemes. Research supported by Microsoft Station Q, Danish National Research Foundation, Villum Foundation, Lundbeck Foundation and the European Commission.

  8. Electrical transport and thermoelectric properties of boron carbide nanowires.

    PubMed

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-07

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200-450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  9. Electrical transport and thermoelectric properties of boron carbide nanowires

    NASA Astrophysics Data System (ADS)

    Kirihara, Kazuhiro; Mukaida, Masakazu; Shimizu, Yoshiki

    2017-04-01

    The electrical transport and thermoelectric property of boron carbide nanowires synthesized by a carbothermal method are reported. It is demonstrated that the nanowires achieve a higher Seebeck coefficient and power factor than those of the bulk samples. The conduction mechanism of the nanowires at low temperatures below 300 K is different from that of the sintered-polycrystalline and single-crystal bulk samples. In a temperature range of 200–450 K, there is a crossover between electrical conduction by variable-range hopping and phonon-assisted hopping. The inhomogeneous carbon concentration and planar defects, such as twins and stacking faults, in the nanowires are thought to modify the bonding nature and electronic structure of the boron carbide crystal substantially, causing differences in the electrical conductivity and Seebeck coefficient. The effect of boundary scattering of phonon at nanostructured surface on the thermal conductivity reduction is discussed.

  10. One-step synthesis of vertically aligned anatase thornbush-like TiO2 nanowire arrays on transparent conducting oxides for solid-state dye-sensitized solar cells.

    PubMed

    Roh, Dong Kyu; Chi, Won Seok; Ahn, Sung Hoon; Jeon, Harim; Kim, Jong Hak

    2013-08-01

    Herein, we report a facile synthesis of high-density anatase-phase vertically aligned thornbush-like TiO2 nanowires (TBWs) on transparent conducting oxide glasses. Morphologically controllable TBW arrays of 9 μm in length are generated through a one-step hydrothermal reaction at 200 °C over 11 h using potassium titanium oxide oxalate dehydrate, diethylene glycol (DEG), and water. The TBWs consist of a large number of nanoplates or nanorods, as confirmed by SEM and TEM imaging. The morphologies of TBWs are controllable by adjusting DEG/water ratios. TBW diameters gradually decrease from 600 (TBW600) to 400 (TBW400) to 200 nm (TBW200) and morphologies change from nanoplates to nanorods with an increase in DEG content. TBWs are utilized as photoanodes for quasi-solid-state dye-sensitized solar cells (qssDSSCs) and solid-state DSSCs (ssDSSCs). The energy-conversion efficiency of qssDSSCs is in the order: TBW200 (5.2%)>TBW400 (4.5%)>TBW600 (3.4%). These results can be attributed to the different surface areas, light-scattering effects, and charge transport rates, as confirmed by dye-loading measurements, reflectance spectroscopy, and incident photon-to-electron conversion efficiency and intensity-modulated photovoltage spectroscopy/intensity-modulated photocurrent spectroscopy analyses. TBW200 is further treated with a graft-copolymer-directed organized mesoporous TiO2 to increase the surface area and interconnectivity of TBWs. As a result, the energy-conversion efficiency of the ssDSSC increases to 6.7% at 100 mW cm(-2) , which is among the highest values for N719-dye-based ssDSSCs.

  11. Reliable Fabrication of Metal Contacts on Silicon Nanowire Forests.

    PubMed

    Dimaggio, Elisabetta; Pennelli, Giovanni

    2016-07-13

    We present a technique for the fabrication of an electrical (and thermal) contact on the top ends of a large number of vertical silicon nanowires, which are fabricated perpendicularly to a silicon wafer (silicon nanowire forest). The technique is based on electrochemical deposition of copper and has been developed on silicon nanowire forests, fabricated by metal assisted chemical etching. We demonstrate that copper grows selectively only on the top end of the silicon nanowires, forming a layer onto the top of the forest. The presence of a predeposited metal seed is fundamental for the selective growth, meanwhile the process is very strong with respect to other parameters, such as concentration of the electrolytic solution and current density, used during the metal deposition. Typical I-V characteristics of top-to-bottom conduction through silicon nanowire forests with different n-doping are shown and discussed.

  12. Temperature effects on electrical transport in semiconducting nanoporous carbon nanowires

    NASA Astrophysics Data System (ADS)

    Samuel, B. A.; Rajagopalan, R.; Foley, H. C.; Haque, M. A.

    2008-07-01

    In this paper we report on the effect of temperature on the electrical conductivity of amorphous and nanoporous (pores size around 0.5 nm) carbon nanowires. Poly(furfuryl alcohol) nanowires with diameter varying from 150 to 250 nm were synthesized by a template-based technique and upon pyrolysis yielded amorphous carbon nanowires with nanosized pores in them. We observed significant (as high as 700%) decrease in electrical resistance when the nanowire surface temperature was increased from room temperature to 160 °C. On the basis of the experimental and microscopy evidence, we infer a thermally activated carrier transport mechanism to be the primary electrical transport mechanism, at elevated temperatures, in these semiconducting, amorphous, and nanoporous carbon nanowires.

  13. Super-Joule heating in graphene and silver nanowire network

    SciTech Connect

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali E-mail: alam@purdue.edu; Janes, David B.; Alam, Muhammad A. E-mail: alam@purdue.edu

    2015-04-06

    Transistors, sensors, and transparent conductors based on randomly assembled nanowire networks rely on multi-component percolation for unique and distinctive applications in flexible electronics, biochemical sensing, and solar cells. While conduction models for 1-D and 1-D/2-D networks have been developed, typically assuming linear electronic transport and self-heating, the model has not been validated by direct high-resolution characterization of coupled electronic pathways and thermal response. In this letter, we show the occurrence of nonlinear “super-Joule” self-heating at the transport bottlenecks in networks of silver nanowires and silver nanowire/single layer graphene hybrid using high resolution thermoreflectance (TR) imaging. TR images at the microscopic self-heating hotspots within nanowire network and nanowire/graphene hybrid network devices with submicron spatial resolution are used to infer electrical current pathways. The results encourage a fundamental reevaluation of transport models for network-based percolating conductors.

  14. Gallium nitride nanowire based nanogenerators and light-emitting diodes.

    PubMed

    Chen, Chih-Yen; Zhu, Guang; Hu, Youfan; Yu, Jeng-Wei; Song, Jinghui; Cheng, Kai-Yuan; Peng, Lung-Han; Chou, Li-Jen; Wang, Zhong Lin

    2012-06-26

    Single-crystal n-type GaN nanowires have been grown epitaxially on a Mg-doped p-type GaN substrate. Piezoelectric nanognerators based on GaN nanowires are investigated by conductive AFM, and the results showed an output power density of nearly 12.5 mW/m(2). Luminous LED modules based on n-GaN nanowires/p-GaN substrate have been fabricated. CCD images of the lighted LED and the corresponding electroluminescence spectra are recorded at a forward bias. Moreover, the GaN nanowire LED can be lighted up by the power provided by a ZnO nanowire based nanogenerator, demonstrating a self-powered LED using wurtzite-structured nanomaterials.

  15. Structural characterization of nanowires and nanowire arrays

    NASA Astrophysics Data System (ADS)

    Becker, Catherine Rose

    Nanowires, which have diameter less than a few hundred nanometers and high aspect ratios, may have the same properties as their corresponding bulk materials, or may exhibit unique properties due to their confined dimensions and increased surface to volume ratios. They are a popular field of technological investigation in applications that depend on the transport of charge carriers, because of expectations that microcircuit miniaturization will lead to the next boom in the electronics industry. In this work, the high spatial resolution afforded by transmission electron microscopy (TEM) is used to study nanowires formed by electrochemical deposition into porous alumina templates. The goal is to determine the effect of the synthesis and subsequent processing on the microstructure and crystallinity of the wires. A thorough understanding of the microstructural features of a material is vital for optimizing its performance in a desired application. Two material systems were studied in this work. The first is bismuth telluride (Bi 2Te3), which is used in thermoelectric applications. The second is metallic copper, the electrochemical deposition of which is of interest for interconnects in semiconductor devices. The first part of this work utilized TEM to obtain a thorough characterization of the microstructural features of individual Bi2Te3 nanowires following release from the templates. As deposited, the nanowires are fine grained and exhibit significant lattice strain. Annealing increases the grain size and dislocations are created to accommodate the lattice strain. The degree of these microstructural changes depends on the thermal treatment. However, no differences were seen in the nanowire microstructure as a function of the synthetic parameters. The second part of this work utilized a modified dark field TEM technique in order to obtain a spatially resolved, semi-quantitative understanding of the evolution of preferred orientation as a function of the electrochemical

  16. Nanowire Photovoltaic Devices

    NASA Technical Reports Server (NTRS)

    Forbes, David

    2015-01-01

    Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

  17. Metallic nanowire networks

    DOEpatents

    Song, Yujiang; Shelnutt, John A.

    2012-11-06

    A metallic nanowire network synthesized using chemical reduction of a metal ion source by a reducing agent in the presence of a soft template comprising a tubular inverse micellar network. The network of interconnected polycrystalline nanowires has a very high surface-area/volume ratio, which makes it highly suitable for use in catalytic applications.

  18. Effects of length dispersity and film fabrication on the sheet resistance of copper nanowire transparent conductors

    NASA Astrophysics Data System (ADS)

    Borchert, James W.; Stewart, Ian E.; Ye, Shengrong; Rathmell, Aaron R.; Wiley, Benjamin J.; Winey, Karen I.

    2015-08-01

    Development of thin-film transparent conductors (TC) based on percolating networks of metal nanowires has leaped forward in recent years, owing to the improvement of nanowire synthetic methods and modeling efforts by several research groups. While silver nanowires are the first commercially viable iteration of this technology, systems based on copper nanowires are not far behind. Here we present an analysis of TCs composed of copper nanowire networks on sheets of polyethylene terephthalate that have been treated with various oxide-removing post treatments to improve conductivity. A pseudo-2D rod network modeling approach has been modified to include lognormal distributions in length that more closely reflect experimental data collected from the nanowire TCs. In our analysis, we find that the copper nanowire TCs are capable of achieving comparable electrical performance to silver nanowire TCs with similar dimensions. Lastly, we present a method for more accurately determining the nanowire area coverage in a TC over a large area using Rutherford Backscattering Spectrometry (RBS) to directly measure the metal content in the TCs. These developments will aid research and industry groups alike in the characterization of nanowire based TCs.Development of thin-film transparent conductors (TC) based on percolating networks of metal nanowires has leaped forward in recent years, owing to the improvement of nanowire synthetic methods and modeling efforts by several research groups. While silver nanowires are the first commercially viable iteration of this technology, systems based on copper nanowires are not far behind. Here we present an analysis of TCs composed of copper nanowire networks on sheets of polyethylene terephthalate that have been treated with various oxide-removing post treatments to improve conductivity. A pseudo-2D rod network modeling approach has been modified to include lognormal distributions in length that more closely reflect experimental data collected

  19. The Electrodeposition of Lead Telluride Nanowires for Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Hillman, Peter

    The electrodeposition of PbTe nanowires for thermoelectric applications is presented in this thesis. The Pb-Te electrochemical system was investigated to determine the optimal conditions for deposition. It was found that citric acid complexed tellurium in solution shifting its reduction potential cathodically. The shift in reduction potential led to the deposition of pure PbTe without any observable excess tellurium. Nanowires of PbTe were doped p-type and n-type through the addition of thallium and indium to the plating solution. Indium-doped nanowire arrays showed a linear relation between lattice parameter and atomic percent indium confirming successful incorporation. The lattice parameter trend in thallium-doped nanowire arrays was linear only after annealing. In the case of thallium doping, thallium tellurides were formed, which upon annealing formed a solid solution with PbTe. The results of the thallium doping study led to the investigation of the Tl-Te electrochemical system. Cyclic voltammagrams were used to determine the deposition mechanism of TlTe and Tl5Te3. Thin films and nanowire arrays of these compounds were deposited. This was the first study of the electrochemical Tl-Te system and the first report of the electrodeposition of TlTe and Tl5Te3. Thermoelectric measurements were conducted on thin films and nanowire arrays of PbTe. The Seebeck coefficient and resistivity of PbTe thin film were measured. Results from thin films were complicated by the Pt substrate on which PbTe was deposited. Subtracting the effects of the Pt layer suggested PbTe thin films could have a large zT, however further work is needed to confirm this result. Resistivity measurements on nanowire arrays were also conducted. Despite efforts to minimize the oxidation of PbTe nanowires, good electrical contacts could not be created. The resistivity of nanowire arrays were orders of magnitude higher than expected. As a result of their low conductivity, the thermoelectric efficiency

  20. Printing nanotube/nanowire for flexible microsystems

    NASA Astrophysics Data System (ADS)

    Tortorich, Ryan P.; Choi, Jin-Woo

    2014-04-01

    Printing has become an emerging manufacturing technology for mechanics, electronics, and consumer products. Additionally, both nanotubes and nanowires have recently been used as materials for sensors and electrodes due to their unique electrical and mechanical properties. Printed electrodes and conductive traces particularly offer versatility of fabricating low-cost, disposable, and flexible electrical devices and microsystems. While various printing methods such as screen printing have been conventional methods for printing conductive traces and electrodes, inkjet printing has recently attracted great attention due to its unique advantages including no template requirement, rapid printing at low cost, on-demand printing capability, and precise control of the printed material. Computer generated conductive traces or electrode patterns can simply be printed on a thin film substrate with proper conductive ink consisting of nanotubes or nanowires. However, in order to develop nanotube or nanowire ink, there are a few challenges that need to be addressed. The most difficult obstacle to overcome is that of nanotube/nanowire dispersion within a solution. Other challenges include adjusting surface tension and controlling viscosity of the ink as well as treating the surface of the printing substrate. In an attempt to pave the way for nanomaterial inkjet printing, we present a method for preparing carbon nanotube ink as well as its printing technique. A fully printed electrochemical sensor using inkjet-printed carbon nanotube electrodes is also demonstrated as an example of the possibilities for this technology.

  1. Semiconductor nanowire lasers

    NASA Astrophysics Data System (ADS)

    Eaton, Samuel W.; Fu, Anthony; Wong, Andrew B.; Ning, Cun-Zheng; Yang, Peidong

    2016-06-01

    The discovery and continued development of the laser has revolutionized both science and industry. The advent of miniaturized, semiconductor lasers has made this technology an integral part of everyday life. Exciting research continues with a new focus on nanowire lasers because of their great potential in the field of optoelectronics. In this Review, we explore the latest advancements in the development of nanowire lasers and offer our perspective on future improvements and trends. We discuss fundamental material considerations and the latest, most effective materials for nanowire lasers. A discussion of novel cavity designs and amplification methods is followed by some of the latest work on surface plasmon polariton nanowire lasers. Finally, exciting new reports of electrically pumped nanowire lasers with the potential for integrated optoelectronic applications are described.

  2. Porous silicon nanowires for lithium rechargeable batteries.

    PubMed

    Yoo, Jung-Keun; Kim, Jongsoon; Lee, Hojun; Choi, Jaesuk; Choi, Min-Jae; Sim, Dong Min; Jung, Yeon Sik; Kang, Kisuk

    2013-10-25

    Porous silicon nanowire is fabricated by a simple electrospinning process combined with a magnesium reduction; this material is investigated for use as an anode material for lithium rechargeable batteries. We find that the porous silicon nanowire electrode from the simple and scalable method can deliver a high reversible capacity with an excellent cycle stability. The enhanced performance in terms of cycling stability is attributed to the facile accommodation of the volume change by the pores in the interconnect and the increased electronic conductivity due to a multi-level carbon coating during the fabrication process.

  3. Porous silicon nanowires for lithium rechargeable batteries

    NASA Astrophysics Data System (ADS)

    Yoo, Jung-Keun; Kim, Jongsoon; Lee, Hojun; Choi, Jaesuk; Choi, Min-Jae; Sim, Dong Min; Jung, Yeon Sik; Kang, Kisuk

    2013-10-01

    Porous silicon nanowire is fabricated by a simple electrospinning process combined with a magnesium reduction; this material is investigated for use as an anode material for lithium rechargeable batteries. We find that the porous silicon nanowire electrode from the simple and scalable method can deliver a high reversible capacity with an excellent cycle stability. The enhanced performance in terms of cycling stability is attributed to the facile accommodation of the volume change by the pores in the interconnect and the increased electronic conductivity due to a multi-level carbon coating during the fabrication process.

  4. Nanotubes, Nanowires, and Nanocantilevers in Biosensor Development

    SciTech Connect

    Wang, Jun; Liu, Guodong; Lin, Yuehe

    2007-03-08

    In this chapter, the reviews on biosensor development based on 1-D nanomaterials, CNTs, semiconducting nanowires, and some cantilevers will be introduced. The emphasis of this review will be placed on CNTs and electrochemical/electronic biosensor developments. Section 2 of this chapter gives a detailed description of carbon nanotubes-based biosensor development, from fabrication of carbon nanotubes, the strategies for construction of carbon nanotube based biosensors to their bioapplications. In the section of the applications of CNTs based biosensors, various detection principles, e. g. electrochemical, electronic, and optical method, and their applications are reviewed in detail. Section 3 introduces the method for synthesis of semiconducting nanowires, e.g. silicon nanowires, conducting polymer nanowires and metal oxide nanowires and their applications in DNA and proteins sensing. Section 4 simply describes the development for nanocantilevers based biosensors and their application in DNA and protein diagnosis. Each section starts from a brief introduction and then goes into details. Finally in the Conclusion section, the development of 1-D nanomaterials based biosensor development is summarized.

  5. Core-shell silicon nanowire solar cells.

    PubMed

    Adachi, M M; Anantram, M P; Karim, K S

    2013-01-01

    Silicon nanowires can enhance broadband optical absorption and reduce radial carrier collection distances in solar cell devices. Arrays of disordered nanowires grown by vapor-liquid-solid method are attractive because they can be grown on low-cost substrates such as glass, and are large area compatible. Here, we experimentally demonstrate that an array of disordered silicon nanowires surrounded by a thin transparent conductive oxide has both low diffuse and specular reflection with total values as low as < 4% over a broad wavelength range of 400 nm < λ < 650 nm. These anti-reflective properties together with enhanced infrared absorption in the core-shell nanowire facilitates enhancement in external quantum efficiency using two different active shell materials: amorphous silicon and nanocrystalline silicon. As a result, the core-shell nanowire device exhibits a short-circuit current enhancement of 15% with an amorphous Si shell and 26% with a nanocrystalline Si shell compared to their corresponding planar devices.

  6. Mechanosensitive behavior of bacterial cyclic nucleotide gated (bCNG) ion channels: Insights into the mechanism of channel gating in the mechanosensitive channel of small conductance superfamily.

    PubMed

    Malcolm, Hannah R; Elmore, Donald E; Maurer, Joshua A

    2012-01-20

    We have recently identified and characterized the bacterial cyclic nucleotide gated (bCNG) subfamily of the larger mechanosensitive channel of small conductance (MscS) superfamily of ion channels. The channel domain of bCNG channels exhibits significant sequence homology to the mechanosensitive subfamily of MscS in the regions that have previously been used as a hallmark for channels that gate in response to mechanical stress. However, we have previously demonstrated that three of these channels are unable to rescue Escherichiacoli from osmotic downshock. Here, we examine an additional nine bCNG homologues and further demonstrate that the full-length bCNG channels are unable to rescue E. coli from hypoosmotic stress. However, limited mechanosensation is restored upon removal of the cyclic nucleotide binding domain. This indicates that the C-terminal domain of the MscS superfamily can drive channel gating and further highlight the ability of a superfamily of ion channels to be gated by multiple stimuli.

