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Sample records for nbn nanowire single

  1. Fabrication and Characterization of Superconducting NbN Nanowire Single Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stern, Jeffrey A.; Farr, William H.

    2006-01-01

    We report on the fabrication and characterization of high-speed, single photon detectors using superconducting NbN nanowires at a wavelength of 1064 nm. A 15 by 15 micron detector with a detector efficiency of 40% has been measured. Due to kinetic inductance, the recovery time of such large area detectors is longer than that of smaller or single wire detectors. The recovery time of our detectors (50 ns) has been characterized by measuring the inter-arrival time statistics of our detector.

  2. Characterization of NbN films for superconducting nanowire single photon detectors

    SciTech Connect

    Mcdonald, Ross D; Ayala - Valenzuela, Oscar E; Weisse - Bernstein, Nina R; Williamson, Todd L; Hoffbauer, M. A.; Graf, M. J.; Rabin, M. W.

    2011-01-14

    Nanoscopic superconducting meander patterns offer great promise as a new class of cryogenic radiation sensors capable of single photon detection. To realize this potential, control of the superconducting properties on the nanoscale is imperative. To this end, Superconducting Nanowire Single Photon Detectors (SNSPDs) are under development by means Energetic Neutral Atom Beam Lithography and Epitaxy, or ENABLE. ENABLE can growth highly-crystalline, epitaxial thin-film materials, like NbN, at low temperatures; such wide-ranging control of fabrication parameters is enabling the optimization of film properties for single photon detection. T{sub c}, H{sub c2}, {zeta}{sub GL} and J{sub c} of multiple thin films and devices have been studied as a function of growth conditions. The optimization of which has already produced devices with properties rivaling all reports in the existing literature.

  3. High efficiency and rapid response superconducting NbN nanowire single photon detector based on asymmetric split ring metamaterial

    SciTech Connect

    Li, Guanhai; Chen, Xiaoshuang; Wang, Shao-Wei Lu, Wei

    2014-06-09

    With asymmetric split ring metamaterial periodically placed on top of the niobium nitride (NbN) nanowire meander, we theoretically propose a kind of metal-insulator-metallic metamaterial nanocavity to enhance absorbing efficiency and shorten response time of the superconducting NbN nanowire single photon detector (SNSPD) operating at wavelength of 1550 nm. Up to 99.6% of the energy is absorbed and 96.5% dissipated in the nanowire. Meanwhile, taking advantage of this high efficiency absorbing cavity, we implement a more sparse arrangement of the NbN nanowire of the filling factor 0.2, which significantly lessens the nanowire and crucially boosts the response time to be only 40% of reset time in previous evenly spaced meander design. Together with trapped mode resonance, a standing wave oscillation mechanism is presented to explain the high efficiency and broad bandwidth properties. To further demonstrate the advantages of the nanocavity, a four-pixel SNSPD on 10 μm × 10 μm area is designed to further reduce 75% reset time while maintaining 70% absorbing efficiency. Utilizing the asymmetric split ring metamaterial, we show a higher efficiency and more rapid response SNSPD configuration to contribute to the development of single photon detectors.

  4. Fabrication and Characterization of Superconducting NbN Nanowire Single Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stern, Jeffrey A.; Farr, William H.

    2006-01-01

    This viewgraph presentation describes the fabrication of large area superconducting Niobium Nitride nanowire single photon detectors. The topics include: 1) Introduction and Motivation; 2) Operation of SNSPD Detectors; 3) NbTiN Deposition; 4) Fabrication Details; 5) Backside Coupled SNSPD; 6) Measurement Apparatus; 7) Electrical Response of a 15x15 micrometer SNSPD to 1064nm radiation; 8) Detector Efficiency vs Bias Current; 9) Interarrival Time Plot; 10) Detector Linearity; and 11) Conclusion.

  5. Quantum and thermal phase slips in superconducting niobium nitride (NbN) ultrathin crystalline nanowire: application to single photon detection.

    PubMed

    Delacour, Cécile; Pannetier, Bernard; Villegier, Jean-Claude; Bouchiat, Vincent

    2012-07-11

    We present low-temperature electronic transport properties of superconducting nanowires obtained by nanolithography of 4-nm-thick niobium nitride (NbN) films epitaxially grown on sapphire substrate. Below 6 K, clear evidence of phase slippages is observed in the transport measurements. Upon lowering the temperature, we observe the signatures of a crossover between a thermal and a quantum behavior in the phase slip regimes. We find that phase slips are stable even at the lowest temperatures and that no hotspot is formed. The photoresponse of these nanowires is measured as a function of the light irradiation wavelength and temperature and exhibits a behavior comparable with previous results obtained on thicker films.

  6. Broadening of hot-spot response spectrum of superconducting NbN nanowire single-photon detector with reduced nitrogen content

    NASA Astrophysics Data System (ADS)

    Henrich, D.; Dörner, S.; Hofherr, M.; Il'in, K.; Semenov, A.; Heintze, E.; Scheffler, M.; Dressel, M.; Siegel, M.

    2012-10-01

    The spectral detection efficiency and the dark count rate of superconducting nanowire single-photon detectors (SNSPD) have been studied systematically on detectors made from thin NbN films with different chemical compositions. Reduction of the nitrogen content in the 4 nm thick NbN films results in a decrease of the dark count rates more than two orders of magnitude and in a red shift of the cut-off wavelength of the hot-spot SNSPD response. The observed phenomena are explained by an improvement of uniformity of NbN films that has been confirmed by a decrease of resistivity and an increase of the ratio of the measured critical current to the depairing current. The latter factor is considered as the most crucial for both the cut-off wavelength and the dark count rates of SNSPD. Based on our results we propose a set of criteria for material properties to optimize SNSPD in the infrared spectral region.

  7. Fabrication of superconducting NbN meander nanowires by nano-imprint lithography

    NASA Astrophysics Data System (ADS)

    Mei, Yang; Li-Hua, Liu; Lu-Hui, Ning; Yi-Rong, Jin; Hui, Deng; Jie, Li; Yang, Li; Dong-Ning, Zheng

    2016-01-01

    Superconducting nanowire single photon detector (SNSPD), as a new type of superconducting single photon detector (SPD), has a broad application prospect in quantum communication and other fields. In order to prepare SNSPD with high performance, it is necessary to fabricate a large area of uniform meander nanowires, which is the core of the SNSPD. In this paper, we demonstrate a process of patterning ultra-thin NbN films into meander-type nanowires by using the nano-imprint technology. In this process, a combination of hot embossing nano-imprint lithography (HE-NIL) and ultraviolet nano-imprint lithography (UV-NIL) is used to transfer the meander nanowire structure from the NIL Si hard mold to the NbN film. We have successfully obtained a NbN nanowire device with uniform line width. The critical temperature (Tc) of the superconducting NbN meander nanowires is about 5 K and the critical current (Ic) is about 3.5 μA at 2.5 K. Project supported by the National Basic Research Program of China (Grant Nos. 2011CBA00106 and 2009CB929102) and the National Natural Science Foundation of China (Grant Nos. 11104333 and 10974243).

  8. Inhomogeneous critical current in nanowire superconducting single-photon detectors

    SciTech Connect

    Gaudio, R. Hoog, K. P. M. op 't; Zhou, Z.; Sahin, D.; Fiore, A.

    2014-12-01

    A superconducting thin film with uniform properties is the key to realize nanowire superconducting single-photon detectors (SSPDs) with high performance and high yield. To investigate the uniformity of NbN films, we introduce and characterize simple detectors consisting of short nanowires with length ranging from 100 nm to 15 μm. Our nanowires, contrary to meander SSPDs, allow probing the homogeneity of NbN at the nanoscale. Experimental results, endorsed by a microscopic model, show the strongly inhomogeneous nature of NbN films on the sub-100 nm scale.

  9. Position-Dependent Local Detection Efficiency in a Nanowire Superconducting Single-Photon Detector.

    PubMed

    Renema, J J; Wang, Q; Gaudio, R; Komen, I; op 't Hoog, K; Sahin, D; Schilling, A; van Exter, M P; Fiore, A; Engel, A; de Dood, M J A

    2015-07-01

    We probe the local detection efficiency in a nanowire superconducting single-photon detector along the cross-section of the wire with a far subwavelength resolution. We experimentally find a strong variation in the local detection efficiency of the device. We demonstrate that this effect explains previously observed variations in NbN detector efficiency as a function of device geometry. PMID:26087352

  10. Rise time of voltage pulses in NbN superconducting single photon detectors

    NASA Astrophysics Data System (ADS)

    Smirnov, K. V.; Divochiy, A. V.; Vakhtomin, Yu. B.; Sidorova, M. V.; Karpova, U. V.; Morozov, P. V.; Seleznev, V. A.; Zotova, A. N.; Vodolazov, D. Yu.

    2016-08-01

    We have found experimentally that the rise time of voltage pulse in NbN superconducting single photon detectors increases nonlinearly with increasing the length of the detector L. The effect is connected with dependence of resistance of the detector Rn, which appears after photon absorption, on its kinetic inductance Lk and, hence, on the length of the detector. This conclusion is confirmed by our calculations in the framework of two temperature model.

  11. Single-nanowire photoelectrochemistry

    NASA Astrophysics Data System (ADS)

    Su, Yude; Liu, Chong; Brittman, Sarah; Tang, Jinyao; Fu, Anthony; Kornienko, Nikolay; Kong, Qiao; Yang, Peidong

    2016-07-01

    Photoelectrochemistry is one of several promising approaches for the realization of efficient solar-to-fuel conversion. Recent work has shown that photoelectrodes made of semiconductor nano-/microwire arrays can have better photoelectrochemical performance than their planar counterparts because of their unique properties, such as high surface area. Although considerable research effort has focused on studying wire arrays, the inhomogeneity in the geometry, doping, defects and catalyst loading present in such arrays can obscure the link between these properties and the photoelectrochemical performance of the wires, and correlating performance with the specific properties of individual wires is difficult because of ensemble averaging. Here, we show that a single-nanowire-based photoelectrode platform can be used to reliably probe the current–voltage (I–V) characteristics of individual nanowires. We find that the photovoltage output of ensemble array samples can be limited by poorly performing individual wires, which highlights the importance of improving nanowire homogeneity within an array. Furthermore, the platform allows the flux of photogenerated electrons to be quantified as a function of the lengths and diameters of individual nanowires, and we find that the flux over the entire nanowire surface (7–30 electrons nm–2 s–1) is significantly reduced as compared with that of a planar analogue (∼1,200 electrons nm–2 s–1). Such characterization of the photogenerated carrier flux at the semiconductor/electrolyte interface is essential for designing nanowire photoelectrodes that match the activity of their loaded electrocatalysts.

  12. Single-nanowire photoelectrochemistry

    NASA Astrophysics Data System (ADS)

    Su, Yude; Liu, Chong; Brittman, Sarah; Tang, Jinyao; Fu, Anthony; Kornienko, Nikolay; Kong, Qiao; Yang, Peidong

    2016-07-01

    Photoelectrochemistry is one of several promising approaches for the realization of efficient solar-to-fuel conversion. Recent work has shown that photoelectrodes made of semiconductor nano-/microwire arrays can have better photoelectrochemical performance than their planar counterparts because of their unique properties, such as high surface area. Although considerable research effort has focused on studying wire arrays, the inhomogeneity in the geometry, doping, defects and catalyst loading present in such arrays can obscure the link between these properties and the photoelectrochemical performance of the wires, and correlating performance with the specific properties of individual wires is difficult because of ensemble averaging. Here, we show that a single-nanowire-based photoelectrode platform can be used to reliably probe the current-voltage (I-V) characteristics of individual nanowires. We find that the photovoltage output of ensemble array samples can be limited by poorly performing individual wires, which highlights the importance of improving nanowire homogeneity within an array. Furthermore, the platform allows the flux of photogenerated electrons to be quantified as a function of the lengths and diameters of individual nanowires, and we find that the flux over the entire nanowire surface (7-30 electrons nm-2 s-1) is significantly reduced as compared with that of a planar analogue (˜1,200 electrons nm-2 s-1). Such characterization of the photogenerated carrier flux at the semiconductor/electrolyte interface is essential for designing nanowire photoelectrodes that match the activity of their loaded electrocatalysts.

  13. Single-nanowire photoelectrochemistry.

    PubMed

    Su, Yude; Liu, Chong; Brittman, Sarah; Tang, Jinyao; Fu, Anthony; Kornienko, Nikolay; Kong, Qiao; Yang, Peidong

    2016-07-01

    Photoelectrochemistry is one of several promising approaches for the realization of efficient solar-to-fuel conversion. Recent work has shown that photoelectrodes made of semiconductor nano-/microwire arrays can have better photoelectrochemical performance than their planar counterparts because of their unique properties, such as high surface area. Although considerable research effort has focused on studying wire arrays, the inhomogeneity in the geometry, doping, defects and catalyst loading present in such arrays can obscure the link between these properties and the photoelectrochemical performance of the wires, and correlating performance with the specific properties of individual wires is difficult because of ensemble averaging. Here, we show that a single-nanowire-based photoelectrode platform can be used to reliably probe the current-voltage (I-V) characteristics of individual nanowires. We find that the photovoltage output of ensemble array samples can be limited by poorly performing individual wires, which highlights the importance of improving nanowire homogeneity within an array. Furthermore, the platform allows the flux of photogenerated electrons to be quantified as a function of the lengths and diameters of individual nanowires, and we find that the flux over the entire nanowire surface (7-30 electrons nm(-2) s(-1)) is significantly reduced as compared with that of a planar analogue (∼1,200 electrons nm(-2) s(-1)). Such characterization of the photogenerated carrier flux at the semiconductor/electrolyte interface is essential for designing nanowire photoelectrodes that match the activity of their loaded electrocatalysts. PMID:27018660

  14. Nanowire superconducting single-photon detectors on GaAs for integrated quantum photonic applications

    NASA Astrophysics Data System (ADS)

    Gaggero, A.; Nejad, S. Jahanmiri; Marsili, F.; Mattioli, F.; Leoni, R.; Bitauld, D.; Sahin, D.; Hamhuis, G. J.; Nötzel, R.; Sanjines, R.; Fiore, A.

    2010-10-01

    We demonstrate efficient nanowire superconducting single photon detectors (SSPDs) based on NbN thin films grown on GaAs. NbN films ranging from 3 to 5 nm in thickness have been deposited by dc magnetron sputtering on GaAs substrates at 350 °C. These films show superconducting properties comparable to similar films grown on sapphire and MgO. In order to demonstrate the potential for monolithic integration, SSPDs were fabricated and measured on GaAs/AlAs Bragg mirrors, showing a clear cavity enhancement, with a peak quantum efficiency of 18.3% at λ =1300 nm and T=4.2 K.

  15. Optimisation of NbN thin films on GaAs substrates for in-situ single photon detection in structured photonic devices

    NASA Astrophysics Data System (ADS)

    Reithmaier, G.; Senf, J.; Lichtmannecker, S.; Reichert, T.; Flassig, F.; Voss, A.; Gross, R.; Finley, J. J.

    2013-04-01

    We prepare NbN thin films by DC magnetron sputtering on [100] GaAs substrates, optimise their quality, and demonstrate their use for efficient single photon detection in the near-infrared. The interrelation between the Nb:N content, growth temperature, and crystal quality is established for 4-22 nm thick films. Optimised films exhibit a superconducting critical temperature of 12.6 ± 0.2K for a film thickness of 22 ± 0.5 nm and 10.2 ± 0.2 K for 4 ± 0.5 nm thick films that are suitable for single photon detection. The optimum growth temperature is shown to be ˜475 °C reflecting a trade-off between enhanced surface diffusion, which improves the crystal quality, and arsenic evaporation from the GaAs substrate. Analysis of the elemental composition of the films provides strong evidence that the δ-phase of NbN is formed in optimised samples, controlled primarily via the nitrogen partial pressure during growth. By patterning optimum 4 nm and 22 nm thick films into a 100 nm wide, 369μm long nanowire meander using electron beam lithography and reactive ion etching, we fabricated single photon detectors on GaAs substrates. Time-resolved studies of the photo-response, absolute detection efficiency, and dark count rates of these detectors as a function of the bias current reveal maximum single photon detection efficiencies as high as 21 ± 2% at 4.3 ± 0.1 K with ˜50 k dark counts per second for bias currents of 98%IC at a wavelength of 950 nm. As expected, similar detectors fabricated from 22 nm thick films exhibit much lower efficiencies (0.004%) with very low dark count rates ≤3 cps. The maximum lateral extension of a photo-generated resistive region is estimated to be 30 ± 8 nm, clearly identifying the low detection efficiency and dark count rate of the thick film detectors as arising from hotspot cooling via the heat reservoir provided by the NbN film.

  16. Electrochemically Grown Single Nanowire Sensors

    NASA Technical Reports Server (NTRS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Penner, Reginald; Bangar, Mangesh; Mulchandani, Ashok; Myung, Nosang V.

    2004-01-01

    We report a fabrication technique that is potentially capable of producing arrays of individually addressable nanowire sensors with controlled dimensions, positions, alignments, and chemical compositions. The concept has been demonstrated with electrodeposition of palladium wires with 75 nm to 350 nm widths. We have also fabricated single and double conducting polymer nanowires (polyaniline and polypyrrole) with 100nm and 200nm widths using electrochemical direct growth. Using single Pd nanowires, we have also demonstrated hydrogen sensing. It is envisioned that these are the first steps towards nanowire sensor arrays capable of simultaneously detecting multiple chemical species.

  17. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stern, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire single-photon detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize Nb(x)Ti(1-x)N in the high-superconducting-transition temperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  18. 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.

  19. Single crystalline mesoporous silicon nanowires

    SciTech Connect

    Hochbaum, Allon; Dargas, Daniel; Hwang, Yun Jeong; Yang, Peidong

    2009-08-18

    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. The photoluminescence of these nanowires suggest they are composed of crystalline silicon with small enough dimensions such that these arrays may be useful as photocatalytic substrates or active components of nanoscale optoelectronic devices. A better understanding of this electroless route to mesoporous silicon could lead to facile and general syntheses of different narrow bandgap semiconductor nanostructures for various applications.

  20. Fiber-coupled quantum-communications receiver based on two NbN superconducting single-photon detectors

    NASA Astrophysics Data System (ADS)

    Slysz, W.; Wegrzecki, M.; Bar, J.; Grabiec, P.; Górska, M.; Latta, C.; Zwiller, V.; Pearlman, A.; Cross, A.; Korneev, A.; Kouminov, P.; Smirnov, K.; Voronov, B.; Gol'tsman, G.; Verevkin, A.; Currie, M.; Sobolewski, R.

    2005-09-01

    We present the design and performance of a novel, two-channel single-photon receiver, based on two fiber-coupled NbN superconducting single-photon detectors (SSPDs). The SSPDs are nanostructured superconducting meanders covering an area of 100 μm2 and are known for ultrafast and efficient counting of single, visible-to-infrared photons. Their operation has been explained within a phenomenological hot-electron photoresponse model. Our receiver is intended for fiber-based quantum cryptography and communication systems, operational at near-infrared (NIR) telecommunication wavelengths, λ = 1.3 μm and λ = 1.55 μm. Coupling between the NbN detector and a single-mode optical fiber was achieved using a specially designed, micromechanical photoresist ring, positioned directly over the SSPD active area. The positioning accuracy of the ring was below 1 μm. The receiver with SSPDs was placed (immersed) in a standard liquid-helium transport Dewar and kept without interruption for over two months at 4.2 K. At the same time, the optical fiber inputs and electrical outputs were kept at room temperature. Our best system reached a system quantum efficiency of up to 0.3 % in the NIR radiation range, with the detector coupling efficiency of about 30 %. The response time was measured to be about 250 ps and was limited by our read-out electronics. The measured jitter was close to 35 ps. The presented performance parameters show that our NIR single photon detectors are suitable for practical quantum cryptography and for applications in quantum-correlation experiments.

  1. Electrochemically grown single-nanowire sensors

    NASA Astrophysics Data System (ADS)

    Yun, Minhee; Lee, Choonsup; Vasquez, Richard P.; Penner, Reginald M.; Bangar, Mangesh; Mulchandani, Ashok; Myung, Nosang V.

    2004-12-01

    We report a fabrication technique that is potentially capable of producing arrays of individually addressable nanowire sensors with controlled dimensions, positions, alignments, and chemical compositions. The concept has been demonstrated with electrodeposition of palladium wires with 75 nm to 350 nm widths. We have also fabricated single and double conducting polymer nanowires (polyaniline and polypyrrole) with 100nm and 200nm widths using electrochemical direct growth. Using single Pd nanowires, we have also demonstrated hydrogen sensing. It is envisioned that these are the first steps towards nanowire sensor arrays capable of simultaneously detecting multiple chemical species.

  2. Large-sensitive-area superconducting nanowire single-photon detector at 850 nm with high detection efficiency.

    PubMed

    Li, Hao; Zhang, Lu; You, Lixing; Yang, Xiaoyan; Zhang, Weijun; Liu, Xiaoyu; Chen, Sijing; Wang, Zhen; Xie, Xiaoming

    2015-06-29

    Satellite-ground quantum communication requires single-photon detectors of 850-nm wavelength with both high detection efficiency and large sensitive area. We developed superconducting nanowire single-photon detectors (SNSPDs) on one-dimensional photonic crystals, which acted as optical cavities to enhance the optical absorption, with a sensitive-area diameter of 50 μm. The fabricated multimode fiber coupled NbN SNSPDs exhibited a maximum system detection efficiency (DE) of up to 82% and a DE of 78% at a dark count rate of 100 Hz at 850-nm wavelength as well as a system jitter of 105 ps. PMID:26191739

  3. Effect of the wire width on the intrinsic detection efficiency of superconducting-nanowire single-photon detectors

    SciTech Connect

    Lusche, R. Semenov, A.; Ilin, K.; Siegel, M.; Korneeva, Y.; Trifonov, A.; Korneev, A.; Goltsman, G.; Vodolazov, D.; Hübers, H.-W.

    2014-07-28

    A thorough spectral study of the intrinsic single-photon detection efficiency in superconducting TaN and NbN nanowires with different widths has been performed. The experiment shows that the cut-off of the intrinsic detection efficiency at near-infrared wavelengths is most likely controlled by the local suppression of the barrier for vortex nucleation around the absorption site. Beyond the cut-off quasi-particle diffusion in combination with spontaneous, thermally activated vortex crossing explains the detection process. For both materials, the reciprocal cut-off wavelength scales linearly with the wire width where the scaling factor agrees with the hot-spot detection model.

  4. Electro-thermal simulation of superconducting nanowire avalanche photodetectors

    SciTech Connect

    Marsili, F.; Najafi, F.; Herder, C.; Berggren, K. K.

    2011-01-01

    We developed an electrothermal model of NbN superconducting nanowire avalanche photodetectors (SNAPs) on sapphire substrates. SNAPs are single-photon detectors consisting of the parallel connection of N superconducting nanowires. We extrapolated the physical constants of the model from experimental data and we simulated the time evolution of the device resistance, temperature and current by solving two coupled electrical and thermal differential equations describing the nanowires. The predictions of the model were in good quantitative agreement with the experimental results.

  5. High quality superconducting NbN thin films on GaAs

    NASA Astrophysics Data System (ADS)

    Marsili, Francesco; Gaggero, Alessandro; Li, Lianhe H.; Surrente, Alessandro; Leoni, Roberto; Lévy, Francis; Fiore, Andrea

    2009-09-01

    A very promising way to increase the detection efficiency of nanowire superconducting single-photon detectors (SSPDs) consists in integrating them with advanced optical structures such as distributed Bragg reflectors (DBRs) and optical waveguides. This requires transferring the challenging SSPD technology from the usual substrates, i.e. sapphire and MgO, to an optical substrate like GaAs, on which DBRs and waveguides can be easily obtained. Therefore, we optimized the deposition process of few-nm thick superconducting NbN films on GaAs and AlAs/GaAs-based DBRs at low temperatures (substrate temperature TS = 400 °C), in order to prevent As evaporation. NbN films ranging from 150 to 3 nm in thickness were then deposited on single-crystal MgO, GaAs, MgO-buffered GaAs and DBRs by current-controlled DC magnetron sputtering (planar, circular, balanced configuration) of Nb in an Ar+N2 plasma. 5.5 nm thick NbN films on GaAs exhibit TC = 10.7 K, ΔTC = 1.1 K and RRR = 0.7. The growth of such high quality thin NbN films on GaAs and DBRs has never been reported before.

  6. Single conducting polymer nanowire based conductometric sensors

    NASA Astrophysics Data System (ADS)

    Bangar, Mangesh Ashok

    The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against

  7. 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.

  8. 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

  9. Nb(x)Ti(1-x)N Superconducting-Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Stem, Jeffrey A.; Farr, William H.; Leduc, Henry G.; Bumble, Bruce

    2008-01-01

    Superconducting-nanowire singlephoton detectors (SNSPDs) in which Nb(x)Ti(1-x)N (where x<1) films serve as the superconducting materials have shown promise as superior alternatives to previously developed SNSPDs in which NbN films serve as the superconducting materials. SNSPDs have potential utility in optical communications and quantum cryptography. Nb(x)Ti(1-x)N is a solid solution of NbN and TiN, and has many properties similar to those of NbN. It has been found to be generally easier to stabilize NbxTi1 xN in the high-superconducting-transitiontemperature phase than it is to so stabilize NbN. In addition, the resistivity and penetration depth of polycrystalline films of Nb(x)Ti(1-x)N have been found to be much smaller than those of films of NbN. These differences have been hypothesized to be attributable to better coupling at grain boundaries within Nb(x)Ti(1-x)N films.

  10. Single Nanowire Probe for Single Cell Endoscopy and Sensing

    NASA Astrophysics Data System (ADS)

    Yan, Ruoxue

    The ability to manipulate light in subwavelength photonic and plasmonic structures has shown great potentials in revolutionizing how information is generated, transformed and processed. Chemically synthesized nanowires, in particular, offers a unique toolbox not only for highly compact and integrated photonic modules and devices, including coherent and incoherent light sources, waveguides, photodetectors and photovoltaics, but also for new types of nanoscopic bio-probes for spot cargo delivery and in-situ single cell endoscopy and sensing. Such nanowire probes would enable us to carry out intracellular imaging and probing with high spatial resolution, monitor in-vivo biological processes within single living cells and greatly improve our fundamental understanding of cell functions, intracellular physiological processes, and cellular signal pathways. My work is aimed at developing a material and instrumental platform for such single nanowire probe. Successful optical integration of Ag nanowire plasmonic waveguides, which offers deep subwavelength mode confinement, and conventional photonic waveguides was demonstrated on a single nanowire level. The highest plasmonic-photonic coupling efficiency coupling was found at small coupling angles and low input frequencies. The frequency dependent propagation loss was observed in Ag nanowire and was confirmed by quantitative measurement and in agreement with theoretical expectations. Rational integration of dielectric and Ag nanowire waveguide components into hybrid optical-plasmonic routing devices has been demonstrated. This capability is essential for incorporating sub-100nm Ag nanowire waveguides into optical fiber based nanoprobes for single cell endoscopy. The nanoprobe system based on single nanowire waveguides was demonstrated by optically coupling semiconductor or metal nanowire with an optical fiber with tapered tip. This nanoprobe design requires minimal instrumentation which makes it cost efficient and readily

  11. Full-Color Single Nanowire Pixels for Projection Displays.

    PubMed

    Ra, Yong-Ho; Wang, Renjie; Woo, Steffi Y; Djavid, Mehrdad; Sadaf, Sharif Md; Lee, Jaesoong; Botton, Gianluigi A; Mi, Zetian

    2016-07-13

    Multicolor single InGaN/GaN dot-in-nanowire light emitting diodes (LEDs) were fabricated on the same substrate using selective area epitaxy. It is observed that the structural and optical properties of InGaN/GaN quantum dots depend critically on nanowire diameters. Photoluminescence emission of single InGaN/GaN dot-in-nanowire structures exhibits a consistent blueshift with increasing nanowire diameter. This is explained by the significantly enhanced indium (In) incorporation for nanowires with small diameters, due to the more dominant contribution for In incorporation from the lateral diffusion of In adatoms. Single InGaN/GaN nanowire LEDs with emission wavelengths across nearly the entire visible spectral were demonstrated on a single chip by varying the nanowire diameters. Such nanowire LEDs also exhibit superior electrical performance, with a turn-on voltage ∼2 V and negligible leakage current under reverse bias. The monolithic integration of full-color LEDs on a single chip, coupled with the capacity to tune light emission characteristics at the single nanowire level, provides an unprecedented approach to realize ultrasmall and efficient projection display, smart lighting, and on-chip spectrometer. PMID:27332859

  12. Superconducting nanowire single photon detector on diamond

    SciTech Connect

    Atikian, Haig A.; Burek, Michael J.; Choy, Jennifer T.; Lončar, Marko; Eftekharian, Amin; Jafari Salim, A.; Hamed Majedi, A.

    2014-03-24

    Superconducting nanowire single photon detectors are fabricated directly on diamond substrates and their optical and electrical properties are characterized. Dark count performance and photon count rates are measured at varying temperatures for 1310 nm and 632 nm photons. A multi-step diamond surface polishing procedure is reported, involving iterative reactive ion etching and mechanical polishing to create a suitable diamond surface for the deposition and patterning of thin film superconducting layers. Using this approach, diamond substrates with less than 300 pm Root Mean Square surface roughness are obtained.

  13. Transient Rayleigh scattering from single semiconductor nanowires

    SciTech Connect

    Montazeri, Mohammad; Jackson, Howard E.; Smith, Leigh M.; Yarrison-Rice, Jan M.; Kang, Jung-Hyun; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati

    2013-12-04

    Transient Rayleigh scattering spectroscopy is a new pump-probe technique to study the dynamics and cooling of photo-excited carriers in single semiconductor nanowires. By studying the evolution of the transient Rayleigh spectrum in time after excitation, one can measure the time evolution of the density and temperature of photo-excited electron-hole plasma (EHP) as they equilibrate with lattice. This provides detailed information of dynamics and cooling of carriers including linear and bimolecular recombination properties, carrier transport characteristics, and the energy-loss rate of hot electron-hole plasma through the emission of LO and acoustic phonons.

  14. Effect of temperature on superconducting nanowire single-photon detector noise

    NASA Astrophysics Data System (ADS)

    Bahgat Shehata, A.; Ruggeri, A.; Stellari, F.; Weger, Alan J.; Song, P.; Sunter, K.; Najafi, F.; Berggren, Karl K.; Anant, Vikas

    2015-08-01

    Today Superconducting Nanowire Single-Photon Detectors (SNSPDs) are commonly used in different photon-starved applications, including testing and diagnostics of VLSI circuits. Detecting very faint signals in the near-infrared wavelength range requires not only good detection efficiency, but also very low Dark Count Rate (DCR) and jitter. For example, low noise is crucial to enable ultra-low voltage optical testing of integrated circuits. The effect of detector temperature and background thermal radiation on the noise of superconducting single-photon detectors made of NbN meanders is studied in this paper. It is shown that two different regimes can be identified in the DCR vs. bias current characteristics. At high bias, the dark count rate is dominated by the intrinsic noise of the detector, while at low bias current it is dominated by the detection of stray photons that get onto the SNSPD. Changing the detector temperature changes its switching current and only affects the high bias branch of the characteristics: a reduction of the DCR can be achieved by lowering the SNSPD base temperature. On the other hand, changing the temperature of the single-photon light source (e.g. the VLSI circuit under test) only affects the low bias regime: a lower target temperature leads to a smaller DCR.

  15. Single Pt nanowire electrode: preparation, electrochemistry, and electrocatalysis.

    PubMed

    Li, Yongxin; Wu, Qingqing; Jiao, Shoufeng; Xu, Chaodi; Wang, Lun

    2013-04-16

    A single Pt nanowire electrode (SPNE) was fabricated through HF etching process from Pt disk nanoelectrode and an underpotential deposition (UPD) redox replacement technique. The electrochemical experiments showed that SPNE had steady-state electrochemical responses at redox species solution and the mass transfer rates were affected by the lengths and radii of SPNEs. The prepared SPNEs were utilized to examine the oxygen-reduction reaction in a KOH solution to explore the feasibility of electrocatalytic activity of single Pt nanowire and the results showed that the electrocatalytic activity of SPNE was dependent on the surface position of single Pt nanowire: the tip end position is more active than the sidewall position. Meanwhile, the electrocatalytic activity of SPNE was related to the radius of nanowire. These observations are not only important to understand the structure-function relationship in single nanowire level but have significant implications for the synthesis and selection of novel catalysts with high efficiency used in electrochemistry, energy, bioanalysis, etc.

  16. A single crystalline InP nanowire photodetector

    NASA Astrophysics Data System (ADS)

    Yan, Xin; Li, Bang; Wu, Yao; Zhang, Xia; Ren, Xiaomin

    2016-08-01

    Single crystalline nanowires are critical for achieving high-responsivity, high-speed, and low-noise nanoscale photodetectors. Here, we report a metal-semiconductor-metal photodetector based on a single crystalline InP nanowire. The nanowires are grown by a self-catalyzed method and exhibit stacking-fault-free zinc blende crystal structure. The nanowire exhibits a typical n-type semiconductor property and shows a low room temperature dark current of several hundred pA at moderate biases. A photoresponsivity of 6.8 A/W is obtained at a laser power density of 0.2 mW/cm2. This work demonstrates that single crystalline InP nanowires are good candidates for future optoelectronic device applications.

  17. Synthesis and characterization of single-crystal strontium hexaboride nanowires.

    PubMed

    Jash, Panchatapa; Nicholls, Alan W; Ruoff, Rodney S; Trenary, Michael

    2008-11-01

    Catalyst-assisted growth of single-crystal strontium hexaboride (SrB6) nanowires was achieved by pyrolysis of diborane (B2H6) over SrO powders at 760-800 degrees C and 400 mTorr in a quartz tube furnace. Raman spectra demonstrate that the nanowires are SrB6, and transmission electron microscopy along with selected area diffraction indicate that the nanowires consist of single crystals with a preferred [001] growth direction. Electron energy loss data combined with the TEM images indicate that the nanowires consist of crystalline SrB 6 cores with a thin (1 to 2 nm) amorphous oxide shell. The nanowires have diameters of 10-50 nm and lengths of 1-10 microm.

  18. Single CdTe Nanowire Optical Correlator for Femtojoule Pulses.

    PubMed

    Xin, Chenguang; Yu, Shaoliang; Bao, Qingyang; Wu, Xiaoqin; Chen, Bigeng; Wang, Yipei; Xu, Yingxin; Yang, Zongyin; Tong, Limin

    2016-08-10

    On the basis of the transverse second harmonic generation (TSHG) in a highly nonlinear subwavelength-diameter CdTe nanowire, we demonstrate a single-nanowire optical correlator for femto-second pulse measurement with pulse energy down to femtojoule (fJ) level. Pulses to be measured were equally split and coupled into two ends of a suspending nanowire via tapered optical fibers. The couterpropagating pulses meet each other around the central area of the nanowire, and emit TSHG signal perpendicular to the axis of the nanowire. By transferring the spatial intensity profile of the transverse second harmonic (TSH) image into the time-domain temporal profile of the input pulses, we operate the nanowire as a miniaturized optical correlator. Benefitted from the high nonlinearity and the very small effective mode area of the waveguiding CdTe nanowire, the input energy of the single-nanowire correlator can go down to fJ-level (e.g., 2 fJ/pulse for 1064 nm 200 fs pulses). The miniature fJ-pulse correlator may find applications from low power on-chip optical communication, biophotonics to ultracompact laser spectroscopy. PMID:27414182

  19. Magnetoresistance of nanosized magnetic configurations in single nanowires

    NASA Astrophysics Data System (ADS)

    Wegrowe, J.-E.; Gilbert, S.; Doudin, B.; Ansermet, J.-Ph.

    1998-03-01

    The problem of studying spin configurations at nanoscopic level is that magnetic measurements at this scale cannot be performed using usual magnetometers. We have shown that anisotropic magnetoresistance (AMR) measured with micro-contacts allows spin configurations of a single nanowire to be studied in details. The nanowires are diameter 50 nm and length 6000 nm and are produced by a combination of electrodeposition in track-etched membrane templates and sputtering technics. Magnetoresistance of well-defined spin configurations in single nanowires, like Curling magnetization reversal modes or domain wall, are measured.

  20. A diamond nanowire single-photon source.

    PubMed

    Babinec, Thomas M; Hausmann, Birgit J M; Khan, Mughees; Zhang, Yinan; Maze, Jeronimo R; Hemmer, Philip R; Loncar, Marko

    2010-03-01

    The development of a robust light source that emits one photon at a time will allow new technologies such as secure communication through quantum cryptography. Devices based on fluorescent dye molecules, quantum dots and carbon nanotubes have been demonstrated, but none has combined a high single-photon flux with stable, room-temperature operation. Luminescent centres in diamond have recently emerged as a stable alternative, and, in the case of nitrogen-vacancy centres, offer spin quantum bits with optical readout. However, these luminescent centres in bulk diamond crystals have the disadvantage of low photon out-coupling. Here, we demonstrate a single-photon source composed of a nitrogen-vacancy centre in a diamond nanowire, which produces ten times greater flux than bulk diamond devices, while using ten times less power. This result enables a new class of devices for photonic and quantum information processing based on nanostructured diamond, and could have a broader impact in nanoelectromechanical systems, sensing and scanning probe microscopy. PMID:20154687

  1. A diamond nanowire single-photon source

    NASA Astrophysics Data System (ADS)

    Babinec, Thomas M.; Hausmann, Birgit J. M.; Khan, Mughees; Zhang, Yinan; Maze, Jeronimo R.; Hemmer, Philip R.; Lončar, Marko

    2010-03-01

    The development of a robust light source that emits one photon at a time will allow new technologies such as secure communication through quantum cryptography. Devices based on fluorescent dye molecules, quantum dots and carbon nanotubes have been demonstrated, but none has combined a high single-photon flux with stable, room-temperature operation. Luminescent centres in diamond have recently emerged as a stable alternative, and, in the case of nitrogen-vacancy centres, offer spin quantum bits with optical readout. However, these luminescent centres in bulk diamond crystals have the disadvantage of low photon out-coupling. Here, we demonstrate a single-photon source composed of a nitrogen-vacancy centre in a diamond nanowire, which produces ten times greater flux than bulk diamond devices, while using ten times less power. This result enables a new class of devices for photonic and quantum information processing based on nanostructured diamond, and could have a broader impact in nanoelectromechanical systems, sensing and scanning probe microscopy.

  2. Synthesis of uniform CdS nanowires in high yield and its single nanowire electrical property

    SciTech Connect

    Yan Shancheng; Sun Litao; Qu Peng; Huang Ninping; Song Yinchen; Xiao Zhongdang

    2009-10-15

    Large-scale high quality CdS nanowires with uniform diameter were synthesized by using a rapid and simple solvothermal route. Field emission scan electron microscopy (FESEM) and transmission electron microscopy (TEM) images show that the CdS nanowires have diameter of about 26 nm and length up to several micrometres. High resolution TEM (HRTEM) study indicates the single-crystalline nature of CdS nanowires with an oriented growth along the c-axis direction. The optical properties of the products were characterized by UV-vis absorption spectra, photoluminescence spectra and Raman spectra. The resistivity, electron concentration and electron mobility of single NW are calculated by fitting the symmetric I-V curves measured on single NW by the metal-semiconductor-metal model based on thermionic field emission theory. - Graphical abstract: Large-scale high quality CdS nanowires (NWs) with uniform diameter were synthesized by using a rapid and simple solvothermal route. The reaction time is reduced to 2 h, comparing to other synthesis which needed long reaction time up to 12 h. In addition, the as-prepared CdS nanowires have more uniform diameter and high yield. More importantly, the I-V curve of present single CdS nanowire has a good symmetric characteristic as expected by the theory.

  3. Hopping conduction in single ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Ma, Yong-Jun; Zhang, Ze; Zhou, Feng; Lu, Li; Jin, Aizi; Gu, Changzhi

    2005-06-01

    ZnO nanowires were synthesized by chemical vapour deposition (CVD). The dc electrical conductivity of a single ZnO nanowire was investigated over a wide temperature range from 300 to 6 K. It is found that the temperature dependence of conductivity follows the relation \\ln \\rho \\sim T^{-1/2} . The conductivity data suggest that the dominant conduction mechanism is Efros-Shklovskii variable-range hopping conduction. The strong electron-electron interaction in the nanowire is also proved by the I-V and d I/d V curves, on which there emerges a Coulomb gap-like structure at low temperatures.

  4. Photoresponse experiments on NbN proximized nanostructures

    NASA Astrophysics Data System (ADS)

    Pepe, G. P.; Parlato, L.; Pagliarulo, V.; Marrocco, N.; De Lisio, C.; Peluso, G.; Barone, A.; Taino, T.; Myoren, H.; Casaburi, A.; Ejrnaes, M.; Cristiano, R.

    2010-06-01

    Among superconducting materials used in developing high performance nanowire detectors, NbN demonstrated to have unique characteristics in terms of fast response time, quantum efficiency and photon-number resolving capability. We investigated the role of proximity effect on superconducting NbN thin films covered by a weak ferromagnetic NiCu thin layer. Hetero-structures NbN/NiCu have been deposited by DC magnetron sputtering on MgO substrates without any heating. Characterization in terms of morphological, transport, and ultra-fast optical properties has been done. Superconducting nanowires with meander-type geometries (48 micron lengths and <500 nm widths) have been designed and fabricated. Preliminary results concerning their photoresponse to 1550nm laser irradiation are presented.

  5. Synthesis and magnetic properties of single-crystalline magnetite nanowires

    NASA Astrophysics Data System (ADS)

    Han, Qin; Liu, Zhenghui; Xu, Yingying; Zhang, Han

    2007-09-01

    By carefully controlling the reaction conditions, nanowires of Fe 3O 4 are directly acquired from nanowires of α-Fe 2O 3 in a reduced atmosphere at 410-430 °C. X-ray diffraction, Raman spectrum, and transmission electron microscopic analyses demonstrate that the product is single-crystalline Fe 3O 4. The nanowires have diameters of 40-90 nm and lengths of 10-20 μm, which are close to those of the pristine α-Fe 2O 3 nanowires. By studying different growth conditions, we find that hydrogen can push the conversion of the crystal structures, while temperature determines the chemical composition of the final products. The magnetic properties of as-prepared Fe 3O 4 nanowires are measured using a quantum design magnetic property measurement system. The nanowires show a ferrimagnetic behavior at room temperature and their magnetic properties are strongly influenced by surface and interface effects. The Verwey transition temperature ( TV=116 K) is found to be a little lower than that of bulk materials, which can be attributed to the small deviation from stoichiometry caused by the oxygen vacancies near the surfaces. Below 12 K, the nanowires show a spin-glass-like behavior owing to the disordered frozen magnetic state at the surfaces.

  6. Materialization of single multicomposite nanowire: entrapment of ZnO nanoparticles in polyaniline nanowire

    PubMed Central

    2011-01-01

    We present materialization of single multicomposite nanowire (SMNW)-entrapped ZnO nanoparticles (NPs) via an electrochemical growth method, which is a newly developed fabrication method to grow a single nanowire between a pair of pre-patterned electrodes. Entrapment of ZnO NPs was controlled via different conditions of SMNW fabrication such as an applied potential and mixture ratio of NPs and aniline solution. The controlled concentration of ZnO NP results in changes in the physical properties of the SMNWs, as shown in transmission electron microscopy images. Furthermore, the electrical conductivity and elasticity of SMNWs show improvement over those of pure polyaniline nanowire. The new nano-multicomposite material showed synergistic effects on mechanical and electrical properties, with logarithmical change and saturation increasing ZnO NP concentration. PMID:21711928

  7. General hypothesis governing the growth of single-crystal nanowires

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2010-06-01

    The growth and growth rates of single-crystal nanowires by vapor phase mechanisms have been studied. A hypothesis has been proposed, which lays down foundation for the nanowire growth. It redefines the basic concepts of droplets from seeds and describes the fundamental basis of the adhesive properties of droplets. A set of droplet characteristics has been defined, a model in the framework of the hypothesis has been developed, and theoretical calculations have been performed. Experiments have also been carried out. Close correspondences between the theoretical and the experimental results lend support for the hypothesis and the model. Additional experimental evidences quantify the validity of the hypothesis. The calculated results resolve conflicts and controversies. They address the roles of catalysts in the growth of single-crystal nanowires. They shed light on the basic differences in the growth of thin and thick nanowires. They elucidate possible relationship between eutectic temperature and activation energy in the vapor-liquid-solid growth. They provide ground rules that govern the relative supplies of constituent vapor species for the growth of compound semiconductor nanowires. They explain how the same alloyed droplet (e.g., Au/Ga) is activated differently under the influence of different nonmetal elements of different nanowires (for example, As of GaAs, P of GaP, and N of GaN). They demonstrate, for example, that the nanowire growth may be achieved by means that creates thermodynamic imbalance and nanopores inside the seeds at temperatures far below the seed's melting temperature. Alloying in the vapor-solid-liquid mechanism is one such means where growth of even thick nanowires (radius of rD≥50 nm) is possible at temperatures far below the eutectic temperature. The hypothesis, is called the simple, novel, and malleable (SNM) hypothesis. This hypothesis, together with the model, appears to have solved the basic origin of the nanowire growth. It

  8. Waveguide-Coupled Superconducting Nanowire Single-Photon Detectors

    NASA Technical Reports Server (NTRS)

    Beyer, Andrew D.; Briggs, Ryan M.; Marsili, Francesco; Cohen, Justin D.; Meenehan, Sean M.; Painter, Oskar J.; Shaw, Matthew D.

    2015-01-01

    We have demonstrated WSi-based superconducting nanowire single-photon detectors coupled to SiNx waveguides with integrated ring resonators. This photonics platform enables the implementation of robust and efficient photon-counting detectors with fine spectral resolution near 1550 nm.

  9. Harmonics Generation by Surface Plasmon Polaritons on Single Nanowires

    PubMed Central

    2016-01-01

    We present experimental observations of visible wavelength second- and third-harmonic generation on single plasmonic nanowires of variable widths. We identify that near-infrared surface plasmon polaritons, which are guided along the nanowire, act as the source of the harmonics generation. We discuss the underlying mechanism of this nonlinear process, using a combination of spatially resolved measurements and numerical simulations to show that the visible harmonics are generated via a combination of both local and propagating plasmonic modes. Our results provide the first demonstration of nanoscale nonlinear optics with guided, propagating plasmonic modes on a lithographically defined chip, opening up new routes toward integrated optical circuits for information processing. PMID:27563688

  10. Direct Photonic-Plasmonic Coupling and Routing in Single Nanowires

    SciTech Connect

    Yan, Rouxue; Pausauskie, Peter; Huang, Jiaxing; Yang, Piedong

    2009-10-20

    Metallic nanoscale structures are capable of supporting surface plasmon polaritons (SPPs), propagating collective electron oscillations with tight spatial confinement at the metal surface. SPPs represent one of the most promising structures to beat the diffraction limit imposed by conventional dielectric optics. Ag nano wires have drawn increasing research attention due to 2D sub-100 nm mode confinement and lower losses as compared with fabricated metal structures. However, rational and versatile integration of Ag nanowires with other active and passive optical components, as well as Ag nanowire based optical routing networks, has yet to be achieved. Here, we demonstrate that SPPs can be excited simply by contacting a silver nanowire with a SnO2 nanoribbon that serves both as an unpolarized light source and a dielectric waveguide. The efficient coupling makes it possible to measure the propagation-distance-dependent waveguide spectra and frequency-dependent propagation length on a single Ag nanowire. Furthermore, we have demonstrated prototypical photonic-plasmonic routing devices, which are essential for incorporating low-loss Ag nanowire waveguides as practical components into high-capacity photonic circuits.

  11. Thermal and transport properties of a single nickel nanowire

    NASA Astrophysics Data System (ADS)

    Ou, Min-Nan; Chen, Yang-Yuan; Wu, Maw-Kuen; Yang, Tzong-Jer; Lee, P. C.; Harutyunyan, S. R.; Chen, C. D.; Lai, S. J.

    2008-03-01

    Starting with a 100 nm nickel film grown on a Si3N4/Si substrate by thermal evaporator, a suspended nickel nanowire (Ni-NW) was fabricated through e-beam lithography and etching processes. The Ni-NW was a part of 4-probes circuit which is designed for electrical, thermal and thermopower measurements. The resistivity (ρ) and thermal conductivity (κ) of a single nickel nanowire have been measured in the temperature range from 4 to 300 K by 4-probes method and the self-heating-3φ technique. At 300 K the thermal conductivity of nanowire is ˜ 20% of the bulk, it diminishes to lower value as temperature decreases, the consequence is opposite to that in the bulk in which it decreases with temperature increase. The result might be explained by the restriction of mean free paths of electron/phonon--phonon interactions due to the grain boundaries. The small relative resistivity ratio (RRR ˜ 2) confirms the polycrystalline characteristic of the nanowire. The thermopower (Seedbeck coefficient S) was also investigated by temperature gradient built up between two ends of the nanowire. The figure of merit ZT=S^2σ/κ in the one-dimension specimen will be discussed.

  12. 1D-transport properties of single superconducting lead nanowires

    NASA Astrophysics Data System (ADS)

    Michotte, S.; Mátéfi-Tempfli, S.; Piraux, L.

    2003-09-01

    We report on the transport properties of single superconducting lead nanowires grown by an electrodeposition technique, embedded in a nanoporous track-etched polymer membrane. The nanowires are granular, have uniform diameter of ∼40 nm and a very large aspect ratio (∼500). The diameter of the nanowire is small enough to ensure a 1D superconducting regime in a wide temperature range below Tc. The non-zero resistance in the superconducting state and its variation caused by fluctuations of the superconducting order parameter were measured versus temperature, magnetic field, and applied DC current (or voltage). The current induced breakdowns in the V- I characteristics may be explained by the formation of phase slip centers. Moreover, DC voltage driven measurements reveal the existence of a new S-shape behavior near the formation of these phase slip centers.

  13. Single GaAs/GaAsP coaxial core-shell nanowire lasers.

    PubMed

    Hua, Bin; Motohisa, Junichi; Kobayashi, Yasunori; Hara, Shinjiroh; Fukui, Takashi

    2009-01-01

    Highly uniform GaAs/GaAsP coaxial nanowires were prepared via selective-area metal organic vapor phase epitaxy. Photoluminescence spectra from a single nanowire indicate that the obtained heterostructures can produce near-infrared (NIR) lasing under pulsed light excitation. The end facets of a single nanowire form a natural mirror surface to create an axial cavity, which realizes resonance and give stimulated emission. This study is a considerable advance toward the realization of nanowire-based NIR light sources.

  14. ``Hot spots'' growth on single nanowire controlled by electric charge

    NASA Astrophysics Data System (ADS)

    Xi, Shaobo; Liu, Xuehua; He, Ting; Tian, Lei; Wang, Wenhui; Sun, Rui; He, Weina; Zhang, Xuetong; Zhang, Jinping; Ni, Weihai; Zhou, Xiaochun

    2016-06-01

    ``Hot spots'' - a kind of highly active site, which are usually composed of some unique units, such as defects, interfaces, catalyst particles or special structures - can determine the performance of nanomaterials. In this paper, we study a model system, i.e. ``hot spots'' on a single Ag nanowire in the galvanic replacement reaction (GRR), by dark-field microscopy. The research reveals that electric charge can be released by the formation reaction of AgCl, and consequently the electrochemical potential on Ag nanowire drops. The electric charge could induce the reduction of Ag+ to form the ``hot spots'' on the nanowire during the GRR. The appearance probability of ``hot spots'' is almost even along the Ag nanowire, while it is slightly lower near the two ends. The spatial distance between adjacent ``hot spots'' is also controlled by the charge, and obeys a model based on Boltzmann distribution. In addition, the distance distribution here has an advantage in electron transfer and energy saving. Therefore, it's necessary to consider the functions of electric charge during the synthesis or application of nanomaterials.``Hot spots'' - a kind of highly active site, which are usually composed of some unique units, such as defects, interfaces, catalyst particles or special structures - can determine the performance of nanomaterials. In this paper, we study a model system, i.e. ``hot spots'' on a single Ag nanowire in the galvanic replacement reaction (GRR), by dark-field microscopy. The research reveals that electric charge can be released by the formation reaction of AgCl, and consequently the electrochemical potential on Ag nanowire drops. The electric charge could induce the reduction of Ag+ to form the ``hot spots'' on the nanowire during the GRR. The appearance probability of ``hot spots'' is almost even along the Ag nanowire, while it is slightly lower near the two ends. The spatial distance between adjacent ``hot spots'' is also controlled by the charge, and obeys a

  15. "Hot spots" growth on single nanowire controlled by electric charge.

    PubMed

    Xi, Shaobo; Liu, Xuehua; He, Ting; Tian, Lei; Wang, Wenhui; Sun, Rui; He, Weina; Zhang, Xuetong; Zhang, Jinping; Ni, Weihai; Zhou, Xiaochun

    2016-06-01

    "Hot spots" - a kind of highly active site, which are usually composed of some unique units, such as defects, interfaces, catalyst particles or special structures - can determine the performance of nanomaterials. In this paper, we study a model system, i.e. "hot spots" on a single Ag nanowire in the galvanic replacement reaction (GRR), by dark-field microscopy. The research reveals that electric charge can be released by the formation reaction of AgCl, and consequently the electrochemical potential on Ag nanowire drops. The electric charge could induce the reduction of Ag(+) to form the "hot spots" on the nanowire during the GRR. The appearance probability of "hot spots" is almost even along the Ag nanowire, while it is slightly lower near the two ends. The spatial distance between adjacent "hot spots" is also controlled by the charge, and obeys a model based on Boltzmann distribution. In addition, the distance distribution here has an advantage in electron transfer and energy saving. Therefore, it's necessary to consider the functions of electric charge during the synthesis or application of nanomaterials.

  16. "Hot spots" growth on single nanowire controlled by electric charge.

    PubMed

    Xi, Shaobo; Liu, Xuehua; He, Ting; Tian, Lei; Wang, Wenhui; Sun, Rui; He, Weina; Zhang, Xuetong; Zhang, Jinping; Ni, Weihai; Zhou, Xiaochun

    2016-06-01

    "Hot spots" - a kind of highly active site, which are usually composed of some unique units, such as defects, interfaces, catalyst particles or special structures - can determine the performance of nanomaterials. In this paper, we study a model system, i.e. "hot spots" on a single Ag nanowire in the galvanic replacement reaction (GRR), by dark-field microscopy. The research reveals that electric charge can be released by the formation reaction of AgCl, and consequently the electrochemical potential on Ag nanowire drops. The electric charge could induce the reduction of Ag(+) to form the "hot spots" on the nanowire during the GRR. The appearance probability of "hot spots" is almost even along the Ag nanowire, while it is slightly lower near the two ends. The spatial distance between adjacent "hot spots" is also controlled by the charge, and obeys a model based on Boltzmann distribution. In addition, the distance distribution here has an advantage in electron transfer and energy saving. Therefore, it's necessary to consider the functions of electric charge during the synthesis or application of nanomaterials. PMID:27240743

  17. Single-crystal poly(3,4-ethylenedioxythiophene) nanowires with ultrahigh conductivity.

    PubMed

    Cho, Boram; Park, Kyung S; Baek, Jangmi; Oh, Hyun S; Koo Lee, Yong-Eun; Sung, Myung M

    2014-06-11

    We developed single-crystal poly(3,4-ethylenedioxythiopene) (PEDOT) nanowires with ultrahigh conductivity using liquid-bridge-mediated nanotransfer printing with vapor phase polymerization. The single-crystal PEDOT nanowires are formed from 3,4-ethylenedioxythiophene (EDOT) monomers that are self-assembled and crystallized during vapor phase polymerization process within nanoscale channels of a mold having FeCl3 catalysts. These PEDOT nanowires, aligned according to the pattern in the mold, are then directly transferred to specific positions on a substrate to generate a nanowire array by a direct printing process. The PEDOT nanowires have closely packed single-crystalline structures with orthorhombic lattice units. The conductivity of the single-crystal PEDOT nanowires is an average of 7619 S/cm with the highest up to 8797 S/cm which remarkably exceeds literature values of PEDOT nanostructures/thin films. Such distinct conductivity enhancement of single-crystal PEDOT nanowires can be attributed to improved carrier mobility in PEDOT nanowires. To demonstrate usefulness of single-crystal PEDOT nanowires, we fabricated an organic nanowire field-effect transistor array contacting the ultrahigh conductive PEDOT nanowires as metal electrodes.

  18. New Generation of Superconducting Nanowire Single-Photon Detectors

    NASA Astrophysics Data System (ADS)

    Goltsman, G. N.

    2015-09-01

    We present an overview of recent results for new generation of infrared and optical superconducting nanowire single-photon detectors (SNSPDs) that has already demonstrated a performance that makes them devices-of-choice for many applications. SNSPDs provide high efficiency for detecting individual photons while keeping dark counts and timing jitter minimal. Besides superior detection performance over a broad optical bandwidth, SNSPDs are also compatible with an integrated optical platform as a crucial requirement for applications in emerging quantum photonic technologies. By embedding SNSPDs in nanophotonic circuits we realize waveguide integrated single photon detectors which unite all desirable detector properties in a single device.

  19. Imaging Single ZnO Vertical Nanowire Laser Cavities using UV-Laser Scanning Confocal Microscopy

    SciTech Connect

    Gargas, D.J.; Toimil-Molares, M.E.; Yang, P.

    2008-11-17

    We report the fabrication and optical characterization of individual ZnO vertical nanowire laser cavities. Dilute nanowire arrays with interwire spacing>10 ?m were produced by a modified chemical vapor transport (CVT) method yielding an ideal platform for single nanowire imaging and spectroscopy. Lasing characteristics of a single vertical nanowire are presented, as well as high-resolution photoluminescence imaging by UV-laser scanning confocal microscopy. In addition, three-dimensional (3D) mapping of the photoluminescence emission performed in both planar and vertical dimensions demonstrates height-selective imaging useful for vertical nanowires and heteronanostructures emerging in the field of optoelectronics and nanophotonics.

  20. Field emission from single-crystalline HfC nanowires

    SciTech Connect

    Yuan, Jinshi; Tang, Jie; Zhang Han; Shinya, Norio; Nakajima, Kiyomi; Qin, Lu-Chang

    2012-03-12

    Single HfC nanowire field emitter/electrode structures have been fabricated using nano-assembling and electron beam induced deposition. Field ion microscopy has been applied to study the atomic arrangement of facets formed on a field evaporation-modified HfC nanowire tip. Field evaporation and crystal form studies suggest that the {l_brace}111{r_brace} and {l_brace}110{r_brace} crystal planes have lower work functions, while the {l_brace}100{r_brace}, {l_brace}210{r_brace}, and {l_brace}311{r_brace} planes have higher work functions. Field emission measurement permits us to obtain that the work function of the {l_brace}111{r_brace} crystal plane is about 3.4 eV.

  1. Fabrication of single-crystal Si nanowires by ultrahigh vacuum magnetron sputtering.

    NASA Astrophysics Data System (ADS)

    Knepper, J. W.; Zhao, X. W.; Yang, F. Y.

    2006-03-01

    Semiconductor nanowires have attracted great interests due to the intriguing fundamental science and technological application they provide. Many semiconductor materials have been made into single crystal nanowires with superior crystal quality and high mobility. Among them, silicon is particularly interesting because silicon is the foundation of modern electronic technology. A majority of the nanowire synthesis used laser-assisted catalyst growth or chemical vapor deposition. Here we reported a different approach to the fabrication of semiconductor nanowires using ultrahigh vacuum magnetron sputtering. Using thin Au layers as catalyst via vopor-liquid-solid mechanism, single crystal Si nanowires have been grown on Si substrates at a temperature of ˜700 C. Electron microscopy revealed that most Si nanowires grew epitaxially on Si(111) surfaces. Si nanowires are perpendicular to the Si(111) surface with a Si/Au alloy sphere on the top of the nanowires. The growth of Si nanowires on Si wafers with other orientations and amorphous silicon oxide layers was also observed, but with much less probability. The diameter of the Si nanowires is about 200 nm using Au layers as catalyst. The nanowire diameter can be controlled to smaller size by patterning the Au layers into small dots to reduce the catalyst size. Si nanowires fabricated by ultrahigh vacuum sputter at a base pressure of 10̂-10 torr are high purity and can be easily doped to desirable carrier concentration.

  2. Oscillations of electrical conductivity in single bismuth nanowires

    NASA Astrophysics Data System (ADS)

    Cornelius, T. W.; Toimil-Molares, M. E.; Karim, S.; Neumann, R.

    2008-03-01

    Bismuth nanowires were electrochemically deposited in ion track-etched polycarbonate membranes. Single wires with diameters ranging between 70 and 550nm were created in membranes with one single nanopore and their electrical resistance was investigated while leaving them embedded in the template. The specific electrical conductivity oscillates as a function of wire diameter. The modulations are discussed on the basis of quantum-size effects which lead to a splitting of the energy bands into subbands and, thus, cause an oscillation of the density of states at the Fermi level depending on the diameter.

  3. High gain single GaAs nanowire photodetector

    NASA Astrophysics Data System (ADS)

    Wang, Hao

    2013-08-01

    An undoped single GaAs nanowire (NW) photodetector based on a metal-semiconductor-metal Schottky diode structure is fabricated by a focused ion beam method. The photoconductive gain of the device reaches 20 000 at low laser excitation. Bias-dependence of gain proves that the surface contributes more to the gain at higher bias because of an increased surface charge region. The spectral response demonstrates not only the band-edge absorption profile of the single GaAs NW, but also the existence of leaky-mode resonance.

  4. Long-range superconducting proximity effect in template-fabricated single-crystal nanowires

    NASA Astrophysics Data System (ADS)

    Liu, Haidong; Ye, Zuxin; Luo, Zhiping; Rathnayaka, K. D. D.; Wu, Wenhao

    2012-12-01

    A long-range superconducting proximity effect is investigated in single-crystal nanowires of Zn, Sn, and Pb, of length up to 60 μm, electrochemically deposited into the pores of anodic aluminum oxide membranes and polycarbonate membranes. Using an in situ self-contacting method, single nanowires are electrically contacted on both ends to a pair of macroscopic film electrodes of Au, Sn, or Pb pre-fabricated on both surfaces of the membranes. Superconductivity in the nanowires is strongly suppressed when Au electrodes are used. When electrodes having higher superconducting transition temperatures are used, the nanowires become superconducting at the transition temperatures of the electrodes. Microscopy analyses of the structure and the chemical composition of the nanowires are presented, which demonstrate a sharp interface between the nanowires and the macroscopic film electrodes. Measurements of the I-V characteristics provide evidence that this proximity effect occurs along the length of the nanowires.

  5. Integrated freestanding single-crystal silicon nanowires: conductivity and surface treatment.

    PubMed

    Lee, Chung-Hoon; Ritz, Clark S; Huang, Minghuang; Ziwisky, Michael W; Blise, Robert J; Lagally, Max G

    2011-02-01

    Integrated freestanding single-crystal silicon nanowires with typical dimension of 100 nm × 100 nm × 5 µm are fabricated by conventional 1:1 optical lithography and wet chemical silicon etching. The fabrication procedure can lead to wafer-scale integration of silicon nanowires in arrays. The measured electrical transport characteristics of the silicon nanowires covered with/without SiO(2) support a model of Fermi level pinning near the conduction band. The I-V curves of the nanowires reveal a current carrier polarity reversal depending on Si-SiO(2) and Si-H bonds on the nanowire surfaces.

  6. Single-Crystal Diamond Nanowire Tips for Ultrasensitive Force Microscopy.

    PubMed

    Tao, Y; Degen, C L

    2015-12-01

    We report the fabrication, integration, and assessment of sharp diamond tips for ultrasensitive force microscopy experiments. Two types of tips, corresponding to the upper and lower halves of a diamond nanowire, were fabricated by top-down plasma etching from a single-crystalline substrate. The lower, surface-attached halves can be directly integrated into lithographically defined nanostructures, like cantilevers. The upper, detachable halves result in diamond nanowires with a tunable diameter (50-500 nm) and lengths of a few microns. Tip radii were around 10 nm and tip apex angles around 15°. We demonstrate the integration of diamond nanowires for use as scanning tips onto ultrasensitive pendulum-style silicon cantilevers. We find the noncontact friction and frequency jitter to be exceptionally low, with no degradation in the intrinsic mechanical quality factor (Q ≈ 130,000) down to tip-to-surface distances of about 10 nm. Our results are an encouraging step toward further improvement of the sensitivity and resolution of force-detected magnetic resonance imaging. PMID:26517172

  7. NBN Gene Polymorphisms and Cancer Susceptibility: A Systemic Review

    PubMed Central

    Berardinelli, Francesco; di Masi, Alessandra; Antoccia, Antonio

    2013-01-01

    The relationship between DNA repair failure and cancer is well established as in the case of rare, high penetrant genes in high cancer risk families. Beside this, in the last two decades, several studies have investigated a possible association between low penetrant polymorphic variants in genes devoted to DNA repair pathways and risk for developing cancer. This relationship would be also supported by the observation that DNA repair processes may be modulated by sequence variants in DNA repair genes, leading to susceptibility to environmental carcinogens. In this framework, the aim of this review is to provide the reader with the state of the art on the association between common genetic variants and cancer risk, limiting the attention to single nucleotide polymorphisms (SNPs) of the NBN gene and providing the various odd ratios (ORs). In this respect, the NBN protein, together with MRE11 and RAD50, is part of the MRN complex which is a central player in the very early steps of sensing and processing of DNA double-strand breaks (DSBs), in telomere maintenance, in cell cycle control, and in genomic integrity in general. So far, many papers were devoted to ascertain possible association between common synonymous and non-synonymous NBN gene polymorphisms and increased cancer risk. However, the results still remain inconsistent and inconclusive also in meta-analysis studies for the most investigated E185Q NBN miscoding variant. PMID:24396275

  8. Optimised quantum hacking of superconducting nanowire single-photon detectors.

    PubMed

    Tanner, Michael G; Makarov, Vadim; Hadfield, Robert H

    2014-03-24

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack. PMID:24664022

  9. Optimised quantum hacking of superconducting nanowire single-photon detectors.

    PubMed

    Tanner, Michael G; Makarov, Vadim; Hadfield, Robert H

    2014-03-24

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

  10. Optimised quantum hacking of superconducting nanowire single-photon detectors

    NASA Astrophysics Data System (ADS)

    Tanner, Michael G.; Makarov, Vadim; Hadfield, Robert H.

    2014-03-01

    We explore bright-light control of superconducting nanowire single-photon detectors (SNSPDs) in the shunted configuration (a practical measure to avoid latching). In an experiment, we simulate an illumination pattern the SNSPD would receive in a typical quantum key distribution system under hacking attack. We show that it effectively blinds and controls the SNSPD. The transient blinding illumination lasts for a fraction of a microsecond and produces several deterministic fake clicks during this time. This attack does not lead to elevated timing jitter in the spoofed output pulse, and hence does not introduce significant errors. Five different SNSPD chip designs were tested. We consider possible countermeasures to this attack.

  11. Detection mechanism of superconducting nanowire single-photon detectors

    NASA Astrophysics Data System (ADS)

    Engel, A.; Renema, J. J.; Il'in, K.; Semenov, A.

    2015-11-01

    In this paper we intend to give a comprehensive description of the current understanding of the detection mechanism in superconducting nanowire single-photon detectors. We will review key experimental results related to the detection mechanism, e.g. the variations of the detection probability as a function of bias current, temperature or magnetic field. Commonly used detection models will be introduced and we will analyze their predictions in view of the experimental observations. Although none of the proposed detection models is able to describe all experimental data, it is becoming increasingly clear that vortices are essential for the formation of the initial normal-conducting domain that triggers a detection event.

  12. Photocurrent Spectroscopy of Single Wurtzite GaAs Nanowires

    SciTech Connect

    Kim, D. C.; Ahtapodov, L.; Boe, A. B.; Moses, A. F.; Dheeraj, D. L.; Fimland, B. O.; Weman, H.; Choi, J. W.; Ji, H.; Kim, G. T.

    2011-12-23

    Photocurrent of single wurtzite GaAs nanowires grown by Au-assisted molecular beam epitaxy is measured at room and low temperature (10 K). At room temperature a high photo-response with more than two orders of magnitude increase of current is observed. The wavelength dependence of the photocurrent shows a sharp change near the zinc blende GaAs band gap. The absence of the free exciton peak in the low temperature photocurrent spectrum, and problems related to determining the exact position of the energy bandgap of wurtzite GaAs from the observed data are discussed.

  13. 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. PMID:27086560

  14. Electrical properties of single CuO nanowires for device fabrication: Diodes and field effect transistors

    SciTech Connect

    Florica, Camelia; Costas, Andreea; Boni, Andra Georgia; Negrea, Raluca; Preda, Nicoleta E-mail: encu@infim.ro; Pintilie, Lucian; Enculescu, Ionut E-mail: encu@infim.ro; Ion, Lucian

    2015-06-01

    High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited.

  15. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    NASA Astrophysics Data System (ADS)

    Ramazani, A.; Almasi Kashi, M.; Montazer, A. H.

    2014-03-01

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  16. Fabrication of single crystalline, uniaxial single domain Co nanowire arrays with high coercivity

    SciTech Connect

    Ramazani, A. Almasi Kashi, M.; Montazer, A. H.

    2014-03-21

    Whilst Co nanorods with high coercivity were synthesized during recent years, they did not achieve the same results as for Co nanowires embedded in solid templates. In the present work, Co nanowire arrays (NWAs) with high coercivity were successfully fabricated in porous aluminum oxide template under optimum conditions by using pulsed ac electrodeposition technique. Magnetic properties and crystalline characteristics of the nanowires were investigated by hysteresis loop measurements, first-order reversal curve (FORC) analysis, X-ray diffraction (XRD), and selected area electron diffraction (SAED) patterns. Hysteresis loop measurements showed high coercivity of about 4.8 kOe at room temperature together with optimum squareness of 1, resulting in an increase of the previous maximum coercivity for Co NWAs up to 45%. XRD and SAED patterns revealed a single crystalline texture along the [0002] direction, indicating the large magnetocrystalline anisotropy. On the other hand, FORC analysis confirmed a single domain structure for the Co NWAs. In addition, the reversal mechanism of the single crystalline, single domain Co NWAs was studied which resulted in the fixed easy axis with a coherent rotation. Accordingly, these nanowires might offer promising applications in high density bit patterned media and low power logic devices.

  17. Photon Cascade from a Single Crystal Phase Nanowire Quantum Dot.

    PubMed

    Bouwes Bavinck, Maaike; Jöns, Klaus D; Zieliński, Michal; Patriarche, Gilles; Harmand, Jean-Christophe; Akopian, Nika; Zwiller, Val

    2016-02-10

    We report the first comprehensive experimental and theoretical study of the optical properties of single crystal phase quantum dots in InP nanowires. Crystal phase quantum dots are defined by a transition in the crystallographic lattice between zinc blende and wurtzite segments and therefore offer unprecedented potential to be controlled with atomic layer accuracy without random alloying. We show for the first time that crystal phase quantum dots are a source of pure single-photons and cascaded photon-pairs from type II transitions with excellent optical properties in terms of intensity and line width. We notice that the emission spectra consist often of two peaks close in energy, which we explain with a comprehensive theory showing that the symmetry of the system plays a crucial role for the hole levels forming hybridized orbitals. Our results state that crystal phase quantum dots have promising quantum optical properties for single photon application and quantum optics. PMID:26806321

  18. Thermal and quantum phase slips in niobium-nitride nanowires based on suspended carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Masuda, Kohei; Moriyama, Satoshi; Morita, Yoshifumi; Komatsu, Katsuyoshi; Takagi, Tasuku; Hashimoto, Takayuki; Miki, Norihisa; Tanabe, Takasumi; Maki, Hideyuki

    2016-05-01

    Superconducting nanowires have attracted considerable attention due to their unique quantum-mechanical properties, as well as their potential as next-generation quantum nanodevices, such as single-photon detectors, phase-slip (PS) qubits, and other hybrid structures. In this study, we present the results of one-dimensional (1D) superconductivity in nanowires fabricated by coating suspended carbon nanotubes with a superconducting thin niobium nitride (NbN) film. In the resistance-temperature characteristic curves, hallmarks of 1D superconductivity with PS events are observed with unconventional negative magnetoresistance. We also confirm that a crossover occurs between thermal and quantum PSs as the temperature is lowered.

  19. Fabrication and temperature dependence of the resistance of single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Wang, X. F.; Zhang, J.; Shi, H. Z.; Wang, Y. W.; Meng, G. W.; Peng, X. S.; Zhang, L. D.; Fang, J.

    2001-04-01

    Single-crystalline Bi nanowires with diameters ranging from 20 to 70 nm were prepared by electrodeposition using nanoporous aluminum oxide membranes rather than the more usual track-etched polycarbonate membranes. X-ray diffraction and selected area electron diffraction investigations revealed that the nanowires are essentially single crystalline and highly oriented. The temperature dependence of zero-field resistance of different diameter nanowires indicated that these Bi nanowires undergo a semimetal-semiconductor transition due to two-dimensional quantum confinement effects. The resistance maximum was observed at 50 K in zero magnetic field for 20 nm Bi nanowires, while the resistance minimum at 258 K for 50 nm Bi nanowires, due to the quantum size effect.

  20. Anomalous Long-Range Proximity Effect in Template-Fabricated Single-Crystal Superconducting Nanowires

    NASA Astrophysics Data System (ADS)

    Wu, Wenhao; Liu, Haidong; Ye, Zuxin; Luo, Zhiping; Rathnayaka, K. D. D.

    2008-03-01

    We report an anomalous proximity effect observed in single-crystal nanowires of Zn, Sn, and Pb of length up to 60 μm. These nanowires were electrochemically deposited into the pores of anodic aluminum oxide membranes and polycarbonate membranes. Using an in situ self-contacting method, single nanowires were electrically contacted on both ends to a pair of macroscopic film electrodes of Au, Sn, and Pb pre-fabricated on both surfaces of the membranes. We observed that superconductivity in the nanowires was strongly suppressed when Au electrodes were used. When superconducting electrodes with higher transition temperatures were used, the nanowires became superconducting at the transition temperatures of the electrodes. We will present measurements of the sample resistance and the I-V characteristics at various temperatures and magnetic fields. Scanning electron microscopy and transmission electron microscopy analyses of the structure and the composition of the nanowires will also be presented.

  1. Molecular beam epitaxy of single crystalline GaN nanowires on a flexible Ti foil

    NASA Astrophysics Data System (ADS)

    Calabrese, Gabriele; Corfdir, Pierre; Gao, Guanhui; Pfüller, Carsten; Trampert, Achim; Brandt, Oliver; Geelhaar, Lutz; Fernández-Garrido, Sergio

    2016-05-01

    We demonstrate the self-assembled growth of vertically aligned GaN nanowire ensembles on a flexible Ti foil by plasma-assisted molecular beam epitaxy. The analysis of single nanowires by transmission electron microscopy reveals that they are single crystalline. Low-temperature photoluminescence spectroscopy demonstrates that in comparison to standard GaN nanowires grown on Si, the nanowires prepared on the Ti foil exhibit an equivalent crystalline perfection, a higher density of basal-plane stacking faults, but a reduced density of inversion domain boundaries. The room-temperature photoluminescence spectrum of the nanowire ensemble is not influenced or degraded by the bending of the substrate. The present results pave the way for the fabrication of flexible optoelectronic devices based on GaN nanowires on metal foils.

  2. Light-Induced Charge Transport within a Single Asymmetric Nanowire

    SciTech Connect

    Liu, Chong; Hwang, Yun Yeong; Jeong, Hoon Eui; Yang, Peidong

    2011-01-21

    Artificial photosynthetic systems using semiconductor materials have been explored for more than three decades in order to store solar energy in chemical fuels such as hydrogen. By mimicking biological photosynthesis with two light-absorbing centers that relay excited electrons in a nanoscopic space, a dual-band gap photoelectrochemical (PEC) system is expected to have higher theoretical energy conversion efficiency than a single band gap system. This work demonstrates the vectorial charge transport of photo-generated electrons and holes within a single asymmetric Si/TiO2 nanowire using Kelvin probe force microscopy (KPFM). Under UV illumination, higher surface potential was observed on the n-TiO₂ side, relative to the potential of the p-Si side, as a result of majority carriers’ recombination at the Si/TiO₂ interface. These results demonstrate a new approach to investigate charge separation and transport in a PEC system. This asymmetric nanowire heterostructure, with a dual band gap configuration and simultaneously exposed anode and cathode surfaces represents an ideal platform for the development of technologies for the generation of solar fuels, although better photoanode materials remain to be discovered.

  3. Germanium-catalyzed growth of single-crystal GaN nanowires

    NASA Astrophysics Data System (ADS)

    Saleem, Umar; Wang, Hong; Peyrot, David; Olivier, Aurélien; Zhang, Jun; Coquet, Philippe; Ng, Serene Lay Geok

    2016-04-01

    We report the use of Germanium (Ge) as catalyst for Gallium Nitride (GaN) nanowires growth. High-yield growth has been achieved with Ge nanoparticles obtained by dewetting a thin layer of Ge on a Si (100) substrate. The nanowires are long and grow straight with very little curvature. The GaN nanowires are single-crystalline and show a Wurtzite structure growing along the [0001] axis. The growth follows a metal-free Vapor-Liquid-Solid (VLS) mechanism, further allowing a CMOS technology compatibility. The synthesis of nanowires has been done using an industrial Low Pressure Chemical Vapor Deposition (LPCVD) system.

  4. Cold welding of copper nanowires with single-crystalline and twinned structures: A comparison study

    NASA Astrophysics Data System (ADS)

    Huang, Rao; Shao, Gui-Fang; Wen, Yu-Hua

    2016-09-01

    In this article, molecular simulations were adopted to explore the cold welding processes of copper nanowires with both single-crystalline and fivefold twinned structures. It was verified that the twinned nanowires exhibited enhanced strength but lowered elastic limit and ductility. Both nanowires could be successfully welded through rather small loadings, although their stress-strain responses toward compression were different. Meanwhile, more stress was accumulated in the twinned nanowire due to repulsive force of the twin boundaries against the nucleation and motions of dislocations. Moreover, by characterizing the structure evolutions in the welding process, it can be ascertained that perfect atomic order was finally built at the weld region in both nanowires. This comparison study will be of great importance to future mechanical processing of metallic nanowires.

  5. A high-temperature single-photon source from nanowire quantum dots.

    PubMed

    Tribu, Adrien; Sallen, Gregory; Aichele, Thomas; André, Régis; Poizat, Jean-Philippe; Bougerol, Catherine; Tatarenko, Serge; Kheng, Kuntheak

    2008-12-01

    We present a high-temperature single-photon source based on a quantum dot inside a nanowire. The nanowires were grown by molecular beam epitaxy in the vapor-liquid-solid growth mode. We utilize a two-step process that allows a thin, defect-free ZnSe nanowire to grow on top of a broader, cone-shaped nanowire. Quantum dots are formed by incorporating a narrow zone of CdSe into the nanowire. We observe intense and highly polarized photoluminescence even from a single emitter. Efficient photon antibunching is observed up to 220 K, while conserving a normalized antibunching dip of at most 36%. This is the highest reported temperature for single-photon emission from a nonblinking quantum-dot source and principally allows compact and cheap operation by using Peltier cooling.

  6. Single-crystal superconducting nanowires of NbSe{sub 2} fabricated by reactive plasma etching

    SciTech Connect

    Mills, Shaun A.; Staley, Neal E.; Wisser, Jacob J.; Shen, Chenyi; Xu, Zhuan; Liu, Ying

    2014-02-03

    We present the preparation and measurements of nanowires of single-crystal NbSe{sub 2}. These nanowires were prepared on ultrathin (≲10 nm) flakes of NbSe{sub 2} mechanically exfoliated from a bulk single crystal using a process combining electron beam lithography and reactive plasma etching. The electrical contacts to the nanowires were prepared using Ti/Au. Our technique, which overcomes several limitations of methods developed previously for fabricating superconducting nanowires, also allows for the preparation of complex superconducting nanostructures with a desired geometry. Current-voltage characteristics of individual superconducting single-crystal nanowires with widths down to 30 nm and cross-sectional areas as low as 270 nm{sup 2} were measured.

  7. Superconducting nanowire single-photon detectors: physics and applications

    NASA Astrophysics Data System (ADS)

    Natarajan, Chandra M.; Tanner, Michael G.; Hadfield, Robert H.

    2012-06-01

    Single-photon detectors based on superconducting nanowires (SSPDs or SNSPDs) have rapidly emerged as a highly promising photon-counting technology for infrared wavelengths. These devices offer high efficiency, low dark counts and excellent timing resolution. In this review, we consider the basic SNSPD operating principle and models of device behaviour. We give an overview of the evolution of SNSPD device design and the improvements in performance which have been achieved. We also evaluate device limitations and noise mechanisms. We survey practical refrigeration technologies and optical coupling schemes for SNSPDs. Finally we summarize promising application areas, ranging from quantum cryptography to remote sensing. Our goal is to capture a detailed snapshot of an emerging superconducting detector technology on the threshold of maturity.

  8. Waveguide-integrated single- and multi-photon detection at telecom wavelengths using superconducting nanowires

    SciTech Connect

    Ferrari, Simone; Kahl, Oliver; Kovalyuk, Vadim; Goltsman, Gregory N.; Korneev, Alexander; Pernice, Wolfram H. P.

    2015-04-13

    We investigate single- and multi-photon detection regimes of superconducting nanowire detectors embedded in silicon nitride nanophotonic circuits. At near-infrared wavelengths, simultaneous detection of up to three photons is observed for 120 nm wide nanowires biased far from the critical current, while narrow nanowires below 100 nm provide efficient single photon detection. A theoretical model is proposed to determine the different detection regimes and to calculate the corresponding internal quantum efficiency. The predicted saturation of the internal quantum efficiency in the single photon regime agrees well with plateau behavior observed at high bias currents.

  9. Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.

    PubMed

    Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

    2011-12-23

    Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product.

  10. Single quantum dot (QD) manipulation on nanowire using dielectrophoretic (DEP) force

    NASA Astrophysics Data System (ADS)

    Kim, J.; Lee, S. Y.; Suh, J.-K. F.; Park, J. H.; Shin, H. J.

    2011-02-01

    Au nanowires of 100 nm, 200nm and 400 nm widths with micro scale Au electrode were fabricated as electrodes to apply high electric field gradient for strong DEP force within the nanometer range. Au nanowires were fabricated on a silicon dioxide (SiO2) using lift-off process after e-beam lithography and e-beam evaporation. E-beam resister (ER) was patterned and a 50 nm thick Au layer. Photo resister (PR) was patterned to make Au microelectrode and did lift-off process. The Au nanowires with microelectrode were covered with SiO2 layer deposited with PECVD resulting in 1 um thick. Opened end of gold nanowires, the target surface for QD immobilization, were formed using etching processes. Single QD immobilization on the nanowire end-facet was accomplished through positive DEP force. Sine wave of 8 Vpp intensity and 3 MHz frequency was applied and it induced electric field of 108 V/m intensity and electric field gradient around Au nanowire to make strong positive DEP. Optical analysis confirmed the attachment of single QD on the nanowire. A single 25 nm diameter QD was manipulated on 100 nm, 200 nm and 400 nm width nanowires when 8 Vpp, 3 MHz sine wave was applied.

  11. Growth of single-crystalline cobalt silicide nanowires and their field emission property

    PubMed Central

    2013-01-01

    In this work, cobalt silicide nanowires were synthesized by chemical vapor deposition processes on Si (100) substrates with anhydrous cobalt chloride (CoCl2) as precursors. Processing parameters, including the temperature of Si (100) substrates, the gas flow rate, and the pressure of reactions were varied and studied; additionally, the physical properties of the cobalt silicide nanowires were measured. It was found that single-crystal CoSi nanowires were grown at 850°C ~ 880°C and at a lower gas flow rate, while single-crystal Co2Si nanowires were grown at 880°C ~ 900°C. The crystal structure and growth direction were identified, and the growth mechanism was proposed as well. This study with field emission measurements demonstrates that CoSi nanowires are attractive choices for future applications in field emitters. PMID:23819795

  12. Growth of single conductive nanowires at prescribed loci

    NASA Astrophysics Data System (ADS)

    Cheng, Chuanding; Haynie, Donald T.

    2005-12-01

    Conductive 75 nm diameter nanowires have been self-assembled from aqueous solution between 15μm gap electrodes on a SiO2 substrate at predefined locations. Nanowire assembly was initiated by application an electric field, and it occurred along the direction of field lines where the field is strongest. Certain salts of palladium, but not of related metals, yielded nanowires under comparable conditions. The simple and straightforward approach to nanowire assembly outlined here could be used for nano/microscale device interconnection at precise positions at room temperature, important for device development, integration, and packaging.

  13. 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.

  14. Subcellular Neural Probes from Single-Crystal Gold Nanowires

    PubMed Central

    2014-01-01

    Size reduction of neural electrodes is essential for improving the functionality of neuroprosthetic devices, developing potent therapies for neurological and neurodegenerative diseases, and long-term brain–computer interfaces. Typical neural electrodes are micromanufactured devices with dimensions ranging from tens to hundreds of micrometers. Their further miniaturization is necessary to reduce local tissue damage and chronic immunological reactions of the brain. Here we report the neural electrode with subcellular dimensions based on single-crystalline gold nanowires (NWs) with a diameter of ∼100 nm. Unique mechanical and electrical properties of defect-free gold NWs enabled their implantation and recording of single neuron-activities in a live mouse brain despite a ∼50× reduction of the size compared to the closest analogues. Reduction of electrode dimensions enabled recording of neural activity with improved spatial resolution and differentiation of brain activity in response to different social situations for mice. The successful localization of the epileptic seizure center was also achieved using a multielectrode probe as a demonstration of the diagnostics potential of NW electrodes. This study demonstrated the realism of single-neuron recording using subcellular-sized electrodes that may be considered a pivotal point for use in diverse studies of chronic brain diseases. PMID:25112683

  15. Characterization of superconducting nanowire single-photon detector with artificial constrictions

    SciTech Connect

    Zhang, Ling; Liu, Dengkuan; Wu, Junjie; He, Yuhao; Lv, Chaolin; You, Lixing Zhang, Weijun; Zhang, Lu; Liu, Xiaoyu; Wang, Zhen Xie, Xiaoming

    2014-06-15

    Statistical studies on the performance of different superconducting nanowire single-photon detectors (SNSPDs) on one chip suggested that random constrictions existed in the nanowire that were barely registered by scanning electron microscopy. With the aid of advanced e-beam lithography, artificial geometric constrictions were fabricated on SNSPDs as well as single nanowires. In this way, we studied the influence of artificial constrictions on SNSPDs in a straight forward manner. By introducing artificial constrictions with different wire widths in single nanowires, we concluded that the dark counts of SNSPDs originate from a single constriction. Further introducing artificial constrictions in SNSPDs, we studied the relationship between detection efficiency and kinetic inductance and the bias current, confirming the hypothesis that constrictions exist in SNSPDs.

  16. 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

    2016-03-01

    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.

  17. 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

    2016-03-01

    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. PMID:26882441

  18. Diameter-dependent thermoelectric figure of merit in single-crystalline Bi nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Jeongmin; Lee, Seunghyun; Brovman, Yuri M.; Kim, Philip; Lee, Wooyoung

    2015-03-01

    The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects.The diameter-dependent thermoelectric properties of individual single-crystalline Bi nanowires grown by the on-film formation of nanowires method have been investigated. The electrical resistivity, Seebeck coefficient, and thermal conductivity were measured as functions of the nanowire diameter using an individual nanowire device. The thermoelectric figure of merit (ZT) calculated from the measured thermoelectric properties shows an increase from the bulk value to a maximum value of 0.28 at 109 nm-diameter, followed by a decrease upon further decreasing the diameter. This non-monotonic diameter dependence of ZT in Bi nanowires reveals simultaneous positive and negative contributions to the thermoelectric efficiency, driven by the change in intrinsic properties, which originates from the diameter-dependent classical and quantum size effects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06412g

  19. Long-Range Superconducting Proximity Effect in Template-Fabricated Single-Crystal Nanowires

    NASA Astrophysics Data System (ADS)

    Wu, Wenhao; Liu, Haidong; Wei, Zhiyuan; Schultz, Isabel

    2011-03-01

    We study a superconducting proximity effect observed in single-crystal nanowires of Zn, Sn, and Pb of length up to 60 μ m. These nanowires are electrochemically deposited into the pores of anodic aluminum oxide membranes and polycarbonate membranes. Using an in situ self-contacting method, single nanowires are electrically contacted on both ends to a pair of macroscopic film electrodes of Au, Sn, or Pb pre-fabricated on both surfaces of the membranes. Superconductivity in the nanowires is strongly suppressed when Au electrodes are used. When electrodes having higher superconducting transition temperatures are used, the nanowires become superconducting at the transition temperatures of the electrodes. Microscopy analyses of the structure and the chemical composition of the nanowires will be presented. Measurements of sample resistance and I - V characteristics at various temperatures and magnetic fields will also be presented. Furthermore, the effects of the length, the diameter, and the residual resistance ratio of the nanowires on the proximity induced superconductivity will be analyzed and discussed. Supported by NSF DMR-0551813 and DMR-0606529.

  20. Charge transport in single CuO nanowires

    SciTech Connect

    Wu, Junnan; Yin, Bo; Wu, Fei; Myung, Yoon; Banerjee, Parag

    2014-11-03

    Charge transport in single crystal, p-type cupric oxide (CuO) nanowire (NW) was studied through temperature based (120 K–400 K) current-voltage measurements. CuO NW with a diameter of 85 nm was attached to Au electrodes 2.25 μm apart, using dielectrophoresis. At low electrical field (<0.89 × 10{sup 3 }V/cm), an ohmic conduction is observed with an activation energy of 272 meV. The injected electrons fill traps with an average energy, E{sub T} = 26.6 meV and trap density, N{sub T} = 3.4 × 10{sup 15 }cm{sup −3}. After the traps are saturated, space charge limited current mechanism becomes dominant. For 120 K ≤ T ≤ 210 K phonon scattering limits mobility. For T ≥ 220 K, a thermally activated mobility is observed and is attributed to small polaron hopping with an activation energy of 44 meV. This mechanism yields a hole mobility of 0.0015 cm{sup 2}/V s and an effective hole concentration of 4 × 10{sup 18 }cm{sup −3} at 250 K.

  1. Electrical transport properties of single-crystal Al nanowires

    NASA Astrophysics Data System (ADS)

    Brunbauer, Florian M.; Bertagnolli, Emmerich; Majer, Johannes; Lugstein, Alois

    2016-09-01

    Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10-9 Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 1012 A m-2 before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron-phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K.

  2. Electrical transport properties of single-crystal Al nanowires

    NASA Astrophysics Data System (ADS)

    Brunbauer, Florian M.; Bertagnolli, Emmerich; Majer, Johannes; Lugstein, Alois

    2016-09-01

    Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10‑9 Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 1012 A m‑2 before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron–phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K.