  7. Monitoring structural influences on quantum transport in InAs nanowires

    NASA Astrophysics Data System (ADS)

    Frielinghaus, Robert; Flöhr, Kilian; Sladek, Kamil; Weirich, Thomas E.; Trellenkamp, Stefan; Hardtdegen, Hilde; Schäpers, Thomas; Schneider, Claus M.; Meyer, Carola

    2012-08-01

    A sample design that allows for quantum transport and transmission electron microscopy (TEM) on individual suspended nanostructures is used to investigate moderately n-type doped InAs nanowires (NWs). The nanowires were grown by metal organic vapor phase epitaxy. Universal conductance fluctuations in the nanowires are investigated at temperatures down to 0.35 K. These fluctuations show two different temperature dependences. The very same nanowire segments investigated in transport are subsequently analyzed by TEM revealing crystal phase mixing. However, we find no correspondence between the atomic structure of the wires and the temperature dependences of the conductance fluctuations.

  8. Semiconductor Nanowires: What's Next?

    SciTech Connect

    Yang, Peidong; Yan, Ruoxue; Fardy, Melissa

    2010-04-28

    In this perspective, we take a critical look at the research progress within the nanowire community for the past decade. We discuss issues on the discovery of fundamentally new phenomena versus performance benchmarking for many of the nanowire applications. We also notice that both the bottom-up and top-down approaches have played important roles in advancing our fundamental understanding of this new class of nanostructures. Finally we attempt to look into the future and offer our personal opinions on what the future trends will be in nanowire research.

  9. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    PubMed

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices.

  10. A force sensor using nanowire arrays to understand biofilm formation (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Sahoo, Prasana K.; Cavalli, Alessandro; Pelegati, Vitor B.; Murillo, Duber M.; Souza, Alessandra A.; Cesar, Carlos L.; Bakkers, Erik P. A. M.; Cotta, Monica A.

    2016-03-01

    Understanding the cellular signaling and function at the nano-bio interface can pave the way towards developing next-generation smart diagnostic tools. From this perspective, limited reports detail so far the cellular and subcellular forces exerted by bacterial cells during the interaction with abiotic materials. Nanowire arrays with high aspect ratio have been used to detect such small forces. In this regard, live force measurements were performed ex-vivo during the interaction of Xylella fastidiosa bacterial cells with InP nanowire arrays. The influence of nanowire array topography and surface chemistry on the response and motion of bacterial cells was studied in detail. The nanowire arrays were also functionalized with different cell adhesive promoters, such as amines and XadA1, an afimbrial protein of X.fastidiosa. By employing the well-defined InP nanowire arrays platform, and single cell confocal imaging system, we were able to trace the bacterial growth pattern, and show that their initial attachment locations are strongly influenced by the surface chemistry and nanoscale surface topography. In addition, we measure the cellular forces down to few nanonewton range using these nanowire arrays. In case of nanowire functionalized with XadA1, the force exerted by vertically and horizontally attached single bacteria on the nanowire is in average 14% and 26% higher than for the pristine array, respectively. These results provide an excellent basis for live-cell force measurements as well as unravel the range of forces involved during the early stages of bacterial adhesion and biofilm formation.

  11. Gas sensor based on metal-insulator transition in VO2 nanowire thermistor.

    PubMed

    Strelcov, Evgheni; Lilach, Yigal; Kolmakov, Andrei

    2009-06-01

    Using temperature driven sharp metal-insulator phase transition in single crystal VO(2) nanowires, the realization of a novel gas sensing concept has been tested. Varying the temperature of the nanowire close to the transition edge, the conductance of the nanowire becomes extremely responsive to the tiny changes in molecular composition, pressure, and temperature of the ambient gas environment. This gas sensing analog of the transition edge sensor radiometry used in astrophysics opens new opportunities in gas sensorics.

  12. Porous silicon nanowires.

    PubMed

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-10-05

    In this mini-review, we summarize recent progress in the synthesis, properties and applications of a new type of one-dimensional nanostructures-single crystalline porous silicon nanowires. The growth of porous silicon nanowires starting from both p- and n-type Si wafers with a variety of dopant concentrations can be achieved through either one-step or two-step reactions. The mechanistic studies indicate the dopant concentration of Si wafers, oxidizer concentration, etching time and temperature can affect the morphology of the as-etched silicon nanowires. The porous silicon nanowires are both optically and electronically active and have been explored for potential applications in diverse areas including photocatalysis, lithium ion batteries, gas sensors and drug delivery.

  13. Variation in electrical properties of gamma irradiated cadmium selenate nanowires

    NASA Astrophysics Data System (ADS)

    Chauhan, R. P.; Rana, Pallavi; Narula, Chetna; Panchal, Suresh; Choudhary, Ritika

    2016-07-01

    Preparation of low-dimensional materials attracts more and more interest in the last few years, mainly due to the wide field of potential commercial applications ranging from life sciences, medicine and biotechnology to communication and electronics. One-dimensional systems are the smallest dimension structures that can be used for efficient transport of electrons and thus expected to be critical to the function and integration of nanoscale devices. Nanowires with well controlled morphology and extremely high aspect ratio can be obtained by replicating a nanoporous polymer ion-track membrane with cylindrical pores of controlled dimensions. With this technique, materials can be deposited within the pores of the membrane by electrochemical reduction of the desired ion. In the present study, cadmium selenate nanowires were synthesized potentiostatically via template method. These synthesized nanowires were then exposed to gamma rays by using a 60Co source at the Inter University Accelerator Centre, New Delhi, India. Structural, morphological, electrical and elemental characterizations were made in order to analyze the effect of gamma irradiation on the synthesized nanowires. I-V measurements of cadmium selenate nanowires, before and after irradiation were made with the help of Keithley 2400 source meter and Ecopia probe station. A significant change in the electrical conductivity of cadmium selenate nanowires was found after gamma irradiation. The crystallography of the synthesized nanowires was also studied using a Rigaku X-ray diffractrometer equipped with Cu-Kα radiation. XRD patterns of irradiated samples showed no variation in the peak positions or phase change.

  14. Nanowire Photonic Systems

    DTIC Science & Technology

    2009-12-22

    synthesis of silicon and gallium-indium nitride alloy nanowire heterostructures to provide building blocks for photonic devices that can span the...the Si-nanowire etching profile follows the order in which dopants were introduced during synthesis : First boron for p-type, no dopant for i-type... synthesis of nanoscale building blocks, (ii) characterization of fundamental physical properties of the building blocks, and (iii) assembly of

  15. Assembling silver nanowires using optoelectronic tweezers

    NASA Astrophysics Data System (ADS)

    Zhang, Shuailong; Cooper, Jonathan M.; Neale, Steve L.

    2016-03-01

    Light patterned dielectrophoresis or optoelectronic tweezers (OET) has been proved to be an effective micromanipulation technology for cell separation, cell sorting and control of cell interactions. Apart from being useful for cell biology experiments, the capability of moving small objects accurately also makes OET an attractive technology for other micromanipulation applications. In particular, OET has the potential to be used for efficiently and accurately assembling small optoelectronic/electronic components into circuits. This approach could produce a step change in the size of the smallest components that are routinely assembled; down from the current smallest standard component size of 400×200 μm (0402 metric) to components a few microns across and even nanostructured components. In this work, we have demonstrated the use of OET to manipulate conductive silver nanowires into different patterns. The silver nanowires (typical diameter: 60 nm; typical length: 10 μm) were suspended in a 15 mS/m solution of KCL in water and manipulated by positive dielectrophoresis force generated by OET. A proof-of-concept demonstration was also made to prove the feasibility of using OET to manipulate silver nanowires to form a 150-μm-long conductive path between two isolated electrodes. It can be seen that the resistance between two electrodes was effectively brought down to around 700 Ω after the silver nanowires were assembled and the solution evaporated. Future work in this area will focus on increasing the conductivity of these tracks, encapsulating the assembled silver nanowires to prevent silver oxidation and provide mechanical protection, which can be achieved via 3D printing and inkjet printing technology.

  16. Nanowire Electron Scattering Spectroscopy

    NASA Technical Reports Server (NTRS)

    Hunt, Brian; Bronikowsky, Michael; Wong, Eric; VonAllmen, Paul; Oyafuso, Fablano

    2009-01-01

    Nanowire electron scattering spectroscopy (NESS) has been proposed as the basis of a class of ultra-small, ultralow-power sensors that could be used to detect and identify chemical compounds present in extremely small quantities. State-of-the-art nanowire chemical sensors have already been demonstrated to be capable of detecting a variety of compounds in femtomolar quantities. However, to date, chemically specific sensing of molecules using these sensors has required the use of chemically functionalized nanowires with receptors tailored to individual molecules of interest. While potentially effective, this functionalization requires labor-intensive treatment of many nanowires to sense a broad spectrum of molecules. In contrast, NESS would eliminate the need for chemical functionalization of nanowires and would enable the use of the same sensor to detect and identify multiple compounds. NESS is analogous to Raman spectroscopy, the main difference being that in NESS, one would utilize inelastic scattering of electrons instead of photons to determine molecular vibrational energy levels. More specifically, in NESS, one would exploit inelastic scattering of electrons by low-lying vibrational quantum states of molecules attached to a nanowire or nanotube.

  17. Electronic Structures of Free-Standing Nanowires made from Indirect Bandgap Semiconductor Gallium Phosphide

    PubMed Central

    Liao, Gaohua; Luo, Ning; Chen, Ke-Qiu; Xu, H. Q.

    2016-01-01

    We present a theoretical study of the electronic structures of freestanding nanowires made from gallium phosphide (GaP)—a III-V semiconductor with an indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal cross sections. Based on tight binding models, both the band structures and wave functions of the nanowires are calculated. For the [001]-oriented GaP nanowires, the bands show anti-crossing structures, while the bands of the [111]-oriented nanowires display crossing structures. Two minima are observed in the conduction bands, while the maximum of the valence bands is always at the Γ-point. Using double group theory, we analyze the symmetry properties of the lowest conduction band states and highest valence band states of GaP nanowires with different sizes and directions. The band state wave functions of the lowest conduction bands and the highest valence bands of the nanowires are evaluated by spatial probability distributions. For practical use, we fit the confinement energies of the electrons and holes in the nanowires to obtain an empirical formula. PMID:27307081

  18. Relative influence of surface states and bulk impurities on the electrical properties of Ge nanowires.

    PubMed

    Zhang, Shixiong; Hemesath, Eric R; Perea, Daniel E; Wijaya, Edy; Lensch-Falk, Jessica L; Lauhon, Lincoln J

    2009-09-01

    We quantitatively examine the relative influence of bulk impurities and surface states on the electrical properties of Ge nanowires with and without phosphorus (P) doping. The unintentional impurity concentration in nominally undoped Ge nanowires is less than 2 x 10(17) cm(-3) as determined by atom probe tomography. Surprisingly, P doping of approximately 10(18) cm(-3) reduces the nanowire conductivity by 2 orders of magnitude. By modeling the contributions of dopants, impurities, and surface states, we confirm that the conductivity of nominally undoped Ge nanowires is mainly due to surface state induced hole accumulation rather than impurities introduced by catalyst. In P-doped nanowires, the surface states accept the electrons generated by the P dopants, reducing the conductivity and leading to ambipolar behavior. In contrast, intentional surface-doping results in a high conductivity and recovery of n-type characteristics.

  19. Transparent metal oxide nanowire transistors

    NASA Astrophysics Data System (ADS)

    Chen, Di; Liu, Zhe; Liang, Bo; Wang, Xianfu; Shen, Guozhen

    2012-05-01

    With the features of high mobility, a high electric on/off ratio and excellent transparency, metal oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent metal oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality metal oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent metal oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent metal oxide nanowire transistors.

  20. Transparent metal oxide nanowire transistors.

    PubMed

    Chen, Di; Liu, Zhe; Liang, Bo; Wang, Xianfu; Shen, Guozhen

    2012-05-21

    With the features of high mobility, a high electric on/off ratio and excellent transparency, metal oxide nanowires are excellent candidates for transparent thin-film transistors, which is one of the key technologies to realize transparent electronics. This article provides a comprehensive review of the state-of-the-art research activities that focus on transparent metal oxide nanowire transistors. It begins with the brief introduction to the synthetic methods for high quality metal oxide nanowires, and the typical nanowire transfer and printing techniques with emphasis on the simple contact printing methodology. High performance transparent transistors built on both single nanowires and nanowire thin films are then highlighted. The final section deals with the applications of transparent metal oxide nanowire transistors in the field of transparent displays and concludes with an outlook on the current perspectives and future directions of transparent metal oxide nanowire transistors.

  1. A review on germanium nanowires.

    PubMed

    Pei, Li Z; Cai, Zheng Y

    2012-01-01

    Ge nanowires exhibit wide application potential in the fields of nanoscale devices due to their excellently optical and electrical properties. This article reviews the recent progress and patents of Ge nanowires. The recent progress and patents for the synthesis of Ge nanowires using chemical vapor deposition, laser ablation, thermal evaporation, template method and supercritical fluid-liquid-solid method are demonstrated. Amorphous germanium oxide layer and defects existing in Ge nanowires result in poor Ohmic contact between Ge nanowires and electrodes. Therefore, Ge nanowires should be passivated in order to deposit connecting electrodes before applied in nanoelectronic devices. The experimental progress and patents on the application of Ge nanowires as field effect transistors, lithium batteries, photoresistors, memory cell and fluid sensors are discussed. Finally, the future development of Ge nanowires for the synthesis and practical application is also discussed.

  2. Electrodeposition of platinum-iridium alloy nanowires for hermetic packaging of microelectronics.

    PubMed

    Petrossians, Artin; Whalen, John J; Weiland, James D; Mansfeld, Florian

    2012-01-01

    An electrodeposition technique was applied for fabrication of dense platinum-iridium alloy nanowires as interconnect structures in hermetic microelectronic packaging to be used in implantable devices. Vertically aligned arrays of platinum-iridium alloy nanowires with controllable length and a diameter of about 200 nm were fabricated using a cyclic potential technique from a novel electrodeposition bath in nanoporous aluminum oxide templates. Ti/Au thin films were sputter deposited on one side of the alumina membranes to form a base material for electrodeposition. Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) were used to characterize the morphology and the chemical composition of the nanowires, respectively. SEM micrographs revealed that the electrodeposited nanowires have dense and compact structures. EDS analysis showed a 60:40% platinum-iridium nanowire composition. Deposition rates were estimated by determining nanowire length as a function of deposition time. High Resolution Transmission Electron Microscopy (HRTEM) images revealed that the nanowires have a nanocrystalline structure with grain sizes ranging from 3 nm to 5 nm. Helium leak tests performed using a helium leak detector showed leak rates as low as 1 × 10(-11) mbar L s(-1) indicating that dense nanowires were electrodeposited inside the nanoporous membranes. Comparison of electrical measurements on platinum and platinum-iridium nanowires revealed that platinum-iridium nanowires have improved electrical conductivity.

  3. Effects of length dispersity and film fabrication on the sheet resistance of copper nanowire transparent conductors.

    PubMed

    Borchert, James W; Stewart, Ian E; Ye, Shengrong; Rathmell, Aaron R; Wiley, Benjamin J; Winey, Karen I

    2015-09-14

    Development of thin-film transparent conductors (TC) based on percolating networks of metal nanowires has leaped forward in recent years, owing to the improvement of nanowire synthetic methods and modeling efforts by several research groups. While silver nanowires are the first commercially viable iteration of this technology, systems based on copper nanowires are not far behind. Here we present an analysis of TCs composed of copper nanowire networks on sheets of polyethylene terephthalate that have been treated with various oxide-removing post treatments to improve conductivity. A pseudo-2D rod network modeling approach has been modified to include lognormal distributions in length that more closely reflect experimental data collected from the nanowire TCs. In our analysis, we find that the copper nanowire TCs are capable of achieving comparable electrical performance to silver nanowire TCs with similar dimensions. Lastly, we present a method for more accurately determining the nanowire area coverage in a TC over a large area using Rutherford Backscattering Spectrometry (RBS) to directly measure the metal content in the TCs. These developments will aid research and industry groups alike in the characterization of nanowire based TCs.

  4. Catalyst patterning for nanowire devices

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

    2004-01-01

    Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

  5. All Nanowire Integrated Sensor Circuitry

    DTIC Science & Technology

    2008-04-01

    of single crystalline nanomaterials. Highly ordered and parallel arrays of optically active CdSe nanowires and high mobility Ge/Si nanowires are...for enabling the fabrication of the all- nanowire sensor circuitry. First, highly aligned CdSe and Ge/Si NW arrays were assembled at pre-defined...FETs (Tl and T2) amplifying the photoresponse of a CdSe nanosensor. (B) Schematic of the all- nanowire optical sensor circuit based on ordered

  6. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2009-06-09

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  7. Lipid nanotube or nanowire sensor

    DOEpatents

    Noy, Aleksandr; Bakajin, Olgica; Letant, Sonia; Stadermann, Michael; Artyukhin, Alexander B.

    2010-06-29

    A sensor apparatus comprising a nanotube or nanowire, a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer. Also a biosensor apparatus comprising a gate electrode; a source electrode; a drain electrode; a nanotube or nanowire operatively connected to the gate electrode, the source electrode, and the drain electrode; a lipid bilayer around the nanotube or nanowire, and a sensing element connected to the lipid bilayer.

  8. Dielectrophoretic investigation of Bi₂Te₃ nanowires-a microfabricated thermoelectric characterization platform for measuring the thermoelectric and structural properties of single nanowires.

    PubMed

    Wang, Zhi; Kojda, Danny; Peranio, Nicola; Kroener, Michael; Mitdank, Rüdiger; Toellner, William; Nielsch, Kornelius; Fischer, Saskia F; Gutsch, Sebastian; Zacharias, Margit; Eibl, Oliver; Woias, Peter

    2015-03-27

    In this article a microfabricated thermoelectric nanowire characterization platform to investigate the thermoelectric and structural properties of single nanowires is presented. By means of dielectrophoresis (DEP), a method to manipulate and orient nanowires in a controlled way to assemble them onto our measurement platform is introduced. The thermoelectric platform fabricated with optimally designed DEP electrodes results in a yield of nanowire assembly of approximately 90% under an applied peak-to-peak ac signal Vpp = 10 V and frequency f = 20 MHz within a series of 200 experiments. Ohmic contacts between the aligned single nanowire and the electrodes on the platform are established by electron beam-induced deposition. The Seebeck coefficient and electrical conductivity of electrochemically synthesized Bi2Te3 nanowires are measured to be -51 μV K(-1) and (943 ± 160)/(Ω(-1) cm(-1)), respectively. Chemical composition and crystallographic structure are obtained using transmission electron microscopy. The selected nanowire is observed to be single crystalline over its entire length and no grain boundaries are detected. At the surface of the nanowire, 66.1 ± 1.1 at.% Te and 34.9 ± 1.1 at.% Bi are observed. In contrast, chemical composition of 64.2 at.% Te and 35.8 at.% Bi is detected in the thick center of the nanowire.

  9. The influence of ionized impurity scattering on the thermopower of Si nanowires.

    PubMed

    Oh, Jung Hyun; Jang, Moon-Gyu; Shin, Mincheol

    2013-12-18

    The thermopower of Si nanowires was investigated on the basis of electronic transport theory, taking into account ionized impurity scattering as well as electron-phonon scattering. It was found that the enhancement of the Seebeck coefficient in nanowires arising from quantum confinement is unimportant due to the ionized impurity scattering associated with donor deactivation. Furthermore, because the electrical conductivity is degraded significantly as the nanowire size becomes smaller, despite the accompanying slightly enhanced Seebeck coefficient, the reduction of the nanowire size is not beneficial, at least for the thermopower of devices.

  10. Direct Conversion of Perovskite Thin Films into Nanowires with Kinetic Control for Flexible Optoelectronic Devices.

    PubMed

    Zhu, Pengchen; Gu, Shuai; Shen, Xinpeng; Xu, Ning; Tan, Yingling; Zhuang, Shendong; Deng, Yu; Lu, Zhenda; Wang, Zhenlin; Zhu, Jia

    2016-02-10

    With significant progress in the past decade, semiconductor nanowires have demonstrated unique features compared to their thin film counterparts, such as enhanced light absorption, mechanical integrity and reduced therma conductivity, etc. However, technologies of semiconductor thin film still serve as foundations of several major industries, such as electronics, displays, energy, etc. A direct path to convert thin film to nanowires can build a bridge between these two and therefore facilitate the large-scale applications of nanowires. Here, we demonstrate that methylammonium lead iodide (CH3NH3PbI3) nanowires can be synthesized directly from perovskite film by a scalable conversion process. In addition, with fine kinetic control, morphologies, and diameters of these nanowires can be well-controlled. Based on these perovskite nanowires with excellent optical trapping and mechanical properties, flexible photodetectors with good sensitivity are demonstrated.