  3. Electromigration in focused ion beam deposited tungsten single nanowires

    NASA Astrophysics Data System (ADS)

    Mandal, Pabitra; Das, Bipul; Raychaudhuri, A. K.

    As the focused ion beam induced deposited (FIBID) nanowires (NWs) of W, Pt are being used in nanoelectronic technology to connect individual nanodevices, repairing damaged interconnects in integrated circuit (IC), electromigration study in FIBID-NWs has become essential. Briefly, when a thin conductor, like metallic Al, Cu interconnects in an IC chip carry quite high current density ~1012 A/m2, ions or atoms start migrating. Such migration causes void and hillock formation leading to interconnect discontinuity, short circuit and ultimately IC failure. Our electromigration study in single FIBID-NWs of W reveals that failure in NWs of width and thickness ~100 nm occurs typically at 1011 A/m2. Most notably, void and hillock always form in opposite polarity compared to typical metallic NWs. Such distinctly new outcome is explained via electromigration driven by direct force (ionic charge*electric field) opposed to wind force driven migration observed in metallic NWs. As FIBID-NWs are composite in nature, different species (e.g., Ga, W and C) migrate with different degree and direction depending on their oxidation state, leading to redistribution of species across NW length and formation of a Ga rich hillock. S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata-98, India.

  4. Electrical transport properties of single-crystal Al nanowires.

    PubMed

    Brunbauer, Florian M; Bertagnolli, Emmerich; Majer, Johannes; Lugstein, Alois

    2016-09-23

    Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10(-9) Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 10(12) A m(-2) before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron-phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K. PMID:27533003

  5. Charge transport in single CuO nanowires

    NASA Astrophysics Data System (ADS)

    Wu, Junnan; Yin, Bo; Wu, Fei; Myung, Yoon; Banerjee, Parag

    2014-11-01

    Charge transport in single crystal, p-type cupric oxide (CuO) nanowire (NW) was studied through temperature based (120 K-400 K) current-voltage measurements. CuO NW with a diameter of 85 nm was attached to Au electrodes 2.25 μm apart, using dielectrophoresis. At low electrical field (<0.89 × 103 V/cm), an ohmic conduction is observed with an activation energy of 272 meV. The injected electrons fill traps with an average energy, ET = 26.6 meV and trap density, NT = 3.4 × 1015 cm-3. After the traps are saturated, space charge limited current mechanism becomes dominant. For 120 K ≤ T ≤ 210 K phonon scattering limits mobility. For T ≥ 220 K, a thermally activated mobility is observed and is attributed to small polaron hopping with an activation energy of 44 meV. This mechanism yields a hole mobility of 0.0015 cm2/V s and an effective hole concentration of 4 × 1018 cm-3 at 250 K.

  6. Room temperature GaAsSb single nanowire infrared photodetectors.

    PubMed

    Li, Ziyuan; Yuan, Xiaoming; Fu, Lan; Peng, Kun; Wang, Fan; Fu, Xiao; Caroff, Philippe; White, Thomas P; Hoe Tan, Hark; Jagadish, Chennupati

    2015-11-01

    Antimonide-based ternary III-V nanowires (NWs) allow for a tunable bandgap over a wide range, which is highly interesting for optoelectronics applications, and in particular for infrared photodetection. Here we demonstrate room temperature operation of GaAs0.56Sb0.44 NW infrared photodetectors grown by metal organic vapor phase epitaxy. These GaAs0.56Sb0.44 NWs have uniform axial composition and show p-type conductivity with a peak field-effect mobility of ∼12 cm(2) V(-1) s(-1)). Under light illumination, single GaAs0.56Sb0.44 NW photodetectors exhibited typical photoconductor behavior with an increased photocurrent observed with the increase of temperature owing to thermal activation of carrier trap states. A broadband infrared photoresponse with a long wavelength cutoff at ∼1.66 μm was obtained at room temperature. At a low operating bias voltage of 0.15 V a responsivity of 2.37 (1.44) A/W with corresponding detectivity of 1.08 × 10(9) (6.55 × 10(8)) cm√Hz/W were achieved at the wavelength of 1.3 (1.55) μm, indicating that ternary GaAs0.56Sb0.44 NWs are promising photodetector candidates for small footprint integrated optical telecommunication systems. PMID:26451616

  7. Electrical transport properties of single-crystal Al nanowires.

    PubMed

    Brunbauer, Florian M; Bertagnolli, Emmerich; Majer, Johannes; Lugstein, Alois

    2016-09-23

    Single-crystal Al nanowires (NWs) were fabricated by thermally induced substitution of vapor-liquid-solid grown Ge NWs by Al. The resistivity of the crystalline Al (c-Al) NWs was determined to be ρ = (131 ± 27) × 10(-9) Ω m, i.e. approximately five times higher than for bulk Al, but they withstand remarkably high current densities of up to 1.78 × 10(12) A m(-2) before they ultimately melt due to Joule heating. The maximum current density before failure correlates with the NW diameter, with thinner NWs tolerating significantly higher current densities due to efficient heat dissipation and the reduced lattice heating in structures smaller than the electron-phonon scattering length. The outstanding current-carrying capacity of the c-Al NWs clearly exceeds those of common conductors and surpasses requirements for metallization of future high-performance devices. The linear temperature coefficient of the resistance of c-Al NWs appeared to be lower than for bulk Al and a transition to a superconducting state in c-Al NWs was observed at a temperature of 1.46 K.

  8. Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique

    NASA Astrophysics Data System (ADS)

    Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

    2014-04-01

    Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin-avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin-biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

  9. Fabrication of enzyme-degradable and size-controlled protein nanowires using single particle nano-fabrication technique.

    PubMed

    Omichi, Masaaki; Asano, Atsushi; Tsukuda, Satoshi; Takano, Katsuyoshi; Sugimoto, Masaki; Saeki, Akinori; Sakamaki, Daisuke; Onoda, Akira; Hayashi, Takashi; Seki, Shu

    2014-04-28

    Protein nanowires exhibiting specific biological activities hold promise for interacting with living cells and controlling and predicting biological responses such as apoptosis, endocytosis and cell adhesion. Here we report the result of the interaction of a single high-energy charged particle with protein molecules, giving size-controlled protein nanowires with an ultra-high aspect ratio of over 1,000. Degradation of the human serum albumin nanowires was examined using trypsin. The biotinylated human serum albumin nanowires bound avidin, demonstrating the high affinity of the nanowires. Human serum albumin-avidin hybrid nanowires were also fabricated from a solid state mixture and exhibited good mechanical strength in phosphate-buffered saline. The biotinylated human serum albumin nanowires can be transformed into nanowires exhibiting a biological function such as avidin-biotinyl interactions and peroxidase activity. The present technique is a versatile platform for functionalizing the surface of any protein molecule with an extremely large surface area.

  10. Microchip for the Measurement of Seebeck Coefficients of Single Nanowires

    NASA Astrophysics Data System (ADS)

    Völklein, F.; Schmitt, M.; Cornelius, T. W.; Picht, O.; Müller, S.; Neumann, R.

    2009-07-01

    Bismuth nanowires were electrochemically grown in ion track-etched polycarbonate membranes. Micromachining and microlithography were employed to realize a newly developed microchip for Seebeck coefficient measurements on individual nanowires. By anisotropic etching of a (100) Si wafer, an 800-nm-thick SiO2/Si3N4 membrane was prepared in the chip center. The low thermal conductivity of the membrane is crucial to obtain the required temperature difference Δ T along the nanowire. The wire is electrically contacted to thin metal pads which are patterned by a new method of microscopic exposure of photoresist and a lift-off process. A Δ T between the two pairs of contact pads, located on the membrane, is established by a thin-film heater. Applying the known Seebeck coefficient of a reference film, the temperature difference at this gap is determined. Using Δ T and the measured Seebeck voltage U of the nanowire, its Seebeck coefficient can be calculated.

  11. Spin splitting anisotropy in single diluted magnetic nanowire heterostructures.

    PubMed

    Szymura, Małgorzata; Wojnar, Piotr; Kłopotowski, Łukasz; Suffczyński, Jan; Goryca, Mateusz; Smoleński, Tomasz; Kossacki, Piotr; Zaleszczyk, Wojciech; Wojciechowski, Tomasz; Karczewski, Grzegorz; Wojtowicz, Tomasz; Kossut, Jacek

    2015-03-11

    We study the impact of the nanowire shape anisotropy on the spin splitting of excitonic photoluminescence. The experiments are performed on individual ZnMnTe/ZnMgTe core/shell nanowires as well as on ZnTe/ZnMgTe core/shell nanowires containing optically active magnetic CdMnTe insertions. When the magnetic field is oriented parallel to the nanowire axis, the spin splitting is several times larger than for the perpendicular field. We interpret this pronounced anisotropy as an effect of mixing of valence band states arising from the strain present in the core/shell geometry. This interpretation is further supported by theoretical calculations which allow to reproduce experimental results.

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

    PubMed Central

    Cardoza-Contreras, Marlene N.; Romo-Herrera, José M.; Ríos, Luis A.; García-Gutiérrez, R.; Zepeda, T. A.; Contreras, Oscar E.

    2015-01-01

    Low concentrations of hazardous gases are difficult to detect with common gas sensors. Using semiconductor nanostructures as a sensor element is an alternative. Single ZnO nanowire gas sensor devices were fabricated by manipulation and connection of a single nanowire into a four-electrode aluminum probe in situ in a dual-beam scanning electron microscope-focused ion beam with a manipulator and a gas injection system in/column. The electrical response of the manufactured devices shows response times up to 29 s for a 121 ppm of H2 pulse, with a variation in the nanowire resistance appreciable at room temperature and at 373.15 K of approximately 8% and 14% respectively, showing that ZnO nanowires are good candidates to detect low concentrations of H2. PMID:26690158

  13. Space-and-time-resolved spectroscopy of single GaN nanowires

    SciTech Connect

    Upadhya, Prashanth C.; Martinez, Julio A.; Li, Qiming; Wang, George T.; Swartzentruber, Brian S.; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2015-06-29

    Gallium nitride nanowires have garnered much attention in recent years due to their attractive optical and electrical properties. An understanding of carrier transport, relaxation, and recombination in these quasi-one-dimensional nanosystems is therefore important in optimizing them for various applications. Here, we present ultrafast optical microscopic measurements on single GaN nanowires. Our experiments, performed while varying the light polarization, excitation fluence, and position, give insight into the mechanisms governing carrier dynamics in these nanosystems.

  14. Simultaneous high-resolution scanning Bragg contrast and ptychographic imaging of a single solar cell nanowire

    PubMed Central

    Wallentin, Jesper; Wilke, Robin N.; Osterhoff, Markus; Salditt, Tim

    2015-01-01

    Simultaneous scanning Bragg contrast and small-angle ptychographic imaging of a single solar cell nanowire are demonstrated, using a nanofocused hard X-ray beam and two detectors. The 2.5 µm-long nanowire consists of a single-crystal InP core of 190 nm diameter, coated with amorphous SiO2 and polycrystalline indium tin oxide. The nanowire was selected and aligned in real space using the small-angle scattering of the 140 × 210 nm X-ray beam. The orientation of the nanowire, as observed in small-angle scattering, was used to find the correct rotation for the Bragg condition. After alignment in real space and rotation, high-resolution (50 nm step) raster scans were performed to simultaneously measure the distribution of small-angle scattering and Bragg diffraction in the nanowire. Ptychographic reconstruction of the coherent small-angle scattering was used to achieve sub-beam spatial resolution. The small-angle scattering images, which are sensitive to the shape and the electron density of all parts of the nanowire, showed a homogeneous profile along the nanowire axis except at the thicker head region. In contrast, the scanning Bragg diffraction microscopy, which probes only the single-crystal InP core, revealed bending and crystalline inhomogeneity. Both systematic and non-systematic real-space movement of the nanowire were observed as it was rotated, which would have been difficult to reveal only from the Bragg scattering. These results demonstrate the advantages of simultaneously collecting and analyzing the small-angle scattering in Bragg diffraction experiments. PMID:26664342

  15. Single Si nanowire (diameter ≤ 100 nm) based polarization sensitive near-infrared photodetector with ultra-high responsivity.

    PubMed

    Das, K; Mukherjee, S; Manna, S; Ray, S K; Raychaudhuri, A K

    2014-10-01

    We report the fabrication and optical response of boron-doped single silicon nanowire-based metal-semiconductor-metal photodetector. Typical single nanowire devices with diameter of ∼80-100 nm and electrode spacing of ∼1 μm were made using electron-beam lithography from nanowires, grown by a metal-assisted chemical etching process. A high responsivity, of the order of 10(4) A W(-1), was observed even at zero bias in a single nanowire photodetector with peak responsivity in the near-infrared region. The responsivity was found to increase with increasing bias and decreasing nanowire diameter. Finite element based optical simulation was proposed to explain the diameter dependent performance of a single nanowire. The observed photoresponse is sensitive to the polarization of exciting light source, allowing the device to act as a polarization-dependent near-infrared photodetector.

  16. Single-fluxon controlled resistance switching in centimeter-long superconducting gallium-indium eutectic nanowires.

    PubMed

    Zhao, Weiwei; Bischof, Jesse L; Hutasoit, Jimmy; Liu, Xin; Fitzgibbons, Thomas C; Hayes, John R; Sazio, Pier J A; Liu, Chaoxing; Jain, Jainendra K; Badding, John V; Chan, M H W

    2015-01-14

    The ability to manipulate a single quantum object, such as a single electron or a single spin, to induce a change in a macroscopic observable lies at the heart of nanodevices of the future. We report an experiment wherein a single superconducting flux quantum, or a fluxon, can be exploited to switch the resistance of a nanowire between two discrete values. The experimental geometry consists of centimeter-long nanowires of superconducting Ga-In eutectic, with spontaneously formed Ga nanodroplets along the length of the nanowire. The nonzero resistance occurs when a Ga nanodroplet traps one or more superconducting fluxons, thereby driving a Josephson weak-link created by a second nearby Ga nanodroplet normal. The fluxons can be inserted or flipped by careful manipulation of the magnetic field or temperature to produce one of many metastable states of the system. PMID:25426926

  17. Graphene Enhances Li Storage Capacity of Porous Single-crystalline Silicon Nanowires

    SciTech Connect

    Wang, X.; Han, W.

    2010-12-01

    We demonstrated that graphene significantly enhances the reversible capacity of porous silicon nanowires used as the anode in Li-ion batteries. We prepared our experimental nanomaterials, viz., graphene and porous single-crystalline silicon nanowires, respectively, using a liquid-phase graphite exfoliation method and an electroless HF/AgNO{sub 3} etching process. The Si porous nanowire/graphene electrode realized a charge capacity of 2470 mAh g{sup -1} that is much higher than the 1256 mAh g{sup -1} of porous Si nanowire/C-black electrode and 6.6 times the theoretical capacity of commercial graphite. This relatively high capacity could originate from the favorable charge-transportation characteristics of the combination of graphene with the porous Si 1D nanostructure.

  18. Ultrafast Photodetection in the Quantum Wells of Single AlGaAs/GaAs-Based Nanowires

    NASA Astrophysics Data System (ADS)

    Erhard, N.; Zenger, S.; Morkötter, S.; Rudolph, D.; Weiss, M.; Krenner, H. J.; Karl, H.; Abstreiter, G.; Finley, J. J.; Koblmüller, G.; Holleitner, A. W.

    2015-10-01

    We investigate the ultrafast optoelectronic properties of single Al0.3Ga0.7As/GaAs-core-shell-nanowires. The nanowires contain GaAs-based quantum wells. For a resonant excitation of the quantum wells, we find a picosecond photocurrent which is consistent with an ultrafast lateral expansion of the photogenerated charge carriers. This Dember-effect does not occur for an excitation of the GaAs-based core of the nanowires. Instead, the core exhibits an ultrafast displacement current and a photo-thermoelectric current at the metal Schottky contacts. Our results uncover the optoelectronic dynamics in semiconductor core-shell nanowires comprising quantum wells, and they demonstrate the possibility to use the low-dimensional quantum well states therein for ultrafast photoswitches and photodetectors.

  19. Electromigration and potentiometry measurements of single-crystalline Ag nanowires under UHV conditions.

    PubMed

    Kaspers, M R; Bernhart, A M; Meyer Zu Heringdorf, F-J; Dumpich, G; Möller, R

    2009-07-01

    We report on in situ electromigration and potentiometry measurements on single-crystalline Ag nanowires under ultra-high vacuum (UHV) conditions, using a four-probe scanning tunnelling microscope (STM). The Ag nanowires are grown in place by self-organization on a 4° vicinal Si(001) surface. Two of the four available STM tips are used to contact the nanowire. The positioning of the tips is controlled by a scanning electron microscope (SEM). Potentiometry measurements on an Ag nanowire were carried out using a third tip to determine the resistance per length. During electromigration measurements current densities of up to 1 × 10(8) A cm(-2) could be achieved. We use artificially created notches in the wire to initiate electromigration and to control the location of the electromigration process. At the position of the notch, electromigration sets in and is observed quasi-continuously by the SEM.

  20. Temperature dependent electrical transport in single Ge nanowires near insulator-metal transition

    NASA Astrophysics Data System (ADS)

    Raychaudhuri, Arup Kumar; Seth, Shaili; Das, Kaustuv

    We report low temperature (4K <= T <= 300K) electrical transport in single strands of Germanium Nanowires of radius well below 50 nm. The nanowires, grown from vapour phase with Au catalyst have carrier concentrations ranging from intrinsic to near the insulator-metal transition boundary. The nanowires were characterized extensively by High Resolution Transmission Electron Microscope and established their crystalline quality. A single nanowire dispersed on a Si/SiO2 substrate was connected by Cr/Au contacts made by electron beam lithography in 2-probe / 4-probe configurations. The undoped nanowires have a room temperature resistivity (ρ) of 2 ohm.cm or more (estimated carrier concentration ~1015/cm3) and below the 25K (where it shows carrier freeze out) the ρ rises to high value of 35 ohm.cm. For nanowires with ρ <= .01 ohm.cm at 300K , low temperature ρ becomes finite, signaling transition to a metallic state with negative temperature co-efficient of ρ. The critical composition for the insulator-metal transition is more than an order higher than that observed in the bulk. At low T (<25K) resistivity data in this regime can be fitted to weak-localization form ρ =ρ0 - aTp/2 with ρ0 the NW's ~ 0.5-3.5 mohm.cm, with the exponent p ~ 3-4 as expected from theoretical predictions. Acknowldge Financial Support from Department od Science and Technology, Government of India for Sponsored Project.

  1. Single domain to vortex state transition in multilayered cobalt/copper nanowires

    NASA Astrophysics Data System (ADS)

    Wong, Jared; Greene, Peter; Dumas, Randy K.; Liu, Kai

    2008-08-01

    Multilayered magnetic nanowires provide ideal platforms for nanomagnetism and spin-transport studies. They exhibit complex magnetization reversal behaviors as dimensions of the magnetic components are varied, which are difficult to probe since the magnetic entities are buried inside the nanowires. We have captured magnetic and magnetoresistance "fingerprints" of Co nanodiscs in Co/Cu multilayered nanowires as they undergo a single domain to vortex state transition, using a first-order reversal curve (FORC) method. The Co/Cu multilayered nanowires have been synthesized by pulsed electrodeposition into nanoporous polycarbonate membranes. In 50 nm diameter nanowires of [Co(5nm)/Cu(8nm)]400, a 10% magnetoresistance effect is observed at 300 K. In 200 nm diameter nanowires, the magnetic configurations can be tuned by adjusting the Co nanodisc aspect ratio. The thinnest nanodiscs exhibit single domain behavior. The thicker ones exhibit vortex states, where the nucleation and annihilation of the vortices are manifested as butterfly-like features in the FORC distributions. The magnetoresistance effect shows different characteristics, which correspond to the different magnetic configurations of the Co nanodiscs.

  2. A four-pixel single-photon pulse-position array fabricated from WSi superconducting nanowire single-photon detectors

    SciTech Connect

    Verma, V. B. Horansky, R.; Lita, A. E.; Mirin, R. P.; Nam, S. W.; Marsili, F.; Stern, J. A.; Shaw, M. D.

    2014-02-03

    We demonstrate a scalable readout scheme for an infrared single-photon pulse-position camera consisting of WSi superconducting nanowire single-photon detectors. For an N × N array, only 2 × N wires are required to obtain the position of a detection event. As a proof-of-principle, we show results from a 2 × 2 array.

  3. Bias dependent photocurrent characteristics of copper sulfide single nanowires

    NASA Astrophysics Data System (ADS)

    Kim, Jungdong; Oh, Eunsoon; Yang, Yiming; Yu, Dong

    2016-07-01

    We studied the photocurrent characteristics of copper sulfide nanowire devices under bias voltages. Under global illumination by a laser beam on the nanowire devices, the magnitude of the photocurrent was often found to be asymmetric with respect to the bias, and in some cases, even the direction of the photocurrent remained unchanged for a bias in the opposite direction. Such an unusual bias dependence can be explained by the asymmetry of the Schottky contacts near the electrodes and by the bias dependent electric field at the contacts, as was confirmed by using scanning photocurrent microscopy.

  4. Direct Observation of the Collision of Single Pt Nanoparticles onto Single-Crystalline Gold Nanowire Electrodes.

    PubMed

    Shin, Changhwan; Bae, Hyeonhu; Kang, Mijeong; Kim, Bongsoo; Kwon, Seong Jung

    2016-08-01

    We observed the collision of single Pt nanoparticles (NPs) onto an Au nanowire (NW) electrode by using electrocatalytic amplification. Previously, such observations had typically been performed by using a microscale disk-type ultramicroelectrode (UME). The use of a NW electrode decreased the background noise current and provided a shielding effect, owing to adsorption of the NPs onto the insulating sheath. Therefore, the transient current signal that was caused by the collision of single NPs could be more clearly distinguished from the background current by using a NW electrode instead of a UME. Furthermore, the use of a NW electrode increased the collisional frequency and the magnitude of the transient current signal. The experimental data were analyzed by using a theoretical model and a random walk simulation model. PMID:27305586

  5. Magnetothermopower and magnetoresistance of single Co-Ni/Cu multilayered nanowires

    NASA Astrophysics Data System (ADS)

    Böhnert, Tim; Niemann, Anna Corinna; Michel, Ann-Kathrin; Bäßler, Svenja; Gooth, Johannes; Tóth, Bence G.; Neuróhr, Katalin; Péter, László; Bakonyi, Imre; Vega, Victor; Prida, Victor M.; Nielsch, Kornelius

    2014-10-01

    The magnetothermopower and the magnetoresistance of single Co-Ni/Cu multilayered nanowires with various thicknesses of the Cu spacer are investigated. Both kinds of measurement are performed as a function of temperature (50-325 K) and under applied magnetic fields perpendicular to the nanowire axis, with magnitudes up to -15% at room temperature. A linear relation between thermopower S and electrical conductivity σ of the nanowires is found, with the magnetic field as an implicit variable. Combining the linear behavior of the S vs σ relation and the Mott formula, the energy derivative of the resistivity is determined. In order to extract the true nanowire materials parameters from the measured thermopower, a simple model based on the Mott formula is employed to distinguish the individual thermopower contributions of the sample. By assuming that the nondiffusive thermopower contributions of the nanowire can be neglected, it is found that the magnetic-field-induced changes of thermopower and resistivity are equivalent. The emphasis in the present paper is on the comparison of the magnetoresistance and magnetothermopower results and it is found that the same correlation is valid between the two sets of data for all samples, irrespective of the relative importance of the giant magnetoresistance or anisotropic magnetoresistance contributions in the various individual nanowires.

  6. Formation of nanowires via single particle-triggered linear polymerization of solid-state aromatic molecules.

    PubMed

    Horio, Akifumi; Sakurai, Tsuneaki; Lakshmi, G B V S; Kumar Avasthi, Devesh; Sugimoto, Masaki; Yamaki, Tetsuya; Seki, Shu

    2016-08-11

    Nanowires occupy a prestigious place in nanoelectronics, nanomechanics, and biomimetics. Although there are notable methods to grow nanowires via self-assembly, there is a key drawback in the need to find out the specific conditions appropriate for each system. In this sense, universal techniques to fabricate such nanowires from various organic materials have been sought for the continued progress of the related research field. Here we report one of the promising and facile methodologies to quantitatively produce nanowires with controlled geometrical parameters. In this method, referred to as "Single Particle-Triggered Linear Polymerization (STLiP)", organic thin films on a supporting substrate were irradiated with high-energy charged particles, accelerated by particle accelerators. Each particle penetrates from the top of the films to the substrate while gradually releasing kinetic energy along its trajectory (ion track), generating reactive intermediates such as radical species that eventually induce propagation reactions. The resulting polymerized products were integrated into nanowires with uniform diameter and length that can be isolated via development with appropriate organic solvents. Considering the widely applicable nature of STLiP to organic materials, the present technique opens a new door for access to a number of functional nanowires and their assembly.

  7. The role of oxidative etching in the synthesis of ultrathin single-crystalline Au nanowires.

    PubMed

    Kisner, Alexandre; Heggen, Marc; Fernández, Enrique; Lenk, Steffi; Mayer, Dirk; Simon, Ulrich; Offenhäusser, Andreas; Mourzina, Yulia

    2011-08-16

    The fabrication of ultrathin single-crystal Au nanowires with high aspect ratio and that are stable in air is challenging. Recently, a simple wet-chemical approach using oleylamine has been reported for the synthesis of Au nanowires with micrometer length and 2 nm in diameter. Despite efforts to understand the mechanism of the reaction, an ultimate question about the role of oxygen (O(2)) during the synthesis remained unclear. Here we report that the synthesis of ultrathin Au nanowires employing oleylamine is strongly affected by the amount of O(2) absorbed in the reaction solution. Saturating the solution with O(2) leads to both a high-yield production of nanowires and an increase in their length. Nanowires with diameters of about 2 nm and lengths of 8 μm, which corresponds to an aspect ratio of approximately 4000, were produced. The role of oxygen is attributed to the enhanced oxidation of twin defects on Au nanoparticles formed in the first stage of the reaction. Understanding the role of oxidative etching is crucial to significantly increasing the yield and the length of ultrathin Au nanowires.

  8. Formation of nanowires via single particle-triggered linear polymerization of solid-state aromatic molecules.

    PubMed

    Horio, Akifumi; Sakurai, Tsuneaki; Lakshmi, G B V S; Kumar Avasthi, Devesh; Sugimoto, Masaki; Yamaki, Tetsuya; Seki, Shu

    2016-08-11

    Nanowires occupy a prestigious place in nanoelectronics, nanomechanics, and biomimetics. Although there are notable methods to grow nanowires via self-assembly, there is a key drawback in the need to find out the specific conditions appropriate for each system. In this sense, universal techniques to fabricate such nanowires from various organic materials have been sought for the continued progress of the related research field. Here we report one of the promising and facile methodologies to quantitatively produce nanowires with controlled geometrical parameters. In this method, referred to as "Single Particle-Triggered Linear Polymerization (STLiP)", organic thin films on a supporting substrate were irradiated with high-energy charged particles, accelerated by particle accelerators. Each particle penetrates from the top of the films to the substrate while gradually releasing kinetic energy along its trajectory (ion track), generating reactive intermediates such as radical species that eventually induce propagation reactions. The resulting polymerized products were integrated into nanowires with uniform diameter and length that can be isolated via development with appropriate organic solvents. Considering the widely applicable nature of STLiP to organic materials, the present technique opens a new door for access to a number of functional nanowires and their assembly. PMID:27355341

  9. Single ZnO nanowire ultraviolet detector with free-recovered contact performance

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Wang, Liang; Li, Xin; Li, Zhenhu; Feng, Shuanglong; Lu, Wenqiang

    2016-06-01

    In this paper, a single ZnO nanowire ultraviolet detector was firstly fabricated by a single ZnO nanowire and silver paint, which can be free-recovered from a Schottky contact to an Ohmic contact. Key effect factors such as the illumination and bias voltage of the free-recovered performance were also investigated. Meanwhile, the reason for the recoverable contact was further confirmed in detail. This result is beneficial for developing the highly sensitive ZnO based ultraviolet detector.

  10. Resonant tunnelling features in a suspended silicon nanowire single-hole transistor

    SciTech Connect

    Llobet, Jordi; Pérez-Murano, Francesc E-mail: z.durrani@imperial.ac.uk; Krali, Emiljana; Wang, Chen; Jones, Mervyn E.; Durrani, Zahid A. K. E-mail: z.durrani@imperial.ac.uk; Arbiol, Jordi

    2015-11-30

    Suspended silicon nanowires have significant potential for a broad spectrum of device applications. A suspended p-type Si nanowire incorporating Si nanocrystal quantum dots has been used to form a single-hole transistor. Transistor fabrication uses a novel and rapid process, based on focused gallium ion beam exposure and anisotropic wet etching, generating <10 nm nanocrystals inside suspended Si nanowires. Electrical characteristics at 10 K show Coulomb diamonds with charging energy ∼27 meV, associated with a single dominant nanocrystal. Resonant tunnelling features with energy spacing ∼10 meV are observed, parallel to both diamond edges. These may be associated either with excited states or hole–acoustic phonon interactions, in the nanocrystal. In the latter case, the energy spacing corresponds well with reported Raman spectroscopy results and phonon spectra calculations.

  11. Magnetization and electric transport properties of single-crystal MgB2 nanowires.

    PubMed

    Wu, Cen-Shawn; Chang, Yu-Cheng; Chen, Weimeng; Chen, Chinping; Feng, Qingrong

    2012-11-23

    High quality single-crystal magnesium diboride (MgB(2)) nanowires with lengths exceeding 10 μm were successfully synthesized by hybrid physical chemical vapor deposition. The magnetization and electrical transport properties of single-crystal MgB(2) nanowires (NWs) were measured. The superconducting transition temperature of the NWs was 37 K, as confirmed by magnetization measurements. The disordered behavior of the nanowires was observed by four-terminal current-voltage characteristic measurements of an individual NW from T = 10 to 300 K. The temperature-dependent resistivity curves for seven NWs collapsed into a universal curve described by the variable range hopping model, showing intrinsic nonmetallic transport properties. This implies that the granular superconducting defect states are critical to the superconductivity of the individual MgB(2) NWs.

  12. Single Material Band Gap Engineering in GaAs Nanowires

    SciTech Connect

    Spirkoska, D.; Abstreiter, G.; Efros, A.; Conesa-Boj, S.; Morante, J. R.; Arbiol, J.; Fontcuberta i Morral, A.

    2011-12-23

    The structural and optical properties of GaAs nanowire with mixed zinc-blende/wurtzite structure are presented. High resolution transmission electron microscopy indicates the presence of a variety of shorter and longer segments of zinc-blende or wurtzite crystal phases. Sharp photoluminescence lines are observed with emission energies tuned from 1.515 eV down to 1.43 eV. The downward shift of the emission peaks can be understood by carrier confinement at the wurtzite/zinc-blende heterojunction, in quantum wells and in random short period superlattices existent in these nanowires, assuming the theoretical staggered band-offset between wurtzite and zinc-blende GaAs.

  13. Effect of Ions and Ionic Strength on Surface Plasmon Absorption of Single Gold Nanowires.

    PubMed

    Baral, Susil; Green, Andrew J; Richardson, Hugh H

    2016-06-28

    The local temperature change from a single optically excited gold nanowire, lithographically prepared on Al0.94Ga0.06N embedded with Er(3+) ions, is measured in air, pure water, and various concentrations of aqueous solutions of ionic solutes of NaCl, Na2SO4, and MgSO4. The absorption cross section of the nanowire under pure water (2.25 × 10(-14) m(2)) and different solution ionic strength is measured from the slopes of temperature change versus laser intensity plots. Addition of charges into the solution decreases the amount of heat generated during optical excitation of the gold nanostructures because the absorption cross section of the gold nanowire is attenuated. A Langmuir-type behavior of the absorption cross section with ionic strength is observed that is identified with an increase in the occupancy of screened interfacial charges. The absorption cross section of the nanowire decreases with ionic strength until a saturation value of 9 × 10(-15) m(2), where saturation in the occupancy of screened interfacial charge occurs. Dynamic measurements of temperature for a single gold nanowire immersed in a microchannel flow cell show a sharp and fast temperature drop for the flow of ionic solution compared to the pure (deionized) water, suggesting that the technique can be developed as a sensor probe to detect the presence of ions in solution.

  14. Magnetoresistance characteristics in individual Fe{sub 3}O{sub 4} single crystal nanowire

    SciTech Connect

    Reddy, K. M. Punnoose, Alex; Hanna, Charles; Padture, Nitin P.

    2015-05-07

    We report on the magnetoresistance (MR) and electron transport measurements observed on a single crystal magnetite nanowire prepared using a hydrothermal synthesis method. High-resolution electron microscopy revealed the single crystal magnetite nanowires with 80–120 nm thickness and up to 8 μm in length. Magnetic measurements showed the typical Verwey transition around 120 K with a 100 Oe room temperature coercivity and 45 emu/g saturation magnetization, which are comparable to bulk magnetite. Electrical resistance measurements in 5–300 K temperature range were performed by scanning gate voltage and varying applied magnetic field. Electrical resistivity of the nanowire was found to be around 5 × 10{sup −4} Ω m, slightly higher than the bulk and has activation energy of 0.07 eV. A negative MR of about 0.7% is observed for as-synthesized nanowires at 0.3 T applied field. MR scaled with increasing applied magnetic field representing the field-induced alignment of magnetic domain. These results are attributed to the spin-polarized electron transport across the antiphase boundaries, which implicate promising applications for nanowires in magnetoelectronics.

  15. Electronic and magnetic properties of single-wall GeC nanotubes filled with iron nanowires

    NASA Astrophysics Data System (ADS)

    Wang, Su-Fang; Chen, Li-Yong; Zhang, Jian-Min; Xu, Ke-Wei

    2012-06-01

    Under GGA, the structural, electronic and magnetic properties of single-wall (8, 8) GeC nanotubes filled with iron Fen nanowires (n = 5, 9, 13 and 21) have been investigated systematically using the first-principles PAW potential within DFT. We find that the initial shapes of the Fe5@(8, 8), Fe9@(8, 8) and Fe13@(8, 8) systems are preserved without any visible changes after optimization. But for the Fe21@(8, 8) system, the initial shapes are distorted largely for both nanowire and nanotube. The binding processes of Fen@(8, 8) systems are exothermic, and Fe5@(8, 8) system is the most stable structure. The pristine (8, 8) GeCNT is nonmagnetic and direct semiconductor with a wide band gap of about 2.65 eV. Projected densities of states onto different shell Fe atoms show that the separation between the bonding and antibonding d states is reduced as going from the core Fe atom to the outermost shell Fe atom. The spin polarization of the Fen@(8, 8) systems and free-standing nanowires are higher than that in bulk Fe. And the spin polarization generally decreases with the number n of the Fe atoms increasing for both the Fen@(8, 8) systems and free-standing nanowires. Both the largest spin polarization value itself and not more decrease with respect to value of free-standing Fe5 nanowire suggest the Fe5@(8, 8) system could be of interest for the use in electron spin injection. The magnetism is mainly confined within the inner Fe nanowire for these combined systems. More importantly, the Fe5 nanowire encapsulated inside (8, 8) GeCNT is under the protection of the GeCNT to prevent from oxidation, thus may stably exist in atmosphere for long time and can be expected to have potential applications in building nanodevices.

  16. Resistance of Single Ag Nanowire Junctions and Their Role in the Conductivity of Nanowire Networks.

    PubMed

    Bellew, Allen T; Manning, Hugh G; Gomes da Rocha, Claudia; Ferreira, Mauro S; Boland, John J

    2015-11-24

    Networks of silver nanowires appear set to replace expensive indium tin oxide as the transparent conducting electrode material in next generation devices. The success of this approach depends on optimizing the material conductivity, which until now has largely focused on minimizing the junction resistance between wires. However, there have been no detailed reports on what the junction resistance is, nor is there a known benchmark for the minimum attainable sheet resistance of an optimized network. In this paper, we present junction resistance measurements of individual silver nanowire junctions, producing for the first time a distribution of junction resistance values and conclusively demonstrating that the junction contribution to the overall resistance can be reduced beyond that of the wires through standard processing techniques. We find that this distribution shows the presence of a small percentage (6%) of high-resistance junctions, and we show how these may impact the performance of network-based materials. Finally, through combining experiment with a rigorous model, we demonstrate the important role played by the network skeleton and the specific connectivity of the network in determining network performance. PMID:26448205

  17. A near-infrared 64-pixel superconducting nanowire single photon detector array with integrated multiplexed readout

    SciTech Connect

    Allman, M. S. Verma, V. B.; Stevens, M.; Gerrits, T.; Horansky, R. D.; Lita, A. E.; Mirin, R.; Nam, S. W.; Marsili, F.; Beyer, A.; Shaw, M. D.; Kumor, D.

    2015-05-11

    We demonstrate a 64-pixel free-space-coupled array of superconducting nanowire single photon detectors optimized for high detection efficiency in the near-infrared range. An integrated, readily scalable, multiplexed readout scheme is employed to reduce the number of readout lines to 16. The cryogenic, optical, and electronic packaging to read out the array as well as characterization measurements are discussed.

  18. Selective patterned growth of single-crystal organic nanowires of Ag-TCNQ with chemical raction method

    SciTech Connect

    Xiao, Kai; Tao, Jing; Puretzky, Alexander A; Ivanov, Ilia N; Retterer, Scott T; Pennycook, Stephen J; Geohegan, David B

    2008-01-01

    Abstract: We report for the selective-area chemical synthesis of semiconductor single-crystal organic nanowires of silver-tetracyanoquinodimethane (Ag-TCNQ). Straight and smooth Ag-TCNQ nanowires can be produced and patterned on micrometer and nanometer scale on silicon substrates covered with a thin layer of Ag film through the reaction of TCNQ and Ag in a simple gas-solid chemical reaction process. Ag-TCNQ nanowires are characterized by UV-vis, IR and Raman spectroscopy, respectively. The Ag-TCNQ nanowires grows preferentially along the [100] direction of strong - stacking of Ag-TCNQ molecules. Nanodevices based on these nanowires are fabricated using focus ion beam (FIB) technique. Electrical properties are characterized and I-V hysteresis is observed, which shows memory effect with electrical switching of three orders on-off ratio. These nanowires could be potential for use in optical storage, ultrahigh-density nanoscale memory and logic devices.

  19. Stress induced growth of Sn nanowires in a single step by sputtering method

    SciTech Connect

    Yadav, A. Kothari, D. C.; Patel, N.; Miotello, A.

    2015-06-24

    Sn nanowires in aluminum film have been synthesized in a single step by co-sputtering of Al and Sn targets. Due to immiscibility of Sn and Al, co-sputtering leads to generation of stress in the composite film. In order to attain thermodynamic equilibrium, Sn separates from Al and diffuses towards the grain boundaries. External perturbation due to ambient atmosphere leads to corrosion at the grain boundaries forming pits which provide path for Sn to evolve. Owing to this, extrusion of Sn nanowires from Al film occurs to release the residual stress in the film.

  20. Proton irradiation effects on the thermoelectric properties in single-crystalline Bi nanowires

    SciTech Connect

    Chang, Taehoo; Kim, Jeongmin; Song, Min-Jung; Lee, Wooyoung

    2015-05-15

    The effects of proton irradiation on the thermoelectric properties of Bi nanowires (Bi-NWs) were investigated. Single crystalline Bi-NWs were grown by the on-film formation of nanowires method. The devices based on individual Bi-NWs were irradiated with protons at different energies. The total number of displaced atoms was estimated using the Kinchin-Pease displacement model. The electric conductivity and Seebeck coefficient in the Bi-NW devices were investigated before and after proton irradiation at different temperatures. Although the Seebeck coefficient remained stable at various irradiation energies, the electrical conductivity significantly declined with increasing proton energy up to 40 MeV.

  1. Electric field dependent photocurrent decay length in single lead sulfide nanowire field effect transistors.

    PubMed

    Graham, Rion; Miller, Chris; Oh, Eunsoon; Yu, Dong

    2011-02-01

    We determined the minority carrier diffusion length to be ∼1 μm in single PbS nanowire field effect transistors by scanning photocurrent microscopy. PbS nanowires grown by the vapor-liquid-solid method were p-type with hole mobilities up to 49 cm(2)/(V s). We measured a photoresponse time faster than 14 μs with near-unity charge separation efficiency at the contacts. For the first time, we also observed a field-dependent photocurrent decay length, indicating a drift dominant carrier transport at high bias.

  2. Bipolar electrochemical method for dynamic in situ control of single metal nanowire growth.

    PubMed

    Wood, Marissa; Zhang, Bo

    2015-03-24

    Fabrication plays a key role in determining the unique electrical, optical, and catalytic properties of metal nanowires. Here we present a bipolar electrochemical method for dynamically monitoring and controlling the rate of single metal nanowire growth in situ without a direct electrical connection. Solutions of a metal precursor and a reducing agent are placed on either side of a silica nanochannel, and a pair of electrodes is used to apply a tunable electric potential across the channel. Metal nanowire growth is initiated by chemical reduction when the two solutions meet and continues until the nanochannel is blocked by the formation of a short metal wire segment. Further growth is driven by a bipolar electrochemical mechanism which enables the reduction of metal precursor ions at one end of the nanowire and the oxidation of the reducing agent at the other. The growth rate is monitored in real time by simultaneously recording both the faradaic current and optical microscope video and can be adjusted accordingly by changing the applied electric potential. The resulting nanowire is solid, electrically insulated, and can be used as a bipolar nanoelectrode. This technique can be extended to other electrochemical systems, as well, and provides a confined reaction space for studying the dynamics of any process that can be optically or electrically monitored.

  3. Bipolar electrochemical method for dynamic in situ control of single metal nanowire growth.

    PubMed

    Wood, Marissa; Zhang, Bo

    2015-03-24

    Fabrication plays a key role in determining the unique electrical, optical, and catalytic properties of metal nanowires. Here we present a bipolar electrochemical method for dynamically monitoring and controlling the rate of single metal nanowire growth in situ without a direct electrical connection. Solutions of a metal precursor and a reducing agent are placed on either side of a silica nanochannel, and a pair of electrodes is used to apply a tunable electric potential across the channel. Metal nanowire growth is initiated by chemical reduction when the two solutions meet and continues until the nanochannel is blocked by the formation of a short metal wire segment. Further growth is driven by a bipolar electrochemical mechanism which enables the reduction of metal precursor ions at one end of the nanowire and the oxidation of the reducing agent at the other. The growth rate is monitored in real time by simultaneously recording both the faradaic current and optical microscope video and can be adjusted accordingly by changing the applied electric potential. The resulting nanowire is solid, electrically insulated, and can be used as a bipolar nanoelectrode. This technique can be extended to other electrochemical systems, as well, and provides a confined reaction space for studying the dynamics of any process that can be optically or electrically monitored. PMID:25695464

  4. Single-nanowire solar cells beyond the Shockley-Queisser limit

    NASA Astrophysics Data System (ADS)

    Krogstrup, Peter; Jørgensen, Henrik Ingerslev; Heiss, Martin; Demichel, Olivier; Holm, Jeppe V.; Aagesen, Martin; Nygard, Jesper; Fontcuberta I Morral, Anna

    2013-04-01

    Light management is of great importance in photovoltaic cells, as it determines the fraction of incident light entering the device. An optimal p-n junction combined with optimal light absorption can lead to a solar cell efficiency above the Shockley-Queisser limit. Here, we show how this is possible by studying photocurrent generation for a single core-shell p-i-n junction GaAs nanowire solar cell grown on a silicon substrate. At 1 sun illumination, a short-circuit current of 180 mA cm-2 is obtained, which is more than one order of magnitude higher than that predicted from the Lambert-Beer law. The enhanced light absorption is shown to be due to a light-concentrating property of the standing nanowire, as shown by photocurrent maps of the device. The results imply new limits for the maximum efficiency obtainable with III-V based nanowire solar cells under 1 sun illumination.

  5. Bias-free true random number generation using superconducting nanowire single-photon detectors

    NASA Astrophysics Data System (ADS)

    He, Yuhao; Zhang, Weijun; Zhou, Hui; You, Lixing; Lv, Chaolin; Zhang, Lu; Liu, Xiaoyu; Wu, Junjie; Chen, Sijing; Ren, Min; Wang, Zhen; Xie, Xiaoming

    2016-08-01

    We demonstrate a bias-free true random number generator (TRNG) based on single photon detection using superconducting nanowire single photon detectors (SNSPDs). By comparing the photon detection signals of two consecutive laser pulses and extracting the random bits by the von Neumann correction method, we achieved a random number generation efficiency of 25% (a generation rate of 3.75 Mbit s-1 at a system clock rate of 15 MHz). Using a multi-channel superconducting nanowire single photon detector system with controllable pulse signal amplitudes, we detected the single photons with photon number resolution and positional sensitivity, which could further increase the random number generation efficiency. In a three-channel SNSPD system, the random number bit generation efficiency was improved to 75%, corresponding to a generation rate of 7.5 Mbit s-1 with a 10 MHz system clock rate. All of the generated random numbers successfully passed the statistical test suite.