  11. The concentration effect of capping agent for synthesis of silver nanowire by using the polyol method

    SciTech Connect

    Lin, Jian-Yang; Hsueh, Yu-Lee; Huang, Jung-Jie

    2014-06-01

    Silver nanowires were synthesized by the polyol method employing ethylene glycol, Poly(N-vinylpyrrolidone) (PVP) and silver nitrate (AgNO{sub 3}) as the precursors. Most of the studies used metal salts (PtCl{sub 2}, NaCl) as seed precursor to synthesize the silver nanowires. In the study, the metal salts were not used and the concentration of capping agent was changed to observe the aspect ratio of silver nanowires. The experimental results showed that controlling synthesis temperature, Poly(N-vinylpyrrolidone) (PVP) molecular weight, reactant concentrations, and addition rates of AgNO{sub 3} affects the growth characteristics of silver nanowires. Field-emission scanning electron microscopy, UV–vis spectrophotometry, and X-ray diffractometry were employed to characterize the silver nanowires. As increasing the concentration of PVP, the silver nanowire diameter widened and resulted in a smaller aspect ratio. We successfully prepared silver nanowires (diameter: 170 nm, length: 20 μm). The silver nanowire thin film suspension showed high transmittance, low sheet resistance, and may be used for transparent conductive film applications. - Graphical abstract: The FE-SEM image shows that nanostructures with considerable quantities of silver nanowires can also be produced when the PVP (Mw=360 K)/AgNO{sub 3} molar ratio was 2.5. - Highlights: • The polyol method was used to synthesize of silver nanowire. • The metal seed precursors were not used before synthesizing the silver nanowires. • The silver nanowire diameter and length was 170 nm and 20 μm, respectively. • Silver nanowire film with high transmittance (>85%) and low sheet resistance (<110 Ω/sq)

  12. Ballistic thermal transport in silicon nanowires

    NASA Astrophysics Data System (ADS)

    Maire, Jeremie; Anufriev, Roman; Nomura, Masahiro

    2017-02-01

    We have experimentally investigated the impact of dimensions and temperature on the thermal conductivity of silicon nanowires fabricated using a top-down approach. Both the width and temperature dependences of thermal conductivity agree with those in the existing literature. The length dependence of thermal conductivity exhibits a transition from semi-ballistic thermal phonon transport at 4 K to fully diffusive transport at room temperature. We additionally calculated the phonon dispersion in these structures in the framework of the theory of elasticity and showed that the thermal conductance increases with width. This agrees with our experimental observations and supports the pertinence of using the modified phonon dispersion at low temperatures.

  13. Phonon spectroscopy in a Bi2Te3 nanowire array

    NASA Astrophysics Data System (ADS)

    Bessas, Dimitrios; Töllner, William; Aabdin, Zainul; Peranio, Nicola; Sergueev, Ilya; Wille, Hans-Christian; Eibl, Oliver; Nielsch, Kornelius; Hermann, Raphaël P.

    2013-10-01

    The lattice dynamics in an array of 56 nm diameter Bi2Te3 nanowires embedded in a self-ordered amorphous alumina membrane were investigated microscopically using 125Te nuclear inelastic scattering. The element specific density of phonon states is measured on nanowires in two perpendicular orientations and the speed of sound is extracted. Combined high energy synchrotron radiation diffraction and transmission electron microscopy was carried out on the same sample and the crystallinity was investigated. The nanowires grow almost perpendicular to the c-axis, partly with twinning. The average speed of sound in the 56 nm diameter Bi2Te3 nanowires is ~7% smaller with respect to bulk Bi2Te3 and a decrease in the macroscopic lattice thermal conductivity by ~13% due to nanostructuration and to the reduced speed of sound is predicted.

  14. Personal thermal management by metallic nanowire-coated textile.

    PubMed

    Hsu, Po-Chun; Liu, Xiaoge; Liu, Chong; Xie, Xing; Lee, Hye Ryoung; Welch, Alex J; Zhao, Tom; Cui, Yi

    2015-01-14

    Heating consumes large amount of energy and is a primary source of greenhouse gas emission. Although energy-efficient buildings are developing quickly based on improving insulation and design, a large portion of energy continues to be wasted on heating empty space and nonhuman objects. Here, we demonstrate a system of personal thermal management using metallic nanowire-embedded cloth that can reduce this waste. The metallic nanowires form a conductive network that not only is highly thermal insulating because it reflects human body infrared radiation but also allows Joule heating to complement the passive insulation. The breathability and durability of the original cloth is not sacrificed because of the nanowires' porous structure. This nanowire cloth can efficiently warm human bodies and save hundreds of watts per person as compared to traditional indoor heaters.

  15. Conductometric chemical sensor based on individual CuO nanowires

    NASA Astrophysics Data System (ADS)

    Li, Dongdong; Hu, Jun; Wu, Ruqian; Lu, Jia G.

    2010-12-01

    CuO nanowires with high crystalline quality are synthesized via a simple thermal oxidation method. Charge conduction on individual nanowires under a transverse electric field exhibits an intrinsic p-type semiconducting behavior. Variations in signal transducer in different chemical gas environments are measured on individual CuO nanowire field effect transistors. They demonstrate good performance to both NO2 and ethanol gasses. In particular, the nanowire chemical sensor reveals a reverse response to ethanol vapor under temperature variation. Experimental results and first-principles calculations indicate that ethanol is oxidized in air at high temperature, resulting in the production of CO2 and H2O. The strong H2O adsorption leads to the reversal behavior, due to the electron transfer from H2O molecules to the CuO surface.

  16. Optical Control of Electrons in Au Nanowires

    NASA Astrophysics Data System (ADS)

    Jones, Eric; Basnet, Gobind; Huang, Wayne; Flanders, Bret; Batelaan, Herman

    2016-05-01

    Gold nanowires, with diameters less than 100 nm, are novel sources for electron field emission. Their geometry confines the propagation of conduction electrons, giving rise to effects not seen in the bulk, such as ballistic currents and surface plasmon polaritons (SPPs). Dynamics within the wire are probed with laser-induced field emission from the nanowire tip. A balanced Mach-Zehnder interferometer is used to split and delay pulses up to 170 ps from a Ti:Saph oscillator (800 nm, 50 fs) in a pump-probe scheme. The output beamsplitter of the interferometer is mounted on a translation stage to control the separation of the pump and probe beams with sub-micron precision. The beams are focused to 3 μm spots on the tip and shaft of a nanowire, mounted under vacuum at 2 × 10-7 mTorr, by an off-axis parabolic mirror. Field-emitted electrons are counted by a channel electron multiplier. We discuss experimental results of our pump-probe experiments taken at different pump positions. Optical control of electron dynamics within these nanowires may lead to a truly on-demand source of single and multiple electron pulses. We gratefully acknowledge support from NSF awards 1306565 and 1430519.

  17. Nanoscale Joule heating and electromigration enhanced ripening of silver nanowire contacts.

    PubMed

    Song, Tze-Bin; Chen, Yu; Chung, Choong-Heui; Yang, Yang Michael; Bob, Brion; Duan, Hsin-Sheng; Li, Gang; Tu, King-Ning; Huang, Yu; Yang, Yang

    2014-03-25

    Solution-processed metallic nanowire thin film is a promising candidate to replace traditional indium tin oxide as the next-generation transparent and flexible electrode. To date however, the performance of these electrodes is limited by the high contact resistance between contacting nanowires; so improving the point contacts between these nanowires remains a major challenge. Existing methods for reducing the contact resistance require either a high processing power, long treatment time, or the addition of chemical reagents, which could lead to increased manufacturing cost and damage the underlying substrate or device. Here, a nanoscale point reaction process is introduced as a fast and low-power-consumption way to improve the electrical contact properties between metallic nanowires. This is achieved via current-assisted localized joule heating accompanied by electromigration. Localized joule heating effectively targets the high-resistance contact points between nanowires, leading to the automatic removal of surface ligands, welding of contacting nanowires, and the reshaping of the contact pathway between the nanowires to form a more desirable geometry of low resistance for interwire conduction. This result shows the interplay between thermal and electrical interactions at the highly reactive nanocontacts and highlights the control of the nanoscale reaction as a simple and effective way of turning individual metallic nanowires into a highly conductive interconnected nanowire network. The temperature of the adjacent device layers can be kept close to room temperature during the process, making this method especially suitable for use in devices containing thermally sensitive materials such as polymer solar cells.

  18. Enhancement of electrical and thermomechanical properties of silver nanowire composites by the introduction of nonconductive nanoparticles: experiment and simulation.

    PubMed

    Nam, Seungwoong; Cho, Hyun W; Lim, Soonho; Kim, Daeheum; Kim, Heesuk; Sung, Bong J

    2013-01-22

    Electrically conductive polymer nanocomposites have been applied extensively in many fields to develop the next generation of devices. Large amounts of conductive nanofillers in polymer matrices are, however, often required for a sufficiently high electrical conductivity, which in turn deteriorates the desired thermomechanical properties. We illustrate a novel but facile strategy to improve the electrical conductivity and the thermomechanical property of silver nanowire/polymer nanocomposites. We find that one may increase the electrical conductivity of silver nanowire/polymer nanocomposites by up to about 8 orders of magnitude by introducing silica nanoparticles with nanocomposites. The electrical percolation threshold volume fraction of silver nanowires decreases from 0.12 to 0.02. Thermomechanical properties also improve as silica nanoparticles are introduced. We carry out extensive Monte Carlo simulations to elucidate the effects of silica nanoparticles at a molecular level and find that van der Waals attractive interaction between silica nanoparticles and silver nanowires dominates over the depletion-induced interaction between silver nanowires, thus improving the dispersion of silver nanowires. Without silica nanoparticles, silver nanowires tend to aggregate, which is why additional silver nanowires are required for a desired electrical conductivity. On the other hand, with silica nanoparticles mixed, the electrical percolating network is likely to form at a smaller volume fraction of silver nanowires.

  19. A novel WS2 nanowire-nanoflake hybrid material synthesized from WO3 nanowires in sulfur vapor

    NASA Astrophysics Data System (ADS)

    Asres, Georgies Alene; Dombovari, Aron; Sipola, Teemu; Puskás, Robert; Kukovecz, Akos; Kónya, Zoltán; Popov, Alexey; Lin, Jhih-Fong; Lorite, Gabriela S.; Mohl, Melinda; Toth, Geza; Lloyd Spetz, Anita; Kordas, Krisztian

    2016-05-01

    In this work, WS2 nanowire-nanoflake hybrids are synthesized by the sulfurization of hydrothermally grown WO3 nanowires. The influence of temperature on the formation of products is optimized to grow WS2 nanowires covered with nanoflakes. Current-voltage and resistance-temperature measurements carried out on random networks of the nanostructures show nonlinear characteristics and negative temperature coefficient of resistance indicating that the hybrids are of semiconducting nature. Bottom gated field effect transistor structures based on random networks of the hybrids show only minor modulation of the channel conductance upon applied gate voltage, which indicates poor electrical transport between the nanowires in the random films. On the other hand, the photo response of channel current holds promise for cost-efficient solution process fabrication of photodetector devices working in the visible spectral range.

  20. A novel WS2 nanowire-nanoflake hybrid material synthesized from WO3 nanowires in sulfur vapor

    PubMed Central

    Asres, Georgies Alene; Dombovari, Aron; Sipola, Teemu; Puskás, Robert; Kukovecz, Akos; Kónya, Zoltán; Popov, Alexey; Lin, Jhih-Fong; Lorite, Gabriela S.; Mohl, Melinda; Toth, Geza; Lloyd Spetz, Anita; Kordas, Krisztian

    2016-01-01

    In this work, WS2 nanowire-nanoflake hybrids are synthesized by the sulfurization of hydrothermally grown WO3 nanowires. The influence of temperature on the formation of products is optimized to grow WS2 nanowires covered with nanoflakes. Current-voltage and resistance-temperature measurements carried out on random networks of the nanostructures show nonlinear characteristics and negative temperature coefficient of resistance indicating that the hybrids are of semiconducting nature. Bottom gated field effect transistor structures based on random networks of the hybrids show only minor modulation of the channel conductance upon applied gate voltage, which indicates poor electrical transport between the nanowires in the random films. On the other hand, the photo response of channel current holds promise for cost-efficient solution process fabrication of photodetector devices working in the visible spectral range. PMID:27180902

  1. Heat transmission between a profiled nanowire and a thermal bath

    SciTech Connect

    Blanc, Christophe; Heron, Jean-Savin; Fournier, Thierry; Bourgeois, Olivier

    2014-07-28

    Thermal transport through profiled and abrupt contacts between a nanowire and a reservoir has been investigated by thermal conductance measurements. It is demonstrated that above 1 K the transmission coefficients are identical between abrupt and profiled junctions. This shows that the thermal transport is principally governed by the nanowire itself rather than by the resistance of the thermal contact. These results are perfectly compatible with the previous theoretical models. The thermal conductance measured at sub-Kelvin temperatures is discussed in relation to the universal value of the quantum of thermal conductance.

  2. Characterization of individual straight and kinked boron carbide nanowires

    NASA Astrophysics Data System (ADS)

    Cui, Zhiguang

    Boron carbides represent a class of ceramic materials with p-type semiconductor natures, complex structures and a wide homogeneous range of carbon compositions. Bulk boron carbides have long been projected as promising high temperature thermoelectric materials, but with limited performance. Bringing the bulk boron carbides to low dimensions (e.g., nanowires) is believed to be an option to enhance their thermoelectric performance because of the quantum size effects. However, the fundamental studies on the microstructure-thermal property relation of boron carbide nanowires are elusive. In this dissertation work, systematic structural characterization and thermal conductivity measurement of individual straight and kinked boron carbide nanowires were carried out to establish the true structure-thermal transport relation. In addition, a preliminary Raman spectroscopy study on identifying the defects in individual boron carbide nanowires was conducted. After the synthesis of single crystalline boron carbide nanowires, straight nanowires accompanied by the kinked ones were observed. Detailed structures of straight boron carbide nanowires have been reported, but not the kinked ones. After carefully examining tens of kinked nanowires utilizing Transmission Electron Microscopy (TEM), it was found that they could be categorized into five cases depending on the stacking faults orientations in the two arms of the kink: TF-TF, AF-TF, AF-AF, TF-IF and AF-IF kinks, in which TF, AF and IF denotes transverse faults (preferred growth direction perpendicular to the stacking fault planes), axial faults (preferred growth direction in parallel with the stacking fault planes) and inclined faults (preferred growth direction neither perpendicular to nor in parallel with the stacking fault planes). Simple structure models describing the characteristics of TF-TF, AF-TF, AF-AF kinked nanowires are constructed in SolidWorks, which help to differentiate the kinked nanowires viewed from the zone

  3. Atomic-Scale Spectroscopy of Polydiacetylene Nanowires

    NASA Astrophysics Data System (ADS)

    Giridharagopal, Rajiv; Kelly, K. F.

    2006-03-01

    In recent years, the appeal of organic electronic devices has spurred interest in conducting polymers, such as polydiacetylene. Polydiacetylene nanowires offer numerous possibilities for application in molecular electronics, and they are a model system for understanding conduction mechanisms in polymers. We have used scanning tunneling microscopy to investigate monolayer films of pentacosadiynoic acid formed on highly ordered pyrolytic graphite using the Langmuir-Blodgett and Langmuir-Schaeffer deposition techniques and subsequently polymerized to form polydiacetylene nanowires. By applying a novel method of microwave frequency mixing at the STM tip junction, we have obtained capacitance-voltage spectroscopic data to characterize the wires across a range of bias voltages, tunneling gap resistances, and microwave mixing frequencies.

  4. Piezoresistive boron doped diamond nanowire

    DOEpatents

    Sumant, Anirudha V.; Wang, Xinpeng

    2016-09-13

    A UNCD nanowire comprises a first end electrically coupled to a first contact pad which is disposed on a substrate. A second end is electrically coupled to a second contact pad also disposed on the substrate. The UNCD nanowire is doped with a dopant and disposed over the substrate. The UNCD nanowire is movable between a first configuration in which no force is exerted on the UNCD nanowire and a second configuration in which the UNCD nanowire bends about the first end and the second end in response to a force. The UNCD nanowire has a first resistance in the first configuration and a second resistance in the second configuration which is different from the first resistance. The UNCD nanowire is structured to have a gauge factor of at least about 70, for example, in the range of about 70 to about 1,800.

  5. Enhanced thermoelectric performance of rough silicon nanowires.

    PubMed

    Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz; Liang, Wenjie; Garnett, Erik C; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-01-10

    Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

  6. Deposition and post-processing techniques for transparent conductive films

    DOEpatents

    Christoforo, Mark Greyson; Mehra, Saahil; Salleo, Alberto; Peumans, Peter

    2015-01-13

    In one embodiment, a method is provided for fabrication of a semitransparent conductive mesh. A first solution having conductive nanowires suspended therein and a second solution having nanoparticles suspended therein are sprayed toward a substrate, the spraying forming a mist. The mist is processed, while on the substrate, to provide a semitransparent conductive material in the form of a mesh having the conductive nanowires and nanoparticles. The nanoparticles are configured and arranged to direct light passing through the mesh. Connections between the nanowires provide conductivity through the mesh.

  7. Metallic Nanowire Interconnections for Integrated Circuit Fabrication

    NASA Technical Reports Server (NTRS)

    Ng, Hou Tee (Inventor); Li, Jun (Inventor); Meyyappan, Meyya (Inventor)

    2007-01-01

    A method for fabricating an electrical interconnect between two or more electrical components. A conductive layer is provided on a substarte and a thin, patterned catalyst array is deposited on an exposed surface of the conductive layer. A gas or vapor of a metallic precursor of a metal nanowire (MeNW) is provided around the catalyst array, and MeNWs grow between the conductive layer and the catalyst array. The catalyst array and a portion of each of the MeNWs are removed to provide exposed ends of the MeNWs.

  8. Thermoelectric Properties of Nanowires with a Graphitic Shell.

    PubMed

    Lee, Jong Woon; Lee, Eun Kyung; Kim, Byung Sung; Lee, Jae Hyun; Kim, Hee Goo; Jang, Hyeon Sik; Hwang, Sung Woo; Choi, Byoung Lyong; Whang, Dongmok

    2015-07-20

    A thermoelectric device that can generate electricity from waste heat can play an important role in a global energy solution. However, the strongly correlated thermoelectric properties have remained a major hurdle for the highly efficient conversion of thermoelectric energy. Herein, the electrical and thermal properties of Si and SiO2 nanowires with few-layer graphitic shells are demonstrated; these structures exhibit enhanced electrical properties but no increase in thermal conductivity. The main path of the phonons through the structures is the core nanowire, which has a large cross-sectional area relative to that of the graphitic shell layer. However, the electrical conductivities of the nanowires with shell structures are high because of the good electrical conductivity of the graphitic shell, despite its small cross-sectional area.