  6. Bias-free true random number generation using superconducting nanowire single-photon detectors

    NASA Astrophysics Data System (ADS)

    He, Yuhao; Zhang, Weijun; Zhou, Hui; You, Lixing; Lv, Chaolin; Zhang, Lu; Liu, Xiaoyu; Wu, Junjie; Chen, Sijing; Ren, Min; Wang, Zhen; Xie, Xiaoming

    2016-08-01

    We demonstrate a bias-free true random number generator (TRNG) based on single photon detection using superconducting nanowire single photon detectors (SNSPDs). By comparing the photon detection signals of two consecutive laser pulses and extracting the random bits by the von Neumann correction method, we achieved a random number generation efficiency of 25% (a generation rate of 3.75 Mbit s‑1 at a system clock rate of 15 MHz). Using a multi-channel superconducting nanowire single photon detector system with controllable pulse signal amplitudes, we detected the single photons with photon number resolution and positional sensitivity, which could further increase the random number generation efficiency. In a three-channel SNSPD system, the random number bit generation efficiency was improved to 75%, corresponding to a generation rate of 7.5 Mbit s‑1 with a 10 MHz system clock rate. All of the generated random numbers successfully passed the statistical test suite.

  7. Ultrafast room temperature single-photon source from nanowire-quantum dots.

    PubMed

    Bounouar, S; Elouneg-Jamroz, M; Hertog, M den; Morchutt, C; Bellet-Amalric, E; André, R; Bougerol, C; Genuist, Y; Poizat, J-Ph; Tatarenko, S; Kheng, K

    2012-06-13

    Epitaxial semiconductor quantum dots are particularly promising as realistic single-photon sources for their compatibility with manufacturing techniques and possibility to be implemented in compact devices. Here, we demonstrate for the first time single-photon emission up to room temperature from an epitaxial quantum dot inserted in a nanowire, namely a CdSe slice in a ZnSe nanowire. The exciton and biexciton lines can still be resolved at room temperature and the biexciton turns out to be the most appropriate transition for single-photon emission due to a large nonradiative decay of the bright exciton to dark exciton states. With an intrinsically short radiative decay time (≈300 ps) this system is the fastest room temperature single-photon emitter, allowing potentially gigahertz repetition rates.

  8. Salt flux synthesis of single and bimetallic carbide nanowires

    NASA Astrophysics Data System (ADS)

    Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

    2016-07-01

    Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ˜15-20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

  9. Salt flux synthesis of single and bimetallic carbide nanowires

    NASA Astrophysics Data System (ADS)

    Leonard, Brian M.; Waetzig, Gregory R.; Clouser, Dale A.; Schmuecker, Samantha M.; Harris, Daniel P.; Stacy, John M.; Duffee, Kyle D.; Wan, Cheng

    2016-07-01

    Metal carbide compounds have a broad range of interesting properties and are some of the hardest and highest melting point compounds known. However, their high melting points force very high reaction temperatures and thus limit the formation of high surface area nanomaterials. To avoid the extreme synthesis temperatures commonly associated with these materials, a new salt flux technique has been employed to reduce reaction temperatures and form these materials in the nanometer regime. Additionally, the use of multiwall carbon nanotubes as a reactant further reduces the diffusion distance and provides a template for the final carbide materials. The metal carbide compounds produced through this low temperature salt flux technique maintain the nanowire morphology of the carbon nanotubes but increase in size to ∼15–20 nm diameter due to the incorporation of metal in the carbon lattice. These nano-carbides not only have nanowire like shape but also have much higher surface areas than traditionally prepared metal carbides. Finally, bimetallic carbides with composition control can be produced with this method by simply using two metal precursors in the reaction. This method provides the ability to produce nano sized metal carbide materials with size, morphology, and composition control and will allow for these compounds to be synthesized and studied in a whole new size and temperature regime.

  10. Electrical properties of ZnO single nanowires

    NASA Astrophysics Data System (ADS)

    Stiller, Markus; Barzola-Quiquia, José; Zoraghi, Mahsa; Esquinazi, Pablo

    2015-10-01

    We have investigated the electrical resistance R(T) of ZnO nanowires of ≈ 400 nm diameter as a function of temperature, between 30 K and 300 K, and frequency in the range 40 Hz to 30 MHz. The measurements were done on the as-prepared and after low-energy proton implantation at room temperature. The temperature dependence of the resistance of the wire, before proton implantation, can be well described by two processes in parallel. One process is the fluctuation induced tunneling conductance (FITC) and the other the usual thermally activated process. The existence of a tunneling conductance was also observed in the current-voltage (I-V) results, and can be well described by the FITC model. Impedance spectroscopy measurements in the as-prepared state and at room temperature, indicate and support the idea of two contributions of these two transport processes in the nanowires. Electron backscatter diffraction confirms the existence of different crystalline regions. After the implantation of H+ a third thermally activated process is found that can be explained by taking into account the impurity band splitting due to proton implantation.

  11. Enhanced photoabsorption in front-tapered single-nanowire solar cells.

    PubMed

    Zhan, Yaohui; Li, Xiaofeng; Wu, Shaolong; Li, Ke; Yang, Zhenhai; Shang, Aixue

    2014-10-01

    Vertically aligned single-nanowire is verified to be a unique building block to realize the high-efficiency solar cell beyond Schockley-Queisser limit. We proposed a front-tapered vertically aligned single-nanowire solar cell (V-SNSC) and investigated numerically the possibility of this configuration to improve the photoabsorption efficiency compared to the conventional designs, by using 2.5D full-wave finite-element method. The influences of the feature sizes of aspect ratio, bottom radius, and nanowire length on the light-trapping properties were explored; the detailed field distribution and carrier generation rate were revealed as well based on the theory of dielectric resonant antenna, in order to elucidate the underlying physical mechanism. Results showed that, compared with the cylindrical counterparts, the absorption capability of V-SNSCs could be greatly enhanced by using a front-tapered configuration with less material utilized, and that such a positive effect can be further strengthened by increasing the nanowire length. The proposed configuration provides a promising approach to engineer the photoabsorption in the photovoltaic and other optoelectronic devices.

  12. Monolithic carbon structures including suspended single nanowires and nanomeshes as a sensor platform

    NASA Astrophysics Data System (ADS)

    Lim, Yeongjin; Heo, Jeong-Il; Madou, Marc; Shin, Heungjoo

    2013-11-01

    With the development of nanomaterial-based nanodevices, it became inevitable to develop cost-effective and simple nanofabrication technologies enabling the formation of nanomaterial assembly in a controllable manner. Herein, we present suspended monolithic carbon single nanowires and nanomeshes bridging two bulk carbon posts, fabricated in a designed manner using two successive UV exposure steps and a single pyrolysis step. The pyrolysis step is accompanied with a significant volume reduction, resulting in the shrinkage of micro-sized photoresist structures into nanoscale carbon structures. Even with the significant elongation of the suspended carbon nanowire induced by the volume reduction of the bulk carbon posts, the resultant tensional stress along the nanowire is not significant but grows along the wire thickness; this tensional stress gradient and the bent supports of the bridge-like carbon nanowire enhance structural robustness and alleviate the stiction problem that suspended nanostructures frequently experience. The feasibility of the suspended carbon nanostructures as a sensor platform was demonstrated by testing its electrochemical behavior, conductivity-temperature relationship, and hydrogen gas sensing capability.

  13. Single-crystal apatite nanowires sheathed in graphitic shells: synthesis, characterization, and application.

    PubMed

    Jeong, Namjo; Cha, Misun; Park, Yun Chang; Lee, Kyung Mee; Lee, Jae Hyup; Park, Byong Chon; Lee, Junghoon

    2013-07-23

    Vertically aligned one-dimensional hybrid structures, which are composed of apatite and graphitic structures, can be beneficial for orthopedic applications. However, they are difficult to generate using the current method. Here, we report the first synthesis of a single-crystal apatite nanowire encapsulated in graphitic shells by a one-step chemical vapor deposition. Incipient nucleation of apatite and its subsequent transformation to an oriented crystal are directed by derived gaseous phosphorine. Longitudinal growth of the oriented apatite crystal is achieved by a vapor-solid growth mechanism, whereas lateral growth is suppressed by the graphitic layers formed through arrangement of the derived aromatic hydrocarbon molecules. We show that this unusual combination of the apatite crystal and the graphitic shells can lead to an excellent osteogenic differentiation and bony fusion through a programmed smart behavior. For instance, the graphitic shells are degraded after the initial cell growth promoted by the graphitic nanostructures, and the cells continue proliferation on the bare apatite nanowires. Furthermore, a bending experiment indicates that such core-shell nanowires exhibited a superior bending stiffness compared to single-crystal apatite nanowires without graphitic shells. The results suggest a new strategy and direction for bone grafting materials with a highly controllable morphology and material conditions that can best stimulate bone cell differentiation and growth. PMID:23755838

  14. Effect of (L:D) Aspect Ratio on Single Polypyrrole Nanowire FET Device

    PubMed Central

    Shirale, Dhammanand J.; Bangar, Mangesh A.; Chen, Wilfred; Myung, Nosang V.

    2010-01-01

    Effect of different aspect ratio (length to diameter ratio, L:D) on single polypyrrole (Ppy) nanowire based field effect transistor (FET) sensor for real time pH monitoring was studied. Ppy nanowires with diameters of ~60, ~80 and ~200 nm were synthesized using electrochemical deposition inside anodized aluminium oxide (AAO) template and were assembled using AC dielectrophoretic alignment followed by maskless anchoring on a pair of gold electrodes separated with different gap lengths. Microfabricated gold electrode patterns with gap size between 1 - 4 μm were developed by means of MEMS technique (photolithography). Using field effect transistor geometry with pair of microfabricated gold contact electrodes serving as a source and a drain, and a platinum (Pt) mesh (anchored in a microfluidic channel) was used as a gate electrode. When effect of different aspect ratio of the nanowire were compared, higher sensitivity was recorded for higher aspect ratio. The sensitivity was further improved by modulating the gate potential. These FET sensors based on single polypyrrole nanowire exhibited excellent and tunable sensitivity towards pH variations. PMID:21743822

  15. Electrically injected near-infrared light emission from single InN nanowire p-i-n diode

    SciTech Connect

    Le, Binh Huy; Zhao, Songrui; Tran, Nhung Hong; Mi, Zetian

    2014-12-08

    We report on the achievement of electroluminescence emission of single InN p-i-n nanowire devices. InN p-i-n nanowire structures were grown directly on Si substrate by plasma-assisted molecular beam epitaxy and subsequently transferred to foreign substrate for the fabrication of single nanowire light emitting diodes. Electroluminescence emission with a peak energy of 0.71 eV (1.75 μm) was observed at 77 K. The measurement of near-bandgap electroluminescence provides unambiguous evidence for the achievement of p-type conduction of InN.

  16. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1). PMID:27609560

  17. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Wang, Di; Hahn, Horst; Dasgupta, Subho

    2016-10-01

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm2 V-1 s-1.

  18. Exciton-Exciton Annihilation in Copper-Phthalocyanine Single-Crystal Nanowires

    SciTech Connect

    Ma, Yingzhong; Xiao, Kai; Shaw, Robert W

    2012-01-01

    Femtosecond one-color pump-probe spectroscopy was applied to study exciton dynamics in single-crystal copper-phthalocyanine (CuPc) nanowires grown on an opaque silicon substrate. The transient reflectance kinetics measured at different pump fluences exhibit a remarkable intensity-dependent decay behavior which accelerates significantly with increasing pump pulse intensity. All the kinetic decays can be satisfactorily described using a bi-exponential decay function with lifetimes of 22 and 204 ps, and corresponding relative amplitudes depending on the pump intensity. The accelerated decay behavior observed at high pump intensities arises from a nonlinear exciton-exciton annihilation process. While this phenomenon has been found previously in crystalline metallophthalocyanine (MPc) polymorphs such as colloidal particles and thin films, the results obtained using the CuPc nanowires are markedly distinct, namely, much longer decay times and a linear intensity dependence of the initial peak amplitudes. Despite these differences, detailed data analysis further shows that, as found for other metal-phthalocyanine polymorphs, exciton-exciton annihilation in the CuPc nanowires is one-dimensional (1D) diffusion-limited, which possibly involves intra-chain exciton diffusion along 1D molecular stacks. The significantly long-lived excitons of CuPc nanowires in comparison to those of other crystalline polymorphs make them particularly suitable for photovoltaic applications.

  19. Facile fabrication of electrolyte-gated single-crystalline cuprous oxide nanowire field-effect transistors.

    PubMed

    Stoesser, Anna; von Seggern, Falk; Purohit, Suneeti; Nasr, Babak; Kruk, Robert; Dehm, Simone; Di Wang; Hahn, Horst; Dasgupta, Subho

    2016-10-14

    Oxide semiconductors are considered to be one of the forefront candidates for the new generation, high-performance electronics. However, one of the major limitations for oxide electronics is the scarcity of an equally good hole-conducting semiconductor, which can provide identical performance for the p-type metal oxide semiconductor field-effect transistors as compared to their electron conducting counterparts. In this quest, here we present a bulk synthesis method for single crystalline cuprous oxide (Cu2O) nanowires, their chemical and morphological characterization and suitability as active channel material in electrolyte-gated, low-power, field-effect transistors (FETs) for portable and flexible logic circuits. The bulk synthesis method used in the present study includes two steps: namely hydrothermal synthesis of the nanowires and the removal of the surface organic contaminants. The surface treated nanowires are then dispersed on a receiver substrate where the passive electrodes are structured, followed by printing of a composite solid polymer electrolyte (CSPE), chosen as the gate insulator. The characteristic electrical properties of individual nanowire FETs are found to be quite interesting including accumulation-mode operation and field-effect mobility of 0.15 cm(2) V(-1) s(-1).

  20. In Situ Observation of the Electrochemical Lithiation of a Single SnO2 Nanowire Electrode

    SciTech Connect

    Huang, J Y; Zhong, L; Wang, C M; Sullivan, J P; Xu, W; Zhang, L Q; Mao, S X; Hudak, N S; Liu, X H; Subramanian, A; Fan, H Y; Qi, L A; Kushima, A; Li, J

    2010-12-09

    We report the creation of a nanoscale electrochemical device inside a transmission electron microscope—consisting of a single tin dioxide (SnO{sub 2}) nanowire anode, an ionic liquid electrolyte, and a bulk lithium cobalt dioxide (LiCoO{sub 2}) cathode—and the in situ observation of the lithiation of the SnO{sub 2} nanowire during electrochemical charging. Upon charging, a reaction front propagated progressively along the nanowire, causing the nanowire to swell, elongate, and spiral. The reaction front is a “Medusa zone” containing a high density of mobile dislocations, which are continuously nucleated and absorbed at the moving front. This dislocation cloud indicates large in-plane misfit stresses and is a structural precursor to electrochemically driven solid-state amorphization. Because lithiation-induced volume expansion, plasticity, and pulverization of electrode materials are the major mechanical effects that plague the performance and lifetime of high-capacity anodes in lithium-ion batteries, our observations provide important mechanistic insight for the design of advanced batteries.

  1. Soluble polymer-based, blown bubble assembly of single- and double-layer nanowires with shape control.

    PubMed

    Wu, Shiting; Huang, Kai; Shi, Enzheng; Xu, Wenjing; Fang, Ying; Yang, Yanbing; Cao, Anyuan

    2014-04-22

    We present here an efficient blown bubble method for large-scale assembly of semiconducting nanowires, with simultaneous control on the material shape. As-synthesized Te nanowires in powder form are dispersed in a polymethylmethacrylate (PMMA) solution, assembled in a large size bubble blown from the solution, and then transferred (repeatedly) to arbitrary substrates. By this way, we have obtained single-layer (aligned) and double-layer (crossed) Te nanowires as well as buckled Te nanosprings which are converted from initially straight nanowires in situ during bubble blowing. The PMMA bubble film can be removed by direct dissolution in acetone to expose nanostructures with clean surface while maintaining original configuration. After matrix removal, these clean nanowire and nanospring arrays can be fabricated into functional nanoelectronic devices such as photodetectors and gas sensors with high performance.

  2. Atomic size effects studied by transport in single silicide nanowires

    NASA Astrophysics Data System (ADS)

    Miccoli, I.; Edler, F.; Pfnür, H.; Appelfeller, S.; Dähne, M.; Holtgrewe, K.; Sanna, S.; Schmidt, W. G.; Tegenkamp, C.

    2016-03-01

    Ultrathin metallic silicide nanowires with extremely high aspect ratios can be easily grown, e.g., by deposition of rare earth elements on semiconducting surfaces. These wires play a pivotal role in fundamental research and open intriguing perspectives for CMOS applications. However, the electronic properties of these one-dimensional systems are extremely sensitive to atomic-sized defects, which easily alter the transport characteristics. In this study, we characterized comprehensively TbSi2 wires grown on Si(100) and correlated details of the atomic structure with their electrical resistivities. Scanning tunneling microscopy (STM) as well as all transport experiments were performed in situ using a four-tip STM system. The measurements are complemented by local spectroscopy and density functional theory revealing that the silicide wires are electronically decoupled from the Si template. On the basis of a quasiclassical transport model, the size effect found for the resistivity is quantitatively explained in terms of bulk and surface transport channels considering details of atomic-scale roughness. Regarding future applications the full wealth of these robust nanostructures will emerge only if wires with truly atomically sharp interfaces can be reliably grown.

  3. Improvement of infrared single-photon detectors absorptance by integrated plasmonic structures

    PubMed Central

    Csete, Mária; Sipos, Áron; Szalai, Anikó; Najafi, Faraz; Szabó, Gábor; Berggren, Karl K.

    2013-01-01

    Plasmonic structures open novel avenues in photodetector development. Optimized illumination configurations are reported to improve p-polarized light absorptance in superconducting-nanowire single-photon detectors (SNSPDs) comprising short- and long-periodic niobium-nitride (NbN) stripe-patterns. In OC-SNSPDs consisting of ~quarter-wavelength dielectric layer closed by a gold reflector the highest absorptance is attainable at perpendicular incidence onto NbN patterns in P-orientation due to E-field concentration at the bottom of nano-cavities. In NCAI-SNSPDs integrated with nano-cavity-arrays consisting of vertical and horizontal gold segments off-axis illumination in S-orientation results in polar-angle-independent perfect absorptance via collective resonances in short-periodic design, while in long-periodic NCAI-SNSPDs grating-coupled surface waves promote EM-field transportation to the NbN stripes and result in local absorptance maxima. In NCDAI-SNSPDs integrated with nano-cavity-deflector-array consisting of longer vertical gold segments large absorptance maxima appear in 3p-periodic designs due to E-field enhancement via grating-coupled surface waves synchronized with the NbN stripes in S-orientation, which enable to compensate fill-factor-related retrogression. PMID:23934331

  4. Controlled manipulation and in situ mechanical measurement of single co nanowire with a laser-induced cavitation bubble.

    PubMed

    Huang, Xiaohu; Quinto-Su, Pedro A; Gonzalez-Avila, S Roberto; Wu, Tom; Ohl, Claus-Dieter

    2010-10-13

    The flow induced by a single laser-induced cavitation bubble is used to manipulate individual Co nanowires. The short-lived (<20 μs) bubble with a maximum size of 45 μm is created in an aqueous solution with a laser pulse. Translation, rotation, and radial motion of the nanowire can be selectively achieved by varying the initial distance and orientation of the bubble with respect to the nanowire. Depending on the initial distance, the nanowire can be either pushed away or pulled toward the laser focus. No translation is observed for a distance further than approximately 60 μm, while at closer distance, the nanowire can be bent as a result of the fast flow induced during the bubble collapse. Studying the dynamics of the shape recovery allows an estimation of the Young's modulus of the nanowire. The low measured Young's modulus (in a range from 9.6 to 13.0 GPa) of the Co nanowire is attributed to a softening effect due to structural defects and surface oxidation layer. Our study suggests that this bubble-based technique allows selectively transporting, orienting, and probing individual nanowires and may be exploited for constructing functional nanodevices.

  5. Broadband ultrafast superconducting NbN detector for electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Gousev, Yu. P.; Gol'Tsman, G. N.; Semenov, A. D.; Gershenzon, E. M.; Nebosis, R. S.; Heusinger, M. A.; Renk, K. F.

    1994-04-01

    The paper shows that the NbN thin film detector combines, in an optimum way, both high sensitivity and short response, and it has, in addition, a broadband sensitivity from the submillimeter (or millimeter) wave range to visible light. Details of the experiment presents the performance and operating conditions of the broadband ultrafast superconducting NbN detector for electromagnetic radiation.

  6. Raman spectroscopy of GaN and AlGaN nanowires: from ensemble to single nanowire study

    NASA Astrophysics Data System (ADS)

    Wang, J.; Bayon, C.; Demangeot, F.; Pechou, R.; Mlayah, A.; Cros, A.; Daudin, B.

    2013-03-01

    Self-assembled GaN nanowires (NWs) currently are a subject of sustained interest in the scientific community motivated by both their potential applications for new LEDs, which should take benefit of the improved crystalline quality of those nano-objects, due to a strongly reduced defects density. In addition, interest of the scientific community for these 1D nano-systems is also related to the new fundamental questions opened by their strongly anisotropic geometry, and to their potential as possible building blocks for future nano-electronic devices. In this context, Raman spectroscopy has been increasingly used to study nitride NWs and several new phenomena have been reported to date with respect to these one-dimensional structures. In this work, both GaN and AlGaN nanowires grown by plasma-assisted Molecular Beam Epitaxy (MBE) have been experimentally investigated by scanning electron microscopy, atomic force microscopy and micro-Raman spectroscopy. Experimental results are analyzed and compared to theoretical ones obtained by dielectric models and Discrete Dipole Approximation (DDA) method. Evidence is given for original surface effects in the optical phonon physics related to both structural anisotropy of the material and 1D geometry of the GaN NWs. By using UV resonant excitation for AlGaN NWs in the whole range of composition, we demonstrate the selective excitation of AlGaN with the Al composition matching the energy of the exciting photons. Finally, we analyzed Raman data from single GaN NW after deposition on a flat substrate and we discuss the nature of strongly polarized A1(TO) phonon as a function of the NWs aspect ratio.

  7. Nano-optical observation of cascade switching in a parallel superconducting nanowire single photon detector

    SciTech Connect

    Heath, Robert M. Tanner, Michael G.; Casaburi, Alessandro; Hadfield, Robert H.; Webster, Mark G.; San Emeterio Alvarez, Lara; Jiang, Weitao; Barber, Zoe H.; Warburton, Richard J.

    2014-02-10

    The device physics of parallel-wire superconducting nanowire single photon detectors is based on a cascade process. Using nano-optical techniques and a parallel wire device with spatially separate pixels, we explicitly demonstrate the single- and multi-photon triggering regimes. We develop a model for describing efficiency of a detector operating in the arm-trigger regime. We investigate the timing response of the detector when illuminating a single pixel and two pixels. We see a change in the active area of the detector between the two regimes and find the two-pixel trigger regime to have a faster timing response than the one-pixel regime.

  8. Non-degenerate pump-probe spectroscopy of single GaN nanowires

    SciTech Connect

    Upadhya, Prashanth C; Taylor, Antoinette J; Prasankumar, Rohiy P; Wang, George T; Martinez, Julio A; Li, Qiming; Swartzentruber, Brian S

    2010-01-01

    Spatially-resolved ultrafast transient absorption measurements on a single GaN nanowire give insight into carrier relaxation dynamics as a function of the probe polarization and position on the nanowire on a femtosecond timescale. The synthesis and optical characterization of semiconductor nanowires (NWs) has gained considerable attention in recent years owing to their unique electronic and optical properties that arise from their anisotropic geometry, large surface to volume ratio and two-dimensional quasiparticle confinement, Post-growth characterization of their properties is crucial in understanding the fundamental physical processes that can lead to enhanced functionality of NW-based devices, In particular, it is important to understand the carrier relaxation pathways in individual NWs, since the geometry of these nanostructures can significantly influence carrier recombination and/or trapping. In this respect, ultrafast optical techniques offer reliable and non-contact spectroscopic tools to study carrier dynamics in semiconductor nanostructures. In summary, time-resolved optical pump-probe spectroscopy was performed on single GaN NWs. These measurements give insight into the different processes that govern carrier capture, particularly at surface states, and relaxation in individual nanostructures. Our experiments thus demonstrate the value of single-particle ultrafast optical spectroscopy in understanding the physical processes that govern the properties of semiconductor NWs, while suggesting approaches to optimize NW-based devices for nanophotonic applications.

  9. Formation of long single quantum dots in high quality InSb nanowires grown by molecular beam epitaxy.

    PubMed

    Fan, Dingxun; Li, Sen; Kang, N; Caroff, Philippe; Wang, L B; Huang, Y Q; Deng, M T; Yu, C L; Xu, H Q

    2015-09-28

    We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO2 substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ∼700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Landég-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ∼300 μeV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.

  10. Formation of long single quantum dots in high quality InSb nanowires grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Fan, Dingxun; Li, Sen; Kang, N.; Caroff, Philippe; Wang, L. B.; Huang, Y. Q.; Deng, M. T.; Yu, C. L.; Xu, H. Q.

    2015-09-01

    We report on realization and transport spectroscopy study of single quantum dots (QDs) made from InSb nanowires grown by molecular beam epitaxy (MBE). The nanowires employed are 50-80 nm in diameter and the QDs are defined in the nanowires between the source and drain contacts on a Si/SiO2 substrate. We show that highly tunable QD devices can be realized with the MBE-grown InSb nanowires and the gate-to-dot capacitance extracted in the many-electron regimes is scaled linearly with the longitudinal dot size, demonstrating that the devices are of single InSb nanowire QDs even with a longitudinal size of ~700 nm. In the few-electron regime, the quantum levels in the QDs are resolved and the Landé g-factors extracted for the quantum levels from the magnetotransport measurements are found to be strongly level-dependent and fluctuated in a range of 18-48. A spin-orbit coupling strength is extracted from the magnetic field evolutions of a ground state and its neighboring excited state in an InSb nanowire QD and is on the order of ~300 μeV. Our results establish that the MBE-grown InSb nanowires are of high crystal quality and are promising for the use in constructing novel quantum devices, such as entangled spin qubits, one-dimensional Wigner crystals and topological quantum computing devices.

  11. Localized tip enhanced Raman spectroscopic study of impurity incorporated single GaN nanowire in the sub-diffraction limit

    SciTech Connect

    Patsha, Avinash E-mail: dhara@igcar.gov.in; Dhara, Sandip; Tyagi, A. K.

    2015-09-21

    The localized effect of impurities in single GaN nanowires in the sub-diffraction limit is reported using the study of lattice vibrational modes in the evanescent field of Au nanoparticle assisted tip enhanced Raman spectroscopy (TERS). GaN nanowires with the O impurity and the Mg dopants were grown by the chemical vapor deposition technique in the catalyst assisted vapor-liquid-solid process. Symmetry allowed Raman modes of wurtzite GaN are observed for undoped and doped nanowires. Unusually very strong intensity of the non-zone center zone boundary mode is observed for the TERS studies of both the undoped and the Mg doped GaN single nanowires. Surface optical mode of A{sub 1} symmetry is also observed for both the undoped and the Mg doped GaN samples. A strong coupling of longitudinal optical (LO) phonons with free electrons, however, is reported only in the O rich single nanowires with the asymmetric A{sub 1}(LO) mode. Study of the local vibration mode shows the presence of Mg as dopant in the single GaN nanowires.

  12. Void-assisted plasticity in Ag nanowires with a single twin structure

    NASA Astrophysics Data System (ADS)

    Zheng, He; Wang, Jiangwei; Huang, Jian Yu; Wang, Jianbo; Mao, Scott X.

    2014-07-01

    By employing the in situ transmission electron microscopy (TEM) technique, tensile deformation behaviors of a silver nanowire (NW) with a single twin structure were studied. Our observations revealed that the initial stage of plastic deformation was dominated by surface-mediated partial dislocation activities. Strikingly, the void formation and growth were shown to govern the later stage of plasticity, leading to the ductile type of fracture in NWs. Possible void nucleation and growth mechanisms were discussed. Additionally, TEM images show the transformation from bi-crystal to polycrystal in the fracture area, likely due to the void activity. Our results have implications in the assembly of functional structures applying nano-building blocks.By employing the in situ transmission electron microscopy (TEM) technique, tensile deformation behaviors of a silver nanowire (NW) with a single twin structure were studied. Our observations revealed that the initial stage of plastic deformation was dominated by surface-mediated partial dislocation activities. Strikingly, the void formation and growth were shown to govern the later stage of plasticity, leading to the ductile type of fracture in NWs. Possible void nucleation and growth mechanisms were discussed. Additionally, TEM images show the transformation from bi-crystal to polycrystal in the fracture area, likely due to the void activity. Our results have implications in the assembly of functional structures applying nano-building blocks. Electronic supplementary information (ESI) available: Detailed nanowire diameter information and supplementary movies. See DOI: 10.1039/c3nr04731h

  13. Broadband Phase-Sensitive Single InP Nanowire Photoconductive Terahertz Detectors.

    PubMed

    Peng, Kun; Parkinson, Patrick; Boland, Jessica L; Gao, Qian; Wenas, Yesaya C; Davies, Christopher L; Li, Ziyuan; Fu, Lan; Johnston, Michael B; Tan, Hark H; Jagadish, Chennupati

    2016-08-10

    Terahertz time-domain spectroscopy (THz-TDS) has emerged as a powerful tool for materials characterization and imaging. A trend toward size reduction, higher component integration, and performance improvement for advanced THz-TDS systems is of increasing interest. The use of single semiconducting nanowires for terahertz (THz) detection is a nascent field that has great potential to realize future highly integrated THz systems. In order to develop such components, optimized material optoelectronic properties and careful device design are necessary. Here, we present antenna-optimized photoconductive detectors based on single InP nanowires with superior properties of high carrier mobility (∼1260 cm(2) V(-1) s(-1)) and low dark current (∼10 pA), which exhibit excellent sensitivity and broadband performance. We demonstrate that these nanowire THz detectors can provide high quality time-domain spectra for materials characterization in a THz-TDS system, a critical step toward future application in advanced THz-TDS system with high spectral and spatial resolution.

  14. Alignment, rotation, and spinning of single plasmonic nanoparticles and nanowires using polarization dependent optical forces.

    PubMed

    Tong, Lianming; Miljković, Vladimir D; Käll, Mikael

    2010-01-01

    We demonstrate optical alignment and rotation of individual plasmonic nanostructures with lengths from tens of nanometers to several micrometers using a single beam of linearly polarized near-infrared laser light. Silver nanorods and dimers of gold nanoparticles align parallel to the laser polarization because of the high long-axis dipole polarizability. Silver nanowires, in contrast, spontaneously turn perpendicular to the incident polarization and predominantly attach at the wire ends, in agreement with electrodynamics simulations. Wires, rods, and dimers all rotate if the incident polarization is turned. In the case of nanowires, we demonstrate spinning at an angular frequency of approximately 1 Hz due to transfer of spin angular momentum from circularly polarized light. PMID:20030391

  15. Antibacterial activity of single crystalline silver-doped anatase TiO2 nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangyu; Li, Meng; He, Xiaojing; Hang, Ruiqiang; Huang, Xiaobo; Wang, Yueyue; Yao, Xiaohong; Tang, Bin

    2016-05-01

    Well-ordered, one-dimensional silver-doped anatase TiO2 nanowire (AgNW) arrays have been prepared through a hydrothermal growth process on the sputtering-deposited AgTi layers. Electron microscope analyses reveal that the as-synthesized AgNW arrays exhibit a single crystalline phase with highly uniform morphologies, diameters ranging from 85 to 95 nm, and lengths of about 11 μm. Silver is found to be doped into TiO2 nanowire evenly and mainly exists in the zerovalent state. The AgNW arrays show excellent efficient antibacterial activity against Escherichia coli (E. coli), and all of the bacteria can be killed within 1 h. Additionally, the AgNW arrays can still kill E. coli after immersion for 60 days, suggesting the long-term antibacterial property. The technique reported here is environmental friendly for formation of silver-containing nanostructure without using any toxic organic solvents.

  16. An organic-inorganic broadband photodetector based on a single polyaniline nanowire doped with quantum dots.

    PubMed

    Yang, Xianguang; Liu, Yong; Lei, Hongxiang; Li, Baojun

    2016-08-25

    The capability to detect light over a broad waveband is highly important for practical optoelectronic applications and has been achieved with photodetectors of one-dimensional inorganic nanomaterials such as Si, ZnO, and GaN. However, achieving high speed responsivity over an entire waveband within such a photodetector remains a challenge. Here we demonstrate a broadband photodetector using a single polyaniline nanowire doped with quantum dots that is highly responsive over a broadband from 350 to 700 nm. The high responsivity is due to the high density of trapping states at the enormous interfaces between polyaniline and quantum dots. The interface trapping can effectively reduce the recombination rate and enhance the efficiency for light detection. Furthermore, a tunable spectral range can be achieved by size-based spectral tuning of quantum dots. The use of organic-inorganic hybrid polyaniline nanowires in broadband photodetection may offer novel functionalities in optoelectronic devices and circuits. PMID:27417337

  17. An organic-inorganic broadband photodetector based on a single polyaniline nanowire doped with quantum dots.

    PubMed

    Yang, Xianguang; Liu, Yong; Lei, Hongxiang; Li, Baojun

    2016-08-25

    The capability to detect light over a broad waveband is highly important for practical optoelectronic applications and has been achieved with photodetectors of one-dimensional inorganic nanomaterials such as Si, ZnO, and GaN. However, achieving high speed responsivity over an entire waveband within such a photodetector remains a challenge. Here we demonstrate a broadband photodetector using a single polyaniline nanowire doped with quantum dots that is highly responsive over a broadband from 350 to 700 nm. The high responsivity is due to the high density of trapping states at the enormous interfaces between polyaniline and quantum dots. The interface trapping can effectively reduce the recombination rate and enhance the efficiency for light detection. Furthermore, a tunable spectral range can be achieved by size-based spectral tuning of quantum dots. The use of organic-inorganic hybrid polyaniline nanowires in broadband photodetection may offer novel functionalities in optoelectronic devices and circuits.

  18. Investigation into Photoconductivity in Single CNF/TiO2-Dye Core–Shell Nanowire Devices

    PubMed Central

    2010-01-01

    A vertically aligned carbon nanofiber array coated with anatase TiO2 (CNF/TiO2) is an attractive possible replacement for the sintered TiO2 nanoparticle network in the original dye-sensitized solar cell (DSSC) design due to the potential for improved charge transport and reduced charge recombination. Although the reported efficiency of 1.1% in these modified DSSC’s is encouraging, the limiting factors must be identified before a higher efficiency can be obtained. This work employs a single nanowire approach to investigate the charge transport in individual CNF/TiO2 core–shell nanowires with adsorbed N719 dye molecules in dark and under illumination. The results shed light on the role of charge traps and dye adsorption on the (photo) conductivity of nanocrystalline TiO2 CNF’s as related to dye-sensitized solar cell performance. PMID:20802786

  19. Experimental test of theories of the detection mechanism in a nanowire superconducting single photon detector.

    PubMed

    Renema, J J; Gaudio, R; Wang, Q; Zhou, Z; Gaggero, A; Mattioli, F; Leoni, R; Sahin, D; de Dood, M J A; Fiore, A; van Exter, M P

    2014-03-21

    We report an experimental test of the photodetection mechanism in a nanowire superconducting single photon detector. Detector tomography allows us to explore the 0.8-8 eV energy range via multiphoton excitations. High accuracy results enable a detailed comparison of the experimental data with theories for the mechanism of photon detection. We show that the temperature dependence of the efficiency of the superconducting single photon detector is determined not by the critical current but by the current associated with vortex unbinding. We find that both quasiparticle diffusion and vortices play a role in the detection event.

  20. Tunable plasmon modes in single silver nanowire optical antennas characterized by far-field microscope polarization spectroscopy.

    PubMed

    Fu, Ming; Qian, Lihua; Long, Hua; Wang, Kai; Lu, Peixiang; Rakovich, Yury P; Hetsch, Frederik; Susha, Andrei S; Rogach, Andrey L

    2014-08-01

    Performing far-field microscope polarization spectroscopy and finite element method simulations, we investigated experimentally and theoretically the surface plasmon modes in single Ag nanowire antennas. Our results show that the surface plasmon resonances in the single Ag nanowire antenna can be tuned from the dipole plasmon mode to a higher order plasmon mode, which would result in the emission with different intensities and polarization states, for the semiconductor quantum dots coupled to the nanowire antenna. The fluorescence polarization is changed with different polarized excitation of the 800 nm light beam, while it remains parallel to the Ag nanowire axis at the 400 nm excitation. The 800 nm incident light interacts nonresonantly with the dipole plasmon mode with the polarized excitation parallel to the Ag nanowire axis, while it excites a higher order plasmon mode with the perpendicular excitation. Under excitation of 400 nm, either the parallel or perpendicular excitation can only result in a dipole plasmon mode. In addition, we demonstrate that the single Ag nanowire antenna can work as an energy concentrator for enhancing the two-photon excited fluorescence of semiconductor quantum dots.

  1. Heterojunction metal-oxide-metal Au-Fe{sub 3}O{sub 4}-Au single nanowire device for spintronics

    SciTech Connect

    Reddy, K. M. Punnoose, Alex; Hanna, Charles; Padture, Nitin P.

    2015-05-07

    In this report, we present the synthesis of heterojunction magnetite nanowires in alumina template and describe magnetic and electrical properties from a single nanowire device for spintronics applications. Heterojunction Au-Fe-Au nanowire arrays were electrodeposited in porous aluminum oxide templates, and an extensive and controlled heat treatment process converted Fe segment to nanocrystalline cubic magnetite phase with well-defined Au-Fe{sub 3}O{sub 4} interfaces as confirmed by the transmission electron microscopy. Magnetic measurements revealed Verwey transition shoulder around 120 K and a room temperature coercive field of 90 Oe. Current–voltage (I-V) characteristics of a single Au-Fe{sub 3}O{sub 4}-Au nanowire have exhibited Ohmic behavior. Anomalous positive magnetoresistance of about 0.5% is observed on a single nanowire, which is attributed to the high spin polarization in nanowire device with pure Fe{sub 3}O{sub 4} phase and nanocontact barrier. This work demonstrates the ability to preserve the pristine Fe{sub 3}O{sub 4} and well defined electrode contact metal (Au)–magnetite interface, which helps in attaining high spin polarized current.

  2. Current-phase relationship of granular NbN weak links, inferred from Josephson interferometer characteristics

    SciTech Connect

    Claassen, J.H.

    1982-05-01

    Small-area dc superconducting quantum interference devices (SQUID's) were made using ultra-short variable-thickness microbridges of NbN. The bridges had an effective length of approx.500 A and a width of approx.1.5 ..mu..m. Analysis of the response to magnetic flux permits interferences to be drawn about the current-phase relationship (CPR) of the bridges. Contrary to predictions of Ginzburg--Landau theory for microbridges of these dimensions, it is found that the CPR is single valued and probably close to ideal (sinusoidal) over a large temperature range (>2.5 K). The discrepancy with theory may be due to the granular nature of the NbN films.

  3. Reversible Sodium Ion Insertion in Single Crystalline Manganese Oxide Nanowires with Long Cycle Life

    SciTech Connect

    Cao, Yuliang; Xiao, Lifen; Wang, Wei; Choi, Daiwon; Nie, Zimin; Yu, Jianguo; Saraf, Laxmikant V.; Yang, Zhenguo; Liu, Jun

    2011-07-26

    Single crystalline Na4Mn9O18 nanowires were synthesized via pyrolysis of polyacrylate salt precursors prepared by in-situ polymerization of the metal salts and acrylate acid, followed by calcinations at an appropriate temperature to achieve good crystalline structure and uniform nanowire morphology with an average diameter of 50 nm. The Na4Mn9O18 nanowires have shown a high, reversible, and near theoretical sodium ion insertion capacity (128 mA h g-1 at 0.1C), excellent long cyclability (77% capacity retention for 1000 cycles at 0.5 C), along with good rate capability. Good capacity and charge-discharge stability are also observed for full cell experiments using a pyrolyzed carbon as the anode, therefore demonstrating the potential of these materials for sodium-ion batteries for large scale energy storage. Furthermore, this research shows that a good crystallinity and small particles are required to enhance the Na-ion diffusion and increase the stability of the electrode materials for long charge-discharge cycles.

  4. Chemical to electrical transduction mechanisms from single metal oxide nanowire measurements: response time constant analysis

    NASA Astrophysics Data System (ADS)

    Morante, J. R.

    2013-11-01

    Insight into chemical to electrical transduction mechanisms taking place at the surface of a single metal oxide nanowire is reported due to its outstanding importance for determining the characteristics of resistive solid state gas sensors. The surface chemical reaction kinetics is discussed considering competitiveness phenomena among different active sites and gas species on the nanowire taken as a metal oxide monocrystal at the nanoscale level. Experimental results for different representative gas molecules are shown to determine and understand sensor selectivity. The reported gas species are carbon monoxide and water vapour as general reference molecules, and ethanol and ammonia species as special references for gas-solid interactions, respectively, on acid and basic sites. Kinetic properties are proposed as particular signatures for each of the possible surface chemical reactions, allowing their identification and distinction. Likewise, features such as thermal inertia limitation and effects of the molecular and monoatomic absorbed oxygen are also estimated considering operation working modes based on nanowire self-heating. Furthermore, the applicability of a surface electrical field on a one-dimensional metal oxide nanostructure to enhance the surface ionization of the absorbed molecules is also reviewed as a new type of metal oxide based nanosensor for achieving improved selectivity.

  5. Optoelectronically probing the density of nanowire surface trap states to the single state limit

    SciTech Connect

    Dan, Yaping

    2015-02-02

    Surface trap states play a dominant role in the optoelectronic properties of nanoscale devices. Understanding the surface trap states allows us to properly engineer the device surfaces for better performance. But characterization of surface trap states at nanoscale has been a formidable challenge using the traditional capacitive techniques. Here, we demonstrate a simple but powerful optoelectronic method to probe the density of nanowire surface trap states to the single state limit. In this method, we choose to tune the quasi-Fermi level across the bandgap of a silicon nanowire photoconductor, allowing for capture and emission of photogenerated charge carriers by surface trap states. The experimental data show that the energy density of nanowire surface trap states is in a range from 10{sup 9 }cm{sup −2}/eV at deep levels to 10{sup 12 }cm{sup −2}/eV near the conduction band edge. This optoelectronic method allows us to conveniently probe trap states of ultra-scaled nano/quantum devices at extremely high precision.

  6. Nanostructures of the binary nitrides, BN, TiN, and NbN, prepared by the urea-route

    SciTech Connect

    Gomathi, A.; Rao, C.N.R. . E-mail: cnrrao@jncasr.ac.in

    2006-05-25

    By heating mixtures of H{sub 3}BO{sub 3}, TiCl{sub 4}, and NbCl{sub 5} with urea in 1:6 molar ratios in the 900-1000 deg. C range, nanoparticles of BN, TiN, and NbN have been obtained, respectively. The nanoparticles are crystalline and have been characterized by electron microscopy and other techniques. By carrying out the urea reaction over Au islands deposited on Si substrates, nanowires of TiN could be obtained.

  7. Growth and Physical Property Study of Single Nanowire (Diameter ~45 nm) of Half Doped Manganite

    DOE PAGESBeta

    Datta, Subarna; Chandra, Sayan; Samanta, Sudeshna; Das, K.; Srikanth, H.; Ghosh, Barnali

    2013-01-01

    We repormore » t here the growth and characterization of functional oxide nanowire of hole doped manganite of La 0.5 Sr 0.5 MnO 3 (LSMO). We also report four-probe electrical resistance measurement of a single nanowire of LSMO (diameter ~45 nm) using focused ion beam (FIB) fabricated electrodes. The wires are fabricated by hydrothermal method using autoclave at a temperature of 270 °C. The elemental analysis and physical property like electrical resistivity are studied at an individual nanowire level. The quantitative determination of Mn valency and elemental mapping of constituent elements are done by using Electron Energy Loss Spectroscopy (EELS) in the Transmission Electron Microscopy (TEM) mode. We address the important issue of whether as a result of size reduction the nanowires can retain the desired composition, structure, and physical properties. The nanowires used are found to have a ferromagnetic transition ( T C ) at around 325 K which is very close to the bulk value of around 330 K found in single crystal of the same composition. It is confirmed that the functional behavior is likely to be retained even after size reduction of the nanowires to a diameter of 45 nm. The electrical resistivity shows insulating behavior within the measured temperature range which is similar to the bulk system.« less

  8. Single nanowire green InGaN/GaN light emitting diodes

    NASA Astrophysics Data System (ADS)

    Zhang, Guogang; Li, Ziyuan; Yuan, Xiaoming; Wang, Fan; Fu, Lan; Zhuang, Zhe; Ren, Fang-Fang; Liu, Bin; Zhang, Rong; Tan, Hark Hoe; Jagadish, Chennupati

    2016-10-01

    Single nanowire (NW) green InGaN/GaN light-emitting diodes (LEDs) were fabricated by top-down etching technology. The electroluminescence (EL) peak wavelength remains approximately constant with an increasing injection current in contrast to a standard planar LED, which suggests that the quantum-confined Stark effect is significantly reduced in the single NW device. The strain relaxation mechanism is studied in the single NW LED using Raman scattering analysis. As compared to its planar counterpart, the EL peak of the NW LED shows a redshift, due to electric field redistribution as a result of changes in the cavity mode pattern after metallization. Our method has important implication for single NW optoelectronic device applications.

  9. Nanojunctions in conducting polypyrrole single nanowire made by focused electron beam: Charge transport characteristics

    SciTech Connect

    Koo, Min Ho; Hong, Young Ki; Park, Dong Hyuk; Jo, Seong Gi; Joo, Jinsoo

    2011-07-15

    A focused electron (E)-beam with various doses was irradiated on the intended positions of conducting polypyrrole (PPy) single nanowire (NW) to fabricate nanojunctions. The current-voltage characteristics and their temperature dependence of the PPy single NW with nanojunctions were measured and analyzed. By increasing the E-beam dose and the number of nanojunctions, the current level of the single NW was dramatically decreased, and the conductance gap became more severe as the temperature decreased. The charge transport behavior varied from three-dimensional variable range hopping to fluctuation induced tunneling models, depending on the dose of focused E-beam. From micro-Raman spectra, the focused E-beam irradiation induced the de-doped states and conformational modification of polymer chains in the nanojunctions. The results suggest that the nanojunctions made by focused E-beam acted as a quasi-potential barrier for charge conduction in the conducting PPy single NW.