  9. Thermal and electromechanical characterization of top-down fabricated p-type silicon nanowires

    NASA Astrophysics Data System (ADS)

    Bosseboeuf, Alain; Allain, Pierre Etienne; Parrain, Fabien; Le Roux, Xavier; Isac, Nathalie; Jacob, Serge; Poizat, Alexis; Coste, Philippe; Maaroufi, Seiffedine; Walther, Arnaud

    2015-01-01

    In this paper we report thermal conductivity and piezoresistivity measurements of top-down fabricated highly boron doped (NA = 1.5 × 1019 cm-3) suspended Si nanowires. These measurements were performed in a cryogenic probe station respectively by using the 3 omega method and by in situ application of a longitudinal tensile stress to the nanowire under test with a direct four point bending of the Si nanowire die. Nanowires investigated have a thickness of 160 nm, a width in the 80-260 nm range and a length in the 2.5-5.2 μm range. We found that for these geometries, thermal conduction still obeys Fourier’s law and that, as expected, the thermal conductivity is largely reduced when the nanowires width is shrunk, but, to a lower extent than published values for nanowires grown by vapor-liquid-solid (VLS) processes. While a large giant piezoresistance effect was evidenced by various authors when a static stress is applied, we only observed a limited nanowire size dependence of the piezoresistivity in our experiments where a dynamical mechanical loading is applied. This confirms that the giant piezoresistance effect in unbiased Si nanowires is not an intrinsic bulk effect but is dominated by surface related effects in agreement with the piezopinch effect model. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam

  10. Determining factors of thermoelectric properties of semiconductor nanowires

    NASA Astrophysics Data System (ADS)

    Demchenko, Denis O.; Heinz, Peter D.; Lee, Byounghak

    2011-08-01

    It is widely accepted that low dimensionality of semiconductor heterostructures and nanostructures can significantly improve their thermoelectric efficiency. However, what is less well understood is the precise role of electronic and lattice transport coefficients in the improvement. We differentiate and analyze the electronic and lattice contributions to the enhancement by using a nearly parameter-free theory of the thermoelectric properties of semiconductor nanowires. By combining molecular dynamics, density functional theory, and Boltzmann transport theory methods, we provide a complete picture for the competing factors of thermoelectric figure of merit. As an example, we study the thermoelectric properties of ZnO and Si nanowires. We find that the figure of merit can be increased as much as 30 times in 8-Å-diameter ZnO nanowires and 20 times in 12-Å-diameter Si nanowires, compared with the bulk. Decoupling of thermoelectric contributions reveals that the reduction of lattice thermal conductivity is the predominant factor in the improvement of thermoelectric properties in nanowires. While the lattice contribution to the efficiency enhancement consistently becomes larger with decreasing size of nanowires, the electronic contribution is relatively small in ZnO and disadvantageous in Si.

  11. Crystallographic alignment of high-density gallium nitride nanowire arrays.

    PubMed

    Kuykendall, Tevye; Pauzauskie, Peter J; Zhang, Yanfeng; Goldberger, Joshua; Sirbuly, Donald; Denlinger, Jonathan; Yang, Peidong

    2004-08-01

    Single-crystalline, one-dimensional semiconductor nanostructures are considered to be one of the critical building blocks for nanoscale optoelectronics. Elucidation of the vapour-liquid-solid growth mechanism has already enabled precise control over nanowire position and size, yet to date, no reports have demonstrated the ability to choose from different crystallographic growth directions of a nanowire array. Control over the nanowire growth direction is extremely desirable, in that anisotropic parameters such as thermal and electrical conductivity, index of refraction, piezoelectric polarization, and bandgap may be used to tune the physical properties of nanowires made from a given material. Here we demonstrate the use of metal-organic chemical vapour deposition (MOCVD) and appropriate substrate selection to control the crystallographic growth directions of high-density arrays of gallium nitride nanowires with distinct geometric and physical properties. Epitaxial growth of wurtzite gallium nitride on (100) gamma-LiAlO(2) and (111) MgO single-crystal substrates resulted in the selective growth of nanowires in the orthogonal [1\\[Evec]0] and [001] directions, exhibiting triangular and hexagonal cross-sections and drastically different optical emission. The MOCVD process is entirely compatible with the current GaN thin-film technology, which would lead to easy scale-up and device integration.

  12. Study of electronic transport in gamma ray exposed nanowires

    SciTech Connect

    Gehlawat, Devender Chauhan, R.P.

    2014-01-01

    Graphical abstract: A sharp decline in the I–V characteristics of Cu (and Cd) nanowires was experimentally observed after the gamma ray exposure of nanowires. Irradiation induced transformations in the granular properties and the resonance state of electron–phonon coupling beyond a particular value of external field may be accountable for observed shape of I–V characteristics in gamma ray exposed nanowires. - Highlights: • Cu and Cd nanowires were synthesized by technique of electrodeposition in templates. • The nanowires were exposed to different doses of gamma ray photons. • A sharp decline in the current in I–V characteristics (IVC) was observed. • Structural deviation in terms of granular orientations was also analysed. • The electron–phonon coupling may be responsible for observed sharp decline in IVC. - Abstract: One dimensional nanostructures provide the most restricted and narrow channel for the transport of charge carriers and therefore 1D structures preserve their significance from the viewpoint of electronic devices. The net radiation effect on nanomaterials is expected to be more (due to their increased reactivity and lesser bulk volume) than their bulk counterparts. Radiation often modifies the structure and simultaneously the other physical properties of materials. In this manner, the irradiation phenomenon could be counted as a strong criterion to induce changes in the structural and electrical properties of nanowires. We have studied the effect of gamma rays on the electronic flow through Cu and Cd nanowires by plotting their I–V characteristics (IVC). The IVC of gamma ray exposed nanowires was found to be a combination of the linear and nonlinear regions and a decreasing pattern in the electrical conductivity (calculated from the linear portion of IVC) was observed as we increased the dose of gamma rays.

  13. Self-assembled nanowire array capacitors: capacitance and interface state profile

    NASA Astrophysics Data System (ADS)

    Li, Qiliang; Xiong, Hao D.; Liang, Xuelei; Zhu, Xiaoxiao; Gu, Diefeng; Ioannou, Dimitris E.; Baumgart, Helmut; Richter, Curt A.

    2014-04-01

    Direct characterization of the capacitance and interface states is very important for understanding the electronic properties of a nanowire transistor. However, the capacitance of a single nanowire is too small to precisely measure. In this work we have fabricated metal-oxide-semiconductor capacitors based on a large array of self-assembled Si nanowires. The capacitance and conductance of the nanowire array capacitors are directly measured and the interface state profile is determined by using the conductance method. We demonstrate that the nanowire array capacitor is an effective platform for studying the electronic properties of nanoscale interfaces. This approach provides a useful and efficient metrology for the study of the physics and device properties of nanoscale metal-oxide-semiconductor structures.

  14. Self-assembled nanowire array capacitors: capacitance and interface state profile.

    PubMed

    Li, Qiliang; Xiong, Hao D; Liang, Xuelei; Zhu, Xiaoxiao; Gu, Diefeng; Ioannou, Dimitris E; Baumgart, Helmut; Richter, Curt A

    2014-04-04

    Direct characterization of the capacitance and interface states is very important for understanding the electronic properties of a nanowire transistor. However, the capacitance of a single nanowire is too small to precisely measure. In this work we have fabricated metal-oxide-semiconductor capacitors based on a large array of self-assembled Si nanowires. The capacitance and conductance of the nanowire array capacitors are directly measured and the interface state profile is determined by using the conductance method. We demonstrate that the nanowire array capacitor is an effective platform for studying the electronic properties of nanoscale interfaces. This approach provides a useful and efficient metrology for the study of the physics and device properties of nanoscale metal-oxide-semiconductor structures.

  15. Heteromultimerization of prokaryotic bacterial cyclic nucleotide-gated (bCNG) ion channels, members of the mechanosensitive channel of small conductance (MscS) superfamily.

    PubMed

    Malcolm, Hannah R; Heo, Yoon-Young; Elmore, Donald E; Maurer, Joshua A

    2014-12-30

    Traditionally, prokaryotic channels are thought to exist as homomultimeric assemblies, while many eukaryotic ion channels form complex heteromultimers. Here we demonstrate that bacterial cyclic nucleotide-gated channels likely form heteromultimers in vivo. Heteromultimer formation is indicated through channel modeling, pull-down assays, and real-time polymerase chain reaction analysis. Our observations demonstrate that prokaryotic ion channels can display complex behavior and regulation akin to that of their eukaryotic counterparts.

  16. Improving Performance via Blocking Layers in Dye-Sensitized Solar Cells Based on Nanowire Photoanodes.

    PubMed

    Li, Luping; Xu, Cheng; Zhao, Yang; Chen, Shikai; Ziegler, Kirk J

    2015-06-17

    Electron recombination in dye-sensitized solar cells (DSSCs) results in significant electron loss and performance degradation. However, the reduction of electron recombination via blocking layers in nanowire-based DSSCs has rarely been investigated. In this study, HfO2 or TiO2 blocking layers are deposited on nanowire surfaces via atomic layer deposition (ALD) to reduce electron recombination in nanowire-based DSSCs. The control cell consisting of ITO nanowires coated with a porous shell of TiO2 by TiCl4 treatment yields an efficiency of 2.82%. The efficiency increases dramatically to 5.38% upon the insertion of a 1.3 nm TiO2 compact layer between the nanowire surface and porous TiO2 shell. This efficiency enhancement implies that porous sol-gel coatings on nanowires (e.g., via TiCl4 treatment) result in significant electron recombination in nanowire-based DSSCs, while compact coatings formed by ALD are more advantageous because of their ability to act as a blocking layer. By comparing nanowire-based DSSCs with their nanoparticle-based counterparts, we find that the nanowire-based DSSCs suffer more severe electron recombination from ITO due to the much higher surface area exposed to the electrolyte. While the insertion of a high band gap compact layer of HfO2 between the interface of the conductive nanowire and TiO2 shell improves performance, a comparison of the cell performance between TiO2 and HfO2 compact layers indicates that charge collection is suppressed by the difference in energy states. Consequently, the use of high band gap materials at the interface of conductive nanowires and TiO2 is not recommended.

  17. Topological Insulator Nanowires and Nanoribbons

    SciTech Connect

    Kong, D.S.

    2010-06-02

    Recent theoretical calculations and photoemission spectroscopy measurements on the bulk Bi{sub 2}Se{sub 3} material show that it is a three-dimensional topological insulator possessing conductive surface states with nondegenerate spins, attractive for dissipationless electronics and spintronics applications. Nanoscale topological insulator materials have a large surface-to-volume ratio that can manifest the conductive surface states and are promising candidates for devices. Here we report the synthesis and characterization of high quality single crystalline Bi{sub 2}Se{sub 3} nanomaterials with a variety of morphologies. The synthesis of Bi{sub 2}Se{sub 3} nanowires and nanoribbons employs Au-catalyzed vapor-liquid-solid (VLS) mechanism. Nanowires, which exhibit rough surfaces, are formed by stacking nanoplatelets along the axial direction of the wires. Nanoribbons are grown along [11-20] direction with a rectangular crosssection and have diverse morphologies, including quasi-one-dimensional, sheetlike, zigzag and sawtooth shapes. Scanning tunneling microscopy (STM) studies on nanoribbons show atomically smooth surfaces with {approx}1 nm step edges, indicating single Se-Bi-Se-Bi-Se quintuple layers. STM measurements reveal a honeycomb atomic lattice, suggesting that the STM tip couples not only to the top Se atomic layer, but also to the Bi atomic layer underneath, which opens up the possibility to investigate the contribution of different atomic orbitals to the topological surface states. Transport measurements of a single nanoribbon device (four terminal resistance and Hall resistance) show great promise for nanoribbons as candidates to study topological surface states.

  18. Towards low-dimensional hole systems in Be-doped GaAs nanowires.

    PubMed

    Ullah, A R; Gluschke, J G; Krogstrup, P; Sørensen, C B; Nygård, J; Micolich, A P

    2017-03-01

    GaAs was central to the development of quantum devices but is rarely used for nanowire-based quantum devices with InAs, InSb and SiGe instead taking the leading role. p-type GaAs nanowires offer a path to studying strongly confined 0D and 1D hole systems with strong spin-orbit effects, motivating our development of nanowire transistors featuring Be-doped p-type GaAs nanowires, AuBe alloy contacts and patterned local gate electrodes towards making nanowire-based quantum hole devices. We report on nanowire transistors with traditional substrate back-gates and EBL-defined metal/oxide top-gates produced using GaAs nanowires with three different Be-doping densities and various AuBe contact processing recipes. We show that contact annealing only brings small improvements for the moderately doped devices under conditions of lower anneal temperature and short anneal time. We only obtain good transistor performance for moderate doping, with conduction freezing out at low temperature for lowly doped nanowires and inability to reach a clear off-state under gating for the highly doped nanowires. Our best devices give on-state conductivity 95 nS, off-state conductivity 2 pS, on-off ratio [Formula: see text], and sub-threshold slope 50 mV/dec at [Formula: see text] K. Lastly, we made a device featuring a moderately doped nanowire with annealed contacts and multiple top-gates. Top-gate sweeps show a plateau in the sub-threshold region that is reproducible in separate cool-downs and indicative of possible conductance quantisation highlighting the potential for future quantum device studies in this material system.

  19. Towards low-dimensional hole systems in Be-doped GaAs nanowires

    NASA Astrophysics Data System (ADS)

    Ullah, A. R.; Gluschke, J. G.; Krogstrup, P.; Sørensen, C. B.; Nygård, J.; Micolich, A. P.

    2017-03-01

    GaAs was central to the development of quantum devices but is rarely used for nanowire-based quantum devices with InAs, InSb and SiGe instead taking the leading role. p-type GaAs nanowires offer a path to studying strongly confined 0D and 1D hole systems with strong spin–orbit effects, motivating our development of nanowire transistors featuring Be-doped p-type GaAs nanowires, AuBe alloy contacts and patterned local gate electrodes towards making nanowire-based quantum hole devices. We report on nanowire transistors with traditional substrate back-gates and EBL-defined metal/oxide top-gates produced using GaAs nanowires with three different Be-doping densities and various AuBe contact processing recipes. We show that contact annealing only brings small improvements for the moderately doped devices under conditions of lower anneal temperature and short anneal time. We only obtain good transistor performance for moderate doping, with conduction freezing out at low temperature for lowly doped nanowires and inability to reach a clear off-state under gating for the highly doped nanowires. Our best devices give on-state conductivity 95 nS, off-state conductivity 2 pS, on-off ratio ∼ {10}4, and sub-threshold slope 50 mV/dec at T=4 K. Lastly, we made a device featuring a moderately doped nanowire with annealed contacts and multiple top-gates. Top-gate sweeps show a plateau in the sub-threshold region that is reproducible in separate cool-downs and indicative of possible conductance quantisation highlighting the potential for future quantum device studies in this material system.

  20. Copper nanowire arrays for transparent electrodes

    NASA Astrophysics Data System (ADS)

    Gao, Tongchuan; Leu, Paul W.

    2013-08-01

    Metallic nanowires have demonstrated high optical transmission and electrical conductivity with potential for application as transparent electrodes that may be used in flexible devices. In this paper, we systematically investigated the electrical and optical properties of 1D and 2D copper nanowire (Cu NW) arrays as a function of diameter and pitch and compared their performance to that of Cu thin films and our recent results on silver (Ag) NW arrays. Cu NWs exhibit enhanced transmission over thin films due to propagating resonance modes between NWs. For the same geometry, the transmission of Cu NW arrays is about the same as that of Ag NW arrays since the dispersion relation of propagating modes in metal nanowire arrays are independent of the metal permittivity. The sheet resistance is also comparable since the conductivity of Cu is about the same as that of Ag. Just as in Ag NWs, larger Cu NW diameters and pitches are favored for achieving higher solar transmission at a particular sheet resistance. Cu NW arrays may achieve solar transmission >90% with sheet resistances <10 Ω/sq and figure of merit σDC/σop>1000. One of the primary concerns with the use of Cu is oxidation and we also investigated the impact of a nickel (Ni) coating, which can serve as an anti-oxidation layer, on the electrical and optical properties.

  1. Nonlinear Peltier effect and thermoconductance in nanowires

    NASA Astrophysics Data System (ADS)

    Bogachek, E. N.; Scherbakov, A. G.; Landman, Uzi

    1999-10-01

    A theoretical analysis of thermal transport in nanowires, in field-free conditions and under influence of applied magnetic fields, is presented. It is shown that in the nonlinear regime (finite applied voltage) new peaks in the Peltier coefficient appear leading to violation of Onsager's relation between the Peltier and thermopower coefficients. Oscillations of the Peltier coefficient in a magnetic field are demonstrated. The thermoconductance has a steplike quantized structure similar to the electroconductance and it exhibits deviations from the Wiedemann-Franz law. The strong dependence of the thermoconductance on the applied magnetic field leads to the possibility of magnetic blockade of thermal transport in wires with a small number of conducting channels. Possible control of thermal transport in nanowires through external parameters, that is applied through finite voltages and magnetic fields, is discussed.

  2. Lithium ion beam impact on selenium nanowires

    NASA Astrophysics Data System (ADS)

    Panchal, Suresh; Chauhan, R. P.

    2017-03-01

    This study is structured on Li3+ ion irradiation effect on the different properties of selenium (Se) nanowires (NW's) (80 nm). Template technique was employed for the synthesis of Se nanowires. Exploration of the effect of 10 MeV Li3+ ions on Se NW's was done for structural and electrical analysis with the help of characterization tools. X-ray diffraction revealed the variation in peak intensity only, with no peak shifting. The grain size and texture coefficients of various planes were also found to vary. Current-Voltage characteristics (IVC) show an increment in the conductivity up to a fluence of 1×1012 ions/cm2 and a decrease at the next two fluences. The effects of irradiation are presented in this paper and possible reasons for the variation in properties are also discussed in this study.

  3. Silicon nanowire hot electron electroluminescence

    NASA Astrophysics Data System (ADS)

    du Plessis, Monuko; Joubert, Trudi-Heleen

    2016-02-01

    This paper investigates the avalanche electroluminescence characteristics of pn junctions formed in silicon nanowires fabricated in a silicon-on-insula*tor (SOI) technology. Since carriers are confined to the nanowires, it is possible to study the effect of electric field strength on device performance while the current density and carrier concentrations are kept constant. This is achieved by varying the nanowire length while keeping the bias current constant, eventually driving the pn junction into the reach-through bias condition. It is observed that photon emission for photon energies higher than 1.2 eV increases when the nanowire length is reduced, while photon emission with energies less than 1.2 eV decreases. The higher electric field in the nanowire at shorter nanowire lengths enhances the high-energy photon emission and attenuates the low energy photon emission.

  4. A Semimetal Nanowire Rectifier: Balancing Quantum Confinement and Surface Electronegativity.

    PubMed

    Sanchez-Soares, Alfonso; Greer, James C

    2016-12-14

    For semimetal nanowires with diameters on the order of 10 nm, a semimetal-to-semiconductor transition is observed due to quantum confinement effects. Quantum confinement in a semimetal lifts the degeneracy of the conduction and valence bands in a "zero" gap semimetal or shifts energy levels with a "negative" overlap to form conduction and valence bands. For semimetal nanowires with diameters less than 10 nm, the band gap energy can be significantly larger than the thermal energy at room temperature resulting in a new class of semiconductors suitable for nanoelectronics. As a nanowire's diameter is reduced, its surface-to-volume ratio increases rapidly leading to an increased impact of surface chemistry on its electronic structure. Energy level shifts to states in the vicinity of the Fermi energy with varying surface electronegativity are shown to be comparable in magnitude to quantum confinement effects arising in nanowires with diameters of a few nanometer; these two effects can counteract one another leading to semimetallic behavior at nanowire cross sections at which confinement effects would otherwise dominate. Abruptly changing the surface terminating species along the length of a nanowire can lead to an abrupt change in the surface electronegativity. This can result in the formation of a semimetal-semiconductor junction within a monomaterial nanowire without impurity doping nor requiring the formation of a heterojunction. Using density functional theory in tandem with a Green's function approach to determine electronic structure and charge transport, respectively, current rectification is calculated for such a junction. Current rectification ratios of the order of 10(3)-10(5) are predicted at applied biases as low as 300 mV. It is concluded that rectification can be achieved at essentially molecular length scales with conventional biasing, while rivaling the performance of macroscopic semiconductor diodes.