  10. Single-Electron Stochastic Resonance Using Si Nanowire Transistors

    NASA Astrophysics Data System (ADS)

    Nishiguchi, Katsuhiko; Fujiwara, Akira

    2011-06-01

    We demonstrate stochastic resonance (SR) with single electrons (SEs) using nanoscale metal-oxide-semiconductor field-effect transistors (MOSFETs). Input signal applied to a MOSFET modulates SE transport in an average manner based on nonlinear characteristics. On the other hand, an individual SE goes through the MOSFET in a completely random manner, which corresponds to shot noise. SEs transferred to a storage node are counted precisely by the other MOSFET and used as an output signal. The correlation between the input and output signals is improved by taking advantage of extrinsic noise as well as the intrinsic shot noise composed of SEs. It is confirmed that the shot-noise-assisted SR allows fast operation with a simple system. Pattern perception utilizing SR is also demonstrated.

  11. Counting rate enhancements in superconducting nanowire single-photon detectors with improved readout circuits.

    PubMed

    Zhao, Qingyuan; Jia, Tao; Gu, Min; Wan, Chao; Zhang, Labao; Xu, Weiwei; Kang, Lin; Chen, Jian; Wu, Peiheng

    2014-04-01

    Counting rates of superconducting nanowire single-photon detectors are usually estimated at hundreds of MHz by their kinetic-inductive reset time. This maximum is also limited by capacitor coupling effects in conventional readout circuits. In this Letter, we design and demonstrate an improved readout circuit that reduces the reset time and removes circuit limits. The counting rate at the 3 dB compression point is increased by four times for a large active area detector. We also discuss nonlinear dependences of the counting rate on the incident continuous-wave optical power and give a numerical model to explain our observations.

  12. Single CuO nanowires decorated with size-selected Pd nanoparticles for CO sensing in humid atmosphere.

    PubMed

    Steinhauer, Stephan; Singh, Vidyadhar; Cassidy, Cathal; Gspan, Christian; Grogger, Werner; Sowwan, Mukhles; Köck, Anton

    2015-05-01

    We report on conductometric gas sensors based on single CuO nanowires and compare the carbon monoxide (CO) sensing properties of pristine as well as Pd nanoparticle decorated devices in humid atmosphere. Magnetron sputter inert gas aggregation combined with a quadrupole mass filter for cluster size selection was used for single-step Pd nanoparticle deposition in the soft landing regime. Uniformly dispersed, crystalline Pd nanoparticles with size-selected diameters around 5 nm were deposited on single CuO nanowire devices in a four point configuration. During gas sensing experiments in humid synthetic air, significantly enhanced CO response for CuO nanowires decorated with Pd nanoparticles was observed, which validates that magnetron sputter gas aggregation is very well suited for the realization of nanoparticle-functionalized sensors with improved performance. PMID:25854640

  13. Thermoelectric power factor of ternary single-crystalline Sb2Te3- and Bi2Te3-based nanowires.

    PubMed

    Bäßler, Svenja; Böhnert, Tim; Gooth, Johannes; Schumacher, Christian; Pippel, Eckhard; Nielsch, Kornelius

    2013-12-13

    Nanowires of bismuth antimony telluride and bismuth telluride selenide (Bi15Sb29Te56 and Bi38Te55Se7) were grown by template-based pulsed electrodeposition. The composition and the crystallinity of the nanowires were determined by high-resolution transmission electron microscopy. The thermoelectric properties (Seebeck coefficient and electrical conductivity) of single p- and n-type nanowires, with diameter 80 nm and 200 nm, respectively, were determined as a function of temperature before and during heating in a helium atmosphere up to 300 K along the growth direction of the nanowires. After additional annealing in a tellurium atmosphere at 525 K, significantly enhanced transport properties are observed. Bulk-like power factors are achieved. In Bi38Te55Se7 nanowires, the Seebeck coefficients increase to -115 μV K(-1) and the thermoelectric power factors increase to 2820 μW K(-2) m(-1) at room temperature. In Bi15Sb29Te56 nanowires, Seebeck coefficients of up to S = +156 μV K(-1) and power factors of up to 1750 μW K(-2) m(-1) are obtained at room temperature.

  14. Analysis of contact interfaces for single GaN nanowire devices.

    PubMed

    Herrero, Andrew M; Blanchard, Paul T; Bertness, Kris A

    2013-11-15

    Single GaN nanowire (NW) devices fabricated on SiO2 can exhibit a strong degradation after annealing due to the occurrence of void formation at the contact/SiO2 interface. This void formation can cause cracking and delamination of the metal film, which can increase the resistance or lead to a complete failure of the NW device. In order to address issues associated with void formation, a technique was developed that removes Ni/Au contact metal films from the substrates to allow for the examination and characterization of the contact/substrate and contact/NW interfaces of single GaN NW devices. This procedure determines the degree of adhesion of the contact films to the substrate and NWs and allows for the characterization of the morphology and composition of the contact interface with the substrate and nanowires. This technique is also useful for assessing the amount of residual contamination that remains from the NW suspension and from photolithographic processes on the NW-SiO2 surface prior to metal deposition. The detailed steps of this procedure are presented for the removal of annealed Ni/Au contacts to Mg-doped GaN NWs on a SiO2 substrate.

  15. Highly efficient electrochemical responses on single crystalline ruthenium-vanadium mixed metal oxide nanowires.

    PubMed

    Chun, Sung Hee; Choi, Hyun-A; Kang, Minkyung; Koh, Moonjee; Lee, Nam-Suk; Lee, Sang Cheol; Lee, Minyung; Lee, Youngmi; Lee, Chongmok; Kim, Myung Hwa

    2013-09-11

    Highly efficient single crystalline ruthenium-vanadium mixed metal oxide (Ru1-xVxO2, 0≤x≤1) nanowires were prepared on a SiO2 substrate and a commercial Au microelectrode for the first time through a vapor-phase transport process by adjusting the mixing ratios of RuO2 and VO2 precursors. Single crystalline Ru1-xVxO2 nanowires show homogeneous solid-solution characteristics as well as the distinct feature of having remarkably narrow dimensional distributions. The electrochemical observations of a Ru1-xVxO2 (x=0.28 and 0.66)-decorated Au microelectrode using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) demonstrate favorable charge-transfer kinetics of [Fe(CN)6]3-/4- and Ru(NH3)6(3+/2+) couples compared to that of a bare Au microelectrode. The catalytic activity of Ru1-xVxO2 for oxygen and H2O2 reduction at neutral pH increases as the fraction of vanadium increases within our experimental conditions, which might be useful in the area of biofuel cells and biosensors.

  16. Berry's phase manifestation in Aharonov-Bohm oscillations in single Bi nanowires

    NASA Astrophysics Data System (ADS)

    Gitsu, D. V.; Huber, T. E.; Konopko, L. A.; Nikolaeva, A. A.

    2009-02-01

    Here we report on Aharonov-Bohm oscillations of magnetoresistance (MR) of the single Bi nanowires with diameter d<80 nm. The samples were prepared by Ulitovsky technique and represented cylindrical single crystals with the 1011 orientation along the wire axis. Due to semimetal-to-semiconductor transformation and big density of surface states with strong spin-orbit interactions Bi nanowire should effectively become a conducting tube. The equidistant oscillations of the MR have been observed in a wide range of magnetic fields up to 14 T at various temperatures (1.5 K< T< 4.2 K) and angles θ (0< θ < 90°) of the sample orientation relative to the magnetic field. We have obtained longitudinal MR oscillations with periods ΔB1=Φ0/S and ΔB2=Φ0/2S, where Φ0=h/e is the flux quantum and S is the wire cross section. From B approx 8 T down to B=0 the extremums of Φ0/2S oscillations are shifted up to 3π at B=0 which is the manifestation of Berry phase shift due to carriers moving in inhomogeneous magnetic field. An interpretation of the MR oscillations in terms of a subband structure in the surface state band caused by quantum interference is presented.

  17. Enhanced non-volatile resistive switching in suspended single-crystalline ZnO nanowire with controllable multiple states

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Pang, Wei; Zhang, Qing; Chen, Yan; Chen, Xuejiao; Feng, Zhihong; Yang, Jianhua; Zhang, Daihua

    2016-08-01

    Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current–temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization.

  18. Enhanced non-volatile resistive switching in suspended single-crystalline ZnO nanowire with controllable multiple states

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Pang, Wei; Zhang, Qing; Chen, Yan; Chen, Xuejiao; Feng, Zhihong; Yang, Jianhua; Zhang, Daihua

    2016-08-01

    Resistive switching nanostructures are a promising candidate for next-generation non-volatile memories. In this report, we investigate the switching behaviors of single-crystalline ZnO nanowires suspended in air. They exhibit significantly higher current density, lower switching voltage, and more pronounced multiple conductance states compared to nanowires in direct contact with substrate. We attribute the effect to enhanced Joule heating efficiency, reduced surface scattering, and more significantly, the positive feedback established between the current density and local temperature in the suspended nanowires. The proposed mechanism has been quantitatively examined by finite element simulations. We have also demonstrated an innovative approach to initiating the current-temperature mutual enhancement through illumination by ultraviolet light, which further confirmed our hypothesis and enabled even greater enhancement. Our work provides further insight into the resistive switching mechanism of single-crystalline one-dimensional nanostructures, and suggests an effective means of performance enhancement and device optimization.

  19. Metastable Copper-Phthalocyanine Single-Crystal Nanowires and Their Use in Fabricating High-Performance Field-Effect Transistors

    SciTech Connect

    Xiao, Kai; Li, Rongjin; Tao, Jing; Payzant, E Andrew; Ivanov, Ilia N; Puretzky, Alexander A; Hu, Wenping; Geohegan, David B

    2009-01-01

    This paper describes a simple, vapor-phase route to the synthesis of metastable α-phase copper-phthalocyanine (CuPc) single-crystal nanowires through control of the growth temperature. The influence of the growth temperature on the crystal structures, morphology, and size of the CuPc nanostructures was explored by XRD, optical absorption and Transmission Electron Microscopy (TEM). α-CuPc nanowires were successfully incorporated as active semiconductors in field-effect transistors (FETs). Single nanowire devices exhibited the carrier mobilities and current on/off ratios as high as 0.4 cm2/Vs and > 104, respectively, rendering them useful for organic photovoltaic cells, organic light-emitting diodes, field-effect transistors, memories and gas sensors

  20. Study of the Electrochemical System of Antimony-Tellurium in Dimethyl Sulfoxide for Growth of Nanowire Arrays, and an Innovative Method for Single Nanowire Measurements

    NASA Astrophysics Data System (ADS)

    Kalisman, Philip Taubman

    There is a strong interest in thermoelectric materials for energy production and savings. The properties which are integral to thermoelectric performance are typically linked, typically changing one of these properties for the better will change another for the worse. The intertwined nature of these properties has limited bulk thermoelectrics to low efficiencies, which has curbed their use to only niche applications. There has been theoretical and experimental work which has shown that limiting these materials in one or more dimensions will result in deconvolution of properties. Nanowires of well established thermoelectrics should show impressively high performance. Tellurium is attractive in many fields, including thermoelectrics. Nanowires of tellurium have been grown, but with limited success and with out the ability to dope the tellurium. Working on previous work with other systems, tellurium was studied in dimethyl sulfoxide (DMSO). The electrochemical system of tellurium was found to be quite dierent from its aqueous analog, but through comprehensive cyclic voltammetric study, all events were identified and explained. The binary antimony-tellurium system was also studied, as doping of tellurium is integral for many applications. Cyclic voltammograms of this system were studied, and the insight from these studies was used to grow nanowire arrays. Arrays of tellurium were grown and analysis showed that by using DMSO, antimony doped tellurium nanowire arrays could be grown. Furthermore, analysis showed that the antimony doped tellurium interstitially, resulting in a n-type material. Measurements were also performed on arrays and individual wires. Arrays of 1.15% antimony showed ZT of 0.092, with the low ZT attributed to poor contact methods. Although contacting was an obstacle towards measuring whole arrays, single wire measurements were also performed. Single wire measurements were done by a novel method which allows for easy, reproducible measurements of wire

  1. Wafer-scale synthesis of single-crystal zigzag silicon nanowire arrays with controlled turning angles.

    PubMed

    Chen, Huan; Wang, Hui; Zhang, Xiao-Hong; Lee, Chun-Sing; Lee, Shuit-Tong

    2010-03-10

    Silicon nanowires (SiNWs) having curved structures may have unique advantages in device fabrication. However, no methods are available to prepare curved SiNWs controllably. In this work, we report the preparation of three types of single-crystal SiNWs with various turning angles via metal-assisted chemical etching using (111)-oriented silicon wafers near room temperature. The zigzag SiNWs are single crystals and can be p- or n-doped using corresponding Si wafer as substrate. The controlled growth direction is attributed to the preferred movement of Ag nanoparticles along 001 and other directions in Si wafer. Our results demonstrate that metal-assisted chemical etching may be a viable approach to fabricate SiNWs with desired turning angles by utilizing the various crystalline directions in a Si wafer.

  2. Epitaxially aligned cuprous oxide nanowires for all-oxide, single-wire solar cells.

    PubMed

    Brittman, Sarah; Yoo, Youngdong; Dasgupta, Neil P; Kim, Si-in; Kim, Bongsoo; Yang, Peidong

    2014-08-13

    As a p-type semiconducting oxide that can absorb visible light, cuprous oxide (Cu2O) is an attractive material for solar energy conversion. This work introduces a high-temperature, vapor-phase synthesis that produces faceted Cu2O nanowires that grow epitaxially along the surface of a lattice-matched, single-crystal MgO substrate. Individual wires were then fabricated into single-wire, all-oxide diodes and solar cells using low-temperature atomic layer deposition (ALD) of TiO2 and ZnO films to form the heterojunction. The performance of devices made from pristine Cu2O wires and chlorine-exposed Cu2O wires was investigated under one-sun and laser illumination. These faceted wires allow the fabrication of well-controlled heterojunctions that can be used to investigate the interfacial properties of all-oxide solar cells. PMID:25014113

  3. Single-crystalline δ-Ni2Si nanowires with excellent physical properties.

    PubMed

    Chiu, Wen-Li; Chiu, Chung-Hua; Chen, Jui-Yuan; Huang, Chun-Wei; Huang, Yu-Ting; Lu, Kuo-Chang; Hsin, Cheng-Lun; Yeh, Ping-Hung; Wu, Wen-Wei

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  4. Single-crystalline δ-Ni2Si nanowires with excellent physical properties

    PubMed Central

    2013-01-01

    In this article, we report the synthesis of single-crystalline nickel silicide nanowires (NWs) via chemical vapor deposition method using NiCl2·6H2O as a single-source precursor. Various morphologies of δ-Ni2Si NWs were successfully acquired by controlling the growth conditions. The growth mechanism of the δ-Ni2Si NWs was thoroughly discussed and identified with microscopy studies. Field emission measurements show a low turn-on field (4.12 V/μm), and magnetic property measurements show a classic ferromagnetic characteristic, which demonstrates promising potential applications for field emitters, magnetic storage, and biological cell separation. PMID:23782805

  5. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire.

    PubMed

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  6. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire.

    PubMed

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication.

  7. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

    PubMed Central

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-01-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication. PMID:27609521

  8. Frequency-resolved optical gating measurement of ultrashort pulses by using single nanowire

    NASA Astrophysics Data System (ADS)

    Yu, Jiaxin; Liao, Feng; Gu, Fuxing; Zeng, Heping

    2016-09-01

    The use of ultrashort pulses for fundamental studies and applications has been increasing rapidly in the past decades. Along with the development of ultrashort lasers, exploring new pulse diagnositic approaches with higher signal-to-noise ratio have attracted great scientific and technological interests. In this work, we demonstrate a simple technique of ultrashort pulses characterization with a single semiconductor nanowire. By performing a frequency-resolved optical gating method with a ZnO nanowire coupled to tapered optical microfibers, the phase and amplitude of a pulse series are extracted. The generated signals from the transverse frequency conversion process can be spatially distinguished from the input, so the signal-to-noise ratio is improved and permits lower energy pulses to be identified. Besides, since the nanometer scale of the nonlinear medium provides relaxed phase-matching constraints, a measurement of 300-nm-wide supercontinuum pulses is achieved. This system is highly compatible with standard optical fiber systems, and shows a great potential for applications such as on-chip optical communication.

  9. Ternary Synaptic Plasticity Arising from Memdiode Behavior of TiOx Single Nanowire

    NASA Astrophysics Data System (ADS)

    Hong, Deshun; Chen, Yuansha; Sun, Jirong; Shen, Baogen; Group 3 of Magnetism Laboratory, Beijing National Laboratory for Condensed Matter Physics Team

    Electric field-induced resistive switching (RS) effect has been widely explored as a novel nonvolatile memory over the past few years. Recently, the RS behavior with continuous transition has received considerable attention for its promising prospect in neuromorphic simulation. Here, the switching characteristics of a planar-structured TiOx single nanowire device were systematically investigated. It exhibited a strong electrical history-dependent rectifying behavior that was defined as a ''memdiode''. We further demonstrated that a ternary synaptic plasticity could be realized in such a TiOx nanowire device, characterized by the resistance and photocurrent responses. For a given state of the memdiode, a conjugated memristive characteristic and a distinct photocurrent can be simulaneously obtained, resulting in a synchronous implementation of various Hebbian plasticities with the same temporal order of spikes. These intriguing properties of TiOx memdiode provide a feasible way toward the designing of multifunctional electronic synapses as well as programmable artificial neural network This work has been partially supported by the National Basic Research of China (2013CB921700), the ``Strategic Priority Research Program (B)'' of the Chinese Academy of Sciences (XDB07030200) and the National Natural Science Foundation of China (11374339).

  10. Cathodoluminescence of stacking fault bound excitons for local probing of the exciton diffusion length in single GaN nanowires

    SciTech Connect

    Nogues, Gilles Den Hertog, Martien; Auzelle, Thomas; Gayral, Bruno; Daudin, Bruno

    2014-03-10

    We perform correlated studies of individual GaN nanowires in scanning electron microscopy combined to low temperature cathodoluminescence, microphotoluminescence, and scanning transmission electron microscopy. We show that some nanowires exhibit well localized regions emitting light at the energy of a stacking fault bound exciton (3.42 eV) and are able to observe the presence of a single stacking fault in these regions. Precise measurements of the cathodoluminescence signal in the vicinity of the stacking fault give access to the exciton diffusion length near this location.

  11. Probing alloy composition gradient and nanometer-scale carrier localization in single AlGaN nanowires by nanocathodoluminescence

    NASA Astrophysics Data System (ADS)

    Pierret, A.; Bougerol, C.; Gayral, B.; Kociak, M.; Daudin, B.

    2013-08-01

    The optical properties of single AlGaN nanowires grown by plasma-assisted molecular beam epitaxy have been studied by nanocathodoluminescence. Optical emission was found to be position-dependent and to occur in a wide wavelength range, a feature which has been assigned to a composition gradient along the nanowire growth axis, superimposed on local composition fluctuations at the nanometer scale. This behavior is associated with the growth mode of such AlGaN nanowires, which is governed by kinetics, leading to the successive formation of (i) a zone with strong local composition fluctuations followed by (ii) a zone with a marked composition gradient and, eventually, (iii) a zone corresponding to a steady state regime and the formation of a homogeneous alloy.

  12. Probing alloy composition gradient and nanometer-scale carrier localization in single AlGaN nanowires by nanocathodoluminescence.

    PubMed

    Pierret, A; Bougerol, C; Gayral, B; Kociak, M; Daudin, B

    2013-08-01

    The optical properties of single AlGaN nanowires grown by plasma-assisted molecular beam epitaxy have been studied by nanocathodoluminescence. Optical emission was found to be position-dependent and to occur in a wide wavelength range, a feature which has been assigned to a composition gradient along the nanowire growth axis, superimposed on local composition fluctuations at the nanometer scale. This behavior is associated with the growth mode of such AlGaN nanowires, which is governed by kinetics, leading to the successive formation of (i) a zone with strong local composition fluctuations followed by (ii) a zone with a marked composition gradient and, eventually, (iii) a zone corresponding to a steady state regime and the formation of a homogeneous alloy.

  13. Single nanowire electrode electrochemistry of silicon anode by in situ atomic force microscopy: solid electrolyte interphase growth and mechanical properties.

    PubMed

    Liu, Xing-Rui; Deng, Xin; Liu, Ran-Ran; Yan, Hui-Juan; Guo, Yu-Guo; Wang, Dong; Wan, Li-Jun

    2014-11-26

    Silicon nanowires (SiNWs) have attracted great attention as promising anode materials for lithium ion batteries (LIBs) on account of their high capacity and improved cyclability compared with bulk silicon. The interface behavior, especially the solid electrolyte interphase (SEI), plays a significant role in the performance and stability of the electrodes. We report herein an in situ single nanowire atomic force microscopy (AFM) method to investigate the interface electrochemistry of silicon nanowire (SiNW) electrode. The morphology and Young's modulus of the individual SiNW anode surface during the SEI growth were quantitatively tracked. Three distinct stages of the SEI formation on the SiNW anode were observed. On the basis of the potential-dependent morphology and Young's modulus evolution of SEI, a mixture-packing structural model was proposed for the SEI film on SiNW anode.

  14. Photoelectron imaging spectroscopy of niobium mononitride anion NbN(.).

    PubMed

    Berkdemir, Cuneyt; Gunaratne, K Don Dasitha; Cheng, Shi-Bo; Castleman, A W

    2016-07-21

    In this gas-phase photoelectron spectroscopy study, we present the electron binding energy spectrum and photoelectron angular distributions of NbN(-) by the velocity-map imaging technique. The electron binding energy of NbN(-) is measured to be 1.42 ± 0.02 eV from the X band maximum which defines the 0-0 transition between ground states of anion and neutral. Theoretical binding energies which are the vertical and adiabatic detachment energies are computed by density functional theory to compare them with experiment. The ground state of NbN(-) is assigned to the (2)Δ3/2 state and then the electronic transitions originating from this state into X(3)ΔΩ (Ω = 1-3), a(1)Δ2, A(3)Σ1 (-), and b(1)Σ0 (+) states of NbN are reported to interpret the spectral features. As a prospective study for catalytic materials, spectral features of NbN(-) are compared with those of isovalent ZrO(-) and Pd(-). PMID:27448881

  15. Design of a polarization-insensitive superconducting nanowire single photon detector with high detection efficiency

    NASA Astrophysics Data System (ADS)

    Zheng, Fan; Xu, Ruiying; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-03-01

    Superconducting nanowire single photon detectors (SNSPDs) deliver superior performance over their competitors in the near-infrared regime. However, these detectors have an intrinsic polarization dependence on the incident wave because of their one-dimensional meander structure. In this paper, we propose an approach to eliminate the polarization sensitivity of SNSPDs by using near-field optics to increase the absorption of SNSPDs under transverse magnetic (TM) illumination. In addition, an optical cavity is added to our SNSPD to obtain nearly perfect absorption of the incident wave. Numerical simulations show that the maximum absorption of a designed SNSPD can reach 96% at 1550 nm, and indicate that the absorption difference between transverse electric (TE) and TM polarization is less than 0.5% across a wavelength window of 300 nm. Our work provides the first demonstration of the possibility of designing a polarization-insensitive and highly efficient SNSPD without performing device symmetry improvements.

  16. Single micro/nanowire pyroelectric nanogenerators as self-powered temperature sensors.

    PubMed

    Yang, Ya; Zhou, Yusheng; Wu, Jyh Ming; Wang, Zhong Lin

    2012-09-25

    We demonstrated the first application of a pyroelectric nanogenerator as a self-powered sensor (or active sensor) for detecting a change in temperature. The device consists of a single lead zirconate titanate (PZT) micro/nanowire that is placed on a thin glass substrate and bonded at its two ends, and it is packaged by polydimethylsiloxane (PDMS). By using the device to touch a heat source, the output voltage linearly increases with an increasing rate of change in temperature. The response time and reset time of the fabricated sensor are about 0.9 and 3 s, respectively. The minimum detecting limit of the change in temperature is about 0.4 K at room temperature. The sensor can be used to detect the temperature of a finger tip. The electricity generated under a large change in temperature can light up a liquid crystal display (LCD).

  17. An ultra-fast superconducting Nb nanowire single-photon detector for soft x-rays

    SciTech Connect

    Inderbitzin, K.; Engel, A.; Schilling, A.; Il'in, K.; Siegel, M.

    2012-10-15

    Although superconducting nanowire single-photon detectors (SNSPDs) are well studied regarding the detection of infrared/optical photons and keV-molecules, no studies on continuous x-ray photon counting by thick-film detectors have been reported so far. We fabricated a 100 nm thick niobium x-ray SNSPD (an X-SNSPD) and studied its detection capability of photons with keV-energies in continuous mode. The detector is capable to detect photons even at reduced bias currents of 0.4%, which is in sharp contrast to optical thin-film SNSPDs. No dark counts were recorded in extended measurement periods. Strikingly, the signal amplitude distribution depends significantly on the photon energy spectrum.

  18. Fabrication of Fe nanowires on yittrium-stabilized zirconia single crystal substrates by thermal CVD methods

    SciTech Connect

    Kawahito, A.; Yanase, T.; Endo, T.; Nagahama, T.; Shimada, T.

    2015-05-07

    Magnetic nanowires (NWs) are promising as material for use in spintronics and as the precursor of permanent magnets because they have unique properties due to their high aspect ratio. The growth of magnetic Fe whiskers was reported in the 1960s, but the diameter was not on a nanoscale level and the growth mechanism was not fully elucidated. In the present paper, we report the almost vertical growth of Fe NWs on a single crystal yttrium-stabilized zirconia (Y{sub 0.15}Zr{sub 0.85}O{sub 2}) by a thermal CVD method. The NWs show a characteristic taper part on the bottom growing from a trigonal pyramidal nucleus. The taper angle and length can be controlled by changing the growth condition in two steps, which will lead to obtaining uniformly distributed thin Fe NWs for applications.

  19. Low temperature cathodoluminecence and electron beam induced current studies of single GaN nanowires

    NASA Astrophysics Data System (ADS)

    Oh, Eunsoon; Woo Lee, Byoung; Shim, So-Jeong; Choi, Heon-Jin; Hee Son, Byoung; Hwan Ahn, Yeong; Dang, Le Si

    2012-04-01

    Single crystalline GaN nanowires, with 100 nm typical diameters, were grown by chemical vapor deposition method, using Pt catalyst, and characterized by cathodoluminescence and electron beam induced current (EBIC) measurements at 5 K. The near band edge emission was found to be asymmetric and broad, with full width half maximum of around 150 meV, peaking at 3.55 eV, well above the GaN bulk band gap. This blueshift was ascribed to band filling effect resulting from unintentional n-type doping in the range 1019-1020 cm-3. Despite of this heavy doping, EBIC experiments showed that minority carriers can diffuse over 0.2 μm.

  20. Design of a polarization-insensitive superconducting nanowire single photon detector with high detection efficiency.

    PubMed

    Zheng, Fan; Xu, Ruiying; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-01-01

    Superconducting nanowire single photon detectors (SNSPDs) deliver superior performance over their competitors in the near-infrared regime. However, these detectors have an intrinsic polarization dependence on the incident wave because of their one-dimensional meander structure. In this paper, we propose an approach to eliminate the polarization sensitivity of SNSPDs by using near-field optics to increase the absorption of SNSPDs under transverse magnetic (TM) illumination. In addition, an optical cavity is added to our SNSPD to obtain nearly perfect absorption of the incident wave. Numerical simulations show that the maximum absorption of a designed SNSPD can reach 96% at 1550 nm, and indicate that the absorption difference between transverse electric (TE) and TM polarization is less than 0.5% across a wavelength window of 300 nm. Our work provides the first demonstration of the possibility of designing a polarization-insensitive and highly efficient SNSPD without performing device symmetry improvements. PMID:26948672

  1. Giant thermovoltage in single InAs nanowire field-effect transistors.

    PubMed

    Roddaro, Stefano; Ercolani, Daniele; Safeen, Mian Akif; Suomalainen, Soile; Rossella, Francesco; Giazotto, Francesco; Sorba, Lucia; Beltram, Fabio

    2013-08-14

    Millivolt range thermovoltage is demonstrated in single InAs nanowire based field effect transistors. Thanks to a buried heating scheme, we drive both a large thermal bias ΔT > 10 K and a strong field-effect modulation of electric conductance on the nanostructures. This allows the precise mapping of the evolution of the Seebeck coefficient S as a function of the gate-controlled conductivity σ between room temperature and 100 K. Based on these experimental data a novel estimate of the electron mobility is given. This value is compared with the result of standard field-effect based mobility estimates and discussed in relation to the effect of charge traps in the devices. PMID:23869467

  2. Free-space-coupled superconducting nanowire single-photon detectors for infrared optical communications.

    PubMed

    Bellei, Francesco; Cartwright, Alyssa P; McCaughan, Adam N; Dane, Andrew E; Najafi, Faraz; Zhao, Qingyuan; Berggren, Karl K

    2016-02-22

    This paper describes the construction of a cryostat and an optical system with a free-space coupling efficiency of 56.5% ± 3.4% to a superconducting nanowire single-photon detector (SNSPD) for infrared quantum communication and spectrum analysis. A 1K pot decreases the base temperature to T = 1.7 K from the 2.9 K reached by the cold head cooled by a pulse-tube cryocooler. The minimum spot size coupled to the detector chip was 6.6 ± 0.11 µm starting from a fiber source at wavelength, λ = 1.55 µm. We demonstrated photon counting on a detector with an 8 × 7.3 µm2 area. We measured a dark count rate of 95 ± 3.35 kcps and a system detection efficiency of 1.64% ± 0.13%. We explain the key steps that are required to improve further the coupling efficiency.

  3. Point decoration of silicon nanowires: an approach toward single-molecule electrical detection.

    PubMed

    Wang, Jindong; Shen, Fangxia; Wang, Zhenxing; He, Gen; Qin, Jinwen; Cheng, Nongyi; Yao, Maosheng; Li, Lidong; Guo, Xuefeng

    2014-05-12

    Probing interactions of biological systems at the molecular level is of great importance to fundamental biology, diagnosis, and drug discovery. A rational bioassay design of lithographically integrating individual point scattering sites into electrical circuits is capable of realizing real-time, label-free biodetection of influenza H1N1 viruses with single-molecule sensitivity and high selectivity by using silicon nanowires as local reporters in combination with microfluidics. This nanocircuit-based architecture is complementary to more conventional optical techniques, but has the advantages of no bleaching problems and no fluorescent labeling. These advantages offer a promising platform for exploring dynamics of stochastic processes in biological systems and gaining information from genomics to proteomics to improve accurate molecular and even point-of-care clinical diagnosis.

  4. Formation and Stabilization of Single-Crystalline Metastable AuGe Phases in Ge Nanowires

    SciTech Connect

    Sutter, E.; Sutter, P.

    2011-07-22

    We use in situ observations by variable temperature transmission electron microscopy on AuGe alloy drops at the tips of Ge nanowires (NWs) with systematically varying composition to demonstrate the controlled formation of metastable solid phases integrated in NWs. The process, which operates in the regime of vapor-liquid-solid growth, involves a size-dependent depression of the alloy liquidus at the nanoscale that leads to extremely Ge-rich AuGe melts at low temperatures. During slow cooling, these liquid AuGe alloy drops show pronounced departures from equilibrium, i.e., a frustrated phase separation of Ge into the adjacent solid NW, and ultimately crystallize as single-crystalline segments of metastable {gamma}-AuGe. Our findings demonstrate a general avenue for synthesizing NW heterostructures containing stable and metastable solid phases, applicable to a wide range of materials of which NWs form by the vapor-liquid-solid method.

  5. Design of a polarization-insensitive superconducting nanowire single photon detector with high detection efficiency

    PubMed Central

    Zheng, Fan; Xu, Ruiying; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-01-01

    Superconducting nanowire single photon detectors (SNSPDs) deliver superior performance over their competitors in the near-infrared regime. However, these detectors have an intrinsic polarization dependence on the incident wave because of their one-dimensional meander structure. In this paper, we propose an approach to eliminate the polarization sensitivity of SNSPDs by using near-field optics to increase the absorption of SNSPDs under transverse magnetic (TM) illumination. In addition, an optical cavity is added to our SNSPD to obtain nearly perfect absorption of the incident wave. Numerical simulations show that the maximum absorption of a designed SNSPD can reach 96% at 1550 nm, and indicate that the absorption difference between transverse electric (TE) and TM polarization is less than 0.5% across a wavelength window of 300 nm. Our work provides the first demonstration of the possibility of designing a polarization-insensitive and highly efficient SNSPD without performing device symmetry improvements. PMID:26948672

  6. Influence of electron–phonon interactions in single dopant nanowire transistors

    SciTech Connect

    Carrillo-Nuñez, H. Bescond, M. Cavassilas, N.; Dib, E.; Lannoo, M.

    2014-10-28

    Single dopant nanowire transistors can be viewed as the ultimate miniaturization of nano electronic devices. In this work, we theoretically investigate the influence of the electron-phonon coupling on their transport properties using a non-equilibrium Green's function approach in the self-consistent Born approximation. For an impurity located at the center of the wire we find that, at room temperature, acoustic phonons broaden the impurity level so that the bistability predicted in the ballistic regime is suppressed. Optical phonons are found to have a beneficial impact on carrier transport via a phonon-assisted tunneling effect. We discuss the position and temperature dependence of these effects, showing that such systems might be very promising for engineering of ultimate devices.

  7. Plasma enhanced multistate storage capability of single ZnO nanowire based memory

    SciTech Connect

    Lai, Yunfeng Xin, Pucong; Cheng, Shuying; Yu, Jinling; Zheng, Qiao

    2015-01-19

    Multiple-state storage (MSS) is common for resistive random access memory, but the effects of plasma treatment on the MSS and the switching properties have been scarcely investigated. We have demonstrated a stable four-state storage capability of single zinc oxide nanowire (ZnO NW) treated by argon plasma. The electrical switching is attributed to the electron trapping and detrapping from the oxygen vacancies (V{sub o}s). The MSS relates to the electrical-thermal induced distribution of the V{sub o}s which determines electron transport behavior to show different resistance states. Additionally, programming (set and reset) voltages decrease with plasma treatment due to the thickness modulation of the interface barrier.

  8. Excited state dynamics of single metal and semiconductor nanowires studied by transient absorption microscopy

    NASA Astrophysics Data System (ADS)

    Lo, Shun S.; Shi, Hong Y.; Major, Todd A.; Petchsang, Nattasamon; Huang, Libai; Kuno, Masaru K.; Hartland, Gregory V.

    2013-03-01

    Transient absorption microscopy (TAM) is a relatively new technique that allows the study of single nanostructures with sub-picosecond time resolution. Here, we present results for CdTe and Au Nanowires (NW). For the first material, we find an interesting power dependence of the excited dynamics, suggesting that a trap-filling mechanism is responsible for the observed behaviour. Additionally, acoustic phonons were observed, which were well described using continuum elastic models.[2] Carrier diffusion along these NWs are also reported. In the case of Au NWs, the propagation of surface plasmon polaritons was investigated. The results are in agreement with previous studies performed with fluorescence based techniques.[3,4] Unlike fluorescence techniques, multiple measurements on the same nanostructures are possible with TAM allowing one-to-one comparisons under different excitation polarizations and environments. NSF Award CHE-1110560 and CHE-0946447, Univ. of Notre Dame Strategic Research Initiative. L. Huang, DOE (DE-FC02-04ER15533)

  9. Limiting efficiency calculation of silicon single-nanowire solar cells with considering Auger recombination

    SciTech Connect

    Zhai, Xiongfei; Wu, Shaolong; Shang, Aixue; Li, Xiaofeng

    2015-02-09

    Single-nanowire solar cells (SNSCs) have attracted considerable attention due to their unique light-harvesting capability mediated by the optical antenna effect and the high photoconversion efficiency due to the orthogonalization of the carrier collection to the photon incidence. We present a detailed prediction of the light-conversion efficiency of Si SNSCs based on finite-element simulation and thermodynamic balance analysis, with especially focusing on the comparison between SNSCs and film systems. Carrier losses due to radiative and Auger recombinations are introduced in the analysis of the limiting efficiency, which show that the Auger recombination plays a key role in accurately predicting the efficiency of Si SNSCs, otherwise, the device performance would be strongly overestimated. The study paves a more realistic way to evaluate the nanostructured solar cells based on indirect-band photoactive materials.

  10. Superconducting nanowire single-photon detectors with non-periodic dielectric multilayers

    PubMed Central

    Yamashita, Taro; Waki, Kentaro; Miki, Shigehito; Kirkwood, Robert A.; Hadfield, Robert H.; Terai, Hirotaka

    2016-01-01

    We present superconducting nanowire single-photon detectors (SSPDs) on non-periodic dielectric multilayers, which enable us to design a variety of wavelength dependences of optical absorptance by optimizing the dielectric multilayer. By adopting a robust simulation to optimize the dielectric multilayer, we designed three types of SSPDs with target wavelengths of 500 nm, 800 nm, and telecom range respectively. We fabricated SSPDs based on the optimized designs for 500 and 800 nm, and evaluated the system detection efficiency at various wavelengths. The results obtained confirm that the designed SSPDs with non-periodic dielectric multilayers worked well. This versatile device structure can be effective for multidisciplinary applications in fields such as the life sciences and remote sensing that require high efficiency over a precise spectral range and strong signal rejection at other wavelengths. PMID:27775712

  11. Vertical Single-Crystalline Organic Nanowires on Graphene: Solution-Phase Epitaxy and Optical Microcavities.

    PubMed

    Zheng, Jian-Yao; Xu, Hongjun; Wang, Jing Jing; Winters, Sinéad; Motta, Carlo; Karademir, Ertuğrul; Zhu, Weigang; Varrla, Eswaraiah; Duesberg, Georg S; Sanvito, Stefano; Hu, Wenping; Donegan, John F

    2016-08-10

    Vertically aligned nanowires (NWs) of single crystal semiconductors have attracted a great deal of interest in the past few years. They have strong potential to be used in device structures with high density and with intriguing optoelectronic properties. However, fabricating such nanowire structures using organic semiconducting materials remains technically challenging. Here we report a simple procedure for the synthesis of crystalline 9,10-bis(phenylethynyl) anthracene (BPEA) NWs on a graphene surface utilizing a solution-phase van der Waals (vdW) epitaxial strategy. The wires are found to grow preferentially in a vertical direction on the surface of graphene. Structural characterization and first-principles ab initio simulations were performed to investigate the epitaxial growth and the molecular orientation of the BPEA molecules on graphene was studied, revealing the role of interactions at the graphene-BPEA interface in determining the molecular orientation. These free-standing NWs showed not only efficient optical waveguiding with low loss along the NW but also confinement of light between the two end facets of the NW forming a microcavity Fabry-Pérot resonator. From an analysis of the optical dispersion within such NW microcavities, we observed strong slowing of the waveguided light with a group velocity reduced to one-tenth the speed of light. Applications of the vertical single-crystalline organic NWs grown on graphene will benefit from a combination of the unique electronic properties and flexibility of graphene and the tunable optical and electronic properties of organic NWs. Therefore, these vertical organic NW arrays on graphene offer the potential for realizing future on-chip light sources. PMID:27438189

  12. Single trap dynamics in electrolyte-gated Si-nanowire field effect transistors

    SciTech Connect

    Pud, S.; Li, J.; Offenhäusser, A.; Vitusevich, S. A.; Gasparyan, F.; Petrychuk, M.

    2014-06-21

    Liquid-gated silicon nanowire (NW) field effect transistors (FETs) are fabricated and their transport and dynamic properties are investigated experimentally and theoretically. Random telegraph signal (RTS) fluctuations were registered in the nanolength channel FETs and used for the experimental and theoretical analysis of transport properties. The drain current and the carrier interaction processes with a single trap are analyzed using a quantum-mechanical evaluation of carrier distribution in the channel and also a classical evaluation. Both approaches are applied to treat the experimental data and to define an appropriate solution for describing the drain current behavior influenced by single trap resulting in RTS fluctuations in the Si NW FETs. It is shown that quantization and tunneling effects explain the behavior of the electron capture time on the single trap. Based on the experimental data, parameters of the single trap were determined. The trap is located at a distance of about 2 nm from the interface Si/SiO{sub 2} and has a repulsive character. The theory of dynamic processes in liquid-gated Si NW FET put forward here is in good agreement with experimental observations of transport in the structures and highlights the importance of quantization in carrier distribution for analyzing dynamic processes in the nanostructures.

  13. Simultaneous integration of different nanowires on single textured Si (100) substrates.

    PubMed

    Rieger, Torsten; Rosenbach, Daniel; Mussler, Gregor; Schäpers, Thomas; Grützmacher, Detlev; Lepsa, Mihail Ion

    2015-03-11

    By applying a texturing process to silicon substrates, we demonstrate the possibility to integrate III-V nanowires on (100) oriented silicon substrates. Nanowires are found to grow perpendicular to the {111}-oriented facets of pyramids formed by KOH etching. Having control of the substrate orientation relative to the incoming fluxes enables not only the growth of nanowires on selected facets of the pyramids but also studying the influence of the fluxes on the nanowire nucleation and growth. Making use of these findings, we show that nanowires with different dimensions can be grown on the same sample and, additionally, it is even possible to integrate nanowires of different semiconductor materials, for example, GaAs and InAs, on the very same sample.

  14. Clinical relevance of CHEK2 and NBN mutations in the macedonian population

    PubMed Central

    Kostovska, I Maleva; Jakimovska, M; Kubelka-Sabit, K; Karadjozov, M; Arsovski, A; Stojanovska, L; Plaseska-Karanfilska, D

    2015-01-01

    Clinical importance of the most common CHEK2 (IVS2+1 G>A, 1100delC, I157T and del5395) and NBN (R215W and 657del5) gene mutations for breast cancer development in Macedonian breast cancer patients is unknown. We performed a case-control study including 300 Macedonian breast cancer patients and 283 Macedonian healthy controls. Genotyping was done using a fast and highly accurate single-nucleotide primer extension method for the detection of five mutations in a single reaction. The detection of the del5395 was performed using an allele-specific duplex polymerase chain reaction (PCR) assay. We have found that mutations were more frequent in breast cancer patients (n = 13, 4.3%) than in controls (n = 5, 1.8%), although without statistical significance. Twelve patients were heterozygous for one of the analyzed mutations, while one patient had two mutations (NBN R215W and CHEK2 I157T). The most frequent variant was I157T, found in 10 patients and four controls (p = 0.176) and was found to be associated with familial breast cancer (p = 0.041). CHEK2 1100delC and NBN 657del5 were each found in one patient and not in the control group. CHEK2 IVS2+1G>A and del5395 were not found in our cohort. Frequencies of the studied mutations are low and they are not likely to represent alleles of clinical importance in the Macedonian population. PMID:26929905

  15. Low-frequency flicker noise in a MSM device made with single Si nanowire (diameter ≈ 50 nm)

    PubMed Central

    2013-01-01

    Low-frequency flicker noise has been measured in a metal-semiconductor-metal (MSM) device made from a single strand of a single crystalline Si nanowire (diameter approximately 50 nm). Measurement was done with an alternating current (ac) excitation for the noise measurement superimposed with direct current (dc) bias that can be controlled independently. The observed noise has a spectral power density ∝1/fα. Application of the superimposed dc bias (retaining the ac bias unchanged) with a value more than the Schottky barrier height at the junction leads to a large suppression of the noise amplitude along with a change of α from 2 to ≈ 1. The dc bias-dependent part of the noise has been interpreted as arising from the interface region. The residual dc bias-independent flicker noise is suggested to arise from the single strand of Si nanowire, which has the conventional 1/f spectral power density. PMID:23574820

  16. Single nanowire on graphene (SNOG) as an efficient, reproducible, and stable SERS-active platform

    NASA Astrophysics Data System (ADS)

    Kim, Hongki; Seol, Myeong-Lok; Lee, Dong-Il; Lee, Jiyoung; Kang, Il-Suk; Lee, Hyoban; Kang, Taejoon; Choi, Yang-Kyu; Kim, Bongsoo

    2016-04-01

    Developing a well-defined nanostructure that can provide strong, reproducible, and stable SERS signals is quite important for the practical application of surface-enhanced Raman scattering (SERS) sensors. We report here a novel single nanowire (NW) on graphene (SNOG) structure as an efficient, reproducible, and stable SERS-active platform. Au NWs having a well-defined single-crystal geometry on a monolayer graphene-coated metal film can form a well-defined, continuous nanogap structure that provides extremely reproducible and stable SERS signals. The in-NW reproducibility was verified by 2-dimensional Raman mapping, and the NW-to-NW reproducibility was verified by the cumulative curves of 32 SERS spectra. The simulation also indicated that a highly regular, line-shaped hot spot formed between the Au NW and graphene. Furthermore, SNOG platforms showed improved photostability and long-term oxidation immunity. We anticipate that SNOG platforms will be appropriate for practical biological and chemical sensor applications that demand reproducible, stable, and strong signal production.Developing a well-defined nanostructure that can provide strong, reproducible, and stable SERS signals is quite important for the practical application of surface-enhanced Raman scattering (SERS) sensors. We report here a novel single nanowire (NW) on graphene (SNOG) structure as an efficient, reproducible, and stable SERS-active platform. Au NWs having a well-defined single-crystal geometry on a monolayer graphene-coated metal film can form a well-defined, continuous nanogap structure that provides extremely reproducible and stable SERS signals. The in-NW reproducibility was verified by 2-dimensional Raman mapping, and the NW-to-NW reproducibility was verified by the cumulative curves of 32 SERS spectra. The simulation also indicated that a highly regular, line-shaped hot spot formed between the Au NW and graphene. Furthermore, SNOG platforms showed improved photostability and long

  17. Composition-graded nanowire solar cells fabricated in a single process for spectrum-splitting photovoltaic systems.

    PubMed

    Caselli, Derek; Liu, Zhicheng; Shelhammer, David; Ning, Cun-Zheng

    2014-10-01

    Nanomaterials such as semiconductor nanowires have unique features that could enable novel optoelectronic applications such as novel solar cells. This paper aims to demonstrate one such recently proposed concept: Monolithically Integrated Laterally Arrayed Multiple Band gap (MILAMB) solar cells for spectrum-splitting photovoltaic systems. Two cells with different band gaps were fabricated simultaneously in the same process on a single substrate using spatially composition-graded CdSSe alloy nanowires grown by the Dual-Gradient Method in a chemical vapor deposition system. CdSSe nanowire ensemble devices tested under 1 sun AM1.5G illumination achieved open-circuit voltages up to 307 and 173 mV and short-circuit current densities as high as 0.091 and 0.974 mA/cm(2) for the CdS- and CdSe-rich cells, respectively. The open-circuit voltages were roughly three times those of similar CdSSe film cells fabricated for comparison due to the superior optical quality of the nanowires. I-V measurements were also performed using optical filters to simulate spectrum-splitting. The open-circuit voltages and fill factors of the CdS-rich subcells were uniformly larger than the corresponding CdSe-rich cells for similar photon flux, as expected. This suggests that if all wires can be contacted, the wide-gap cell is expected to have greater output power than the narrow-gap cell, which is the key to achieving high efficiencies with spectrum-splitting. This paper thus provides the first proof-of-concept demonstration of simultaneous fabrication of MILAMB solar cells. This approach to solar cell fabrication using single-crystal nanowires for spectrum-splitting photovoltaics could provide a future low-cost high-efficiency alternative to the conventional high-cost high-efficiency tandem cells.

  18. Spatiotemporal Imaging of the Acoustic Field Emitted by a Single Copper Nanowire

    NASA Astrophysics Data System (ADS)

    Jean, Cyril; Belliard, Laurent; Cornelius, Thomas W.; Thomas, Olivier; Pennec, Yan; Cassinelli, Marco; Toimil-Molares, Maria Eugenia; Perrin, Bernard

    2016-10-01

    The monochromatic and geometrically anisotropic acoustic field generated by 400 nm and 120 nm diameter copper nanowires simply dropped on a 10 $\\mu$m silicon membrane is investigated in transmission using three-dimensional time-resolved femtosecond pump-probe experiments. Two pump-probe time-resolved experiments are carried out at the same time on both side of the silicon substrate. In reflection, the first radial breathing mode of the nanowire is excited and detected. In transmission, the longitudinal and shear waves are observed. The longitudinal signal is followed by a monochromatic component associated with the relaxation of the nanowire's first radial breathing mode. Finite Difference Time Domain (FDTD) simulations are performed and accurately reproduce the diffracted field. A shape anisotropy resulting from the large aspect ratio of the nanowire is detected in the acoustic field. The orientation of the underlying nanowires is thus acoustically deduced.

  19. Single trap in liquid gated nanowire FETs: Capture time behavior as a function of current

    SciTech Connect

    Gasparyan, F.; Zadorozhnyi, I.; Vitusevich, S.

    2015-05-07

    The basic reason for enhanced electron capture time, τ{sub c}, of the oxide single trap dependence on drain current in the linear operation regime of p{sup +}-p-p{sup +} silicon field effect transistors (FETs) was established, using a quantum-mechanical approach. A strong increase of τ{sub c} slope dependence on channel current is explained using quantization and tunneling concepts in terms of strong field dependence of the oxide layer single trap effective cross-section, which can be described by an amplification factor. Physical interpretation of this parameter deals with the amplification of the electron cross-section determined by both decreasing the critical field influence as a result of the minority carrier depletion and the potential barrier growth for electron capture. For the NW channel of n{sup +}-p-n{sup +} FETs, the experimentally observed slope of τ{sub c} equals (−1). On the contrary, for the case of p{sup +}-p-p{sup +} Si FETs in the accumulation regime, the experimentally observed slope of τ{sub c} equals (−2.8). It can be achieved when the amplification factor is about 12. Extraordinary high capture time slope values versus current are explained by the effective capture cross-section growth with decreasing electron concentration close to the nanowire-oxide interface.

  20. Charge carrier trapping and acoustic phonon modes in single CdTe nanowires.

    PubMed

    Lo, Shun Shang; Major, Todd A; Petchsang, Nattasamon; Huang, Libai; Kuno, Masaru K; Hartland, Gregory V

    2012-06-26

    Semiconductor nanostructures produced by wet chemical synthesis are extremely heterogeneous, which makes single particle techniques a useful way to interrogate their properties. In this paper the ultrafast dynamics of single CdTe nanowires are studied by transient absorption microscopy. The wires have lengths of several micrometers and lateral dimensions on the order of 30 nm. The transient absorption traces show very fast decays, which are assigned to charge carrier trapping into surface defects. The time constants vary for different wires due to differences in the energetics and/or density of surface trap sites. Measurements performed at the band edge compared to the near-IR give slightly different time constants, implying that the dynamics for electron and hole trapping are different. The rate of charge carrier trapping was observed to slow down at high carrier densities, which was attributed to trap-state filling. Modulations due to the fundamental and first overtone of the acoustic breathing mode were also observed in the transient absorption traces. The quality factors for these modes were similar to those measured for metal nanostructures, and indicate a complex interaction with the environment.

  1. Experimental determination of single CdSe nanowire absorption cross sections through photothermal imaging.

    PubMed

    Giblin, Jay; Syed, Muhammad; Banning, Michael T; Kuno, Masaru; Hartland, Greg

    2010-01-26

    Absorption cross sections ((sigma)abs) of single branched CdSe nanowires (NWs) have been measured by photothermal heterodyne imaging (PHI). Specifically, PHI signals from isolated gold nanoparticles (NPs) with known cross sections were compared to those of individual CdSe NWs excited at 532 nm. This allowed us to determine average NW absorption cross sections at 532 nm of (sigma)abs = (3.17 +/- 0.44) x 10(-11) cm2/microm (standard error reported). This agrees well with a theoretical value obtained using a classical electromagnetic analysis ((sigma)abs = 5.00 x 10(-11) cm2/microm) and also with prior ensemble estimates. Furthermore, NWs exhibit significant absorption polarization sensitivities consistent with prior NW excitation polarization anisotropy measurements. This has enabled additional estimates of the absorption cross section parallel ((sigma)abs) and perpendicular ((sigma)abs(perpendicular) to the NW growth axis, as well as the corresponding NW absorption anisotropy ((rho)abs). Resulting values of (sigma)abs = (5.6 +/- 1.1) x 10(-11) cm2/microm, (sigma)abs(perpendicular) = (1.26 +/- 0.21) x 10(-11) cm2/microm, and (rho)abs = 0.63+/- 0.04 (standard errors reported) are again in good agreement with theoretical predictions. These measurements all indicate sizable NW absorption cross sections and ultimately suggest the possibility of future direct single NW absorption studies.

  2. Quantum Yield of Single Surface Plasmons Generated by a Quantum Dot Coupled with a Silver Nanowire.

    PubMed

    Li, Qiang; Wei, Hong; Xu, Hongxing

    2015-12-01

    The interactions between surface plasmons (SPs) in metal nanostructures and excitons in quantum emitters (QEs) lead to many interesting phenomena and potential applications that are strongly dependent on the quantum yield of SPs. The difficulty in distinguishing all the possible exciton recombination channels hinders the experimental determination of SP quantum yield. Here, we experimentally measured for the first time the quantum yield of single SPs generated by the exciton-plasmon coupling in a system composed of a single quantum dot and a silver nanowire (NW). By utilizing the SP guiding property of the NW, the decay rates of all the exciton recombination channels, i.e., direct free space radiation channel, SP generation channel, and nonradiative damping channel, are quantitatively obtained. It is determined that the optimum emitter-NW coupling distance for the largest SP quantum yield is about 10 nm, resulting from the different distance-dependent decay rates of the three channels. These results are important for manipulating the coupling between plasmonic nanostructures and QEs and developing on-chip quantum plasmonic devices for potential nanophotonic and quantum information applications.

  3. Pulsed laser deposition of single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 core/shell nanowires

    PubMed Central

    2014-01-01

    Single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 (CI/CIGS) core/shell nanowires are fabricated by pulsed laser deposition with Ni nanoparticles as catalyst. The CI/CIGS core/shell nanowires are made up of single-crystalline CI cores surrounded by single-crystalline CIGS shells. The CI/CIGS nanowires are grown at a considerably low temperature (350°C ~ 450°C) by vapor-liquid-solid mode combined with vapor-solid mode. The distribution density of the nanowires increases with the increasing of the deposition duration, and the substrate temperature determines the lengths of the nanowires. The U-V absorption spectra of the CIGS thin films with and without the CI/CIGS core/shell nanowires demonstrate that the CI/CIGS nanowires can remarkably enhance the absorption of CIGS thin films in the spectrum range of 300 to 900 nm. PACS 61.46. + w; 61.41.e; 81.15.Fg; 81.07.b PMID:25520597

  4. Pulsed laser deposition of single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 core/shell nanowires

    NASA Astrophysics Data System (ADS)

    Zhao, Yu; Li, Hui; Zhu, Yan-Yan; Guan, Lei-Lei; Li, Yan-Li; Sun, Jian; Ying, Zhi-Feng; Wu, Jia-Da; Xu, Ning

    2014-12-01

    Single-crystalline Cu7In3/CuIn0.8Ga0.2Se2 (CI/CIGS) core/shell nanowires are fabricated by pulsed laser deposition with Ni nanoparticles as catalyst. The CI/CIGS core/shell nanowires are made up of single-crystalline CI cores surrounded by single-crystalline CIGS shells. The CI/CIGS nanowires are grown at a considerably low temperature (350°C ~ 450°C) by vapor-liquid-solid mode combined with vapor-solid mode. The distribution density of the nanowires increases with the increasing of the deposition duration, and the substrate temperature determines the lengths of the nanowires. The U-V absorption spectra of the CIGS thin films with and without the CI/CIGS core/shell nanowires demonstrate that the CI/CIGS nanowires can remarkably enhance the absorption of CIGS thin films in the spectrum range of 300 to 900 nm.

  5. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals

    NASA Astrophysics Data System (ADS)

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-01

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni

  6. From single III-nitride nanowires to piezoelectric generators: New route for powering nomad electronics

    NASA Astrophysics Data System (ADS)

    Gogneau, N.; Jamond, N.; Chrétien, P.; Houzé, F.; Lefeuvre, E.; Tchernycheva, M.

    2016-10-01

    Ambient energy harvesting using piezoelectric nanomaterials is today considered as a promising way to supply microelectronic devices. Since the first demonstration of electrical energy generation from piezoelectric semiconductor nanowires in 2006, the piezoelectric response of 1D-nanostructures and the development of nanowire-based piezogenerators have become a hot topic in nanoscience. After several years of intense research on ZnO nanowires, III-nitride nanomaterials have started to be explored thanks to their high piezoelectric coefficients and their strong piezogeneration response. This review describes the present status of the field of piezoelectric energy generation with nitride nanowires. After presenting the main motivation and a general overview of the domain, a short description of the main properties of III-nitride nanomaterials is given. Then we review the piezoelectric responses of III-N nanowires and the specificities of the piezogeneration mechanism in these nanostructures. Finally, the design and performance of the macroscopic piezogenerators based on nitride nanowire arrays are described, showing the promise of III-nitride nanowires for ultra-compact and efficient piezoelectric generators.

  7. Single CuO(x) nanowire memristor: forming-free resistive switching behavior.

    PubMed

    Liang, Kai-De; Huang, Chi-Hsin; Lai, Chih-Chung; Huang, Jian-Shiou; Tsai, Hung-Wei; Wang, Yi-Chung; Shih, Yu-Chuan; Chang, Mu-Tung; Lo, Shen-Chuan; Chueh, Yu-Lun

    2014-10-01

    CuOx nanowires were synthesized by a low-cost and large-scale electrochemical process with AAO membranes at room temperature and its resistive switching has been demonstrated. The switching characteristic exhibits forming-free and low electric-field switching operation due to coexistence of significant amount of defects and Cu nanocrystals in the partially oxidized nanowires. The detailed resistive switching characteristics of CuOx nanowire systems have been investigated and possible switching mechanisms are systematically proposed based on the microstructural and chemical analysis via transmission electron microscopy.

  8. Sustained Resistive Switching in a Single Cu:7,7,8,8-tetracyanoquinodimethane Nanowire: A Promising Material for Resistive Random Access Memory

    NASA Astrophysics Data System (ADS)

    Basori, Rabaya; Kumar, Manoranjan; Raychaudhuri, Arup K.

    2016-06-01

    We report a new type of sustained and reversible unipolar resistive switching in a nanowire device made from a single strand of Cu:7,7,8,8-tetracyanoquinodimethane (Cu:TCNQ) nanowire (diameter <100 nm) that shows high ON/OFF ratio (~103), low threshold voltage of switching (~3.5 V) and large cycling endurance (>103). This indicates a promising material for high density resistive random access memory (ReRAM) device integration. Switching is observed in Cu:TCNQ single nanowire devices with two different electrode configuration: symmetric (C-Pt/Cu:TCNQ/C-Pt) and asymmetric (Cu/Cu:TCNQ/C-Pt), where contacts connecting the nanowire play an important role. This report also developed a method of separating out the electrode and material contributions in switching using metal-semiconductor-metal (MSM) device model along with a direct 4-probe resistivity measurement of the nanowire in the OFF as well as ON state. The device model was followed by a phenomenological model of current transport through the nanowire device which shows that lowering of potential barrier at the contacts likely occur due to formation of Cu filaments in the interface between nanowire and contact electrodes. We obtain quantitative agreement of numerically analyzed results with the experimental switching data.

  9. Sustained Resistive Switching in a Single Cu:7,7,8,8-tetracyanoquinodimethane Nanowire: A Promising Material for Resistive Random Access Memory.

    PubMed

    Basori, Rabaya; Kumar, Manoranjan; Raychaudhuri, Arup K

    2016-01-01

    We report a new type of sustained and reversible unipolar resistive switching in a nanowire device made from a single strand of Cu:7,7,8,8-tetracyanoquinodimethane (Cu:TCNQ) nanowire (diameter <100 nm) that shows high ON/OFF ratio (~10(3)), low threshold voltage of switching (~3.5 V) and large cycling endurance (>10(3)). This indicates a promising material for high density resistive random access memory (ReRAM) device integration. Switching is observed in Cu:TCNQ single nanowire devices with two different electrode configuration: symmetric (C-Pt/Cu:TCNQ/C-Pt) and asymmetric (Cu/Cu:TCNQ/C-Pt), where contacts connecting the nanowire play an important role. This report also developed a method of separating out the electrode and material contributions in switching using metal-semiconductor-metal (MSM) device model along with a direct 4-probe resistivity measurement of the nanowire in the OFF as well as ON state. The device model was followed by a phenomenological model of current transport through the nanowire device which shows that lowering of potential barrier at the contacts likely occur due to formation of Cu filaments in the interface between nanowire and contact electrodes. We obtain quantitative agreement of numerically analyzed results with the experimental switching data. PMID:27245099

  10. Sustained Resistive Switching in a Single Cu:7,7,8,8-tetracyanoquinodimethane Nanowire: A Promising Material for Resistive Random Access Memory

    PubMed Central

    Basori, Rabaya; Kumar, Manoranjan; Raychaudhuri, Arup K.

    2016-01-01

    We report a new type of sustained and reversible unipolar resistive switching in a nanowire device made from a single strand of Cu:7,7,8,8-tetracyanoquinodimethane (Cu:TCNQ) nanowire (diameter <100 nm) that shows high ON/OFF ratio (~103), low threshold voltage of switching (~3.5 V) and large cycling endurance (>103). This indicates a promising material for high density resistive random access memory (ReRAM) device integration. Switching is observed in Cu:TCNQ single nanowire devices with two different electrode configuration: symmetric (C-Pt/Cu:TCNQ/C-Pt) and asymmetric (Cu/Cu:TCNQ/C-Pt), where contacts connecting the nanowire play an important role. This report also developed a method of separating out the electrode and material contributions in switching using metal-semiconductor-metal (MSM) device model along with a direct 4-probe resistivity measurement of the nanowire in the OFF as well as ON state. The device model was followed by a phenomenological model of current transport through the nanowire device which shows that lowering of potential barrier at the contacts likely occur due to formation of Cu filaments in the interface between nanowire and contact electrodes. We obtain quantitative agreement of numerically analyzed results with the experimental switching data. PMID:27245099

  11. Visualizing Carrier Diffusion in Individual Single-Crystal Organolead Halide Perovskite Nanowires and Nanoplates.

    PubMed

    Tian, Wenming; Zhao, Chunyi; Leng, Jing; Cui, Rongrong; Jin, Shengye

    2015-10-01

    Single-crystal CH3NH3PbX3 (X = I(-), Cl(-), Br(-)) perovskite nanowires (NWs) and nanoplates (NPs), which demonstrate ultracompact sizes and exceptional photophysical properties, offer promises for applications in nanoscale photonics and optoelectronics. However, traditional electronic and transient techniques are limited by the dimensions of the samples, and characterizations of the carrier behavior (diffusion coefficient, charge mobility and diffusion length) in these NWs and NPs are extremely difficult. Herein, we report the direct visualization of the carrier diffusion process in individual single-crystal CH3NH3PbI3 and CH3NH3PbBr3 NWs and NPs using time-resolved and photoluminescence-scanned imaging microscopy. We report the diffusion coefficient (charge motility), which varies significantly between different NWs and NPs, ranging from 1.59 to 2.41 cm(2) s(-1) (56.4 to 93.9 cm(2) V(-1) s(-1)) for CH3NH3PbI3 and 0.50 to 1.44 cm(2) s(-1) (19.4 to 56.1 cm(2) V(-1) s(-1)) for CH3NH3PbBr3 and find this variation is independent of the shape and size of the sample. The average diffusion length is 14.0 ± 5.1 μm for CH3NH3PbI3 and 6.0 ± 1.6 μm for CH3NH3PbBr3. These results provide information that is essential for the practical applications of the single-crystal perovskite NWs and NPs, and the imaging microscopy may also be applicable to other optoelectronic materials.

  12. Synthesis of single-crystalline Zn metal nanowires utilizing cold-wall physical vapor deposition.

    PubMed

    Kast, Michael; Schroeder, Philipp; Hyun, Youn J; Pongratz, Peter; Bruückl, Hubert

    2007-08-01

    Zinc metal nanowires (NWs) of two different morphologies have been synthesized in a cold-wall physical vapor deposition (CWPVD) chamber at high vacuum conditions and growth temperatures of 150 degrees C. Substrates initially seeded by gold or platinum crystals show NWs of wool-like and/or unidirectional morphologies. Transmission electron microscopy (TEM) studies revealed that the rodlike NWs consist of single-crystalline Zn covered with a thin native oxide. NWs of wool-like morphology are suppressed using platinum as the seed metal. NW growth proceeds via vapor-solid (VS) kinetics without any catalyst particles on the wire tips. The highest observed growth rates exceed the Zn deposition rate by factors up to 860, indicating the dominant role of surface diffusion of Zn adatoms, also along the NWs. The surface diffusion length of Zn adatoms on the NW side facet is determined to be 39 mum. Direct impingement of precursor atoms on the NW tip is not significant for the growth process.

  13. Intrinsic detection efficiency of superconducting nanowire single photon detector in the modified hot spot model

    NASA Astrophysics Data System (ADS)

    Zotova, A. N.; Vodolazov, D. Yu

    2014-12-01

    We theoretically study the dependence of the intrinsic detection efficiency (IDE) of a superconducting nanowire single photon detector on the applied current, I, and magnetic field, H. We find that the current, at which the resistive state appears in the superconducting film, depends on the position of the hot spot (a region with suppressed superconductivity around the place where the photon has been absorbed) with respect to the edges of the film. This circumstance leads to inevitable smooth dependence IDE(I) when IDE ˜ 0.05-1, even for a homogenous straight superconducting film and in the absence of fluctuations. For IDE ≲ 0.05, a much sharper current dependence comes from the fluctuation-assisted vortex entry to the hot spot, which is located near the edge of the film. We find that a weak magnetic field strongly affects IDE when the photon detection is connected with fluctuation-assisted vortex entry to the hot spot (IDE \\ll 1), and it weakly affects IDE when the photon detection is connected with the current-induced vortex nucleation in the film with the hot spot (IDE ˜ 0.05-1).

  14. Modulation of domain wall dynamics in TbFeCo single layer nanowire

    NASA Astrophysics Data System (ADS)

    Ngo, Duc-The; Ikeda, Kotaro; Awano, Hiroyuki

    2012-04-01

    We demonstrate the possibility to write and modulate the magnetic domain walls in a TbFeCo single layer nanowire (300 nm width, 150 μm length). To realize this, a tiny magnetic domain was nucleated by an Oersted field produced by a 1.6 MHz pulse current (35 mA in amplitude, 5-40 ns in length) crossed the wire. To write the wall to the wire, a DC current was used to drive the nucleated domain (with two walls in two sides) to the wire in accordance with spin-transfer torque mechanism. A critical current density of Jc = 3.5 × 1010 Am-2 was required to control the motion of the walls in the wire. It was found that the size of the domain moving in the wire could be adjusted by either external field or the length of the nucleated pulse current. This could be considered as an important note for writing process in domain wall spin-torque devices, especially, memory elements.

  15. Proton radiation hardness of single-nanowire transistors using robust organic gate nanodielectrics

    NASA Astrophysics Data System (ADS)

    Ju, Sanghyun; Lee, Kangho; Janes, David B.; Dwivedi, Ramesh C.; Baffour-Awuah, Habibah; Wilkins, R.; Yoon, Myung-Han; Facchetti, Antonio; Mark, Tobin J.

    2006-08-01

    In this contribution, the radiation tolerance of single ZnO nanowire field-effect transistors (NW-FETs) fabricated with a self-assembled superlattice (SAS) gate insulator is investigated and compared with that of ZnO NW-FETs fabricated with a 60nm SiO2 gate insulator. A total-radiation dose study was performed using 10MeV protons at doses of 5.71 and 285krad(Si ). The threshold voltage (Vth) of the SAS-based ZnO NW-FETs is not shifted significantly following irradiation at these doses. In contrast, Vth parameters of the SiO2-based ZnO NW-FETs display average shifts of ˜-4.0 and ˜-10.9V for 5.71 and 285krad(Si ) H+ irradiation, respectively. In addition, little change is observed in the subthreshold characteristics (off current, subthreshold slope) of the SAS-based ZnO NW-FETs following H+ irradiation. These results strongly argue that the bulk oxide trap density and interface trap density formed within the SAS and/or at the SAS-ZnO NW interface during H+ irradiation are significantly lower than those for the corresponding SiO2 gate dielectrics. The radiation-robust SAS-based ZnO NW-FETs are thus promising candidates for future space-based applications in electronics and flexible displays.

  16. Dynamic polariton condensation in a single GaN nanowire-dielectric microcavity

    NASA Astrophysics Data System (ADS)

    Das, Ayan; Bhattacharya, Pallab; Banerjee, Animesh; Jankowski, Marc

    2012-05-01

    We have experimentally investigated the dynamic polariton condensation behavior in a single GaN nanowire strongly coupled to a dielectric microcavity under nonresonant optical excitation. Both time-integrated and time-resolved polariton luminescence measurements have been made in the temperature range of 25 to 100 K (corresponding to exciton-cavity photon detuning of -3.0 to +4.2 meV). Polariton lasing is observed in the entire temperature range, with the lowest threshold energy of 57 nJ/cm2 measured at 50 K (δ = -1.3 meV). All the measurements indicate that at the lower temperatures the degenerate polariton condensate is not in thermal equilibrium with the phonon bath. At 85 and 100 K (δ = +2.3 and 4.2 meV), the system attains a state close to thermal equilibrium via dynamic Bose condensation. The best results are obtained at Tlatt = 85 K, for which TLP = 88.8 K, and this is the highest temperature recorded for an equilibrium phase transition in exciton-polariton condensates.

  17. Low frequency noise in single GaAsSb nanowires with self-induced compositional gradients.

    PubMed

    Huh, Junghwan; Kim, Dong-Chul; Munshi, A Mazid; Dheeraj, Dasa L; Jang, Doyoung; Kim, Gyu-Tae; Fimland, Bjørn-Ove; Weman, Helge

    2016-09-23

    Due to bandgap tunability, GaAsSb nanowires (NWs) have received a great deal of attention for a variety of optoelectronic device applications. However, electrical and optical properties of GaAsSb are strongly affected by Sb-related defects and scattering from surface states and/or defects, which can limit the performance of GaAsSb NW devices. Thus, in order to utilize the GaAsSb NWs for high performance electronic and optoelectronic devices, it is required to study the material and interface properties (e.g. the interface trap density) in the GaAsSb NW devices. Here, we investigate the low frequency noise in single GaAsSb NWs with self-induced compositional gradients. The current noise spectral density of the GaAsSb NW device showed a typical 1/f noise behavior. The Hooge's noise parameter and the interface trap density of the GaAsSb NW device were found to be ∼2.2 × 10(-2) and ∼2 × 10(12) eV(-1) cm(-2), respectively. By applying low frequency noise measurements, the noise equivalent power, a key figure of merit of photodetectors, was calculated. The observed low frequency noise properties can be useful as guidance for quality and reliability of GaAsSb NW based electronic devices, especially for photodetectors.

  18. Atomistic simulations of nanowelding of single-crystal and amorphous gold nanowires

    SciTech Connect

    Wu, Cheng-Da; Fang, Te-Hua Wu, Chung-Chin

    2015-01-07

    The mechanism and quality of the welding of single-crystal (SC) and amorphous gold nanowires (NWs) with head-to-head contact are studied using molecular dynamics simulations based on the second-moment approximation of the many-body tight-binding potential. The results are discussed in terms of atomic trajectories, slip vectors, stress, and radial distribution function. Simulation results show that the alignment for the amorphous NWs during welding is easier than that for the SC NWs due to the former's relatively stable geometry. A few dislocations nucleate and propagate on the (111) close-packed plane (slip plane) inside the SC NWs during the welding and stretching processes. During welding, an incomplete jointing area first forms through the interactions of the van der Waals attractive force, and the jointing area increases with increasing extent of contact between the two NWs. A crystallization transition region forms in the jointing area for the welding of SC-amorphous or amorphous-SC NWs. With increasing interference, an amorphous gold NW shortens more than does a SC gold NW due to the former's relatively poor strength. The pressure required for welding decreases with increasing temperature.

  19. Low frequency noise in single GaAsSb nanowires with self-induced compositional gradients.

    PubMed

    Huh, Junghwan; Kim, Dong-Chul; Munshi, A Mazid; Dheeraj, Dasa L; Jang, Doyoung; Kim, Gyu-Tae; Fimland, Bjørn-Ove; Weman, Helge

    2016-09-23

    Due to bandgap tunability, GaAsSb nanowires (NWs) have received a great deal of attention for a variety of optoelectronic device applications. However, electrical and optical properties of GaAsSb are strongly affected by Sb-related defects and scattering from surface states and/or defects, which can limit the performance of GaAsSb NW devices. Thus, in order to utilize the GaAsSb NWs for high performance electronic and optoelectronic devices, it is required to study the material and interface properties (e.g. the interface trap density) in the GaAsSb NW devices. Here, we investigate the low frequency noise in single GaAsSb NWs with self-induced compositional gradients. The current noise spectral density of the GaAsSb NW device showed a typical 1/f noise behavior. The Hooge's noise parameter and the interface trap density of the GaAsSb NW device were found to be ∼2.2 × 10(-2) and ∼2 × 10(12) eV(-1) cm(-2), respectively. By applying low frequency noise measurements, the noise equivalent power, a key figure of merit of photodetectors, was calculated. The observed low frequency noise properties can be useful as guidance for quality and reliability of GaAsSb NW based electronic devices, especially for photodetectors. PMID:27528601

  20. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals.

    PubMed

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-21

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices. PMID:27129106

  1. Single InAs/GaSb nanowire low-power CMOS inverter.

    PubMed

    Dey, Anil W; Svensson, Johannes; Borg, B Mattias; Ek, Martin; Wernersson, Lars-Erik

    2012-11-14

    III-V semiconductors have so far predominately been employed for n-type transistors in high-frequency applications. This development is based on the advantageous transport properties and the large variety of heterostructure combinations in the family of III-V semiconductors. In contrast, reports on p-type devices with high hole mobility suitable for complementary metal-oxide-semiconductor (CMOS) circuits for low-power operation are scarce. In addition, the difficulty to integrate both n- and p-type devices on the same substrate without the use of complex buffer layers has hampered the development of III-V based digital logic. Here, inverters fabricated from single n-InAs/p-GaSb heterostructure nanowires are demonstrated in a simple processing scheme. Using undoped segments and aggressively scaled high-κ dielectric, enhancement mode operation suitable for digital logic is obtained for both types of transistors. State-of-the-art on- and off-state characteristics are obtained and the individual long-channel n- and p-type transistors exhibit minimum subthreshold swings of SS = 98 mV/dec and SS = 400 mV/dec, respectively, at V(ds) = 0.5 V. Inverter characteristics display a full signal swing and maximum gain of 10.5 with a small device-to-device variability. Complete inversion is measured at low frequencies although large parasitic capacitances deform the waveform at higher frequencies.

  2. Single Schottky junction FETs based on Si:P nanowires with axially graded doping

    NASA Astrophysics Data System (ADS)

    Barreda, Jorge; Keiper, Timothy; Zhang, Mei; Xiong, Peng

    2015-03-01

    Si nanowires (NWs) with a systematic axial increase in phosphorus doping have been synthesized via a vapor-liquid-solid method. Silane and phosphine precursor gases are utilized for the growth and doping, respectively. The phosphorous doping profile is controlled by the flow ratio of the precursor gases. After the as-grown product is ultrasonically agitated into a solution, the Si NWs are dispersed on a SiO2 substrate with a highly doped Si back gate. Individual NWs are identified for the fabrication of field-effect transistors (FETs) with multiple Cr/Ag contacts along the NW. Two-probe and four-probe measurements are taken systematically under vacuum conditions at room temperature and the contribution from each contact and each NW section between adjacent contacts is determined. The graded doping level, produced by a systematic reduction in dopant density along the length of the NWs, is manifested in the regular increases in the channel and contact resistances. Our Si NWs facilitate the fabrication of asymmetric FETs with one ohmic and one Schottky contact. A significant increase in gate modulation is obtained due to the single Schottky-barrier contact. Characterization details and the applicability for sensing purposes will be discussed.

  3. Low frequency noise in single GaAsSb nanowires with self-induced compositional gradients

    NASA Astrophysics Data System (ADS)

    Huh, Junghwan; Kim, Dong-Chul; Mazid Munshi, A.; Dheeraj, Dasa L.; Jang, Doyoung; Kim, Gyu-Tae; Fimland, Bjørn-Ove; Weman, Helge

    2016-09-01

    Due to bandgap tunability, GaAsSb nanowires (NWs) have received a great deal of attention for a variety of optoelectronic device applications. However, electrical and optical properties of GaAsSb are strongly affected by Sb-related defects and scattering from surface states and/or defects, which can limit the performance of GaAsSb NW devices. Thus, in order to utilize the GaAsSb NWs for high performance electronic and optoelectronic devices, it is required to study the material and interface properties (e.g. the interface trap density) in the GaAsSb NW devices. Here, we investigate the low frequency noise in single GaAsSb NWs with self-induced compositional gradients. The current noise spectral density of the GaAsSb NW device showed a typical 1/f noise behavior. The Hooge’s noise parameter and the interface trap density of the GaAsSb NW device were found to be ˜2.2 × 10-2 and ˜2 × 1012 eV-1 cm-2, respectively. By applying low frequency noise measurements, the noise equivalent power, a key figure of merit of photodetectors, was calculated. The observed low frequency noise properties can be useful as guidance for quality and reliability of GaAsSb NW based electronic devices, especially for photodetectors.

  4. Stereo-epitaxial growth of single-crystal Ni nanowires and nanoplates from aligned seed crystals.

    PubMed

    Lee, Hyoban; Yoo, Youngdong; Kang, Taejoon; Lee, Jiyoung; Kim, Eungwang; Fang, Xiaosheng; Lee, Sungyul; Kim, Bongsoo

    2016-05-21

    Epitaxially grown anisotropic Ni nanostructures are promising building blocks for the development of miniaturized and stereo-integrated data storage kits because they can store multiple magnetic domain walls (DWs). Here, we report stereo-epitaxially grown single-crystalline Ni nanowires (NWs) and nanoplates, and their magnetic properties. Vertical and inclined Ni NWs were grown at the center and edge regions of c-cut sapphire substrates, respectively. Vertical Ni nanoplates were grown on r-cut sapphire substrates. The morphology and growth direction of Ni nanostructures can be steered by seed crystals. Cubic Ni seeds grow into vertical Ni NWs, tetrahedral Ni seeds grow into inclined Ni NWs, and triangular Ni seeds grow into vertical Ni nanoplates. The shapes of the Ni seeds are determined by the interfacial energy between the bottom plane of the seeds and the substrates. The as-synthesized Ni NWs and nanoplates have blocking temperature values greater than 300 K at 500 Oe, verifying that these Ni nanostructures can form large magnetic DWs with high magnetic anisotropy properties. We anticipate that epitaxially grown Ni NWs and nanoplates will be used in various types of 3-dimensional magnetic devices.

  5. Low frequency noise in single GaAsSb nanowires with self-induced compositional gradients

    NASA Astrophysics Data System (ADS)

    Huh, Junghwan; Kim, Dong-Chul; Mazid Munshi, A.; Dheeraj, Dasa L.; Jang, Doyoung; Kim, Gyu-Tae; Fimland, Bjørn-Ove; Weman, Helge

    2016-09-01

    Due to bandgap tunability, GaAsSb nanowires (NWs) have received a great deal of attention for a variety of optoelectronic device applications. However, electrical and optical properties of GaAsSb are strongly affected by Sb-related defects and scattering from surface states and/or defects, which can limit the performance of GaAsSb NW devices. Thus, in order to utilize the GaAsSb NWs for high performance electronic and optoelectronic devices, it is required to study the material and interface properties (e.g. the interface trap density) in the GaAsSb NW devices. Here, we investigate the low frequency noise in single GaAsSb NWs with self-induced compositional gradients. The current noise spectral density of the GaAsSb NW device showed a typical 1/f noise behavior. The Hooge’s noise parameter and the interface trap density of the GaAsSb NW device were found to be ∼2.2 × 10‑2 and ∼2 × 1012 eV‑1 cm‑2, respectively. By applying low frequency noise measurements, the noise equivalent power, a key figure of merit of photodetectors, was calculated. The observed low frequency noise properties can be useful as guidance for quality and reliability of GaAsSb NW based electronic devices, especially for photodetectors.

  6. Optical properties of single wurtzite/zinc-blende ZnSe nanowires grown at low temperature

    SciTech Connect

    Zannier, V.; Cremel, T.; Kheng, K.; Artioli, A.; Ferrand, D.; Grillo, V.

    2015-09-07

    ZnSe nanowires with a dominant wurtzite structure have been grown at low temperature (300 °C) by molecular beam epitaxy assisted by solid Au nanoparticles. The nanowires emission is polarized perpendicularly to their axis in agreement with the wurtzite selection rules. Alternations of wurtzite and zinc-blende regions have been observed by transmission electron microscopy, and their impact on the nanowires optical properties has been studied by microphotoluminescence. The nanowires show a dominant intense near-band-edge emission as well as the ZnSe wurtzite free exciton line. A type II band alignment between zinc-blende and wurtzite ZnSe is evidenced by time-resolved photoluminescence. From this measurement, we deduce values for the conduction and valence band offsets of 98 and 50 meV, respectively.

  7. Decoupling single nanowire mobilities limited by surface scattering and bulk impurity scattering

    SciTech Connect

    Khanal, D. R.; Levander, A. X.; Wu, J.; Yu, K. M.; Liliental-Weber, Z.; Walukiewicz, W.; Grandal, J.; Sanchez-Garcia, M. A.; Calleja, E.

    2011-08-01

    We demonstrate the isolation of two free carrier scattering mechanisms as a function of radial band bending in InN nanowires via universal mobility analysis, where effective carrier mobility is measured as a function of effective electric field in a nanowire field-effect transistor. Our results show that Coulomb scattering limits effective mobility at most effective fields, while surface roughness scattering only limits mobility under very high internal electric fields. High-energy {alpha} particle irradiation is used to vary the ionized donor concentration, and the observed decrease in mobility and increase in donor concentration are compared to Hall effect results of high-quality InN thin films. Our results show that for nanowires with relatively high doping and large diameters, controlling Coulomb scattering from ionized dopants should be given precedence over surface engineering when seeking to maximize nanowire mobility.

  8. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design

    NASA Astrophysics Data System (ADS)

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-04-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ratio of over 40 % in both the photocurrent density and the photoconversion efficiency in a-Si:H SNSCs with a diameter of 200 nm. We further show that the superior performance can be well maintained under a wide range of incident angle and is robust to the blunt crescent edges.

  9. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design.

    PubMed

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-12-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ratio of over 40 % in both the photocurrent density and the photoconversion efficiency in a-Si:H SNSCs with a diameter of 200 nm. We further show that the superior performance can be well maintained under a wide range of incident angle and is robust to the blunt crescent edges. PMID:27129685

  10. X-ray diffraction strain analysis of a single axial InAs1–xPx nanowire segment

    PubMed Central

    Keplinger, Mario; Mandl, Bernhard; Kriegner, Dominik; Holý, Václav; Samuelsson, Lars; Bauer, Günther; Deppert, Knut; Stangl, Julian

    2015-01-01

    The spatial strain distribution in and around a single axial InAs1–xPx hetero-segment in an InAs nanowire was analyzed using nano-focused X-ray diffraction. In connection with finite-element-method simulations a detailed quantitative picture of the nanowire’s inhomogeneous strain state was achieved. This allows for a detailed understanding of how the variation of the nanowire’s and hetero-segment’s dimensions affect the strain in its core region and in the region close to the nanowire’s side facets. Moreover, ensemble-averaging high-resolution diffraction experiments were used to determine statistical information on the distribution of wurtzite and zinc-blende crystal polytypes in the nanowires. PMID:25537589

  11. Direct growth of single-crystal Pt nanowires on Sn@CNT Nanocable: 3D electrodes for highly active electrocatalysts.

    PubMed

    Sun, Shuhui; Zhang, Gaixia; Geng, Dongsheng; Chen, Yougui; Banis, Mohammad Norouzi; Li, Ruying; Cai, Mei; Sun, Xueliang

    2010-01-18

    A newly designed and fabricated novel three dimensional (3D) nanocomposite composed of single-crystal Pt nanowires (PtNW) and a coaxial nanocable support consisting of a tin nanowire and a carbon nanotube (Sn@CNT) is reported. This nanocomposite is fabricated by the synthesis of Sn@CNT nanocables by means of a thermal evaporation method, followed by the direct growth with PtNWs through a facile aqueous solution approach at room temperature. Electrochemical measurements demonstrate that the PtNW--Sn@CNT 3D electrode exhibits enhanced electrocatalytic performance in oxygen reduction reaction (ORR) for polymer electrolyte membrane fuel cells (PEMFCs), methanol oxidation (MOR) for direct methanol fuel cells (DMFCs), and CO tolerance compared with commercial ETEK Pt/C catalyst made of Pt nanoparticles. PMID:20024993

  12. Enhanced Photoelectrical Response of Hydrogenated Amorphous Silicon Single-Nanowire Solar Cells by Front-Opening Crescent Design.

    PubMed

    Yang, Zhenhai; Cao, Guoyang; Shang, Aixue; Lei, Dang Yuan; Zhang, Cheng; Gao, Pingqi; Ye, Jichun; Li, Xiaofeng

    2016-12-01

    We report an approach for substantially enhancing the light-trapping and photoconversion efficiency of hydrogenated amorphous silicon (a-Si:H) single-nanowire solar cells (SNSCs) by engineering the cross section of the nanowire from circular into a front-opening crescent shape. The proposed SNSCs show a broadband and highly tunable optical absorption compared to the conventional circular counterparts under both transverse electric and transverse magnetic incidences, enabling an enhancement ratio of over 40 % in both the photocurrent density and the photoconversion efficiency in a-Si:H SNSCs with a diameter of 200 nm. We further show that the superior performance can be well maintained under a wide range of incident angle and is robust to the blunt crescent edges.

  13. Double Path Interference and Magnetic Oscillations in Cooper Pair Transport through a Single Nanowire.

    PubMed

    Mironov, S V; Mel'nikov, A S; Buzdin, A I

    2015-06-01

    We show that the critical current of the Josephson junction consisting of superconducting electrodes coupled through a nanowire with two conductive channels can reveal the multiperiodic magnetic oscillations. The multiperiodicity originates from the quantum mechanical interference between the channels affected by both the strong spin-orbit coupling and the Zeeman interaction. This minimal two-channel model is shown to explain the complicated interference phenomena observed recently in Josephson transport through Bi nanowires. PMID:26196639

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

    PubMed Central

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

    2015-01-01

    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 () 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 ~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. PMID:26035288

  15. 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.

  16. Orientation effect on the giant stress field induced in a single Ni nanowire by mechanical strain

    NASA Astrophysics Data System (ADS)

    Melilli, G.; Madon, B.; Clochard, M.-C.; Wegrowe, J.-E.

    2015-09-01

    The change of magnetization (i.e. using the inverse magnetostriction effect) allows to investigate at the nanoscale the effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW). The magnetization state is measured locally by anisotropic magnetoresitance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. Due to the inverse magnetostriction, a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≍ 10 K has been evidenced. The coplanarity of the vectors between the magnetization and the magnetic field is broken. A way of studying the effect of the geometry on such a system, is to fabricate oriented polymer templates. Track-etched polymer membranes were thus irradiated at various angles (αirrad) leading, after electrodeposition, to embedded Ni NWs of different orientations. With cylindrical Ni NW oriented normally to the template surface, the induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification results in three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. When the Ni NWs are tilted from the polymer template surface normality, the induced stress field is reduced and the amplification phenomenon is less important.

  17. Single-crystal γ-MnS nanowires conformally coated with carbon.

    PubMed

    Beltran-Huarac, Juan; Resto, Oscar; Carpena-Nuñez, Jennifer; Jadwisienczak, Wojciech M; Fonseca, Luis F; Weiner, Brad R; Morell, Gerardo

    2014-01-22

    We report for the first time the fabrication of single-crystal metastable manganese sulfide nanowires (γ-MnS NWs) conformally coated with graphitic carbon via chemical vapor deposition technique using a single-step route. Advanced spectroscopy and electron microscopy techniques were applied to elucidate the composition and structure of these NWs at the nanoscale, including Raman, XRD, SEM, HRTEM, EELS, EDS, and SAED. No evidence of α-MnS and β-MnS allotropes was found. The γ-MnS/C NWs have hexagonal cross-section and high aspect ratio (∼1000) on a large scale. The mechanical properties of individual γ-MnS/C NWs were examined via in situ uniaxial compression tests in a TEM-AFM. The results show that γ-MnS/C NWs are brittle with a Young's modulus of 65 GPa. The growth mechanism proposed suggests that the bottom-up fabrication of γ-MnS/C NWs is governed by vapor-liquid-solid mechanism catalyzed by bimetallic Au-Ni nanoparticles. The electrochemical performance of γ-MnS/C NWs as an anode material in lithium-ion batteries indicates that they outperform the cycling stability of stable micro-sized α-MnS, with an initial capacity of 1036 mAh g(-1) and a reversible capacity exceeding 503 mAh g(-1) after 25 cycles. This research advances the integration of carbon materials and metal sulfide nanostructures, bringing forth new avenues for potential miniaturization strategies to fabricate 1D core/shell heterostructures with intriguing bifunctional properties that can be used as building blocks in nanodevices. PMID:24392737

  18. Quantum Transport and Nano Angle-resolved Photoemission Spectroscopy on the Topological Surface States of Single Sb2Te3 Nanowires.

    PubMed

    Arango, Yulieth C; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas

    2016-01-01

    We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires. PMID:27581169

  19. Quantum Transport and Nano Angle-resolved Photoemission Spectroscopy on the Topological Surface States of Single Sb2Te3 Nanowires

    PubMed Central

    Arango, Yulieth C.; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C.; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas

    2016-01-01

    We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires. PMID:27581169

  20. High-performance single-crystalline arsenic-doped indium oxide nanowires for transparent thin-film transistors and active matrix organic light-emitting diode displays.