  5. Diamond Nanowire for UV Detection

    DTIC Science & Technology

    2010-02-28

    addition to the stated goal of solar - blind , radiation-hard diamond nanowire UV detectors [3]. The use of diamond nanowires in field-effect transistors could...the next phase. As a result, a working diamond nanowire UV detector can be expected within the coming few months. And, a completely new diamond...attractive candidate for use in ultraviolet ( UV ) light detectors and emitters[2]. Of all known materials, it is the hardest, and has the highest

  6. Fabrication and photonics properties of III-V semiconductor nanowire structures

    NASA Astrophysics Data System (ADS)

    Lin, Tzu-ging

    absorption. Although traditional conductive oxide materials, such as indium tin oxide (ITO) and aluminum zinc oxide (AZO), have been successfully used in solar cell thin film devices, those conductive oxide contact electrodes will have different optical behavior applied in 1D nanowire devices due to 1D optical Mie resonance in nanowires. We found metal contact electrodes, such as silver and copper, will have comparable optical performance with conventional ITO contact electrodes while the semiconductor nanowire devices approaching to 1D limit. Our results also show the contact electrodes will affect the semiconductor materials with different bandgaps through different ways, which can be considered as a guideline for the future device applications.

  7. Quantum charge fluctuations of a proximitized nanowire

    NASA Astrophysics Data System (ADS)

    Lutchyn, Roman M.; Flensberg, Karsten; Glazman, Leonid I.

    2016-09-01

    Motivated by a recent experiment [Nature (London) 531, 206 (2016), 10.1038/nature17162], we consider charging of a nanowire which is proximitized by a superconductor and connected to a normal-state lead by a single-channel junction. The charge Q of the nanowire is controlled by gate voltage e Ng/C . A finite conductance of the contact allows for quantum charge fluctuations, making the function Q (Ng) continuous. It depends on the relation between the superconducting gap Δ and the effective charging energy EC*. The latter is determined by the junction conductance in addition to the geometrical capacitance of the proximitized nanowire. We investigate Q (Ng) at zero magnetic field B and at fields exceeding the critical value Bc corresponding to the topological phase transition [Phys. Rev. Lett. 105, 077001 (2010), 10.1103/PhysRevLett.105.077001; Phys. Rev. Lett. 105, 177002 (2010), 10.1103/PhysRevLett.105.177002]. Unlike the case of Δ =0 , the function Q (Ng) is analytic even in the limit of negligible level spacing in the nanowire. At B =0 and Δ >EC* , the maxima of d Q /d Ng are smeared by 2 e fluctuations described by a single-channel "charge Kondo" physics, whereas the B =0 ,Δ

  8. Silicon nanowire field effect transistor for biosensing

    NASA Astrophysics Data System (ADS)

    Chen, Yu

    Detection and recognition of chemical ions and biological molecules are important in basic science as well as in pharmacology and medicine. Nanotechnology has made it possible to greatly enhance detection sensitivity through the use of nanowires, nanotubes, nanocrystals, nanocantilevers, and quantum dots as sensing platforms. In this work silicon nanowires are used as the conductance channel between the source and drain of a FET (field effect transistor) device and the biomolecular binding on the surface of nanowire modifies the conductance like a change in gate voltage. Due to the high surface-to-volume ratio and unique character of the silicon nanowires, this device has significant advantages in real-time, label-free and highly sensitive detection of a wide range of species, including proteins, nucleic acids and other small molecules. Here we present a biosensor fabricated from CMOS (complementary metal-oxide-semiconductor) compatible top-down methods including electron beam lithography. This method enables scalable manufacturing of multiple sensor arrays with high efficiency. In a systematic study of the device characteristics with different wire widths, we have found the sensitivity of the device increases when wire width decreases. By operating the device in appropriate bias region, the sensitivity of the device can be improved without doping or high temperature annealing. Not only can this device be used to detect the concentration of proteins and metabolites like urea or glucose, but also dynamic information like the dissociation constant can be extracted from the measurement. The device is also used to detect the clinically related cancer antigen CA 15.3 and shows potential application in cancer studies.

  9. Microbial Nanowire Electronic Structure Probed by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Veazey, Joshua P.; Lampa-Pastirk, Sanela; Reguera, Gemma; Tessmer, Stuart H.

    2010-03-01

    Complex molecules produced by living organisms provide laboratories for interesting physical properties. The study of such interesting physics, likewise, gives new insight into intriguing biological processes. We have studied the pilus nanowires expressed by the bacterium, Geobacter sulfurreducens, using high resolution scanning tunneling microscopy (STM). G. sulfurreducens is a metal reducing bacterium that has evolved electrically conductive pili to efficiently transfer electrons across large distances.footnotetextG. Reguera, K.D. McCarthy, T. Mehta, J.S. Nicoll, M.T. Tuominen, and D.R. Lovley, Nature 435, 1098 (2005) Here we employ the electronic sensitivity of STM to resolve the molecular substructure and the local electronic density of states (LDOS) along the nanowire, in an effort to elucidate the mechanism of conduction. We observe LDOS dependent upon the location of the tip above the nanowire.

  10. Laser Processed Silver Nanowire Network Transparent Electrodes for Novel Electronic Devices

    NASA Astrophysics Data System (ADS)

    Spechler, Joshua Allen

    Silver nanowire network transparent conducting layers are poised to make headway into a space previously dominated by transparent conducting oxides due to the promise of a flexible, scaleable, lab-atmosphere processable alternative. However, there are many challenges standing in the way between research scale use and consumer technology scale adaptation of this technology. In this thesis we will explore many, and overcome a few of these challenges. We will address the poor conductivity at the narrow nanowire-nanowire junction points in the network by developing a laser based process to weld nanowires together on a microscopic scale. We address the need for a comparative metric for transparent conductors in general, by taking a device level rather than a component level view of these layers. We also address the mechanical, physical, and thermal limitations to the silver nanowire networks by making composites from materials including a colorless polyimide and titania sol-gel. Additionally, we verify our findings by integrating these processes into devices. Studying a hybrid organic/inorganic heterojunction photovoltaic device we show the benefits of a laser processed electrode. Green phosphorescent organic light emitting diodes fabricated on a solution phase processed silver nanowire based electrode show favorable device metrics compared to a conductive oxide electrode based control. The work in this thesis is intended to push the adoption of silver nanowire networks to further allow new device architectures, and thereby new device applications.

  11. CdSe nanowires grown by using chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Gubur, H. Metin; Septekin, F.; Alpdogan, S.

    2015-10-01

    The Cadmium-selenide (CdSe) nanowire thin films were prepared on glass substrates by using chemical bath deposition (CBD) at 70 °C. Cadmium sulfate and sodium selenosulphate were used as Cd2+ and Se2- ion sources, respectively. The CdSe nanowire film was annealed in an air atmosphere at 573 K for 1 hour. X-ray diffraction (XRD) results showed that the nanowire films as-deposited and annealed had mixed cubic and hexagonal phase. Scanning electron microscopy (SEM) indicated that the CdSe nanowires had lengths ranging from 642 nm to 2.5 μm and diameters ranging from 46 nm to 211 nm. The optical properties of the as-deposited and the annealed nanowire films, an investigated by recording the transmission spectra by using an UV-visible spectrophotometer revealed that the energy band gap decreased (from 1.78 eV to 1.50 eV) upon annealing. The conductivity measurements made by using four-probe methods for both the annealed and the as-deposited films showed that the resistivity, conductivity and activation energy changed upon annealing.

  12. Review on measurement techniques of transport properties of nanowires.

    PubMed

    Rojo, Miguel Muñoz; Calero, Olga Caballero; Lopeandia, A F; Rodriguez-Viejo, J; Martín-Gonzalez, Marisol

    2013-12-07

    Physical properties at the nanoscale are novel and different from those in bulk materials. Over the last few decades, there has been an ever growing interest in the fabrication of nanowire structures for a wide variety of applications including energy generation purposes. Nevertheless, the study of their transport properties, such as thermal conductivity, electrical conductivity or Seebeck coefficient, remains an experimental challenge. For instance, in the particular case of nanostructured thermoelectrics, theoretical calculations have shown that nanowires offer a promising way of enhancing the hitherto low efficiency of these materials in the conversion of temperature differences into electricity. Therefore, within the thermoelectrical community there has been a great experimental effort in the measurement of these quantities in actual nanowires. The measurements of these properties at the nanoscale are also of interest in fields other than energy, such as electrical components for microchips, field effect transistors, sensors, and other low scale devices. For all these applications, knowing the transport properties is mandatory. This review deals with the latest techniques developed to perform the measurement of these transport properties in nanowires. A thorough overview of the most important and modern techniques used for the characterization of different kinds of nanowires will be shown.

  13. A comprehensive study of thermoelectric and transport properties of β-silicon carbide nanowires

    SciTech Connect

    Valentín, L. A.; Betancourt, J.; Fonseca, L. F.; Pettes, M. T.; Shi, L.; Soszyński, M.; Huczko, A.

    2013-11-14

    The temperature dependence of the Seebeck coefficient, the electrical and thermal conductivities of individual β-silicon carbide nanowires produced by combustion in a calorimetric bomb were studied using a suspended micro-resistance thermometry device that allows four-point probe measurements to be conducted on each nanowire. Additionally, crystal structure and growth direction for each measured nanowire was directly obtained by transmission electron microscopy analysis. The Fermi level, the carrier concentration, and mobility of each nanostructure were determined using a combination of Seebeck coefficient and electrical conductivity measurements, energy band structure and transport theory calculations. The temperature dependence of the thermal and electrical conductivities of the nanowires was explained in terms of contributions from boundary, impurity, and defect scattering.

  14. Numerical study of electrical transport in co-percolative metal nanowire-graphene thin-films

    NASA Astrophysics Data System (ADS)

    Gupta, Man Prakash; Kumar, Satish

    2016-11-01

    Nanowires-dispersed polycrystalline graphene has been recently explored as a transparent conducting material for applications such as solar cells, displays, and touch-screens. Metal nanowires and polycrystalline graphene play synergetic roles during the charge transport in the material by compensating for each other's limitations. In the present work, we develop and employ an extensive computational framework to study the essential characteristics of the charge transport not only on an aggregate basis but also on individual constituents' levels in these types of composite thin-films. The method allows the detailed visualization of the percolative current pathways in the material and provides the direct evidence of current crowding in the 1-D nanowires and 2-D polygraphene sheet. The framework is used to study the effects of several important governing parameters such as length, density and orientation of the nanowires, grain density in polygraphene, grain boundary resistance, and the contact resistance between nanowires and graphene. We also present and validate an effective medium theory based generalized analytical model for the composite. The analytical model is in agreement with the simulations, and it successfully predicts the overall conductance as a function of several parameters including the nanowire network density and orientation and graphene grain boundaries. Our findings suggest that the longer nanowires (compared to grain size) with low angle orientation (<40°) with respect to the main carrier transport direction provide significant advantages in enhancing the conductance of the polygraphene sheet. We also find that above a certain value of grain boundary resistance (>60 × intra-grain resistance), the overall conductance becomes nearly independent of grain boundary resistance due to nanowires. The developed model can be applied to study other emerging transparent conducting materials such as nanowires, nanotubes, polygraphene, graphene oxide, and

  15. Growth of Si nanowires in porous carbon with enhanced cycling stability for Li-ion storage

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaoxu; Rui, Xianhong; Zhou, WenWen; Tan, Liping; Yan, Qingyu; Lu, Ziyang; Hng, Huey Hoon

    2014-03-01

    Si nanowires are successfully grown in porous carbon by supercritical fluid-liquid-solid (SFLS) process, which show high specific capacities and charge-discharge cycling stability as anode materials for Li-ion storage. The enhancement capacity and cycling stability of the Si nanowires/porous carbon composite nanostructures is attributed to the porous carbon serving as a highly conductive framework and absorption of volume changes of Si nanowires during the lithiation/delithiation process. At optimized condition, the Si nanowires/porous carbon electrodes maintain reversible capacities of 1678 mAh g-1 for the 100th cycle at a current density of 420 mA g-1, which is much better as compared to that of pure Si nanowires.

  16. Synthesis of Fe Doped ZnO Nanowire Arrays that Detect Formaldehyde Gas.

    PubMed

    Jeon, Yoo Sang; Seo, Hyo Won; Kim, Su Hyo; Kim, Young Keun

    2016-05-01

    Owing to their chemical and thermal stability and doping effects on providing electrons to the conduction band, doped ZnO nanowires have generated interest for use in electronic devices. Here we report hydrothermally grown Fe-doped ZnO nanowires and their gas-sensing properties. The synthesized nanowires have a high crystallinity and are 60 nm in diameter and 1.7 μm in length. Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) are employed to understand the doping effects on the microstructures and gas sensing properties. When the Fe-doped ZnO nanowire arrays were evaluated for gas sensing, responses were recorded through changes in temperature and gas concentration. Gas sensors consisting of ZnO nanowires doped with 3-5 at.% Fe showed optimum formaldehyde (HCHO) sensing performance at each working temperature.

  17. Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

    NASA Astrophysics Data System (ADS)

    Tanta, R.; Madsen, M. H.; Liao, Z.; Krogstrup, P.; Vosch, T.; Nygârd, J.; Jespersen, T. S.

    2015-12-01

    The thermal gradients along indium arsenide nanowires were engineered by a combination of fabricated micro-trenches in the supporting substrate and focused laser irradiation. This allowed local spatial control of thermally activated oxidation reactions of the nanowire on the scale of the diffraction limit. The locality of the oxidation was detected by micro-Raman mapping, and the results were found to be consistent with numerical simulations of the temperature profile. Applying the technique to nanowires in electrical devices the locally oxidized nanowires remained conducting with a lower conductance as expected for an effectively thinner conducting core.

  18. Raman spectroscopy and electrical properties of InAs nanowires with local oxidation enabled by substrate micro-trenches and laser irradiation

    SciTech Connect

    Tanta, R.; Krogstrup, P.; Nygård, J.; Jespersen, T. S.; Madsen, M. H.; Liao, Z.; Vosch, T.

    2015-12-14

    The thermal gradients along indium arsenide nanowires were engineered by a combination of fabricated micro-trenches in the supporting substrate and focused laser irradiation. This allowed local spatial control of thermally activated oxidation reactions of the nanowire on the scale of the diffraction limit. The locality of the oxidation was detected by micro-Raman mapping, and the results were found to be consistent with numerical simulations of the temperature profile. Applying the technique to nanowires in electrical devices the locally oxidized nanowires remained conducting with a lower conductance as expected for an effectively thinner conducting core.

  19. Surface-decorated silicon nanowires: a route to high-ZT thermoelectrics.

    PubMed

    Markussen, Troels; Jauho, Antti-Pekka; Brandbyge, Mads

    2009-07-31

    Based on atomistic calculations of electron and phonon transport, we propose to use surface-decorated silicon nanowires for thermoelectric applications. Two examples of surface decorations are studied to illustrate the underlying ideas: nanotrees and alkyl functionalized silicon nanowires. For both systems we find (i) that the phonon conductance is significantly reduced compared to the electronic conductance leading to high thermoelectric figure of merit ZT, and (ii) for ultrathin wires, surface decoration leads to significantly better performance than surface disorder.

  20. Molecular beam epitaxial growth and characterization of Al(Ga)N nanowire deep ultraviolet light emitting diodes and lasers

    NASA Astrophysics Data System (ADS)

    Mi, Z.; Zhao, S.; Woo, S. Y.; Bugnet, M.; Djavid, M.; Liu, X.; Kang, J.; Kong, X.; Ji, W.; Guo, H.; Liu, Z.; Botton, G. A.

    2016-09-01

    We report on the detailed molecular beam epitaxial growth and characterization of Al(Ga)N nanowire heterostructures on Si and their applications for deep ultraviolet light emitting diodes and lasers. The nanowires are formed under nitrogen-rich conditions without using any metal catalyst. Compared to conventional epilayers, Mg-dopant incorporation is significantly enhanced in nearly strain- and defect-free Al(Ga)N nanowire structures, leading to efficient p-type conduction. The resulting Al(Ga)N nanowire LEDs exhibit excellent performance, including a turn-on voltage of ∼5.5 V for an AlN nanowire LED operating at 207 nm. The design, fabrication, and performance of an electrically injected AlGaN nanowire laser operating in the UV-B band is also presented.

  1. Highly Stretchable and Transparent Supercapacitor by Ag-Au Core-Shell Nanowire Network with High Electrochemical Stability.

    PubMed

    Lee, Habeom; Hong, Sukjoon; Lee, Jinhwan; Suh, Young Duk; Kwon, Jinhyeong; Moon, Hyunjin; Kim, Hyeonseok; Yeo, Junyeob; Ko, Seung Hwan

    2016-06-22

    Stretchable and transparent electronics have steadily attracted huge attention in wearable devices. Although Ag nanowire is the one of the most promising candidates for transparent and stretchable electronics, its electrochemical instability has forbidden its application to the development of electrochemical energy devices such as supercapacitors. Here, we introduce a highly stretchable and transparent supercapacitor based on electrochemically stable Ag-Au core-shell nanowire percolation network electrode. We developed a simple solution process to synthesize the Ag-Au core-shell nanowire with excellent electrical conductivity as well as greatly enhanced chemical and electrochemical stabilities compared to pristine Ag nanowire. The proposed core-shell nanowire-based supercapacitor still possesses fine optical transmittance and outstanding mechanical stability up to 60% strain. The Ag-Au core-shell nanowire can be a strong candidate for future wearable electrochemical energy devices.

  2. Flexible transparent PES/silver nanowires/PET sandwich-structured film for high-efficiency electromagnetic interference shielding.

    PubMed

    Hu, Mingjun; Gao, Jiefeng; Dong, Yucheng; Li, Kai; Shan, Guangcun; Yang, Shiliu; Li, Robert Kwok-Yiu

    2012-05-08

    We have developed a kind of high-yield synthesis strategy for silver nanowires by a two-step injection polyol method. Silver nanowires and polyethylene oxide (PEO) (M(w) = 900,000) were prepared in a homogeneous-coating ink. Wet composite films with different thicknesses were fabricated on a PET substrate by drawn-down rod-coating technology. Silver nanowires on PET substrates present a homogeneous distribution under the assistance of PEO. Then PEO was thermally removed in situ at a relatively low temperature attributed to its special thermal behavior under atmospheric conditions. As-prepared metallic nanowire films on PET substrates show excellent stability and a good combination of conductivity and light transmission. A layer of transparent poly(ethersulfones) (PESs) was further coated on silver nanowire networks by the same coating method to prevent the shedding and corrosion of silver nanowires. Sandwich-structured flexible transparent films were obtained and displayed excellent electromagnetic interference (EMI) shielding effectiveness.

  3. Transparent Conductive Nanofiber Paper for Foldable Solar Cells

    NASA Astrophysics Data System (ADS)

    Nogi, Masaya; Karakawa, Makoto; Komoda, Natsuki; Yagyu, Hitomi; Nge, Thi Thi

    2015-11-01

    Optically transparent nanofiber paper containing silver nanowires showed high electrical conductivity and maintained the high transparency, and low weight of the original transparent nanofiber paper. We demonstrated some procedures of optically transparent and electrically conductive cellulose nanofiber paper for lightweight and portable electronic devices. The nanofiber paper enhanced high conductivity without any post treatments such as heating or mechanical pressing, when cellulose nanofiber dispersions were dropped on a silver nanowire thin layer. The transparent conductive nanofiber paper showed high electrical durability in repeated folding tests, due to dual advantages of the hydrophilic affinity between cellulose and silver nanowires, and the entanglement between cellulose nanofibers and silver nanowires. Their optical transparency and electrical conductivity were as high as those of ITO glass. Therefore, using this conductive transparent paper, organic solar cells were produced that achieved a power conversion of 3.2%, which was as high as that of ITO-based solar cells.