    PubMed

    Chen, Po-Chiang; Shen, Guozhen; Chen, Haitian; Ha, Young-geun; Wu, Chao; Sukcharoenchoke, Saowalak; Fu, Yue; Liu, Jun; Facchetti, Antonio; Marks, Tobin J; Thompson, Mark E; Zhou, Chongwu

    2009-11-24

    We report high-performance arsenic (As)-doped indium oxide (In(2)O(3)) nanowires for transparent electronics, including their implementation in transparent thin-film transistors (TTFTs) and transparent active-matrix organic light-emitting diode (AMOLED) displays. The As-doped In(2)O(3) nanowires were synthesized using a laser ablation process and then fabricated into TTFTs with indium-tin oxide (ITO) as the source, drain, and gate electrodes. The nanowire TTFTs on glass substrates exhibit very high device mobilities (approximately 1490 cm(2) V(-1) s(-1)), current on/off ratios (5.7 x 10(6)), steep subthreshold slopes (88 mV/dec), and a saturation current of 60 microA for a single nanowire. By using a self-assembled nanodielectric (SAND) as the gate dielectric, the device mobilities and saturation current can be further improved up to 2560 cm(2) V(-1) s(-1) and 160 microA, respectively. All devices exhibit good optical transparency (approximately 81% on average) in the visible spectral range. In addition, the nanowire TTFTs were utilized to control green OLEDs with varied intensities. Furthermore, a fully integrated seven-segment AMOLED display was fabricated with a good transparency of 40% and with each pixel controlled by two nanowire transistors. This work demonstrates that the performance enhancement possible by combining nanowire doping and self-assembled nanodielectrics enables silicon-free electronic circuitry for low power consumption, optically transparent, high-frequency devices assembled near room temperature.

  1. Quantum Transport and Nano Angle-resolved Photoemission Spectroscopy on the Topological Surface States of Single Sb2Te3 Nanowires

    NASA Astrophysics Data System (ADS)

    Arango, Yulieth C.; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C.; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas

    2016-09-01

    We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires.

  2. Quantum Transport and Nano Angle-resolved Photoemission Spectroscopy on the Topological Surface States of Single Sb2Te3 Nanowires.

    PubMed

    Arango, Yulieth C; Huang, Liubing; Chen, Chaoyu; Avila, Jose; Asensio, Maria C; Grützmacher, Detlev; Lüth, Hans; Lu, Jia Grace; Schäpers, Thomas

    2016-09-01

    We report on low-temperature transport and electronic band structure of p-type Sb2Te3 nanowires, grown by chemical vapor deposition. Magnetoresistance measurements unravel quantum interference phenomena, which depend on the cross-sectional dimensions of the nanowires. The observation of periodic Aharonov-Bohm-type oscillations is attributed to transport in topologically protected surface states in the Sb2Te3 nanowires. The study of universal conductance fluctuations demonstrates coherent transport along the Aharonov-Bohm paths encircling the rectangular cross-section of the nanowires. We use nanoscale angle-resolved photoemission spectroscopy on single nanowires (nano-ARPES) to provide direct experimental evidence on the nontrivial topological character of those surface states. The compiled study of the bandstructure and the magnetotransport response unambiguosly points out the presence of topologically protected surface states in the nanowires and their substantial contribution to the quantum transport effects, as well as the hole doping and Fermi velocity among other key issues. The results are consistent with the theoretical description of quantum transport in intrinsically doped quasi-one-dimensional topological insulator nanowires.

  3. Single crystalline monoclinic La0.7Sr0.3MnO3 nanowires with high temperature ferromagnetism

    SciTech Connect

    Carretero-Genevrier, Adrian; Gazquez Alabart, Jaume; Idrobo Tapia, Juan C; Oro, Judith; Arbiol, Jordi; Varela del Arco, Maria; Ferain, Etienne; Rodriguez-Carvajal, Juan; Puig, Teresa; Mestres, Narcis; Obradors, Xavier

    2011-01-01

    Porous mixed-valent manganese oxides are a group of multifunctional materials that can be used as molecular sieves, catalysts, battery materials, and gas sensors. However, material properties and thus activity can vary significantly with different synthesis methods or process conditions, such as temperature and time. Here, we report on a new synthesis route for MnO{sub 2} and LaSr-doped molecular sieve single crystalline nanowires based on a solution chemistry methodology combined with the use of nanoporous polymer templates supported on top of single crystalline substrates. Because of the confined nucleation in high aspect ratio nanopores and of the high temperatures attained, new structures with novel physical properties have been produced. During the calcination process, the nucleation and crystallization of {var_epsilon}-MnO{sub 2} nanoparticles with a new hexagonal structure is promoted. These nanoparticles generated up to 30 {mu}m long and flexible hexagonal nanowires at mild growth temperatures (T{sub g} = 700 C) as a consequence of the large crystallographic anisotropy of {var_epsilon}-MnO{sub 2}. The nanocrystallites of MnO{sub 2} formed at low temperatures serve as seeds for the growth of La{sub 0.7}Sr{sub 0.3}MnO{sub 3} nanowires at growth temperatures above 800 C, through the diffusion of La and Sr into the empty 1D-channels of {var_epsilon}-MnO{sub 2}. Our particular growth method has allowed the synthesis of single crystalline molecular sieve (LaSr-2 x 4) monoclinic nanowires with composition La{sub 0.7}Sr{sub 0.3}MnO{sub 3} and with ordered arrangement of La{sup 3+} and Sr{sup 2+} cations inside the 1D-channels. These nanowires exhibit ferromagnetic ordering with strongly enhanced Curie temperature (T{sub c} > 500 K) that probably results from the new crystallographic order and from the mixed valence of manganese.

  4. Synthesis of single crystalline spinel LiMn2O4 nanowires for a lithium ion battery with high power density.

    PubMed

    Hosono, Eiji; Kudo, Tetsuichi; Honma, Itaru; Matsuda, Hirofumi; Zhou, Haoshen

    2009-03-01

    How to improve the specific power density of the rechargeable lithium ion battery has recently become one of the most attractive topics of both scientific and industrial interests. The spinel LiMn2O4 is the most promising candidate as a cathode material because of its low cost and nontoxicity compared with commercial LiCoO2. Moreover, nanostructured electrodes have been widely investigated to satisfy such industrial needs. However, the high-temperature sintering process, which is necessary for high-performance cathode materials based on high-quality crystals, leads the large grain size and aggregation of the nanoparticles which gives poor lithium ion battery performance. So there is still a challenge to synthesize a high-quality single-crystal nanostructured electrode. Among all of the nanostructures, a single crystalline nanowire is the most attractive morphology because the nonwoven fabric morphology constructed by the single crystalline nanowire suppresses the aggregation and grain growth at high temperature, and the potential barrier among the nanosize grains can be ignored. However, the reported single crystalline nanowire is almost the metal oxide with an anisotropic crystal structure because the cubic crystal structure such as LiMn2O4 cannot easily grow in the one-dimentional direction. Here we synthesized high-quality single crystalline cubic spinel LiMn2O4 nanowires based on a novel reaction method using Na0.44MnO2 nanowires as a self-template. These single crystalline spinel LiMn2O4 nanowires show high thermal stability because the nanowire structure is maintained after heating to 800 degrees C for 12 h and excellent performance at high rate charge-discharge, such as 20 A/g, with both a relative flat charge-discharge plateau and excellent cycle stability.

  5. Enhancing the heralded single-photon rate from a silicon nanowire by time and wavelength division multiplexing pump pulses.

    PubMed

    Zhang, X; Jizan, I; He, J; Clark, A S; Choi, D-Y; Chae, C J; Eggleton, B J; Xiong, C

    2015-06-01

    Heralded single photons produced on a silicon chip represent an integrated photon source solution for scalable photonic quantum technologies. The key limitation of such sources is their non-deterministic nature introduced by the stochastic spontaneous four-wave mixing (SFWM) process. Active spatial and temporal multiplexing can improve this by enhancing the single-photon rate without degrading the quantum signal-to-noise ratio. Here, taking advantage of the broad bandwidth of SFWM in a silicon nanowire, we experimentally demonstrate heralded single-photon generation from a silicon nanowire pumped by time and wavelength division multiplexed pulses. We show a 90±5% enhancement on the heralded photon rate at the cost of only 14±2% reduction to the signal-to-noise ratio, close to the performance found using only time division multiplexed pulses. As single-photon events are distributed to multiple wavelength channels, this new scheme overcomes the saturation limit of avalanche single-photon detectors and will improve the ultimate performance of such photon sources. PMID:26030539

  6. Single-Layer Graphene as a Barrier Layer for Intense UV Laser-Induced Damages for Silver Nanowire Network.

    PubMed

    Das, Suprem R; Nian, Qiong; Saei, Mojib; Jin, Shengyu; Back, Doosan; Kumar, Prashant; Janes, David B; Alam, Muhammad A; Cheng, Gary J

    2015-11-24

    Single-layer graphene (SLG) has been proposed as the thinnest protective/barrier layer for wide applications involving resistance to oxidation, corrosion, atomic/molecular diffusion, electromagnetic interference, and bacterial contamination. Functional metallic nanostructures have lower thermal stability than their bulk forms and are therefore susceptible to high energy photons. Here, we demonstrate that SLG can shield metallic nanostructures from intense laser radiation that would otherwise ablate them. By irradiation via a UV laser beam with nanosecond pulse width and a range of laser intensities (in millions of watt per cm(2)) onto a silver nanowire network, and conformally wrapping SLG on top of the nanowire network, we demonstrate that graphene "extracts and spreads" most of the thermal energy away from nanowire, thereby keeping it damage-free. Without graphene wrapping, the radiation would fragment the wires into smaller pieces and even decompose them into droplets. A systematic molecular dynamics simulation confirms the mechanism of SLG shielding. Consequently, particular damage-free and ablation-free laser-based nanomanufacturing of hybrid nanostructures might be sparked off by application of SLG on functional surfaces and nanofeatures. PMID:26447828

  7. Single-step synthesis of In2O3 nanowires decorated with TeO2 nanobeads and their acetone-sensing properties

    NASA Astrophysics Data System (ADS)

    Park, Sunghoon; Kheel, Hyejoon; Sun, Gun-Joo; Park, Sang Eon; Lee, Chongmu

    2016-04-01

    In2O3 nanowires decorated with TeO2 nanobeads were synthesized by a facile single-step thermal evaporation process, and their acetone-gas-sensing properties were examined. The diameters and lengths of the In2O3 nanowires ranged from 10 to 20 nm and up to 100 μm, respectively, whereas the diameters of the TeO2 beads ranged from 50 to 200 nm. The TeO2-decorated In2O3 nanowire sensor showed stronger response to acetone gas than the pristine In2O3 nanowire sensor. The pristine and TeO2-decorated In2O3 nanowires exhibited sensitivity of ~10.13 and ~24.87, respectively, to 200 ppm acetone at 300 °C. The decorated nanowire sensor also showed much more rapid response and recovery than the latter. Both sensors showed the strongest response to acetone gas at 300 °C, respectively. The mechanism and origin of the enhanced acetone-gas-sensing performance of the TeO2-decorated In2O3 nanowire sensor compared to the pristine In2O3 nanowire sensor were discussed in detail. The enhanced sensing performance of the TeO2-decorated In2O3 nanowire is mainly due to the modulation of the potential barrier height at the TeO2-In2O3 interface, high catalytic activity of TeO2, and creation of active adsorption sites by incorporation of TeO2.

  8. Proton radiation hardness of single-nanowire transistors using robust organic gate nanodielectrics

    SciTech Connect

    Ju, Sanghyun; Lee, Kangho; Janes, David B.; Dwivedi, Ramesh C.; Baffour-Awuah, Habibah; Wilkins, R.; Yoon, Myung-Han; Facchetti, Antonio; Mark, Tobin J.

    2006-08-14

    In this contribution, the radiation tolerance of single ZnO nanowire field-effect transistors (NW-FETs) fabricated with a self-assembled superlattice (SAS) gate insulator is investigated and compared with that of ZnO NW-FETs fabricated with a 60 nm SiO{sub 2} gate insulator. A total-radiation dose study was performed using 10 MeV protons at doses of 5.71 and 285 krad(Si). The threshold voltage (V{sub th}) of the SAS-based ZnO NW-FETs is not shifted significantly following irradiation at these doses. In contrast, V{sub th} parameters of the SiO{sub 2}-based ZnO NW-FETs display average shifts of {approx}-4.0 and {approx}-10.9 V for 5.71 and 285 krad(Si) H{sup +} irradiation, respectively. In addition, little change is observed in the subthreshold characteristics (off current, subthreshold slope) of the SAS-based ZnO NW-FETs following H{sup +} irradiation. These results strongly argue that the bulk oxide trap density and interface trap density formed within the SAS and/or at the SAS-ZnO NW interface during H{sup +} irradiation are significantly lower than those for the corresponding SiO{sub 2} gate dielectrics. The radiation-robust SAS-based ZnO NW-FETs are thus promising candidates for future space-based applications in electronics and flexible displays.

  9. Electrically driven polarized single-photon emission from an InGaN quantum dot in a GaN nanowire.

    PubMed

    Deshpande, Saniya; Heo, Junseok; Das, Ayan; Bhattacharya, Pallab

    2013-01-01

    In a classical light source, such as a laser, the photon number follows a Poissonian distribution. For quantum information processing and metrology applications, a non-classical emitter of single photons is required. A single quantum dot is an ideal source of single photons and such single-photon sources in the visible spectral range have been demonstrated with III-nitride and II-VI-based single quantum dots. It has been suggested that short-wavelength blue single-photon emitters would be useful for free-space quantum cryptography, with the availability of high-speed single-photon detectors in this spectral region. Here we demonstrate blue single-photon emission with electrical injection from an In0.25Ga0.75N quantum dot in a single nanowire. The emitted single photons are linearly polarized along the c axis of the nanowire with a degree of linear polarization of ~70%.

  10. Electrically driven polarized single-photon emission from an InGaN quantum dot in a GaN nanowire.

    PubMed

    Deshpande, Saniya; Heo, Junseok; Das, Ayan; Bhattacharya, Pallab

    2013-01-01

    In a classical light source, such as a laser, the photon number follows a Poissonian distribution. For quantum information processing and metrology applications, a non-classical emitter of single photons is required. A single quantum dot is an ideal source of single photons and such single-photon sources in the visible spectral range have been demonstrated with III-nitride and II-VI-based single quantum dots. It has been suggested that short-wavelength blue single-photon emitters would be useful for free-space quantum cryptography, with the availability of high-speed single-photon detectors in this spectral region. Here we demonstrate blue single-photon emission with electrical injection from an In0.25Ga0.75N quantum dot in a single nanowire. The emitted single photons are linearly polarized along the c axis of the nanowire with a degree of linear polarization of ~70%. PMID:23575679

  11. Phase separation in single In(x)Ga(1-x)N nanowires revealed through a hard X-ray synchrotron nanoprobe.

    PubMed

    Segura-Ruiz, J; Martínez-Criado, G; Denker, C; Malindretos, J; Rizzi, A

    2014-03-12

    In this work, we report on the composition, short- and long-range structural order of single molecular beam epitaxy grown In(x)Ga(1-x)N nanowires using a hard X-ray synchrotron nanoprobe. Nano-X-ray fluorescence mapping reveals an axial and radial heterogeneous elemental distribution in the single wires with Ga accumulation at their bottom and outer regions. Polarization-dependent nano-X-ray absorption near edge structure demonstrates that despite the elemental modulation, the tetrahedral order around the Ga atoms remains along the nanowires. Nano-X-ray diffraction mapping on single nanowires shows the existence of at least three different phases at their bottom: an In-poor shell and two In-rich phases. The alloy homogenizes toward the top of the wires, where a single In-rich phase is observed. No signatures of In-metallic precipitates are observed in the diffraction spectra. The In-content along the single nanowires estimated from X-ray fluorescence and diffraction data are in good agreement. A rough picture of these phenomena is briefly presented. We anticipate that this methodology will contribute to a greater understanding of the underlying growth concepts not only of nanowires but also of many nanostructures in materials science.

  12. Single-electron transport in InAs nanowire quantum dots formed by crystal phase engineering

    NASA Astrophysics Data System (ADS)

    Nilsson, Malin; Namazi, Luna; Lehmann, Sebastian; Leijnse, Martin; Dick, Kimberly A.; Thelander, Claes

    2016-05-01

    We report electrical characterization of quantum dots formed by introducing pairs of thin wurtzite (WZ) segments in zinc blende (ZB) InAs nanowires. Regular Coulomb oscillations are observed over a wide gate voltage span, indicating that WZ segments create significant barriers for electron transport. We find a direct correlation of transport properties with quantum dot length and corresponding growth time of the enclosed ZB segment. The correlation is made possible by using a method to extract lengths of nanowire crystal phase segments directly from scanning electron microscopy images, and with support from transmission electron microscope images of typical nanowires. From experiments on controlled filling of nearly empty dots with electrons, up to the point where Coulomb oscillations can no longer be resolved, we estimate a lower bound for the ZB-WZ conduction-band offset of 95 meV.

  13. Anomalous photoconductive behavior of a single InAs nanowire photodetector

    SciTech Connect

    Li, Junshuai; Yan, Xin; Sun, Fukuan; Zhang, Xia Ren, Xiaomin

    2015-12-28

    We report on a bare InAs nanowire photodetector which exhibits an anomalous photoconductive behavior. Under low-power illumination, the current is smaller than the dark current, and monotonously decreases as the excitation power increases. When the excitation power is high enough, the current starts to increase normally. The phenomenon is attributed to different electron mobilities in the “core” and “shell” of a relatively thick nanowire originating from the surface effect, which result in a quickly dropped “core current” and slowly increased “shell current” under illumination.

  14. High performance fiber-coupled NbTiN superconducting nanowire single photon detectors with Gifford-McMahon cryocooler.

    PubMed

    Miki, Shigehito; Yamashita, Taro; Terai, Hirotaka; Wang, Zhen

    2013-04-22

    We present high performance fiber-coupled niobium titanium nitride superconducting nanowire single photon detectors fabricated on thermally oxidized silicon substrates. The best device showed a system detection efficiency (DE) of 74%, dark count rate of 100 c/s, and full width at half maximum timing jitter of 68 ps under a bias current of 18.0 μA with a practical Gifford-McMahon cryocooler system. We also introduced six detectors into the cryocooler and confirmed that the system DE of all detectors was higher than 67% at the dark count rate of 100 c/s.

  15. Amorphization and recrystallization of single-crystalline hydrogen titanate nanowires by N+ ion irradiation

    NASA Astrophysics Data System (ADS)

    Behera, Akshaya K.; Facsko, Stefan; Bandyopadyay, Malay K.; Das, Siddhartha; Chatterjee, Shyamal

    2014-06-01

    We report on the phase transformation of hydrogen titanate (H2Ti3O7) nanowires induced by 50 keV N+ ion irradiation at room temperature with fluences of 1 × 1015 ions/cm2 and 1 × 1016 ions/cm2, respectively. Using transmission electron microscopy, the internal structure of the ion irradiated nanowires is analyzed. At low fluence, a transformation from crystalline H2Ti3O7 to amorphous TiO2 is observed. However, at higher fluence, a remarkable crystalline-amorphous TiO2 core-shell structure is formed. At this higher fluence, the recrystallization occurs in the core of the nanowire and the outer layer remains amorphous. The phase transformation and formation of core-shell structure are explained using the thermal spike model, radiation enhanced diffusion, and classical theory of nucleation and growth under non-equilibrium thermodynamics. X-ray photoelectron spectroscopy and Raman scattering reveal further insight into the structure of the nanowires before and after ion irradiation.

  16. Amorphization and recrystallization of single-crystalline hydrogen titanate nanowires by N{sup +} ion irradiation

    SciTech Connect

    Behera, Akshaya K.; Bandyopadyay, Malay K.; Chatterjee, Shyamal; Facsko, Stefan; Das, Siddhartha

    2014-06-21

    We report on the phase transformation of hydrogen titanate (H{sub 2}Ti{sub 3}O{sub 7}) nanowires induced by 50 keV N{sup +} ion irradiation at room temperature with fluences of 1 × 10{sup 15} ions/cm{sup 2} and 1 × 10{sup 16} ions/cm{sup 2}, respectively. Using transmission electron microscopy, the internal structure of the ion irradiated nanowires is analyzed. At low fluence, a transformation from crystalline H{sub 2}Ti{sub 3}O{sub 7} to amorphous TiO{sub 2} is observed. However, at higher fluence, a remarkable crystalline-amorphous TiO{sub 2} core-shell structure is formed. At this higher fluence, the recrystallization occurs in the core of the nanowire and the outer layer remains amorphous. The phase transformation and formation of core-shell structure are explained using the thermal spike model, radiation enhanced diffusion, and classical theory of nucleation and growth under non-equilibrium thermodynamics. X-ray photoelectron spectroscopy and Raman scattering reveal further insight into the structure of the nanowires before and after ion irradiation.

  17. Structural modulation of nanowire interfaces grown over selectively disrupted single crystal surfaces

    NASA Astrophysics Data System (ADS)

    Garratt, E.; Nikoobakht, B.

    2015-08-01

    Recent breakthroughs in deterministic approaches to the fabrication of nanowire arrays have demonstrated the possibility of fabricating such networks using low-cost scalable methods. In this regard, we have developed a scalable growth platform for lateral fabrication of nanocrystals with high precision utilizing lattice match and symmetry. Using this planar architecture, a number of homo- and heterostructures have been demonstrated including ZnO nanowires grown over GaN. The latter combination produces horizontal, epitaxially formed crystals aligned in the plane of the substrate containing a very low number of intrinsic defects. We use such ordered structures as model systems in the interests of gauging the interfacial structural dynamics in relation to external stimuli. Nanosecond pulses of focused ion beams are used to slightly modify the substrate surface and selectively form lattice disorders in the path of nanowire growth to examine the nanocrystal, namely: its directionality and lattice defects. High resolution electron microscopies are used to reveal some interesting structural effects; for instance, a minimum threshold of surface defects that can divert nanowires. We also discuss data indicating formation of surface strains and show their mitigation during the growth process.

  18. Orientation-and polarization-dependent optical properties of the single Ag nanowire/glass substrate system excited by the evanescent wave

    NASA Astrophysics Data System (ADS)

    Yang, Mu; Cai, Wei; Wang, Yingjie; Sun, Mengtao; Shang, Guangyi

    2016-05-01

    As an important plasmon one-dimensional material, orientation- and polarization-dependent properties of single Ag nanowires/glass substrate system are investigated by a powerful platform consisting of evanescent wave excitation, near-/far-field detection and a micromanipulator. In the case of the nanowire perpendicular or parallel to the incident plane and p- ors-polarized evanescent excitation respectively, optical properties of the nanowire is measured both in far-field and near-field. For the perpendicular situation, scattering light from the nanowire shows strong dependence on the polarization of incident light, and period patterns along the nanowire are observed both in the near- and far-field. The chain of dipole model is used to explain the origin of this pattern. The discrepancy of the period patterns observed in the near- and far-field is due to the different resolution of the near- and far-field detection. For the parallel case, light intensity from the output end also depends on the incident polarization. Both experimental and calculation results show that the polarization dependence effect results from the surface plasmon excitation. These results on the orientation- and polarization-dependent properties of the Ag nanowires detected by the combination of near- and far-field methods would be helpful to understand interactions of one-dimensional plasmonic nanostructures with light.

  19. Orientation-and polarization-dependent optical properties of the single Ag nanowire/glass substrate system excited by the evanescent wave

    PubMed Central

    Yang, Mu; Cai, Wei; Wang, Yingjie; Sun, Mengtao; Shang, Guangyi

    2016-01-01

    As an important plasmon one-dimensional material, orientation- and polarization-dependent properties of single Ag nanowires/glass substrate system are investigated by a powerful platform consisting of evanescent wave excitation, near-/far-field detection and a micromanipulator. In the case of the nanowire perpendicular or parallel to the incident plane and p- ors-polarized evanescent excitation respectively, optical properties of the nanowire is measured both in far-field and near-field. For the perpendicular situation, scattering light from the nanowire shows strong dependence on the polarization of incident light, and period patterns along the nanowire are observed both in the near- and far-field. The chain of dipole model is used to explain the origin of this pattern. The discrepancy of the period patterns observed in the near- and far-field is due to the different resolution of the near- and far-field detection. For the parallel case, light intensity from the output end also depends on the incident polarization. Both experimental and calculation results show that the polarization dependence effect results from the surface plasmon excitation. These results on the orientation- and polarization-dependent properties of the Ag nanowires detected by the combination of near- and far-field methods would be helpful to understand interactions of one-dimensional plasmonic nanostructures with light. PMID:27157123

  20. Epidermal Nbn deletion causes premature hair loss and a phenotype resembling psoriasiform dermatitis.

    PubMed

    Seidel, Philipp; Remus, Martina; Delacher, Michael; Grigaravicius, Paulius; Reuss, David E; Frappart, Lucien; von Deimling, Andreas; Feuerer, Markus; Abdollahi, Amir; Frappart, Pierre-Olivier

    2016-04-26

    Nijmegen Breakage Syndrome is a disease caused by NBN mutations. Here, we report a novel function of Nbn in skin homeostasis. We found that Nbn deficiency in hair follicle (HF) progenitors promoted increased DNA damage signaling, stimulating p16Ink4a up-regulation, Trp53 stabilization and cytokines secretion leading to HF-growth arrest and hair loss. At later stages, the basal keratinocytes layer exhibited also enhanced DNA damage response but in contrast to the one in HF progenitor was not associated with pro-inflammatory cytokines expression, but rather increased proliferation, lack of differentiation and immune response resembling psoriasiform dermatitis. Simultaneous Nbn and Trp53 inactivation significantly exacerbated this phenotype, due to the lack of inhibition of pro-inflammatory cytokines secretion by Trp53. Altogether, we demonstrated novel functions of Nbn in HF maintenance and prevention of skin inflammation and we provide a mechanistic explanation that links cell intrinsic DNA maintenance with large scale morphological tissue alterations.

  1. Size- and structure-dependence of thermal and mechanical behaviors of single-crystalline and polytypic superlattice ZnS nanowires

    SciTech Connect

    Moon, Junghwan; Cho, Maenghyo; Zhou, Min

    2015-06-07

    Molecular dynamics (MD) simulations are carried out to study the thermal and mechanical behaviors of single-crystalline wurtzite (WZ), zinc-blende (ZB), and polytypic superlattice ZnS nanowires containing alternating WZ and ZB regions with thicknesses between 1.85 nm and 29.62 nm under tensile loading. The wires analyzed have diameters between 1.77 nm and 5.05 nm. The Green-Kubo method is used to calculate the thermal conductivity of the wires at different deformed states. A non-equilibrium MD approach is used to analyze the thermal transport behavior at the interfaces between different structural regions in the superlattice nanowires (SLNWs). The Young's modulus and thermal conductivity of ZB nanowires are approximately 2%–12% and 23%–35% lower than those of WZ nanowires, respectively. The lower initial residual compressive stress due to higher irregularity of surface atoms causes the Young's modulus of ZB nanowires to be lower. The dependence of the thermal conductivity on structure comes from differences in phonon group velocities associated with the different wires. The thermal conductivity of polytypic superlattice nanowires is up to 55% lower than that of single-crystalline nanowires, primarily because of phonon scattering at the interfaces and the resulting lower effective phonon mean free paths for each structural region. As the periodic lengths (1.85–29.62 nm) and specimen lengths (14.81–59.24 nm) of SLNWs decrease, these effects become more pronounced, causing the thermal conductivity to further decrease by up to 30%.

  2. Observation of Charge Separation and Space-Charge Region in Single-Crystal P3HT/C60 Heterojunction Nanowires.

    PubMed

    Park, Kyung Sun; Lee, Ki Seok; Baek, Jangmi; Lee, Lynn; Son, Byung Hee; Koo Lee, Yong-Eun; Ahn, Yeong Hwan; Park, Won Il; Kang, Youngjong; Sung, Myung M

    2016-08-22

    We directly observed charge separation and a space-charge region in an organic single-crystal p-n heterojunction nanowire, by means of scanning photocurrent microscopy. The axial p-n heterojunction nanowire had a well-defined planar junction, consisted of P3HT (p-type) and C60 (n-type) single crystals and was fabricated by means of the recently developed inkjet-assisted nanotransfer printing technique. The depletion region formed at the p-n junction was directly observed by exploring the spatial distribution of photogenerated carriers along the heterojunction nanowire under various applied bias voltages. Our study provides a facile approach toward the precise characterization of charge transport in organic heterojunction systems as well as the design of efficient nanoscale organic optoelectronic devices. PMID:27461905

  3. Observation of Charge Separation and Space-Charge Region in Single-Crystal P3HT/C60 Heterojunction Nanowires.

    PubMed

    Park, Kyung Sun; Lee, Ki Seok; Baek, Jangmi; Lee, Lynn; Son, Byung Hee; Koo Lee, Yong-Eun; Ahn, Yeong Hwan; Park, Won Il; Kang, Youngjong; Sung, Myung M

    2016-08-22

    We directly observed charge separation and a space-charge region in an organic single-crystal p-n heterojunction nanowire, by means of scanning photocurrent microscopy. The axial p-n heterojunction nanowire had a well-defined planar junction, consisted of P3HT (p-type) and C60 (n-type) single crystals and was fabricated by means of the recently developed inkjet-assisted nanotransfer printing technique. The depletion region formed at the p-n junction was directly observed by exploring the spatial distribution of photogenerated carriers along the heterojunction nanowire under various applied bias voltages. Our study provides a facile approach toward the precise characterization of charge transport in organic heterojunction systems as well as the design of efficient nanoscale organic optoelectronic devices.

  4. nBn Infrared Detector Containing Graded Absorption Layer

    NASA Technical Reports Server (NTRS)

    Gunapala, Sarath D.; Ting, David Z.; Hill, Cory J.; Bandara, Sumith V.

    2009-01-01

    It has been proposed to modify the basic structure of an nBn infrared photodetector so that a plain electron-donor- type (n-type) semiconductor contact layer would be replaced by a graded n-type III V alloy semiconductor layer (i.e., ternary or quarternary) with appropriate doping gradient. The abbreviation nBn refers to one aspect of the unmodified basic device structure: There is an electron-barrier ("B" ) layer between two n-type ("n" ) layers, as shown in the upper part of the figure. One of the n-type layers is the aforementioned photon-absorption layer; the other n-type layer, denoted the contact layer, collects the photocurrent. The basic unmodified device structure utilizes minority-charge-carrier conduction, such that, for reasons too complex to explain within the space available for this article, the dark current at a given temperature can be orders of magnitude lower (and, consequently, signal-to-noise ratios can be greater) than in infrared detectors of other types. Thus, to obtain a given level of performance, less cooling (and, consequently, less cooling equipment and less cooling power) is needed. [In principle, one could obtain the same advantages by means of a structure that would be called pBp because it would include a barrier layer between two electron-acceptor- type (p-type) layers.] The proposed modifications could make it practical to utilize nBn photodetectors in conjunction with readily available, compact thermoelectric coolers in diverse infrared- imaging applications that could include planetary exploration, industrial quality control, monitoring pollution, firefighting, law enforcement, and medical diagnosis.

  5. 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.

  6. Luminescence and electrical properties of single ZnO/MgO core/shell nanowires

    SciTech Connect

    Grinblat, Gustavo; Comedi, David; Bern, Francis; Barzola-Quiquia, José; Esquinazi, Pablo; Tirado, Mónica

    2014-03-10

    To neutralise the influence of the surface of ZnO nanowires for photonics and optoelectronic applications, we have covered them with insulating MgO film and individually contacted them for electrical characterisation. We show that such a metal-insulator-semiconductor-type nanodevice exhibits a high diode ideality factor of 3.4 below 1 V. MgO shell passivates ZnO surface states and provides confining barriers to electrons and holes within the ZnO core, favouring excitonic ultraviolet radiative recombination, while suppressing defect-related luminescence in the visible and improving electrical conductivity. The results indicate the potential use of ZnO/MgO nanowires as a convenient building block for nano-optoelectronic devices.

  7. Nanowire photonic crystal waveguides for single-atom trapping and strong light-matter interactions

    SciTech Connect

    Yu, S.-P.; Hood, J. D.; Muniz, J. A.; Martin, M. J.; Hung, C.-L.; Kimble, H. J.; Norte, Richard; Meenehan, Seán M.; Cohen, Justin D.; Painter, Oskar

    2014-03-17

    We present a comprehensive study of dispersion-engineered nanowire photonic crystal waveguides suitable for experiments in quantum optics and atomic physics with optically trapped atoms. Detailed design methodology and specifications are provided, as are the processing steps used to create silicon nitride waveguides of low optical loss in the near-IR. Measurements of the waveguide optical properties and power-handling capability are also presented.

  8. Single crystalline cylindrical nanowires - toward dense 3D arrays of magnetic vortices.

    PubMed

    Ivanov, Yurii P; Chuvilin, Andrey; Vivas, Laura G; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-03-31

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories.

  9. Single crystalline cylindrical nanowires – toward dense 3D arrays of magnetic vortices

    PubMed Central

    Ivanov, Yurii P.; Chuvilin, Andrey; Vivas, Laura G.; Kosel, Jurgen; Chubykalo-Fesenko, Oksana; Vázquez, Manuel

    2016-01-01

    Magnetic vortex-based media have recently been proposed for several applications of nanotechnology; however, because lithography is typically used for their preparation, their low-cost, large-scale fabrication is a challenge. One solution may be to use arrays of densely packed cobalt nanowires that have been efficiently fabricated by electrodeposition. In this work, we present this type of nanoscale magnetic structures that can hold multiple stable magnetic vortex domains at remanence with different chiralities. The stable vortex state is observed in arrays of monocrystalline cobalt nanowires with diameters as small as 45 nm and lengths longer than 200 nm with vanishing magnetic cross talk between closely packed neighboring wires in the array. Lorentz microscopy, electron holography and magnetic force microscopy, supported by micromagnetic simulations, show that the structure of the vortex state can be adjusted by varying the aspect ratio of the nanowires. The data we present here introduce a route toward the concept of 3-dimensional vortex-based magnetic memories. PMID:27030143

  10. Quantum detector tomography of a time-multiplexed superconducting nanowire single-photon detector at telecom wavelengths.

    PubMed

    Natarajan, Chandra M; Zhang, Lijian; Coldenstrodt-Ronge, Hendrik; Donati, Gaia; Dorenbos, Sander N; Zwiller, Val; Walmsley, Ian A; Hadfield, Robert H

    2013-01-14

    Superconducting nanowire single-photon detectors (SNSPDs) are widely used in telecom wavelength optical quantum information science applications. Quantum detector tomography allows the positive-operator-valued measure (POVM) of a single-photon detector to be determined. We use an all-fiber telecom wavelength detector tomography test bed to measure detector characteristics with respect to photon flux and polarization, and hence determine the POVM. We study the SNSPD both as a binary detector and in an 8-bin, fiber based, Time-Multiplexed (TM) configuration at repetition rates up to 4 MHz. The corresponding POVMs provide an accurate picture of the photon number resolving capability of the TM-SNSPD. PMID:23388983

  11. Characterization of planar pn heterojunction diodes constructed with Cu2O nanoparticle films and single ZnO nanowires.

    PubMed

    Kwak, Kiyeol; Cho, Kyoungah; Kim, Sangsig

    2013-05-01

    In this study, we fabricate planar pn heterojunction diodes composed of Cu2O nanoparticle (NP) films and single ZnO nanowires (NWs) on SiO2 (300 nm)/Si substrates and investigate their characteristics in the dark and under the illumination of white light and 325 nm wavelength light. The diode at bias voltages of +/- 1 V shows rectification ratios of 10 (in the dark) and 34 (under the illumination of white light). On the other hand, the diode exposed to the 325 nm wavelength light exhibits Ohmic characteristics which are associated with efficient photocurrent generation in both the Cu2O NP film and the single ZnO NW. PMID:23858873

  12. Highly sensitive silicon nanowire biosensor with novel liquid gate control for detection of specific single-stranded DNA molecules.

    PubMed

    Adam, Tijjani; Hashim, U

    2015-05-15

    The study demonstrates the development of a liquid-based gate-control silicon nanowire biosensor for detection of specific single-stranded DNA (ssDNA) molecules. The sensor was fabricated using conventional photolithography coupled with an inductively coupled plasma dry etching process. Prior to the application of DNA to the device, its linear response to pH was confirmed by serial dilution from pH 2 to pH 14. Then, the sensor surface was silanized and directly aminated with (3-aminopropyl) triethoxysilane to create a molecular binding chemistry for biofunctionalization. The resulting Si‒O‒Si‒ components were functionalized with receptor ssDNA, which interacted with the targeted ssDNA to create a field across the silicon nanowire and increase the current. The sensor shows selectivity for the target ssDNA in a linear range from target ssDNA concentrations of 100 pM to 25 nM. With its excellent detection capabilities, this sensor platform is promising for detection of specific biomarkers and other targeted proteins. PMID:25453738

  13. Electrically robust metal nanowire network formation by in-situ interconnection with single-walled carbon nanotubes.

    PubMed

    Woo, Jong Seok; Han, Joong Tark; Jung, Sunshin; Jang, Jeong In; Kim, Ho Young; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

    2014-01-01

    Modulation of the junction resistance between metallic nanowires is a crucial factor for high performance of the network-structured conducting film. Here, we show that under current flow, silver nanowire (AgNW) network films can be stabilised by minimizing the Joule heating at the NW-NW junction assisted by in-situ interconnection with a small amount (less than 3 wt%) of single-walled carbon nanotubes (SWCNTs). This was achieved by direct deposition of AgNW suspension containing SWCNTs functionalised with quadruple hydrogen bonding moieties excluding dispersant molecules. The electrical stabilisation mechanism of AgNW networks involves the modulation of the electrical transportation pathway by the SWCNTs through the SWCNT-AgNW junctions, which results in a relatively lower junction resistance than the NW-NW junction in the network film. In addition, we propose that good contact and Fermi level matching between AgNWs and modified SWCNTs lead to the modulation of the current pathway. The SWCNT-induced stabilisation of the AgNW networks was also demonstrated by irradiating the film with microwaves. The development of the high-throughput fabrication technology provides a robust and scalable strategy for realizing high-performance flexible transparent conductor films.

  14. Si nanowires by a single-step metal-assisted chemical etching process on lithographically defined areas: formation kinetics

    PubMed Central

    2011-01-01

    In this paper, we investigate the formation kinetics of Si nanowires [SiNWs] on lithographically defined areas using a single-step metal-assisted chemical etching process in an aqueous HF/AgNO3 solution. We show that the etch rate of Si, and consequently, the SiNW length, is much higher on the lithographically defined areas compared with that on the non-patterned areas. A comparative study of the etch rate in the two cases under the same experimental conditions showed that this effect is much more pronounced at the beginning of the etching process. Moreover, it was found that in both cases, the nanowire formation rate is linear with temperature in the range from 20°C to 50°C, with almost the same activation energy, as obtained from an Arrhenius plot (0.37 eV in the case of non-patterned areas, while 0.38 eV in the case of lithographically patterned areas). The higher etch rate on lithographically defined areas is mainly attributed to Si surface modification during the photolithographic process. PACS: 68; 68.65-k. PMID:22087735

  15. Electrically Robust Metal Nanowire Network Formation by In-Situ Interconnection with Single-Walled Carbon Nanotubes

    PubMed Central

    Woo, Jong Seok; Han, Joong Tark; Jung, Sunshin; Jang, Jeong In; Kim, Ho Young; Jeong, Hee Jin; Jeong, Seung Yol; Baeg, Kang-Jun; Lee, Geon-Woong

    2014-01-01

    Modulation of the junction resistance between metallic nanowires is a crucial factor for high performance of the network-structured conducting film. Here, we show that under current flow, silver nanowire (AgNW) network films can be stabilised by minimizing the Joule heating at the NW-NW junction assisted by in-situ interconnection with a small amount (less than 3 wt%) of single-walled carbon nanotubes (SWCNTs). This was achieved by direct deposition of AgNW suspension containing SWCNTs functionalised with quadruple hydrogen bonding moieties excluding dispersant molecules. The electrical stabilisation mechanism of AgNW networks involves the modulation of the electrical transportation pathway by the SWCNTs through the SWCNT-AgNW junctions, which results in a relatively lower junction resistance than the NW-NW junction in the network film. In addition, we propose that good contact and Fermi level matching between AgNWs and modified SWCNTs lead to the modulation of the current pathway. The SWCNT-induced stabilisation of the AgNW networks was also demonstrated by irradiating the film with microwaves. The development of the high-throughput fabrication technology provides a robust and scalable strategy for realizing high-performance flexible transparent conductor films. PMID:24763208

  16. Confined-space synthesis of single crystal TiO₂ nanowires in atmospheric vessel at low temperature: a generalized approach.

    PubMed

    Wang, Xiaoyue; Wang, Hai; Zhou, Yu; Liu, Yong; Li, Baojun; Zhou, Xiang; Shen, Hui

    2015-01-30

    Extensive efforts have been devoted to develop innovative synthesis strategies for nanomaterials in order to exploit the true potential of nanotechnology. However, most approaches require high temperature or high pressure to favor crystallization. Here we highlight an unconventional approach for the confined-space synthesis of the single crystal TiO₂ nanowires in the atmospheric vessel at low temperature by cleverly manipulating the unique physical properties of straight-chain saturated fatty acids. Our method also applys to icosane due to its straight-chain saturated hydrocarbon structure and similar physical properties to the saturated fatty acids. Interestingly, we also found that the unsaturated fatty acids can facilitate the crystal growth, but their bent chains lead to the formation of TiO₂ particle aggregates. In addition, we demonstrate the growth of TiO₂ nanowires on arbitrary substrates, which are of great importance for their wider applications. We thus anticipate our presented method to be a possible starting point for non-classical crystallization strategies and be easily adapted for the fabrication of all other inorganic materials.

  17. Study on limiting efficiencies of a-Si:H/μc-Si:H-based single-nanowire solar cells under single and tandem junction configurations

    SciTech Connect

    Zhai, Xiongfei; Cao, Guoyang; Wu, Shaolong E-mail: xfli@suda.edu.cn; Shang, Aixue; Li, Xiaofeng E-mail: xfli@suda.edu.cn

    2015-11-02

    Detailed balance calculations are presented for a-Si:H/μc-Si:H-based single- and tandem-junction single-nanowire solar cells (S- and T-SNSCs). Our study is based on three-dimensional finite-element electromagnetic simulation and thermodynamic balanced analysis, which includes radiative and Auger recombinations simultaneously. We quantify and compare the limiting short-circuit current densities, open-circuit voltages, and light-conversion efficiencies of these highly compact photovoltaic cells, addressing especially the effect of Auger recombination on the open-circuit voltages of SNSCs. Results show that tandem design leads to much higher light-conversion capability than μc-Si:H S-SNSCs, but exhibits superior performance than a-Si:H S-SNSCs only for cells with large radii.

  18. Study on limiting efficiencies of a-Si:H/μc-Si:H-based single-nanowire solar cells under single and tandem junction configurations

    NASA Astrophysics Data System (ADS)

    Zhai, Xiongfei; Cao, Guoyang; Wu, Shaolong; Shang, Aixue; Li, Xiaofeng

    2015-11-01

    Detailed balance calculations are presented for a-Si:H/μc-Si:H-based single- and tandem-junction single-nanowire solar cells (S- and T-SNSCs). Our study is based on three-dimensional finite-element electromagnetic simulation and thermodynamic balanced analysis, which includes radiative and Auger recombinations simultaneously. We quantify and compare the limiting short-circuit current densities, open-circuit voltages, and light-conversion efficiencies of these highly compact photovoltaic cells, addressing especially the effect of Auger recombination on the open-circuit voltages of SNSCs. Results show that tandem design leads to much higher light-conversion capability than μc-Si:H S-SNSCs, but exhibits superior performance than a-Si:H S-SNSCs only for cells with large radii.

  19. Growth of aligned single-crystalline rutile TiO2 nanowires on arbitrary substrates and their application in dye-sensitized solar cells

    SciTech Connect

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

    2010-05-06

    TiO{sub 2} is a wide band gap semiconductor with important applications in photovoltaic cells and photocatalysis. In this paper, we report synthesis of single-crystalline rutile phase TiO{sub 2} nanowires on arbitrary substrates, including fluorine-doped tin oxide (FTO), glass slides, tin-doped indium oxide (ITO), Si/SiO{sub 2}, Si(100), Si(111), and glass rods. By controlling the growth parameters such as growth temperature, precursor concentrations, and so forth, we demonstrate that anisotropic growth of TiO{sub 2} is possible leading to various morphologies of nanowires. Optimization of the growth recipe leads to well-aligned vertical array of TiO{sub 2} nanowires on both FTO and glass substrates. Effects of various titanium precursors on the growth kinetics, especially on the growth rate of nanowires, are also studied. Finally, application of vertical array of TiO{sub 2} nanowires on FTO as the photoanode is demonstrated in dye-sensitized solar cell with an efficiency of 2.9 ± 0.2%.

  20. Highly Ordered Single Crystalline Nanowire Array Assembled Three-Dimensional Nb3O7(OH) and Nb2O5 Superstructures for Energy Storage and Conversion Applications.