  4. Transparent Conductive Nanofiber Paper for Foldable Solar Cells

    PubMed Central

    Nogi, Masaya; Karakawa, Makoto; Komoda, Natsuki; Yagyu, Hitomi; Nge, Thi Thi

    2015-01-01

    Optically transparent nanofiber paper containing silver nanowires showed high electrical conductivity and maintained the high transparency, and low weight of the original transparent nanofiber paper. We demonstrated some procedures of optically transparent and electrically conductive cellulose nanofiber paper for lightweight and portable electronic devices. The nanofiber paper enhanced high conductivity without any post treatments such as heating or mechanical pressing, when cellulose nanofiber dispersions were dropped on a silver nanowire thin layer. The transparent conductive nanofiber paper showed high electrical durability in repeated folding tests, due to dual advantages of the hydrophilic affinity between cellulose and silver nanowires, and the entanglement between cellulose nanofibers and silver nanowires. Their optical transparency and electrical conductivity were as high as those of ITO glass. Therefore, using this conductive transparent paper, organic solar cells were produced that achieved a power conversion of 3.2%, which was as high as that of ITO-based solar cells. PMID:26607742

  5. Transparent Conductive Nanofiber Paper for Foldable Solar Cells.

    PubMed

    Nogi, Masaya; Karakawa, Makoto; Komoda, Natsuki; Yagyu, Hitomi; Nge, Thi Thi

    2015-11-26

    Optically transparent nanofiber paper containing silver nanowires showed high electrical conductivity and maintained the high transparency, and low weight of the original transparent nanofiber paper. We demonstrated some procedures of optically transparent and electrically conductive cellulose nanofiber paper for lightweight and portable electronic devices. The nanofiber paper enhanced high conductivity without any post treatments such as heating or mechanical pressing, when cellulose nanofiber dispersions were dropped on a silver nanowire thin layer. The transparent conductive nanofiber paper showed high electrical durability in repeated folding tests, due to dual advantages of the hydrophilic affinity between cellulose and silver nanowires, and the entanglement between cellulose nanofibers and silver nanowires. Their optical transparency and electrical conductivity were as high as those of ITO glass. Therefore, using this conductive transparent paper, organic solar cells were produced that achieved a power conversion of 3.2%, which was as high as that of ITO-based solar cells.

  6. Scanning probe microscopy of protein nanowires

    NASA Astrophysics Data System (ADS)

    Walsh, Kathleen Ann

    The bacterium Geobacter sulfurreducens grows electrically-conductive pili, which act as protein nanowires, in order to transfer electrons from the cell to electron acceptors in its environment when direct charge transfer through the cell membrane is not feasible. Understanding the electronic structure of the pili can provide insight into fundamental processes of electron transfer in biological systems. This study investigated the electronic structure of these protein nanowires using the toolbox of scanning probe microscopy, specifically scanning tunneling microscopy and point tunneling spectroscopy. These measurements were performed at 77 K and at room temperature. The measured data are compared to theoretical calculations. Density of states measurements using tunneling spectroscopy show that these pili act as narrow-gap biological semiconductors at 77 K. The onset of nonzero density of states remains within the metabolically-relevant voltage range. At room temperature, spectroscopy of the pili retains a gap-like structure, but this pseudogap is raised to a nonzero density of states at even the smallest applied voltages. These pilus nanowires also exhibit a distinct spatial dependence of the density of states across the breadth of the pili.

  7. Diameter-Controlled and Surface-Modified Sb2Se3 Nanowires and Their Photodetector Performance

    NASA Astrophysics Data System (ADS)

    Choi, Donghyeuk; Jang, Yamujin; Lee, Jeehee; Jeong, Gyoung Hwa; Whang, Dongmok; Hwang, Sung Woo; Cho, Kyung-Sang; Kim, Sang-Wook

    2014-10-01

    Due to its direct and narrow band gap, high chemical stability, and high Seebeck coefficient (1800 μVK-1), antimony selenide (Sb2Se3) has many potential applications, such as in photovoltaic devices, thermoelectric devices, and solar cells. However, research on the Sb2Se3 materials has been limited by its low electrical conductivity in bulk state. To overcome this challenge, we suggest two kinds of nano-structured materials, namely, the diameter-controlled Sb2Se3 nanowires and Ag2Se-decorated Sb2Se3 nanowires. The photocurrent response of diameter-controlled Sb2Se3, which depends on electrical conductivity of the material, increases non-linearly with the diameter of the nanowire. The photosensitivity factor (K = Ilight/Idark) of the intrinsic Sb2Se3 nanowire with diameter of 80-100 nm is highly improved (K = 75). Additionally, the measurement was conducted using a single nanowire under low source-drain voltage. The dark- and photocurrent of the Ag2Se-decorated Sb2Se3 nanowire further increased, as compared to that of the intrinsic Sb2Se3 nanowire, to approximately 50 and 7 times, respectively.

  8. Carrier transport in high mobility InAs nanowire junctionless transistors.

    PubMed

    Konar, Aniruddha; Mathew, John; Nayak, Kaushik; Bajaj, Mohit; Pandey, Rajan K; Dhara, Sajal; Murali, K V R M; Deshmukh, Mandar M

    2015-03-11

    The ability to understand and model the performance limits of nanowire transistors is the key to the design of next generation devices. Here, we report studies on high-mobility junctionless gate-all-around nanowire field effect transistor with carrier mobility reaching 2000 cm(2)/V·s at room temperature. Temperature-dependent transport measurements reveal activated transport at low temperatures due to surface donors, while at room temperature the transport shows a diffusive behavior. From the conductivity data, the extracted value of sound velocity in InAs nanowires is found to be an order less than the bulk. This low sound velocity is attributed to the extended crystal defects that ubiquitously appear in these nanowires. Analyzing the temperature-dependent mobility data, we identify the key scattering mechanisms limiting the carrier transport in these nanowires. Finally, using these scattering models, we perform drift-diffusion based transport simulations of a nanowire field-effect transistor and compare the device performances with experimental measurements. Our device modeling provides insight into performance limits of InAs nanowire transistors and can be used as a predictive methodology for nanowire-based integrated circuits.

  9. Observation of surface plasmon polariton pumping of optical eigenmodes of gold-decorated gallium nitride nanowires.

    PubMed

    Sundararajan, Jency Pricilla; Bakharev, Pavel; Niraula, Ishwar; Kengne, Blaise Alexis Fouetio; MacPherson, Quinn; Sargent, Meredith; Hare, Brian; McIlroy, David N

    2012-10-10

    The photocurrent of individual gallium nitride (GaN) nanowires decorated with Au nanoparticles as function of the wavelength of light (405 nm (blue), 532 nm (green), and 632.8 nm (red)) and nanowire diameter (80 to 400 nm) is reported. The photocurrent scales with photon energy but oscillates with nanowire diameter. The oscillations are described in terms of the scattering of surface plasmon polaritons into allowed transverse magnetic electromagnetic modes of the nanowire that have maximum intensities in the undepleted region of the nanowire. These oscillations do not occur below a nanowire diameter of ~200 nm due to the depletion layer formed at the Au-GaN interface, which completely depletes the nanowire, that is, there is an insufficient density of carriers that can be excited into the conduction band. On the basis of estimations of the depletion depth and solutions of the Helmholtz equation, the maxima in the photocurrent for d > 200 nm are assigned to the two lowest azimuthally symmetric transverse magnetic eigenmodes: (m = 0, n = 1) and (m = 0, n = 2), which have maximum electric field intensities within the undepleted region of the GaN nanowire. The outcome of this work could have far reaching implications on the development of nanophotonics.

  10. Single-Nanowire Electrochemical Probe Detection for Internally Optimized Mechanism of Porous Graphene in Electrochemical Devices.

    PubMed

    Hu, Ping; Yan, Mengyu; Wang, Xuanpeng; Han, Chunhua; He, Liang; Wei, Xiujuan; Niu, Chaojiang; Zhao, Kangning; Tian, Xiaocong; Wei, Qiulong; Li, Zijia; Mai, Liqiang

    2016-03-09

    Graphene has been widely used to enhance the performance of energy storage devices due to its high conductivity, large surface area, and excellent mechanical flexibility. However, it is still unclear how graphene influences the electrochemical performance and reaction mechanisms of electrode materials. The single-nanowire electrochemical probe is an effective tool to explore the intrinsic mechanisms of the electrochemical reactions in situ. Here, pure MnO2 nanowires, reduced graphene oxide/MnO2 wire-in-scroll nanowires, and porous graphene oxide/MnO2 wire-in-scroll nanowires are employed to investigate the capacitance, ion diffusion coefficient, and charge storage mechanisms in single-nanowire electrochemical devices. The porous graphene oxide/MnO2 wire-in-scroll nanowire delivers an areal capacitance of 104 nF/μm(2), which is 4.0 and 2.8 times as high as those of reduced graphene oxide/MnO2 wire-in-scroll nanowire and MnO2 nanowire, respectively, at a scan rate of 20 mV/s. It is demonstrated that the reduced graphene oxide wrapping around the MnO2 nanowire greatly increases the electronic conductivity of the active materials, but decreases the ion diffusion coefficient because of the shielding effect of graphene. By creating pores in the graphene, the ion diffusion coefficient is recovered without degradation of the electron transport rate, which significantly improves the capacitance. Such single-nanowire electrochemical probes, which can detect electrochemical processes and behavior in situ, can also be fabricated with other active materials for energy storage and other applications in related fields.

  11. Dielectrophoretic fabrication and characterization of a ZnO nanowire-based UV photosensor.

    PubMed

    Suehiro, Junya; Nakagawa, Nobutaka; Hidaka, Shin-Ichiro; Ueda, Makoto; Imasaka, Kiminobu; Higashihata, Mitsuhiro; Okada, Tatsuo; Hara, Masanori

    2006-05-28

    Wide-gap semiconductors with nanostructures such as nanoparticles, nanorods, nanowires are promising as a new type of UV photosensor. Recently, ZnO (zinc oxide) nanowires have been extensively investigated for electronic and optoelectronic device applications. ZnO nanowires are expected to have good UV response due to their large surface area to volume ratio, and they might enhance the performance of UV photosensors. In this paper, a new fabrication method of a UV photosensor based on ZnO nanowires using dielectrophoresis is demonstrated. Dielectrophoresis (DEP) is the electrokinetic motion of dielectrically polarized materials in non-uniform electric fields. ZnO nanowires, which were synthesized by nanoparticle-assisted pulsed-laser deposition (NAPLD) and suspended in ethanol, were trapped in the microelectrode gap where the electric field became higher. The trapped ZnO nanowires were aligned along the electric field line and bridged the electrode gap. Under UV irradiation, the conductance of the DEP-trapped ZnO nanowires exponentially increased with a time constant of a few minutes. The slow UV response of ZnO nanowires was similar to that observed with ZnO thin films and might be attributed to adsorption and photodesorption of ambient gas molecules such as O(2) or H(2)O. At higher UV intensity, the conductance response became larger. The DEP-fabricated ZnO nanowire UV photosensor could detect UV light down to 10 nW cm(-2) intensity, indicating a higher UV sensitivity than ZnO thin films or ZnO nanowires assembled by other methods.

  12. Graphene-based nanowire supercapacitors.

    PubMed

    Chen, Zhi; Yu, Dingshan; Xiong, Wei; Liu, Peipei; Liu, Yong; Dai, Liming

    2014-04-01

    We present a new type of electrochemical supercapacitors based on graphene nanowires. Graphene oxide (GO)/polypyrrole (PPy) nanowires are prepared via electrodepostion of GO/PPy composite into a micoroporous Al2O3 template, followed by the removal of template. PPy is electrochemically doped by oxygen-containing functional groups of the GO to enhance the charging/discharging rates of the supercapacitor. A high capacitance 960 F g(-1) of the GO/PPy nanowires is obtained due to the large surface area of the vertically aligned nanowires and the intimate contact between the nanowires and the substrate electrode. The capacitive performance remains stable after charging and discharging for 300 cycles. To improve the thermal stability and long-term charge storage, GO is further electrochemically reduced into graphene and PPy is subsequently thermally carbonized, leading to a high capacitance of 200 F g(-1) for the resultant pure reduced graphene oxide/carbon based nanowire supercapacitor. This value of capacitance (200 F g(-1)) is higher than that of conventional porous carbon materials while the reduced graphene oxide/carbon nanowires show a lower Faraday resistance and higher thermal stability than the GO/PPy nanowires.

  13. Univerality, Scaling, and Stability of Metallic Nanowires

    NASA Astrophysics Data System (ADS)

    Stafford, Charles

    2001-03-01

    A remarkably quantitative understanding of the electrical and mechanical properties of simple metal nanowires has been obtained within the free-electron model.^2-4 The force required to pull a gold wire apart exhibits steps of approximately 1nN, which are synchronized with steps of order G_0=2e^2/h in the wire's electrical conductance. Using a Gutzwiller sum over classical periodic orbits,(C. A. Stafford, F. Kassubek, J. Bürki, and H. Grabert, Phys. Rev. Lett. 83), 4836 (1999). we were able to explain why the characteristic size of the force steps is universal, i.e., insensitive to the size and shape of the wire, and of order \\varepsilon_F/λ_F. The statistics of conductance and shot noise in gold nanowires can also be understood quantitatively using a model of quantum-confined electrons including disorder.(J. Bürki, C. A. Stafford, X. Zotos, and D. Baeriswyl, Phys. Rev. B 60), 5000 (1999); J. Bürki and C. A. Stafford, Phys. Rev. Lett. 83, 3342 (1999). A linear stability analysis(F. Kassubek, C. A. Stafford, H. Grabert, and R. E. Goldstein, Nonlinearity 14), 167 (2001). shows that the classical instability of a long wire under surface tension can be completely suppressed by quantum effects, leading to stable cylindrical configurations whose electrical conductance is a magic number 1, 3, 5, 6,... times G_0, providing a possible theoretical explanation for the remarkable stability of long chains of gold atoms, and for the supershell structure observed in the conductance statistics of alkali metal nanowires.

  14. Diameter dependent thermoelectric properties of individual SnTe nanowires

    DOE PAGES

    Xu, E. Z.; Li, Z.; Martinez, J. A.; ...

    2015-01-15

    The lead-free compound tin telluride (SnTe) has recently been suggested to be a promising thermoelectric material. In this work, we report on the first thermoelectric study of individual single-crystalline SnTe nanowires with different diameters ranging from ~ 218 to ~ 913 nm. Measurements of thermopower S, electrical conductivity σ and thermal conductivity κ were carried out on the same nanowires over a temperature range of 25 - 300 K. While the electrical conductivity does not show a strong diameter dependence, the thermopower increases by a factor of two when the nanowire diameter is decreased from ~ 913 nm to ~more » 218 nm. The thermal conductivity of the measured NWs is lower than that of the bulk SnTe, which may arise from the enhanced phonon - surface boundary scattering and phonon-defect scattering. Lastly, temperature dependent figure of merit ZT was determined for individual nanowires and the achieved maximum value at room temperature is about three times higher than that in bulk samples of comparable carrier density.« less

  15. Diameter dependent thermoelectric properties of individual SnTe nanowires

    SciTech Connect

    Xu, E. Z.; Li, Z.; Martinez, J. A.; Sinitsyn, N.; Htoon, H.; Li, Nan; Swartzentruber, B.; Hollingsworth, J. A.; Wang, Jian; Zhang, S. X.

    2015-01-15

    The lead-free compound tin telluride (SnTe) has recently been suggested to be a promising thermoelectric material. In this work, we report on the first thermoelectric study of individual single-crystalline SnTe nanowires with different diameters ranging from ~ 218 to ~ 913 nm. Measurements of thermopower S, electrical conductivity σ and thermal conductivity κ were carried out on the same nanowires over a temperature range of 25 - 300 K. While the electrical conductivity does not show a strong diameter dependence, the thermopower increases by a factor of two when the nanowire diameter is decreased from ~ 913 nm to ~ 218 nm. The thermal conductivity of the measured NWs is lower than that of the bulk SnTe, which may arise from the enhanced phonon - surface boundary scattering and phonon-defect scattering. Lastly, temperature dependent figure of merit ZT was determined for individual nanowires and the achieved maximum value at room temperature is about three times higher than that in bulk samples of comparable carrier density.

  16. Diameter Dependent Thermoelectric Properties of Individual SnTe Nanowires

    NASA Astrophysics Data System (ADS)

    Xu, E. Z.; Li, Z.; Martinez, J.; Sinitsyn, N.; Htoon, H.; Li, N.; Swartzentruber, B.; Hollingsworth, J.; Wang, J.; Zhang, S. X.

    2015-03-01

    Tin telluride (SnTe), a newly discovered topological crystalline insulator, has recently been suggested to be a promising thermoelectric material. In this work, we report on a systematic study of the thermoelectric properties of individual single-crystalline SnTe nanowires with different diameters. Measurements of thermopower, electrical conductivity and thermal conductivity were carried out on the same nanowires over a temperature range of 25 - 300 K. While the electrical conductivity does not show a strong diameter dependence, we found that the thermopower increases by a factor of two when the nanowire diameter is decreased from 913 nm to 218 nm. The thermal conductivity of the measured NWs is lower than that of the bulk SnTe, which may be attributed to the enhanced phonon - surface boundary scattering and phonon-defect scattering. We further calculated the temperature dependent figure of merit ZT for each individual nanowire. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Los Alamos National Laboratory (Contract DE-AC52-06NA25396) and Sandia National Laboratories (Contract DE-AC04-94AL85000). We acknowledge support by the Los Alamos LDRD program.

  17. Development and Applications of Nanowire Nanophotonics

    DTIC Science & Technology

    2006-03-23

    Nanowire Nanophotonics G F49620-03-1-0063 6. AUTHOR(S) Charles. M. Lieber 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION...Release; distribution is unlimited. 13, ABSTRACT (Maximum 200 Words) The controlled and predictable synthesis of nanowires and nanowire heterostrucrures...nitride based nanowire materials, including radial nanowire heterostructures in which the composition and/or doping was modulated perpendicular to the

  18. The Kondo effect and coherent transport in stacking-faults-free wurtzite InAs nanowires

    NASA Astrophysics Data System (ADS)

    Kretinin, Andrey V.; Popovitz-Biro, Ronit; Mahalu, Diana; Oreg, Yuval; Heiblum, Moty; Shtrikman, Hadas

    2011-12-01

    The crystalline perfection of wurtzite InAs nanowires grown by the Vapor-Liquid-Solid Molecular Beam Epitaxy technique in combination with careful fabrication of nanowire-based FET devices allowed us to observe a variety of phenomena associated with mesoscopic coherent transport. When the single nanowire channel is nearly pinched-off the Coulomb blockade conductance oscillations exhibit well-pronounced Kondo effect approaching the conductance unitary limit. At some gate voltages the breaking of odd-even parity of the Kondo effect related to the formation of the triplet ground state is observed. At higher gate voltages when the channel is open we observe the Fabry-Pérot type conductance oscillations. The length of the Fabry-Pérot electron resonator deduced from the period of the oscillations is in agreement with the physical length of the nanowire device.

  19. Integrated chemical and biological systems in nanowire structures towards nano-scale sensors

    NASA Astrophysics Data System (ADS)

    Hernandez, Rose M.

    Nanowires composed of metal and conducting polymers with integrated proteins and chemical systems have been investigated as building blocks for next-generation nano-scale sensors and assemblies. These nanowires were fabricated by combining chemical and electrochemical methods of synthesis of gold and conducting polymers in nanopores of anodized alumina membranes. Polymer nanowires were synthesized from buffer solutions as a mean to promote a biocompatible environment for the incorporation of proteins. A variety of proteins were incorporated into the polymer matrix by entrapment during polymerization that imparted the polymer material with biological functionality. Another class of composite nanowires containing electro-active conducting polymer junctions was developed for applications in chemical sensor arrays. The methodologies described in this thesis provide an inexpensive and straightforward approach to the synthesis of anisotropic nanoparticles incorporating a variety of biological and inorganic species that can be integrated to current microelectronic technologies for the development of nano-scale sensor arrays.

  20. Unveiling the formation pathway of single crystalline porous silicon nanowires.

    PubMed

    Zhong, Xing; Qu, Yongquan; Lin, Yung-Chen; Liao, Lei; Duan, Xiangfeng

    2011-02-01

    Porous silicon nanowire is emerging as an interesting material system due to its unique combination of structural, chemical, electronic, and optical properties. To fully understand their formation mechanism is of great importance for controlling the fundamental physical properties and enabling potential applications. Here we present a systematic study to elucidate the mechanism responsible for the formation of porous silicon nanowires in a two-step silver-assisted electroless chemical etching method. It is shown that silicon nanowire arrays with various porosities can be prepared by varying multiple experimental parameters such as the resistivity of the starting silicon wafer, the concentration of oxidant (H(2)O(2)) and the amount of silver catalyst. Our study shows a consistent trend that the porosity increases with the increasing wafer conductivity (dopant concentration) and oxidant (H(2)O(2)) concentration. We further demonstrate that silver ions, formed by the oxidation of silver, can diffuse upwards and renucleate on the sidewalls of nanowires to initiate new etching pathways to produce a porous structure. The elucidation of this fundamental formation mechanism opens a rational pathway to the production of wafer-scale single crystalline porous silicon nanowires with tunable surface areas ranging from 370 to 30 m(2) g(-1) and can enable exciting opportunities in catalysis, energy harvesting, conversion, storage, as well as biomedical imaging and therapy.

  1. A chemically-responsive nanojunction within a silver nanowire.

    PubMed

    Xing, Wendong; Hu, Jun; Kung, Sheng-Chin; Donavan, Keith C; Yan, Wenbo; Wu, Ruqian; Penner, Reginald M

    2012-03-14

    The formation of a nanometer-scale chemically responsive junction (CRJ) within a silver nanowire is described. A silver nanowire was first prepared on glass using the lithographically patterned nanowire electrodeposition method. A 1-5 nm gap was formed in this wire by electromigration. Finally, this gap was reconnected by applying a voltage ramp to the nanowire resulting in the formation of a resistive, ohmic CRJ. Exposure of this CRJ-containing nanowire to ammonia (NH(3)) induced a rapid (<30 s) and reversible resistance change that was as large as ΔR/R(0) = (+)138% in 7% NH(3) and observable down to 500 ppm NH(3). Exposure to water vapor produced a weaker resistance increase of ΔR/R(0,H(2)O) = (+)10-15% (for 2.3% water) while nitrogen dioxide (NO(2)) exposure induced a stronger concentration-normalized resistance decrease of ΔR/R(0,NO(2)) = (-)10-15% (for 500 ppm NO(2)). The proposed mechanism of the resistance response for a CRJ, supported by temperature-dependent measurements of the conductivity for CRJs and density functional theory calculations, is that semiconducting p-type Ag(x)O is formed within the CRJ and the binding of molecules to this Ag(x)O modulates its electrical resistance.

  2. Three-dimensional nanoelectrode by metal nanowire nonwoven clothes.

    PubMed

    Kawamori, Makoto; Asai, Takahiro; Shirai, Yoshimasa; Yagi, Shunsuke; Oishi, Masatsugu; Ichitsubo, Tetsu; Matsubara, Eiichiro

    2014-01-01

    Metal nanowire nonwoven cloth (MNNC) is a metal sheet that has resulted from intertwined metal nanowires 100 nm in diameter with several dozen micrometers of length. Thus, it is a new metallic material having both a flexibility of the metal sheet and a large specific surface area of the nanowires. As an application that utilizes these properties, we propose a high-cyclability electrode for Li storage batteries, in which an active material is deposited or coated on MNNC. The proposed electrode can work without any binders, conductive additives, and current collectors, which might largely improve a practical gravimetric energy density. Huge electrode surfaces provide efficient ion/electron transports, and sufficient interspaces between the respective nanowires accommodate large volume expansions of the active material. To demonstrate these advantages, we have fabricated a NiO-covered nickel nanowire nonwoven cloth (NNNC) by electroless deposition under a magnetic field and annealing in air. The adequately annealed NNNC was shown to be an excellent conversion-type electrode that exhibits a quite high cyclability, 500 mAh/g at 1 C after 300 cycles, compared to that of a composite electrode consisting of NiO nanoparticles. Thus, the present design concept will contribute to a game-changing technology in future lithium ion battery (LIB) electrodes.

  3. Novel mechanical behaviors of wurtzite CdSe nanowires

    NASA Astrophysics Data System (ADS)

    Fu, Bing; Chen, Li; Xie, Yiqun; Feng, Jie; Ye, Xiang

    2015-09-01

    As an important semiconducting nanomaterial, CdSe nanowires have attracted much attention. Although many studies have been conducted in the electronic and optical properties of CdSe NWs, the mechanical properties of Wurtzite (WZ) CdSe nanowires remain unclear. Using molecular dynamics simulations, we have studied the tensile mechanical properties and behaviors of [0001]-oriented Wurtzite CdSe nanowires. By monitoring the stretching processes of CdSe nanowires, three distinct structures are found: the WZ wire, a body-centered tetragonal structure with four-atom rings (denoted as BCT-4), and a structure that consists of ten-atom rings with two four-atom rings (denoted as TAR-4) which is observed for the first time. Not only the elastic tensile characteristics are highly reversible under unloading, but a reverse transition between TAR-4 and BCT-4 is also observed. The stretching processes also have a strong dependence on temperature. A tubular structure similar to carbon nanotubes is observed at 150 K, a single-atom chain is formed at 300, 350 and 450 K, and a double-atom chain is found at 600 K. Our findings on tensile mechanical properties of WZ CdSe nanowires does not only provide inspiration to future study on other properties of CdSe nanomaterials but also help design and build efficient nanoscale devices.

  4. Quantum Interference and Surface States Effects in Bismuth Nanowires

    NASA Astrophysics Data System (ADS)

    Konopko, L.; Huber, T.; Nikolaeva, A.

    2010-02-01

    We report the observation of Aharonov-Bohm (AB) oscillations for single Bi nanowires with diameter d< 80 nm. The single nanowire samples with glass coating were prepared by the Ulitovsky technique; they were cylindrical single crystals with (10 bar{1} 1) orientation along the wire axis. The surface of Bi nanowire supports surface states which give rise to a significant population of charge carriers with high effective mass that form a highly conducting tube around the nanowire. The oscillations of longitudinal magnetoresistance (MR) of Bi nanowires with two periods Δ B 1 and Δ B 2 proportional to Φ0 and Φ0/2 were observed, where Φ0= h/ e is the flux quantum. From B˜ 8 T down to B = 0 the extremums of Φ0/2 oscillations are shifted up to 3 π at B = 0 which is the manifestation of Berry phase shift due to electron moving in a nonuniform magnetic field. A derivative of MR was measured at various inclined angles. The observed angle variation of the periods is not in agreement with the theoretical dependence Δ( α)=Δ(0)/cos α of the size effect oscillations of the “flux quantization” type. Moreover, the equidistant oscillations of MR exist in transverse magnetic fields under certain rotation angles. An interpretation of the MR oscillations is presented.

  5. Carrier recombination dynamics in individual CdSe nanowires

    NASA Astrophysics Data System (ADS)

    Vietmeyer, Felix; Frantsuzov, Pavel A.; Janko, Boldizsar; Kuno, Masaru

    2011-03-01

    Carrier dynamics in single CdSe nanowires (NWs) have been studied using various techniques. They include measurements of single wire emission intensities as a function of pump fluence, excitation intensity-dependent emission quantum yields, and excited-state lifetimes. Ensemble transient differential absorption studies of induced bleach dynamics have also been conducted. Results of these studies show superlinear growth of the emission intensity as a function of excitation intensity. This is corroborated by single nanowire emission quantum yields that vary as a function of excitation fluence and range from 0.1% to values over 10%. At the same time, measured emission lifetimes are short (<100 ps) while the nanowire band-edge bleach persists for over a nanosecond. To explain all of the abovementioned results, a kinetic model that accounts for both the nature of photogenerated carriers within the wires as well as their subsequent recombination dynamics has been developed.

  6. Hot-rolling nanowire transparent electrodes for surface roughness minimization.

    PubMed

    Hosseinzadeh Khaligh, Hadi; Goldthorpe, Irene A

    2014-01-01

    Silver nanowire transparent electrodes are a promising alternative to transparent conductive oxides. However, their surface roughness presents a problem for their integration into devices with thin layers such as organic electronic devices. In this paper, hot rollers are used to soften plastic substrates with heat and mechanically press the nanowires into the substrate surface. By doing so, the root-mean-square surface roughness is reduced to 7 nm and the maximum peak-to-valley value is 30 nm, making the electrodes suitable for typical organic devices. This simple process requires no additional materials, which results in a higher transparency, and is compatible with roll-to-roll fabrication processes. In addition, the adhesion of the nanowires to the substrate significantly increases.

  7. Silver nanowire decorated heatable textiles

    NASA Astrophysics Data System (ADS)

    Doganay, Doga; Coskun, Sahin; Polat Genlik, Sevim; Emrah Unalan, Husnu

    2016-10-01

    The modification of insulating fabrics with electrically conductive nanomaterials has opened up a novel application field. With the help of Joule heating mechanism, conductive fabrics can be used as mobile heaters. In this work, heatable textiles are fabricated using silver nanowires (Ag NWs). Cotton fabrics are decorated with polyol synthesized Ag NWs via a simple dip-and-dry method. The time-dependent thermal response of the fabrics under different applied voltages is investigated. It is found that the fabrics can be heated to 50 °C under an applied power density of as low as 0.05 W cm-2. Uniform deposition of Ag NWs resulted in the homogeneous generation of heat. In addition, the stability of the fabrics with time and under different bending and washing conditions is examined. Moreover, a simple control circuit is fabricated and integrated in order to demonstrate the high potential of the fabrics for mobile applications. This work provides a roadmap for researchers who would like to work on heatable textiles with metallic NWs.

  8. Silver nanowire decorated heatable textiles.

    PubMed

    Doganay, Doga; Coskun, Sahin; Genlik, Sevim Polat; Unalan, Husnu Emrah

    2016-10-28

    The modification of insulating fabrics with electrically conductive nanomaterials has opened up a novel application field. With the help of Joule heating mechanism, conductive fabrics can be used as mobile heaters. In this work, heatable textiles are fabricated using silver nanowires (Ag NWs). Cotton fabrics are decorated with polyol synthesized Ag NWs via a simple dip-and-dry method. The time-dependent thermal response of the fabrics under different applied voltages is investigated. It is found that the fabrics can be heated to 50 °C under an applied power density of as low as 0.05 W cm(-2). Uniform deposition of Ag NWs resulted in the homogeneous generation of heat. In addition, the stability of the fabrics with time and under different bending and washing conditions is examined. Moreover, a simple control circuit is fabricated and integrated in order to demonstrate the high potential of the fabrics for mobile applications. This work provides a roadmap for researchers who would like to work on heatable textiles with metallic NWs.

  9. III-Nitride Nanowire Lasers

    SciTech Connect

    Wright, Jeremy Benjamin

    2014-07-01

    In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key gure of merit that allows for nanowire lasing is the relatively high optical con nement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices. Two devices were designed to reduce the number of lasing modes to achieve singlemode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode op eration. The rst method involves reducing the diameter of individual nanowires to the cut-o condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter e ciency. Advances in nanowire fabrication, speci cally a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip that emit

  10. III-nitride nanowire lasers

    NASA Astrophysics Data System (ADS)

    Wright, Jeremy Benjamin

    In recent years there has been a tremendous interest in nanoscale optoelectronic devices. Among these devices are semiconductor nanowires whose diameters range from 10-100 nm. To date, nanowires have been grown using many semiconducting material systems and have been utilized as light emitting diodes, photodetectors, and solar cells. Nanowires possess a relatively large index contrast relative to their dielectric environment and can be used as lasers. A key figure of merit that allows for nanowire lasing is the relatively high optical confinement factor. In this work, I discuss the optical characterization of 3 types of III-nitride nanowire laser devices. Two devices were designed to reduce the number of lasing modes to achieve single-mode operation. The third device implements low-group velocity mode lasing with a photonic crystal constructed of an array of nanowires. Single-mode operation is necessary in any application where high beam quality and single frequency operation is required. III-Nitride nanowire lasers typically operate in a combined multi-longitudinal and multi-transverse mode state. Two schemes are introduced here for controlling the optical modes and achieving single-mode operation. The first method involves reducing the diameter of individual nanowires to the cut-off condition, where only one optical mode propagates in the wire. The second method employs distributed feedback (DFB) to achieve single-mode lasing by placing individual GaN nanowires onto substrates with etched gratings. The nanowire-grating substrate acted as a distributed feedback mirror producing single mode operation at 370 nm with a mode suppression ratio (MSR) of 17 dB. The usage of lasers for solid state lighting has the potential to further reduce U.S. lighting energy usage through an increase in emitter efficiency. Advances in nanowire fabrication, specifically a two-step top-down approach, have allowed for the demonstration of a multi-color array of lasers on a single chip

  11. Thermal Transport in Silicon Nanowires at High Temperature up to 700 K.

    PubMed

    Lee, Jaeho; Lee, Woochul; Lim, Jongwoo; Yu, Yi; Kong, Qiao; Urban, Jeffrey J; Yang, Peidong

    2016-07-13

    Thermal transport in silicon nanowires has captured the attention of scientists for understanding phonon transport at the nanoscale, and the thermoelectric figure-of-merit (ZT) reported in rough nanowires has inspired engineers to develop cost-effective waste heat recovery systems. Thermoelectric generators composed of silicon target high-temperature applications due to improved efficiency beyond 550 K. However, there have been no studies of thermal transport in silicon nanowires beyond room temperature. High-temperature measurements also enable studies of unanswered questions regarding the impact of surface boundaries and varying mode contributions as the highest vibrational modes are activated (Debye temperature of silicon is 645 K). Here, we develop a technique to investigate thermal transport in nanowires up to 700 K. Our thermal conductivity measurements on smooth silicon nanowires show the classical diameter dependence from 40 to 120 nm. In conjunction with Boltzmann transport equation, we also probe an increasing contribution of high-frequency phonons (optical phonons) in smooth silicon nanowires as the diameter decreases and the temperature increases. Thermal conductivity of rough silicon nanowires is significantly reduced throughout the temperature range, demonstrating a potential for efficient thermoelectric generation (e.g., ZT = 1 at 700 K).

  12. Ballistic thermal transport in silicon nanowires

    PubMed Central

    Maire, Jeremie; Anufriev, Roman; Nomura, Masahiro

    2017-01-01

    We have experimentally investigated the impact of dimensions and temperature on the thermal conductivity of silicon nanowires fabricated using a top-down approach. Both the width and temperature dependences of thermal conductivity agree with those in the existing literature. The length dependence of thermal conductivity exhibits a transition from semi-ballistic thermal phonon transport at 4 K to fully diffusive transport at room temperature. We additionally calculated the phonon dispersion in these structures in the framework of the theory of elasticity and showed that the thermal conductance increases with width. This agrees with our experimental observations and supports the pertinence of using the modified phonon dispersion at low temperatures. PMID:28150724

  13. In situ observation of the formation process for free-standing Au nanowires with a scanning electron microscope.

    PubMed

    Aiba, Akira; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Tsukagoshi, Kazuhito; Kiguchi, Manabu

    2017-03-10

    We have developed a simultaneous electronic and structural characterization method for studying the formation process for Au nanowires. The method is based on two-probe electronic transport measurement of free-standing Au nanowires and simultaneous structural characterization using scanning electron microscopy (SEM). We measured the electronic currents during the electromigration (EM)-induced narrowing process for the free-standing Au nanowires. A free-standing Au nanowire with a desired conductance value was fabricated by EM. Simultaneous SEM and conductance measurements revealed the EM-induced narrowing process for the Au wires, in which material transfer in the nanowires caused growth towards the positively biased electrode and contact failure at the negatively biased electrode. The narrowed free-standing Au nanowires were stable and could be maintained for more than 10 h without their conductance changing. These results indicate the high stability of the EM-processed Au nanowires compared to Au nanowires fabricated by mechanical elongation or the breaking of Au nanocontacts.

  14. In situ observation of the formation process for free-standing Au nanowires with a scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Aiba, Akira; Kaneko, Satoshi; Fujii, Shintaro; Nishino, Tomoaki; Tsukagoshi, Kazuhito; Kiguchi, Manabu

    2017-03-01

    We have developed a simultaneous electronic and structural characterization method for studying the formation process for Au nanowires. The method is based on two-probe electronic transport measurement of free-standing Au nanowires and simultaneous structural characterization using scanning electron microscopy (SEM). We measured the electronic currents during the electromigration (EM)-induced narrowing process for the free-standing Au nanowires. A free-standing Au nanowire with a desired conductance value was fabricated by EM. Simultaneous SEM and conductance measurements revealed the EM-induced narrowing process for the Au wires, in which material transfer in the nanowires caused growth towards the positively biased electrode and contact failure at the negatively biased electrode. The narrowed free-standing Au nanowires were stable and could be maintained for more than 10 h without their conductance changing. These results indicate the high stability of the EM-processed Au nanowires compared to Au nanowires fabricated by mechanical elongation or the breaking of Au nanocontacts.

  15. Compositional disorder and its effect on the thermoelectric performance of Zn₃P₂ nanowire-copper nanoparticle composites.

    PubMed

    Brockway, Lance; Vasiraju, Venkata; Vaddiraju, Sreeram

    2014-03-28

    Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire-metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn₃P₂ nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn₃P₂ nanowire pellets. In contrast, the use of unfunctionalized Zn₃P₂ nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn₃P₂ nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn₃P₂ nanowire pellets. These composites were found to show a very high zT of 0.23 at 770

  16. Low-temperature heat transfer in nanowires.

    PubMed

    Glavin, B A

    2001-05-07

    A new regime of low-temperature heat transfer in suspended nanowires is predicted. It takes place when (i) only "acoustic" phonon modes of the wire are thermally populated and (ii) phonons are subject to the effective elastic scattering. Qualitatively, the main peculiarities of heat transfer originate due to the appearance of the flexural modes with high density of states in the wire phonon spectrum. They give rise to the T(1/2) temperature dependence of the wire thermal conductance. Experimental situations where the new regime is likely to be detected are discussed.

  17. Wafer-scale patterning of lead telluride nanowires: structure, characterization, and electrical properties.

    PubMed

    Yang, Yongan; Taggart, David K; Brown, Matthew A; Xiang, Chengxiang; Kung, Sheng-Chin; Yang, Fan; Hemminger, John C; Penner, Reginald M

    2009-12-22

    Nanowires of lead telluride (PbTe) were patterned on glass surfaces using lithographically patterned nanowire electrodeposition (LPNE). LPNE involved the fabrication by photolithography of a contoured nickel nanoband that is recessed by approximately 300 nm into a horizontal photoresist trench. Cubic PbTe was then electrodeposited from a basic aqueous solution containing Pb(2+) and TeO(3)(2-) at the nickel nanoband using a cyclic deposition/stripping potential program in which lead-rich PbTe was first deposited in a negative-going potential scan and excess lead was then anodically stripped from the nascent nanowire by scanning in the positive direction to produce near stoichiometric PbTe. Repeating this scanning procedure permitted PbTe nanowires 60-400 nm in width to be obtained. The wire height was controlled over the range of 20-100 nm based upon the nickel film thickness. Nanowires with lengths exceeding 1 cm were prepared in this study. We report the characterization of these nanowires using X-ray diffraction, transmission electron microscopy and electron diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy (XPS). The surface chemical composition of PbTe nanowires was monitored by XPS as a function of time during the exposure of these nanowires to laboratory air. One to two monolayers of a mixed Pb and Te oxide are formed during a 24 h exposure. The electrical conductivity of PbTe nanowires was strongly affected by air oxidation, declining from an initial value of 2.0(+/-1.5) x 10 (4) S/m by 61% (for nanowires with a 20 nm thickness), 55% (for 40 nm), and 12% (for 60 nm).

  18. Chemical and molecular beam epitaxy of III-V nanowires on silicon for photovoltaic application

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, Gokul

    Nanowires, due to their unique structure and carrier transport abilities, have sparked huge interest in the semiconductor industry. An array of nanometric size wires inserted between the p and n conductivity regions of a conventional solar cell or core shell type p-n junction nanowires synergized with semiconductor nanocrystals can lead to faster carrier collection, thereby improving device performance. This work investigates the growth of GaAs and InP semiconductor nanowires on silicon (111) using Chemical Beam Epitaxy (CBE) and Molecular Beam Epitaxy (MBE). Uniform gold nanoparticles acting as growth centers in the Vapor Liquid Solid mode of growth were generated by using the cheap and rapid technique called Nanosphere Lithography (NSL). Variation of the experimental parameters during NSL resulted in honeycomb and hexagonal patterns of gold nanoparticles. A high degree of selectivity was obtained for CBE grown nanowires whereas the MBE grown GaAs nanowires revealed the formation of a thick polycrystalline wetting layer at the interface. The CBE grown InP nanowires mostly maintained the honeycomb structure although they were found to be oriented contrary to the expected <111> direction. SEM analysis of GaAs nanowires grown by CBE showed that during growth, the nanowires may coalesce with each other resulting in unique structures such as bipods, tripods and multipods. High resolution TEM analysis of single GaAs nanowires revealed periodic formation of contrasting materials. Diffraction patterns recorded at these dark contrast areas confirmed the formation of hexagonal wurtzite single crystal structures interspaced with cubic zincblende single crystal structures. These nanowires can be used for photovoltaic applications or as light emitting devices. In addition, the formation of superlattices of different crystal structures can pave the way for novel quantum confined optoelectronic devices.

  19. High-frequency acoustic charge transport in GaAs nanowires.

    PubMed

    Büyükköse, S; Hernández-Mínguez, A; Vratzov, B; Somaschini, C; Geelhaar, L; Riechert, H; van der Wiel, W G; Santos, P V

    2014-04-04

    The oscillating piezoelectric fields accompanying surface acoustic waves are able to transport charge carriers in semiconductor heterostructures. Here, we demonstrate high-frequency (above 1 GHz) acoustic charge transport in GaAs-based nanowires deposited on a piezoelectric substrate. The short wavelength of the acoustic modulation, smaller than the length of the nanowire, allows the trapping of photo-generated electrons and holes at the spatially separated energy minima and maxima of conduction and valence bands, respectively, and their transport along the nanowire with a well defined acoustic velocity towards indium-doped recombination centers.

  20. Transition of Resistive Switching to Bidirectional Diode in Cu2O/Cu Nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Deok-kee; Shin, Ho Sun; Song, Jae Yong

    2012-08-01

    Cu2O/Cu nanowires of about 2 µm length were electrodeposited within anodized aluminum oxide templates in an aqueous acidic solution using template-assisted pulse-reverse electrolysis. In the virgin state, reversible copper filaments were formed by using the copper ions driven by an electric field towards the cathode. Initially, the resistive switching dominated the electrical characteristics of the Cu2O/Cu nanowires due to the low-resistance reversible copper filaments. After the permanent breakup of the copper filaments under the high current density, the Cu2O/Cu nanowire showed bipolar exponential characteristics, which was attributed to mixed ionic and electronic conduction.

  1. Structural and optical properties of axial silicon-germanium nanowire heterojunctions

    SciTech Connect

    Wang, X.; Tsybeskov, L.; Kamins, T. I.; Wu, X.; Lockwood, D. J.

    2015-12-21

    Detailed studies of the structural and optical properties of axial silicon-germanium nanowire heterojunctions show that despite the 4.2% lattice mismatch between Si and Ge they can be grown without a significant density of structural defects. The lattice mismatch induced strain is partially relieved due to spontaneous SiGe intermixing at the heterointerface during growth and lateral expansion of the Ge segment of the nanowire. The mismatch in Ge and Si coefficients of thermal expansion and low thermal conductivity of Si/Ge nanowire heterojunctions are proposed to be responsible for the thermally induced stress detected under intense laser radiation in photoluminescence and Raman scattering measurements.

  2. Observation of rebirth of metallic paths during resistance switching of metal nanowire

    SciTech Connect

    Horiba, K. Nagamura, N.; Toyoda, S.; Oshima, M.; Fujiwara, K.; Takagi, H.; Kumigashira, H.

    2013-11-04

    To clarify the mechanism of resistance-switching phenomena, we have investigated the change in the electronic structure of a Ni nanowire device during resistance-switching operations using scanning photoelectron microscopy techniques. We directly observed the disappearance of density of state (DOS) at the Fermi level (E{sub F}) in a high-resistance state and recovery of a finite DOS at E{sub F} in a low-resistance state. These results are direct evidence that the Ni nanowire is fully oxidized after switching to the high-resistance state and that Ni-metal conductive paths in the oxidized nanowire are recovered in the low-resistance state.

  3. Localized electromechanical interactions in ferroelectric P(VDF-TrFE) nanowires investigated by scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Calahorra, Yonatan; Whiter, Richard A.; Jing, Qingshen; Narayan, Vijay; Kar-Narayan, Sohini

    2016-11-01

    We investigate the electromechanical interactions in individual polyvinylidene fluoride-trifluoroethylene nanowires in response to localized electrical poling via a conducting atomic force microscope tip. Spatially resolved measurements of piezoelectric coefficients and elastic moduli before and after poling reveal a striking dependence on the polarity of the poling field, notably absent in thin films of the same composition. These observations are attributed to the unclamped nature of the nanowires and the inherent asymmetry in their chemical and electrical interactions with the tip and underlying substrate. Our findings provide insights into the mechanism of poling/switching in polymer nanowires critical to ferroelectric device performance.

  4. Schottky barrier heights at the interfaces between pure-phase InAs nanowires and metal contacts

    SciTech Connect

    Feng, Boyong; Huang, Shaoyun E-mail: hqxu@pku.edu.cn; Wang, Jiyin; Pan, Dong; Zhao, Jianghua; Xu, H. Q. E-mail: hqxu@pku.edu.cn

    2016-02-07

    Understanding of the Schottky barriers formed at metal contact-InAs nanowire interfaces is of great importance for the development of high-performance InAs nanowire nanoelectronic and quantum devices. Here, we report a systematical study of InAs nanowire field-effect transistors (FETs) and the Schottky barrier heights formed at the contact-nanowire interfaces. The InAs nanowires employed are grown by molecular beam epitaxy and are high material quality single crystals, and the devices are made by directly contacting the nanowires with a series of metals of different work functions. The fabricated InAs nanowire FET devices are characterized by electrical measurements at different temperatures and the Schottky barrier heights are extracted from the measured temperature and gate-voltage dependences of the channel current. We show that although the work functions of the contact metals are widely spread, the Schottky barrier heights are determined to be distributed over 35–55 meV, showing a weak but not negligible dependence on the metals. The deduced Fermi level in the InAs nanowire channels is found to be in the band gap and very close to the conduction band. The physical origin of the results is discussed in terms of Fermi level pinning by the surface states of the InAs nanowires and a shift in pinned Fermi level induced by the metal-related interface states.

  5. Biocompatible and Antibacterial SnO2 Nanowire Films Synthesized by E-Beam Evaporation Method.

    PubMed

    Prasad, R G S V; Phani, A R; Rao, K N; Kumar, R Rakesh; Prasad, S; Prabhakara, G; Sheeja, M S; Salins, C P; Endrino, J L; Raju, D B

    2015-06-01

    In this work, the biocompatibility and antibacterial activities of novel SnO2 nanowire coatings prepared by electron-beam (E-Beam) evaporation process at low temperatures were studied. The nanowire coatings were characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), and X-ray diffraction (XRD) methods. The results of in vitro cytotoxicity and cell proliferation assays suggested that the SnO2 nanowire coatings were nontoxic and promoted the proliferation of C2C12 and L929 cells (> 90% viability). Cellular activities, cell adhesion, and lactate dehydrogenase activities were consistent with the superior biocompatibility of the nanowire materials. Notably, the nanowire coating showed potent antibacterial activity against six different bacterial strains. The antibacterial activity of the SnO2 material was attributed to the photocatalytic nature of SnO2. The antibacterial activity and biocompatibility of the newly developed SnO2 nanowire coatings may enable their use as coating materials for biomedical implants.

  6. Nanoantennas for nanowire photovoltaics

    SciTech Connect

    Alisafaee, Hossein; Fiddy, Michael A.

    2014-09-15

    We consider the use of plasmonic nanoantenna elements, hemispherical and cylindrical, for application in semiconductor nanowire (NW) vertical arrays. Using Mie theory and a finite element method, scattering and absorption efficiencies are obtained for the desired enhancement of interaction with light in the NWs. We find an optimal mixture of nanoantennae for efficient scattering of solar spectrum in the NW array. Spectral radiation patterns of scattered light are computed, and, for representing the total response of the nanoantenna-equipped NWs to the solar AM1.5G spectrum, the weighted average of scattering patterns for unpolarized normal incidence is obtained showing an advantageous overall directivity toward the NWs.

  7. Single nanowire extinction spectroscopy.

    PubMed

    Giblin, Jay; Vietmeyer, Felix; McDonald, Matthew P; Kuno, Masaru

    2011-08-10

    Here we show the first direct extinction spectra of single one-dimensional (1D) semiconductor nanostructures obtained at room temperature utilizing a spatial modulation approach. (1) For these materials, ensemble averaging in conventional extinction spectroscopy has limited our understanding of the interplay between carrier confinement and their electrostatic interactions. (2-4) By probing individual CdSe nanowires (NWs), we have identified and assigned size-dependent exciton transitions occurring across the visible. In turn, we have revealed the existence of room temperature 1D excitons in the narrowest NWs.

  8. Single crystalline mesoporous silicon nanowires.

    PubMed

    Hochbaum, Allon I; Gargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-10-01

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  9. Nanowire terahertz quantum cascade lasers

    SciTech Connect

    Grange, Thomas

    2014-10-06

    Quantum cascade lasers made of nanowire axial heterostructures are proposed. The dissipative quantum dynamics of their carriers is theoretically investigated using non-equilibrium Green functions. Their transport and gain properties are calculated for varying nanowire thickness, from the classical-wire regime to the quantum-wire regime. Our calculation shows that the lateral quantum confinement provided by the nanowires allows an increase of the maximum operation temperature and a strong reduction of the current density threshold compared to conventional terahertz quantum cascade lasers.

  10. Radiation Stability of Metal Nanowires

    NASA Astrophysics Data System (ADS)

    Bedin, S. A.; Makhin’ko, F. F.; Ovchinnikov, V. V.; Gerasimenko, N. N.; Zagorskiy, D. L.

    2017-01-01

    The aim of this work is to investigate the radiation stability of pure nickel and iron– nickel Fe0.56Ni0.44 alloy nanowires fabricated by matrix synthesis using polymer track membranes and Ar+ and Xe+ (E = 20 keV, j = 300 μA/cm2) beam irradiation. The dependence of the stability of nanowires on their diameter, fluence, and type of implanted ions is investigated. The assumption that the thermalized regions of dense cascades of atomic displacements (thermal spikes) play an important role in the nanowire structure change is made. These regions are nanosized zones of explosive energy release and heated to several thousands of degrees.

  11. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, A.I.; Gargas, Daniel; Jeong Hwang, Yun; Yang, Peidong

    2009-08-04

    Herein we demonstrate a novel electroless etching synthesis of monolithic, single-crystalline, mesoporous silicon nanowire arrays with a high surface area and luminescent properties consistent with conventional porous silicon materials. These porous nanowires also retain the crystallographic orientation of the wafer from which they are etched. Electron microscopy and diffraction confirm their single-crystallinity and reveal the silicon surrounding the pores is as thin as several nanometers. Confocal fluorescence microscopy showed that the photoluminescence (PL) of these arrays emanate from the nanowires themselves, and their PL spectrum suggests that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices.

  12. Carrier dynamics in Si nanowires fabricated by metal-assisted chemical etching.

    PubMed

    Tang, Hao; Zhu, Li-Guo; Zhao, Liang; Zhang, Xuejin; Shan, Jie; Lee, Shuit-Tong

    2012-09-25

    Silicon nanowire arrays fabricated by metal-assisted wet chemical etching have emerged as a promising architecture for solar energy harvesting applications. Here we investigate the dynamics and transport properties of photoexcited carriers in nanowires derived from an intrinsic silicon wafer using the terahertz (THz) time-domain spectroscopy. Both the dynamics and the pump fluence dependence of the photoinduced complex conductivity spectra up to several THz were measured. The photoinduced conductivity spectra follow a Lorentz dependence, arising from surface plasmon resonances in nanowires. The carrier lifetime was observed to approach 0.7 ns, which is limited primarily by surface trapping. The intrinsic carrier mobility was found to be ~1000 cm(2)/(V · s). Compared to other silicon nanostructures, these relative high values observed for both the carrier lifetime and mobility are the consequences of high crystallinity and surface quality of the nanowires fabricated by the metal-assisted wet chemical etching method.

  13. Interactions between semiconductor nanowires and living cells.

    PubMed

    Prinz, Christelle N

    2015-06-17

    Semiconductor nanowires are increasingly used for biological applications and their small dimensions make them a promising tool for sensing and manipulating cells with minimal perturbation. In order to interface cells with nanowires in a controlled fashion, it is essential to understand the interactions between nanowires and living cells. The present paper reviews current progress in the understanding of these interactions, with knowledge gathered from studies where living cells were interfaced with vertical nanowire arrays. The effect of nanowires on cells is reported in terms of viability, cell-nanowire interface morphology, cell behavior, changes in gene expression as well as cellular stress markers. Unexplored issues and unanswered questions are discussed.

  14. Surface States Transport in Topological Insulator Bi_{0.83}Sb_{0.17} Nanowires

    NASA Astrophysics Data System (ADS)

    Konopko, L. A.; Nikolaeva, A. A.; Huber, T. E.; Ansermet, J.-P.

    2016-12-01

    We investigate the transport properties of topological insulator (TI) Bi_{0.83}Sb_{0.17} nanowires. Single-crystal nanowire samples with diameters ranging from 75 nm to 1.1 μ m are prepared using high frequency liquid phase casting in a glass capillary; cylindrical single crystals with (10bar{1}1) orientation along the wire axis are produced. Bi_{0.83}Sb_{0.17} is a narrow-gap semiconductor with an energy gap at the L point of the Brillouin zone, Δ E = 21 meV. The resistance of the samples increases with decreasing temperature, but a decrease in resistance is observed at low temperatures. This effect is a clear manifestation of TI properties (i.e., the presence of a highly conducting zone on the TI surface). When the diameter of the nanowire decreases, the energy gap Δ E grows as 1 / d (for diameter d = 1.1 μ m and d =75 nm Δ E = 21 and 45 meV, respectively), which proves the presence of the quantum size effect in these samples. We investigate the magnetoresistance of Bi_{0.83}Sb_{0.17} nanowires at various magnetic field orientations. Shubnikov-de Haas oscillations are observed in Bi_{0.83}Sb_{0.17} nanowires at T = 1.5 K, demonstrating the existence of high mobility (μ_S = 26{,}700-47{,}000 cm^2V^{-1}s^{-1}) two-dimensional (2D) carriers in the surface areas of the nanowires, which are nearly perpendicular to the C_3 axis. From the linear dependence of the nanowire conductance on nanowire diameter at T = 4.2 K, the square resistance R_sq of the surface states of the nanowires is obtained (R_sq =70 Ohm).

  15. Electronic polymers and DNA self-assembled in nanowire transistors.

    PubMed

    Hamedi, Mahiar; Elfwing, Anders; Gabrielsson, Roger; Inganäs, Olle

    2013-02-11

    Aqueous self-assembly of DNA and molecular electronic materials can lead to the creation of innumerable copies of identical devices, and inherently programmed complex nanocircuits. Here self-assembly of a water soluble and highly conducting polymer PEDOT-S with DNA in aqueous conditions is shown. Orientation and assembly of the conducting DNA/PEDOT-S complex into electrochemical DNA nanowire transistors is demonstrated.

  16. Bacterial Sialidase

    NASA Technical Reports Server (NTRS)

    2004-01-01

    Data shows that elevated sialidase in bacterial vaginosis patients correlates to premature births in women. Bacterial sialidase also plays a significant role in the unusual colonization of Pseudomonas aeruginosa in cystic fibrosis patients. Crystals of Salmonella sialidase have been reproduced and are used for studying the inhibitor-enzyme complexes. These inhibitors may also be used to inhibit a trans-sialidase of Trypanosome cruzi, a very similar enzyme to bacterial sialidase, therefore preventing T. cruzi infection, the causitive agent of Chagas' disease. The Center for Macromolecular Crystallography suggests that inhibitors of bacterial sialidases can be used as prophylactic drugs to prevent bacterial infections in these critical cases.

  17. Thermoelectric properties of electrolessly etched silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sadhu, Jyothi; Tian, Hongxiang; Ma, Jun; Valavala, Krishna; Singh, Piyush; Sinha, Sanjiv

    2013-03-01

    Patterning silicon as nanowires with roughened sidewalls enhances the thermoelectric figure-of-merit ZT by order of magnitude compared to the bulk at 300 K. The enhancement is mainly achieved by the remarkable reduction in the thermal conductivity below 5 W/mK at 300 K with only a negligible effect on the power factor of these nanowires. While the focus remained on understanding the implications of surface disorder on the thermal conductivity, the phonon transport effects on the Seebeck coefficient of these wires remains largely unexplored. We developed an electroless etching technique to generate nanowire arrays (NWAs) with controlled surface roughness, morphology, porosity and doping. We conduct the simultaneous device-level measurements of the Seebeck coefficient and thermal conductivity of the NWAs using frequency domain techniques. We observe that nano-structuring quenches the phonon drag in NWAs thereby reducing the Seebeck coefficient by ~25% compared to the bulk at degenerate doping levels. Further, we observe that the sidewall roughness greater than 3 nm roughness height lowers the thermal conductivity 75% below the Casimir limit with 10% - 15% increase in Seebeck coefficient. The porous NWAs show thermal conductivity close to the amorphous limit of Si with enhancement in the Seebeck coefficient primarily due to the carrier depletion.

  18. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    SciTech Connect

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T.; Martinez, Julio A.

    2015-11-25

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

  19. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    DOE PAGES

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; ...

    2015-11-25

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN coremore » of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.« less

  20. Facile Synthesis of Sub-20 nm Silver Nanowires through a Bromide-Mediated Polyol Method.

    PubMed

    da Silva, Robson Rosa; Yang, Miaoxin; Choi, Sang-Il; Chi, Miaofang; Luo, Ming; Zhang, Chao; Li, Zhi-Yuan; Camargo, Pedro H C; Ribeiro, Sidney José Lima; Xia, Younan

    2016-08-23

    Essentially all of the Ag nanowires reported in the literature have sizes larger than 30 nm in diameter. In this article, we report a simple and robust approach to the synthesis of Ag nanowires with diameters below 20 nm and aspect ratios over 1000 using a one-pot polyol method. The Ag nanowires took a penta-twinned structure, and they could be obtained rapidly (<35 min) and in high morphology purity (>85% of the as-obtained solid product) under atmospheric pressure. The key to the success of this synthesis is to restrain the nanowires from lateral growth by employing both Br(-) ions and poly(vinylpyrrolidone) with a high molecular weight of 1 300 000 g/mol to cap the {100} side faces, together with the use of a syringe pump to slowly introduce AgNO3 into the reaction solution. By optimizing the ratios between the capping agents and AgNO3, we were able to slow down the reduction kinetics and effectively direct the Ag nanowires to grow along the longitudinal direction only. The nanowires showed great mechanical flexibility and could be bent with acute angles without breaking. Because of their small diameters, the transverse localized surface plasmon resonance peak of the Ag nanowires could be pushed down to the ultraviolet region, below 400 nm, making them ideal conductive elements for the fabrication of touch screens, solar cells, and smart windows.