    PubMed

    Zhang, Haimin; Wang, Yun; Liu, Porun; Chou, Shu Lei; Wang, Jia Zhao; Liu, Hongwei; Wang, Guozhong; Zhao, Huijun

    2016-01-26

    Three-dimensional (3D) metal oxide superstructures have demonstrated great potentials for structure-dependent energy storage and conversion applications. Here, we reported a facile hydrothermal method for direct growth of highly ordered single crystalline nanowire array assembled 3D orthorhombic Nb3O7(OH) superstructures and their subsequent thermal transformation into monoclinic Nb2O5 with well preserved 3D nanowire superstructures. The performance of resultant 3D Nb3O7(OH) and Nb2O5 superstructures differed remarkably when used for energy conversion and storage applications. The thermally converted Nb2O5 superstructures as anode material of lithium-ion batteries (LiBs) showed higher capacity and excellent cycling stability compared to the Nb3O7(OH) superstructures, while directly hydrothermal grown Nb3O7(OH) nanowire superstructure film on FTO substrate as photoanode of dye-sensitized solar cells (DSSCs) without the need for further calcination exhibited an overall light conversion efficiency of 6.38%, higher than that (5.87%) of DSSCs made from the thermally converted Nb2O5 film. The high energy application performance of the niobium-based nanowire superstructures with different chemical compositions can be attributed to their large surface area, superior electron transport property, and high light utilization efficiency resulting from a 3D superstructure, high crystallinity, and large sizes. The formation process of 3D nanowire superstructures before and after thermal treatment was investigated and discussed based on our theoretical and experimental results. PMID:26579783

  1. Evanescent-wave pumped room-temperature single-mode GaAs/AlGaAs core-shell nanowire lasers

    SciTech Connect

    Wei, Wei; Zhang, Xia Ren, Xiaomin; Liu, Yange Wang, Zhi

    2014-06-02

    Evanescent-wave pumped room-temperature single-mode GaAs/AlGaAs core-shell nanowire lasers are proposed and demonstrated. The nanowires are axially excited by evanescent wave outside a microfiber with a diameter about 10 μm via a ns-pulse laser. The lasing emission with a low effective threshold less than 90 nJ is achieved at 868.62 nm along with a linewidth of ∼1.8 nm. Moreover, multiple lasing lines in a wavelength range from 852.56 nm to 882.48 nm are observed. The mechanism of diverse lasing wavelengths is revealed. Furthermore, the proposed GaAs/AlGaAs nanowire laser has advantages such as simple structure, easy to operate, and controllable lasing wavelength, tending to be practical in optical communications and integrated photonic circuits.

  2. ZnO nanowires array grown on Ga-doped ZnO single crystal for dye-sensitized solar cells

    PubMed Central

    Hu, Qichang; Li, Yafeng; Huang, Feng; Zhang, Zhaojun; Ding, Kai; Wei, Mingdeng; Lin, Zhang

    2015-01-01

    High quality ZnO nanowires arrays were homoepitaxial grown on Ga-doped ZnO single crystal (GZOSC), which have the advantages of high conductivity, high carrier mobility and high thermal stability. When it was employed as a photoanode in the DSSCs, the cell exhibited a 1.44% power-conversion efficiency under the illumination of one sun (AM 1.5G). The performance is superior to our ZnO nanowires/FTO based DSSCs under the same condition. This enhanced performance is mainly attributed to the perfect interface between the ZnO nanowires and the GZOSC substrate that contributes to lower carrier scattering and recombination rates compared with that grown on traditional FTO substrate. PMID:26099568

  3. Spatially resolved study of polarized micro-photoluminescence spectroscopy on single GaAs nanowires with mixed zincblende and wurtzite phases

    SciTech Connect

    Mukherjee, Amlan; Ghosh, Sandip; Breuer, Steffen; Jahn, Uwe; Geelhaar, Lutz; Grahn, Holger T.

    2015-02-07

    Localized and polarized photoluminescence spectra are observed in single GaAs nanowires with mixed zincblende and wurtzite phases, grown using molecular beam epitaxy. For low excitation intensities, the photoluminescence emission exhibits narrow spectral features predominantly polarized perpendicular to the nanowire axis. For high excitation intensities, the photoluminescence spectra transform into dominant broadened features, which exhibit different peak energies and polarization properties. The strongly polarized emission at high excitation intensities is identified as being due to a spatially direct transition in wurtzite sections of the nanowires. The analysis, including band structure calculations suggests that carriers in the wurtzite sections diffuse into regions where the average low-temperature peak emission energy and crystal field parameter are 1.535 eV and 20 meV, respectively.

  4. Development of palladium nanowires

    NASA Astrophysics Data System (ADS)

    Cheng, Chuanding

    Inherent limitations of traditional lithography have prompted the search for means of achieving self-assembly of nano-scale structures and networks for the next generation of electronic and photonic devices. The nanowire, the basic building block of a nanocircuit, has recently become the focus of intense research. Reports on nanowire synthesis and assembly have appeared in the scientific literature, which include Vapor-Liquid-Solid mechanism, template-based electrochemical fabrication, solvothermal or wet chemistry, and assembly by fluid alignment or microchannel networks. An ideal approach for practical application of nanowires would circumvent technical and economic constraints of templating. Here we report on the self-assembly of highly-ordered metallic nanowires directly from a palladium acetate solution under an applied alternating current (AC) electric field of relatively high intensity and frequency. DNA-templated nanowires are first presented here. DNA molecules were stretched and positioned by electric field, followed by metallization by palladium acetate solution. Palladium nanowire arrays have been found to grow directly between microelectrodes without any template, under an alternating electric field of relatively high intensity and frequency. The wires grew spontaneously along the direction of the electric field and have high uniformity and conductivity. Single 75 nm-diameter palladium nanowires have also been self-assembled from aqueous solution at predefined locations between 15 mum-gap electrodes built on a SiO2 substrate. Nanowire assembly was initiated by application an electric field, and it occurred only along the direction of field lines where the field is strongest. Related metals did not support single nanowire assembly under comparable conditions. Current-limiting circuits for controlled nanowire synthesis, electric field simulation, and growth mechanism were studied. The simple and straightforward approach to nanowire assembly outlined here

  5. High-efficiency superconducting nanowire single-photon detectors fabricated from MoSi thin-films

    NASA Astrophysics Data System (ADS)

    Verma, V. B.; Korzh, B.; Bussières, F.; Horansky, R. D.; Dyer, S. D.; Lita, A. E.; Vayshenker, I.; Marsili, F.; Shaw, M. D.; Zbinden, H.; Mirin, R. P.; Nam, S. W.

    2015-12-01

    We demonstrate high-efficiency superconducting nanowire single-photon detectors (SNSPDs) fabricated from MoSi thin-films. We measure a maximum system detection efficiency (SDE) of 87 +- 0.5 % at 1542 nm at a temperature of 0.7 K, with a jitter of 76 ps, maximum count rate approaching 10 MHz, and polarization dependence as low as 3.4 +- 0.7 % The SDE curves show saturation of the internal efficiency similar to WSi-based SNSPDs at temperatures as high as 2.3 K. We show that at similar cryogenic temperatures, MoSi SNSPDs achieve efficiencies comparable to WSi-based SNSPDs with nearly a factor of two reduction in jitter.

  6. Satellite laser ranging using superconducting nanowire single-photon detectors at 1064  nm wavelength.

    PubMed

    Xue, Li; Li, Zhulian; Zhang, Labao; Zhai, Dongsheng; Li, Yuqiang; Zhang, Sen; Li, Ming; Kang, Lin; Chen, Jian; Wu, Peiheng; Xiong, Yaoheng

    2016-08-15

    Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26''), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit. PMID:27519105

  7. High-efficiency WSi superconducting nanowire single-photon detectors operating at 2.5 K

    SciTech Connect

    Verma, V. B.; Horansky, R. D.; Lita, A. E.; Mirin, R. P.; Nam, S. W.; Korzh, B.; Bussières, F.; Zbinden, H.; Marsili, F.; Shaw, M. D.

    2014-09-22

    We investigate the operation of WSi superconducting nanowire single-photon detectors (SNSPDs) at 2.5 K, a temperature which is ∼70% of the superconducting transition temperature (T{sub C}) of 3.4 K. We demonstrate saturation of the system detection efficiency at 78 ± 2% at a wavelength of 1310 nm, with a jitter of 191 ps. We find that the jitter at 2.5 K is limited by the noise of the readout and can be improved through the use of cryogenic amplifiers. Operation of SNSPDs with high efficiency at temperatures very close to T{sub C} appears to be a unique property of amorphous WSi.

  8. High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

    SciTech Connect

    Wu, Y.; Li, X.; Xu, P.; Wang, Y.; Shen, X.; Liu, X.; Yang, Q.; Hasan, T.

    2015-02-02

    We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 μA) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 μA current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecture offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.

  9. Fabry-Perot Microcavity Modes in Single GaP/GaNP Core/Shell Nanowires.

    PubMed

    Dobrovolsky, Alexander; Stehr, Jan E; Sukrittanon, Supanee; Kuang, Yanjin; Tu, Charles W; Chen, Weimin M; Buyanova, Irina A

    2015-12-16

    Semiconductor nanowires (NWs) are attracting increasing interest as nanobuilding blocks for optoelectronics and photonics. A novel material system that is highly suitable for these applications are GaNP NWs. In this article, we show that individual GaP/GaNP core/shell nanowires (NWs) grown by molecular beam epitaxy on Si substrates can act as Fabry-Perot (FP) microcavities. This conclusion is based on results of microphotoluminescence (μ-PL) measurements performed on individual NWs, which reveal periodic undulations of the PL intensity that follow an expected pattern of FP cavity modes. The cavity is concluded to be formed along the NW axis with the end facets acting as reflecting mirrors. The formation of the FP modes is shown to be facilitated by an increasing index contrast with the surrounding media. Spectral dependence of the group refractive index is also determined for the studied NWs. The observation of the FP microcavity modes in the GaP/GaNP core/shell NWs can be considered as a first step toward achieving lasing in this quasidirect bandgap semiconductor in the NW geometry.

  10. Electrical transport properties of single undoped and n-type doped InN nanowires.

    PubMed

    Richter, T; Lüth, H; Schäpers, Th; Meijers, R; Jeganathan, K; Estévez Hernández, S; Calarco, R; Marso, M

    2009-10-01

    Electrical transport properties of undoped and n-type doped InN nanowires grown by molecular beam epitaxy were studied by current-voltage and back-gate field-effect transistor measurements. The current-voltage characteristics show ohmic behavior in the temperature range between 4 and 300 K. Down to about 120 K a linear decrease in resistance with temperature is observed. The investigation of a large number of nanowires revealed for undoped as well as doped wires an approximately linear relation between the normalized conductance and diameter for wires with a diameter below 100 nm. This shows that the main conduction takes place in the tubular surface accumulation layer of the wires. In contrast, for doped wires with a diameter larger than 100 nm a quadratic dependence of conduction on the diameter was found, which is attributed to bulk conductance as the main contribution. The successful doping of the wires is confirmed by an enhanced conduction and by the results of the back-gate field-effect transistor measurements. PMID:19738304

  11. Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn

    NASA Astrophysics Data System (ADS)

    Zhang, Ying; Wong, Chi Ho; Shen, Junying; Sze, Sin Ting; Zhang, Bing; Zhang, Haijing; Dong, Yan; Xu, Hui; Yan, Zifeng; Li, Yingying; Hu, Xijun; Lortz, Rolf

    2016-09-01

    Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner ‘bulk’ contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state.

  12. Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn

    PubMed Central

    Zhang, Ying; Wong, Chi Ho; Shen, Junying; Sze, Sin Ting; Zhang, Bing; Zhang, Haijing; Dong, Yan; Xu, Hui; Yan, Zifeng; Li, Yingying; Hu, Xijun; Lortz, Rolf

    2016-01-01

    Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner ‘bulk’ contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state. PMID:27595646

  13. Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn.

    PubMed

    Zhang, Ying; Wong, Chi Ho; Shen, Junying; Sze, Sin Ting; Zhang, Bing; Zhang, Haijing; Dong, Yan; Xu, Hui; Yan, Zifeng; Li, Yingying; Hu, Xijun; Lortz, Rolf

    2016-01-01

    Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner 'bulk' contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state. PMID:27595646

  14. Dramatic enhancement of superconductivity in single-crystalline nanowire arrays of Sn.

    PubMed

    Zhang, Ying; Wong, Chi Ho; Shen, Junying; Sze, Sin Ting; Zhang, Bing; Zhang, Haijing; Dong, Yan; Xu, Hui; Yan, Zifeng; Li, Yingying; Hu, Xijun; Lortz, Rolf

    2016-01-01

    Sn is a classical superconductor on the border between type I and type II with critical temperature of 3.7 K. We show that its critical parameters can be dramatically increased if it is brought in the form of loosely bound bundles of thin nanowires. The specific heat displays a pronounced double phase transition at 3.7 K and 5.5 K, which we attribute to the inner 'bulk' contribution of the nanowires and to the surface contribution, respectively. The latter is visible only because of the large volume fraction of the surface layer in relation to the bulk volume. The upper transition coincides with the onset of the resistive transition, while zero resistance is gradually approached below the lower transition. In contrast to the low critical field Hc = 0.03 T of Sn in its bulk form, a magnetic field of more than 3 T is required to fully restore the normal state.

  15. High quantum efficiency and low dark count rate in multi-layer superconducting nanowire single-photon detectors

    SciTech Connect

    Jafari Salim, A. Eftekharian, A.; Hamed Majedi, A.

    2014-02-07

    In this paper, we theoretically show that a multi-layer superconducting nanowire single-photon detector (SNSPD) is capable of approaching characteristics of an ideal SNSPD in terms of the quantum efficiency, dark count, and band-width. A multi-layer structure improves the performance in two ways. First, the potential barrier for thermally activated vortex crossing, which is the major source of dark counts and the reduction of the critical current in SNSPDs is elevated. In a multi-layer SNSPD, a vortex is made of 2D-pancake vortices that form a stack. It will be shown that the stack of pancake vortices effectively experiences a larger potential barrier compared to a vortex in a single-layer SNSPD. This leads to an increase in the experimental critical current as well as significant decrease in the dark count rate. In consequence, an increase in the quantum efficiency for photons of the same energy or an increase in the sensitivity to photons of lower energy is achieved. Second, a multi-layer structure improves the efficiency of single-photon absorption by increasing the effective optical thickness without compromising the single-photon sensitivity.

  16. Electroplating and magnetostructural characterization of multisegmented Co54Ni46/Co85Ni15 nanowires from single electrochemical bath in anodic alumina templates

    PubMed Central

    2013-01-01

    Highly hexagonally ordered hard anodic aluminum oxide membranes, which have been modified by a thin cover layer of SiO2 deposited by atomic layer deposition method, were used as templates for the synthesis of electrodeposited magnetic Co-Ni nanowire arrays having diameters of around 180 to 200 nm and made of tens of segments with alternating compositions of Co54Ni46 and Co85Ni15. Each Co-Ni single segment has a mean length of around 290 nm for the Co54Ni46 alloy, whereas the length of the Co85Ni15 segments was around 430 nm. The composition and crystalline structure of each Co-Ni nanowire segment were determined by transmission electron microscopy and selected area electron diffraction techniques. The employed single-bath electrochemical nanowire growth method allows for tuning both the composition and crystalline structure of each individual Co-Ni segment. The room temperature magnetic behavior of the multisegmented Co-Ni nanowire arrays is also studied and correlated with their structural and morphological properties. PMID:23735184

  17. Monocrystalline NbN nanofilms on a 3C-SiC/Si substrate

    NASA Astrophysics Data System (ADS)

    Gao, J. R.; Hajenius, M.; Tichelaar, F. D.; Klapwijk, T. M.; Voronov, B.; Grishin, E.; Gol'tsman, G.; Zorman, C. A.; Mehregany, M.

    2007-08-01

    The authors have realized NbN (100) nanofilms on a 3C-SiC (100)/Si(100) substrate by dc reactive magnetron sputtering at 800°C. High-resolution transmission electron microscopy (HRTEM) is used to characterize the films, showing a monocrystalline structure and confirming epitaxial growth on the 3C-SiC layer. A film ranging in thickness from 3.4to4.1nm shows a superconducting transition temperature of 11.8K, which is the highest reported for NbN films of comparable thickness. The NbN nano-films on 3C-SiC offer a promising alternative to improve terahertz detectors. For comparison, NbN nanofilms grown directly on Si substrates are also studied by HRTEM.

  18. Mapping active dopants in single silicon nanowires using off-axis electron holography.

    PubMed

    den Hertog, Martien I; Schmid, Heinz; Cooper, David; Rouviere, Jean-Luc; Björk, Mikael T; Riel, Heike; Rivallin, Pierrette; Karg, Siegfried; Riess, Walter

    2009-11-01

    We demonstrate that state-of-the-art off-axis electron holography can be used to map active dopants in silicon nanowires as thin as 60 nm with 10 nm spatial resolution. Experiment and simulation demonstrate that doping concentrations of 10(19) and 10(20) cm(-3) can be measured with a detection threshold of 10(18) cm(-3) with respect to intrinsic silicon. Comparison of experimental data and simulations allows an estimation of the charge density at the wire-oxide interface of -1 x 10(12) electron charges cm(-2). Off-axis electron holography thus offers unique capabilities for a detailed analysis of active dopant concentrations in nanostructures.

  19. Gold nanoparticles-decorated single silver nanowire as an efficient SERS-active substrate

    NASA Astrophysics Data System (ADS)

    Tan, En-zhong

    2014-07-01

    A novel surface-enhanced Raman scattering (SERS)-active substrate based on Au nanoparticles (AuNPs)-coated silver nanowire (AgNW) is obtained by an effective and simple method. The results show that the hybrid structures prepared by this method are powerful SERS-active substrates for the detection of malachite green (MG) molecules with the limit of 1 nmol/L. The excellent enhancing ability mainly comes from two kinds of hot spots. One is from the gaps among the adjacent AuNPs, and the other is the presence of zone between AuNPs and AgNW. In particular, the AuNPs-coated AgNW can be viewed through the objective of the confocal Raman spectrometer due to the length of the AgNW reaches microns, which can improve the repeatability of detection. Moreover, it is of great significance in research of SERS mechanism and application.

  20. Photogating effects of HgTe nanoparticles on a single ZnO nanowire

    NASA Astrophysics Data System (ADS)

    Hojun, Seong; Kyoungah, Cho; Junggwon, Yun; Kiyeol, Kwak; Hyung, Jun Jin; Sangsig, Kim

    2010-08-01

    In this study, we demonstrate the photogating effects of p-type HgTe nanoparticles (NPs) on an n-type ZnO nanowire (NW). The photogating effects are due to the charge separation of the charge carriers photogenerated in the NPs under illumination and the subsequent accumulation of the photogenerated electrons in the pn junction of the NPs and the NW. The presence of the electrons in the junction reduces the current in the ZnO NW. The photogating effects are proved by the different photocurrent behavior of the ZnO NW to which the HgTe NPs are attached from that of a bare ZnO NW. In addition, the dependence of the photogating effects on the power of the incident light is discussed.

  1. Nanowire Solar Cells

    NASA Astrophysics Data System (ADS)

    Garnett, Erik C.; Brongersma, Mark L.; Cui, Yi; McGehee, Michael D.

    2011-08-01

    The nanowire geometry provides potential advantages over planar wafer-based or thin-film solar cells in every step of the photoconversion process. These advantages include reduced reflection, extreme light trapping, improved band gap tuning, facile strain relaxation, and increased defect tolerance. These benefits are not expected to increase the maximum efficiency above standard limits; instead, they reduce the quantity and quality of material necessary to approach those limits, allowing for substantial cost reductions. Additionally, nanowires provide opportunities to fabricate complex single-crystalline semiconductor devices directly on low-cost substrates and electrodes such as aluminum foil, stainless steel, and conductive glass, addressing another major cost in current photovoltaic technology. This review describes nanowire solar cell synthesis and fabrication, important characterization techniques unique to nanowire systems, and advantages of the nanowire geometry.

  2. Single-step multiplex detection of toxic metal ions by Au nanowires-on-chip sensor using reporter elimination.

    PubMed

    Kang, Taejoon; Yoo, Seung Min; Kang, Mijeong; Lee, Hyoban; Kim, Hongki; Lee, Sang Yup; Kim, Bongsoo

    2012-09-01

    We have developed a Au nanowires (NWs)-on-chip surface-enhanced Raman scattering (SERS) multiplex sensor that can sensitively detect multiple toxic metal ions. Most importantly, the reporter elimination method simplified the detection procedure to a single step, which has been much desired for remote environmental monitoring. This sensor has several notable features. First, it shows high reproducibility based on well-defined single-crystalline Au NWs. Second, single-NW-sensors that can detect a specific metal ion are combined for multiplex sensing of metal ions. Third, when a sample solution is put onto the NWs-on-chip sensor, a decrease in the SERS signal of a specific NW-sensor identifies the target metal ion. Simple, rapid, sensitive and quantitative detection of metal ions becomes possible through the measurement of the SERS signals. We successfully detected ions of mercury (Hg(2+)), silver (Ag(+)), and lead (Pb(2+)) coexisting in the same solution by using this sensor. PMID:22728926

  3. NBN gain is predictive for adverse outcome following image-guided radiotherapy for localized prostate cancer

    PubMed Central

    Sykes, Jenna; Zafarana, Gaetano; Chu, Kenneth C.; Ramnarine, Varune R.; Ishkanian, Adrian; Sendorek, Dorota H.S.; Pasic, Ivan; Lam, Wan L.; Jurisica, Igor; van der Kwast, Theo; Milosevic, Michael; Boutros, Paul C.; Bristow, Robert G.

    2014-01-01

    Despite the use of clinical prognostic factors (PSA, T-category and Gleason score), 20-60% of localized prostate cancers (PCa) fail primary local treatment. Herein, we determined the prognostic importance of main sensors of the DNA damage response (DDR): MRE11A, RAD50, NBN, ATM, ATR and PRKDC. We studied copy number alterations in DDR genes in localized PCa treated with image-guided radiotherapy (IGRT; n=139) versus radical prostatectomy (RadP; n=154). In both cohorts, NBN gains were the most frequent genomic alteration (14.4 and 11% of cases, respectively), and were associated with overall tumour genomic instability (p<0.0001). NBN gains were the only significant predictor of 5yrs biochemical relapse-free rate (bRFR) following IGRT (46% versus 77%; p=0.00067). On multivariate analysis, NBN gain remained a significant independent predictor of bRFR after adjusting for known clinical prognostic variables (HR=3.28, 95% CI 1.56–6.89, Wald p-value=0.0017). No DDR-sensing gene was prognostic in the RadP cohort. In vitro studies correlated NBN gene overexpression with PCa cells radioresistance. In conclusion, NBN gain predicts for decreased bRFR in IGRT, but not in RadP patients. If validated independently, Nibrin gains may be the first PCa predictive biomarker to facilitate local treatment decisions using precision medicine approaches with surgery or radiotherapy. PMID:25415046

  4. Nanowire Arrays as Cell Force Sensors To Investigate Adhesin-Enhanced Holdfast of Single Cell Bacteria and Biofilm Stability.

    PubMed

    Sahoo, Prasana K; Janissen, Richard; Monteiro, Moniellen P; Cavalli, Alessandro; Murillo, Duber M; Merfa, Marcus V; Cesar, Carlos L; Carvalho, Hernandes F; de Souza, Alessandra A; Bakkers, Erik P A M; Cotta, Monica A

    2016-07-13

    Surface attachment of a planktonic bacteria, mediated by adhesins and extracellular polymeric substances (EPS), is a crucial step for biofilm formation. Some pathogens can modulate cell adhesiveness, impacting host colonization and virulence. A framework able to quantify cell-surface interaction forces and their dependence on chemical surface composition may unveil adhesiveness control mechanisms as new targets for intervention and disease control. Here we employed InP nanowire arrays to dissect factors involved in the early stage biofilm formation of the phytopathogen Xylella fastidiosa. Ex vivo experiments demonstrate single-cell adhesion forces up to 45 nN, depending on the cell orientation with respect to the surface. Larger adhesion forces occur at the cell poles; secreted EPS layers and filaments provide additional mechanical support. Significant adhesion force enhancements were observed for single cells anchoring a biofilm and particularly on XadA1 adhesin-coated surfaces, evidencing molecular mechanisms developed by bacterial pathogens to create a stronger holdfast to specific host tissues. PMID:27336224

  5. An ultrasensitive electrochemical DNA biosensor based on a copper oxide nanowires/single-walled carbon nanotubes nanocomposite

    NASA Astrophysics Data System (ADS)

    Chen, Mei; Hou, Changjun; Huo, Danqun; Yang, Mei; Fa, Huanbao

    2016-02-01

    Here, we developed a novel and sensitive electrochemical biosensor to detect specific-sequence target DNA. The biosensor was based on a hybrid nanocomposite consisting of copper oxide nanowires (CuO NWs) and carboxyl-functionalized single-walled carbon nanotubes (SWCNTs-COOH). The resulting CuO NWs/SWCNTs layers exhibited a good differential pulse voltammetry (DPV) current response for the target DNA sequences, which we attributed to the properties of CuO NWs and SWCNTs. CuO NWs and SWCNTs hybrid composites with highly conductive and biocompatible nanostructure were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and cyclic voltammetry (CV). Immobilization of the probe DNA on the electrode surface was largely improved due to the unique synergetic effect of CuO NWs and SWCNTs. DPV was applied to monitor the DNA hybridization event, using adriamycin as an electrochemical indicator. Under optimal conditions, the peak currents of adriamycin were linear with the logarithm of target DNA concentrations (ranging from 1.0 × 10-14 to 1.0 × 10-8 M), with a detection limit of 3.5 × 10-15 M (signal/noise ratio of 3). The biosensor also showed high selectivity to single-base mismatched target DNA. Compared with other electrochemical DNA biosensors, we showed that the proposed biosensor is simple to implement, with good stability and high sensitivity.

  6. Fabrication of single phase p-CuInSe{sub 2} nanowire arrays by electrodeposited into anodic alumina templates

    SciTech Connect

    Cheng, Yu-Song; Lang, Hao-Jan; Houng, Mau-Phon

    2015-10-19

    Single-phase CuInSe{sub 2} nanowire (NW) arrays were prepared at various pH values in a heated electrolyte by using pulse electrodeposition techniques and an anodized aluminum oxide template. X-ray diffraction showed that the CuInSe{sub 2} NW nucleation mechanism received H{sup +} constraints when the NWs were deposited at pH 1.7 with a (112) orientation and annealed at 550 °C. The CuInSe{sub 2} NW band gap was determined to be approximately 1 eV through optical measurements. Transmission electron microscopy showed that at the pH value of 1.7, small particles of the single-phase CuInSe{sub 2} NWs aligned along the crystallographic direction are nucleated to form large particles. Scanning electron microscopy revealed that the NW diameter and the length were 80 nm and 2.3 μm, respectively. From Mott–Schottky and Ohmic contact plots, the CuInSe{sub 2} NWs were found to be p-type semiconductors, and their work function was estimated to be approximately 4.69 eV.

  7. Contact properties and surface reaction kinetics of single ZnO nanowire devices fabricated by dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Pau, J. L.; García Núñez, C.; García Marín, A.; Guerrero, C.; Rodríguez, P.; Borromeo, S.; Piqueras, J.

    2014-03-01

    This work describes the development of ZnO nanowire (NW) devices for ultraviolet detection and cost-effective gas sensing. A dielectrophoresis (DEP) flow cell fabricated for the integration of NWs on different substrates is presented. The system includes the possibility to set characteristic parameters such as alternating current (AC) frequency, amplitude or flow speed in order to control NW trapping on specific sites defined by micro-gapped electrodes. The electrical characteristics of the rectifying metal/NW contact fabricated by DEP are investigated in darkness and under direct illumination of the metal-NW interface through the ZnO NW. A significant downshift of the turn-on voltage is observed in the current-voltage characteristics during the illumination with photon energies higher than the ZnO bandgap. The reduction is attributed to a barrier height lowering induced by interface charge emission. The effects of AC bias on the thermal drift of the DC average current in NW devices are also discussed. Finally, the reaction kinetics of ethanol and water vapors on the NW surface are compared through the analysis of the DC current under direct exposure to gas flows. Device responses to more complex compound mixtures such as coffee or mint are also monitored over time, showing different performance in both cases.

  8. Single-crystalline CuO nanowires for resistive random access memory applications

    SciTech Connect

    Hong, Yi-Siang; Chen, Jui-Yuan; Huang, Chun-Wei; Chiu, Chung-Hua; Huang, Yu-Ting; Huang, Ting Kai; He, Ruo Shiuan; Wu, Wen-Wei

    2015-04-27

    Recently, the mechanism of resistive random access memory (RRAM) has been partly clarified and determined to be controlled by the forming and erasing of conducting filaments (CF). However, the size of the CF may restrict the application and development as devices are scaled down. In this work, we synthesized CuO nanowires (NW) (∼150 nm in diameter) to fabricate a CuO NW RRAM nanodevice that was much smaller than the filament (∼2 μm) observed in a bulk CuO RRAM device in a previous study. HRTEM indicated that the Cu{sub 2}O phase was generated after operation, which demonstrated that the filament could be minimize to as small as 3.8 nm when the device is scaled down. In addition, energy dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS) show the resistive switching of the dielectric layer resulted from the aggregated oxygen vacancies, which also match with the I-V fitting results. Those results not only verify the switching mechanism of CuO RRAM but also show RRAM has the potential to shrink in size, which will be beneficial to the practical application of RRAM devices.

  9. Assessing the thermoelectric properties of single InSb nanowires: the role of thermal contact resistance

    NASA Astrophysics Data System (ADS)

    Yazji, S.; Swinkels, M. Y.; De Luca, M.; Hoffmann, E. A.; Ercolani, D.; Roddaro, S.; Abstreiter, G.; Sorba, L.; Bakkers, E. P. A. M.; Zardo, I.

    2016-06-01

    The peculiar shape and dimensions of nanowires (NWs) have opened the way to their exploitation in thermoelectric applications. In general, the parameters entering into the thermoelectric figure of merit are strongly interdependent, which makes it difficult to realize an optimal thermoelectric material. In NWs, instead, the power factor can be increased and the thermal conductivity reduced, thus boosting the thermoelectric efficiency compared to bulk materials. However, the assessment of all the thermoelectric properties of a NW is experimentally very challenging. Here, we focus on InSb NWs, which have proved to be promising thermoelectric materials. The figure of merit is accurately determined by using a novel method based on a combination of Raman spectroscopy and electrical measurements. Remarkably, this type of experiment provides a powerful approach allowing us to neglect the role played by thermal contact resistance. Furthermore, we compare the thermal conductivity determined by this novel method to the one determined on the same sample by the thermal bridge method. In this latter approach, the thermal contact resistance is a non-negligible parameter, especially in NWs with large diameters. We provide experimental evidence of the crucial role played by thermal contact resistance in the assessment of the thermal properties of nanostructures, using two different measurement methods of the thermal conductivity.

  10. 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.

  11. Wafer-Scale Precise Patterning of Organic Single-Crystal Nanowire Arrays via a Photolithography-Assisted Spin-Coating Method.

    PubMed

    Deng, Wei; Zhang, Xiujuan; Wang, Liang; Wang, Jincheng; Shang, Qixun; Zhang, Xiaohong; Huang, Liming; Jie, Jiansheng

    2015-12-01

    A photolithography-assisted spin-coating approach is developed to produce single-crystal organic nanowire (NW) arrays at designated locations with high precision and high efficiency. This strategy enables the large-scale fabrication of organic NW arrays with nearly the same accuracy, reliability, and flexibility as photolithography. The high mobilities of the organic NWs enable the control of the switch of multicolored light-emitting devices with good stability.

  12. Tuning of superconducting nanowire single-photon detector parameters for VLSI circuit testing using time-resolved emission

    NASA Astrophysics Data System (ADS)

    Bahgat Shehata, A.; Stellari, F.

    2015-01-01

    Time-Resolved Emission (TRE) is a truly non-invasive technique based on the detection of intrinsic light emitted by integrated circuits that is used for the detection of timing related faults from the backside of flip-chip VLSI circuits. Single-photon detectors with extended sensitivity in the Near Infrared (NIR) are used to perform time-correlated single-photon counting measurements and retrieve the temporal distribution of the emitted photons, thus identifying gates switching events. The noise, efficiency and jitter performance of the detector are crucial to enable ultra-low voltage waveform sensitivity. For this reason, cryogenically cooled Superconducting Nanowire Single-Photon Detectors (SNSPDs) offer superior performance compared to state-of-the-art Single-Photon Avalanche Diodes (SPADs). In this paper we will discuss how detector front-end electronics parameters, such as bias current, RF attenuation and comparator threshold, can be tailored to optimize the measurement Signal-to-Noise Ratio (SNR), defined as the ratio between the switching emission peak amplitude and the standard deviation of the noise in the time interval in which there are no photons emitted from the circuit. For example, reducing the attenuation and the threshold of the comparator used to detect switching events may lead to an improvement of the jitter, due to the better discrimination of the detector firing, but also a higher sensitivity to external electric noise disturbances. Similarly, by increasing the bias current, both the detection efficiency and the jitter improve, but the noise increases as well. For these reasons an optimization of the SNR is necessary. For this work, TRE waveforms were acquired from a 32 nm Silicon On Insulator (SOI) chip operating down to 0.4 V using different generations of SNSPD systems.

  13. Plasmonic Structure Integrated Single-Photon Detector Configurations to Improve Absorptance and Polarization Contrast

    PubMed Central

    Csete, Mária; Szekeres, Gábor; Szenes, András; Szalai, Anikó; Szabó, Gábor

    2015-01-01

    Configurations capable of maximizing both the absorption component of system detection efficiency and the achievable polarization contrast were determined for 1550 nm polarized light illumination of different plasmonic structure integrated superconducting nanowire single-photon detectors (SNSPDs) consisting of p = 264 nm and P = 792 nm periodic niobium nitride (NbN) patterns on silica substrate. Global effective NbN absorptance maxima appear in case of p/s-polarized light illumination in S/P-orientation (γ = 90°/0° azimuthal angle) and the highest polarization contrast is attained in S-orientation of all devices. Common nanophotonical origin of absorptance enhancement is collective resonance on nanocavity gratings with different profiles, which is promoted by coupling between localized modes in quarter-wavelength metal-insulator-metal nanocavities and laterally synchronized Brewster-Zenneck-type surface waves in integrated SNSPDs possessing a three-quarter-wavelength-scaled periodicity. The spectral sensitivity and dispersion characteristics reveal that device design specific optimal configurations exist. PMID:25654724

  14. Solution-phase synthesis of single-crystal Cu3Si nanowire arrays on diverse substrates with dual functions as high-performance field emitters and efficient anti-reflective layers

    NASA Astrophysics Data System (ADS)

    Yuan, Fang-Wei; Wang, Chiu-Yen; Li, Guo-An; Chang, Shu-Hao; Chu, Li-Wei; Chen, Lih-Juann; Tuan, Hsing-Yu

    2013-09-01

    There is strong and growing interest in applying metal silicide nanowires as building blocks for a new class of silicide-based applications, including spintronics, nano-scale interconnects, thermoelectronics, and anti-reflective coating materials. Solution-phase environments provide versatile materials chemistry as well as significantly lower production costs compared to gas-phase synthesis. However, solution-phase synthesis of silicide nanowires remains challenging due to the lack of fundamental understanding of silicidation reactions. In this study, single-crystalline Cu3Si nanowire arrays were synthesized in an organic solvent. Self-catalyzed, dense single-crystalline Cu3Si nanowire arrays were synthesized by thermal decomposition of monophenylsilane in the presence of copper films or copper substrates at 420 to 475 °C and 10.3 MPa in supercritical benzene. The solution-grown Cu3Si nanowire arrays serve dual functions as field emitters and anti-reflective layers, which are reported on copper silicide materials for the first time. Cu3Si nanowires exhibit superior field-emission properties, with a turn-on-voltage as low as 1.16 V μm-1, an emission current density of 8 mA cm-2 at 4.9 V μm-1, and a field enhancement factor (β) of 1500. Cu3Si nanowire arrays appear black with optical absorption less than 5% between 400 and 800 nm with minimal reflectance, serving as highly efficient anti-reflective layers. Moreover, the Cu3Si nanowires could be grown on either rigid or flexible substrates (PI). This study shows that solution-phase silicide reactions are adaptable for high-quality silicide nanowire growth and demonstrates their promise towards fabrication of metal silicide-based devices.There is strong and growing interest in applying metal silicide nanowires as building blocks for a new class of silicide-based applications, including spintronics, nano-scale interconnects, thermoelectronics, and anti-reflective coating materials. Solution-phase environments

  15. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-01

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.

  16. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy.

    PubMed

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-23

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.

  17. Direct assessment of p-n junctions in single GaN nanowires by Kelvin probe force microscopy.

    PubMed

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-23

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p-n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p-n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p-n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction. PMID:27518150

  18. Long-haul and high-resolution optical time domain reflectometry using superconducting nanowire single-photon detectors

    PubMed Central

    Zhao, Qingyuan; Xia, Lan; Wan, Chao; Hu, Junhui; Jia, Tao; Gu, Min; Zhang, Labao; Kang, Lin; Chen, Jian; Zhang, Xuping; Wu, Peiheng

    2015-01-01

    In classical optical time domain reflectometries (OTDRs), for sensing an 200-km-long fiber, the optical pulses launched are as wide as tens of microseconds to get enough signal-to-noise ratio, while it results in a two-point resolution of kilometers. To both reach long sensing distance and sub-kilometer resolution, we demonstrated a long-haul photon-counting OTDR using a superconducting nanowire single-photon detector. In a 40-minute-long measurement, we obtained a dynamic range of 46.9 dB, corresponding to a maximum sensing distance of 246.8 km, at a two-point resolution of 0.1 km. The time for measuring fiber after 100 km was reduced to one minute, while the fiber end at 217 km was still distinguished well from noise. After reducing the pulse width to 100 ns, the experimental two-point resolution was improved to 20 m while the maximum sensing distance was 209.47 km. PMID:26020163

  19. Direct assessment of p–n junctions in single GaN nanowires by Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Minj, Albert; Cros, Ana; Auzelle, Thomas; Pernot, Julien; Daudin, Bruno

    2016-09-01

    Making use of Kelvin probe force microscopy, in dark and under ultraviolet illumination, we study the characteristics of p–n junctions formed along the axis of self-organized GaN nanowires (NWs). We map the contact potential difference of the single NW p–n junctions to locate the space charge region and directly measure the depletion width and the junction voltage. Simulations indicate a shrinkage of the built-in potential for NWs with small diameter due to surface band bending, in qualitative agreement with the measurements. The photovoltage of the NW/substrate contact is studied by analyzing the response of NW segments with p- and n-type doping under illumination. Our results show that the shifts of the Fermi levels, and not the changes in surface band bending, are the most important effects under above band-gap illumination. The quantitative electrical information obtained here is important for the use of NW p–n junctions as photovoltaic or rectifying devices at the nanoscale, and is especially relevant since the technique does not require the formation of ohmic contacts to the NW junction.

  20. Passive THz Imaging with Superconducting NbN microbolometer Arrays

    NASA Astrophysics Data System (ADS)

    Helistö, Panu

    2007-03-01

    Passive THz imaging applications indoors require temperature difference resolution well below 1 K and integration times down to 0.1 ms. Recently we have shown that such resolution, approaching the photon noise limit, can be achieved using an antenna-coupled superconducting microwire bolometer with about 10 K transition temperature. The bolometer signal is read out with a low-noise room-temperature amplifier, thus eliminating the need for SQUID amplifiers. The readout method utilizes electro-thermal feedback at the I-V curve minimum of a voltage-biased bolometer. At this working point, the very high power gain of the bolometer makes noise matching of the readout to the detector straightforward. The readout amplifier can be used with transition bolometers and calorimeters operating even at mK temperatures. We are presently developing a video-rate THz imager for concealed weapon detection, utilizing conical scanning and a 128-pixel NbN bolometer array, cooled down to 4 K with a pulse-tube cryocooler. We will characterize the bolometer arrays and the readout electrically and compare the results with the theory. We will also present the design of the system and results of preliminary imaging experiments. The work is done in collaboration between VTT, Millilab and NIST.

  1. Coexistence of optically active radial and axial CdTe insertions in single ZnTe nanowire.

    PubMed

    Wojnar, P; Płachta, J; Zaleszczyk, W; Kret, S; Sanchez, Ana M; Rudniewski, R; Raczkowska, K; Szymura, M; Karczewski, G; Baczewski, L T; Pietruczik, A; Wojtowicz, T; Kossut, J

    2016-03-14

    We report on the growth, cathodoluminescence and micro-photoluminescence of individual radial and axial CdTe insertions in ZnTe nanowires. In particular, the cathodoluminescence technique is used to determine the position of each emitting object inside the nanowire. It is demonstrated that depending on the CdTe deposition temperature, one can obtain an emission either from axial CdTe insertions only, or from both, radial and axial heterostructures, simultaneously. At 350 °C CdTe grows only axially, whereas at 310 °C and 290 °C, there is also significant deposition on the nanowire sidewalls resulting in radial core/shell heterostructures. The presence of Cd atoms on the sidewalls is confirmed by energy dispersive X-ray spectroscopy. Micro-photoluminescence study reveals a strong linear polarization of the emission from both types of heterostructures in the direction along the nanowire axis.

  2. Large-scale polyol synthesis of single-crystal bismuth nanowires and the role of NaOH in the synthesis process.

    PubMed

    Wang, Yewu; Kim, Kwang S

    2008-07-01

    A modified polyol process is introduced for the production of single-crystal bismuth (Bi) nanowires with uniform diameters along each wire in relatively high yield. The appropriate amount of NaOH in the solution reacts with Bi(3+) to form water-soluble complexing ions BiO(2)(-). The tiny Bi nanoparticles formed at the initial stage could serve as seeds for the subsequent growth of Bi nanostructures in the refluxing process with the aid of PVP. We find that the amount of NaOH determines the reduction rate of BiO(2)(-), which influences the morphologies of the synthesized Bi nanostructures. High reduction rates result in nanowires and nanoparticles, while low reduction rates result in nanoplates.

  3. Epidermal Nbn deletion causes premature hair loss and a phenotype resembling psoriasiform dermatitis

    PubMed Central

    Seidel, Philipp; Remus, Martina; Delacher, Michael; Grigaravicius, Paulius; Reuss, David E.; Frappart, Lucien; von Deimling, Andreas; Feuerer, Markus; Abdollahi, Amir; Frappart, Pierre-Olivier

    2016-01-01

    Nijmegen Breakage Syndrome is a disease caused by NBN mutations. Here, we report a novel function of Nbn in skin homeostasis. We found that Nbn deficiency in hair follicle (HF) progenitors promoted increased DNA damage signaling, stimulating p16Ink4a up-regulation, Trp53 stabilization and cytokines secretion leading to HF-growth arrest and hair loss. At later stages, the basal keratinocytes layer exhibited also enhanced DNA damage response but in contrast to the one in HF progenitor was not associated with pro-inflammatory cytokines expression, but rather increased proliferation, lack of differentiation and immune response resembling psoriasiform dermatitis. Simultaneous Nbn and Trp53 inactivation significantly exacerbated this phenotype, due to the lack of inhibition of pro-inflammatory cytokines secretion by Trp53. Altogether, we demonstrated novel functions of Nbn in HF maintenance and prevention of skin inflammation and we provide a mechanistic explanation that links cell intrinsic DNA maintenance with large scale morphological tissue alterations. PMID:27050272

  4. Mid-wavelength infrared InAsSb/InSb nBn detector with extended cut-off wavelength

    NASA Astrophysics Data System (ADS)

    Soibel, Alexander; Ting, David Z.; Hill, Cory J.; Fisher, Anita M.; Hoglund, Linda; Keo, Sam. A.; Gunapala, Sarath D.

    2016-09-01

    We extended the cut-off wavelength λc of bulk InAsSb nBn detectors to λc = 4.6 μm at T = 200 K by incorporating series of single InSb monolayer into InAsSb absorber. Detectors with 2 μm thick absorber showed a temperature independent quantum efficiency QEm≈ 0.45 for back-side illumination without antireflection coating. The dark current density was jd = 5 × 10-6 A/cm2 at T = 150 K, and increased to jd = 2 × 10-3 A/cm2 at T = 200 K. At temperatures of T = 150 K and below, the demonstrated photodetectors operate in the background limited performance mode, with detectivity D*(λ) = 3-6 × 1011 cm Hz0.5/W for the background temperature of 300 K, and f/2 field of view.

  5. Porous silicon nanowires.

    PubMed

    Qu, Yongquan; Zhou, Hailong; Duan, Xiangfeng

    2011-10-01

    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.

  6. InSb photodetectors with PIN and nBn designs

    NASA Astrophysics Data System (ADS)

    Evirgen, A.; Abautret, J.; Perez, J. P.; Aït-Kaci, H.; Christol, P.; Fleury, J.; Sik, H.; Nedelcu, A.; Cluzel, R.; Cordat, A.

    2013-12-01

    InSb pin photodiodes and nBn photodetectors were fabricated by Molecular Beam epitaxy (MBE) on InSb (100) n-type substrate and characterized. MBE Growth conditions were carefully studied to obtain high quality InSb layers, exhibiting in pin photodiode design dark current density values as low as 13nA.cm-2 at -50mV and R0A product as high as 6x106 WΩcm2 at 77K. Then, a new unipolar nBn InSb/InAlSb/InSb detector structure on InSb substrate were designed in order to suppress generation-recombination dark current. The first InSb nBn devices were fabricated and preliminary electrical characterizations are reported.

  7. The Structure and Properties of Inductively Coupled Plasma Assisted Magnetron Sputtered Nanocrystalline NbN Coatings in Corrosion Protective Die Casting Molds.

    PubMed

    Chun, Sung-Yong

    2016-02-01

    Niobium nitride coatings for the surface modified die casting molds with various ICP powers have been prepared using ICP assisted magnetron sputtering. The applied ICP power was varied from 0 to 200 W. The deposited coatings were characterized post-deposition using X-ray diffractometry (XRD) and atomic force microscopy (AFM). Single NbN phased coatings with nano-grain sized (<7.6 nm) were identified. The corrosion resistance and hardness of each coating were evaluated from potentiostat and nanoindentator. Superior corrosion protective coatings in excess of 13.9 GPa were deposited with assistance of ICP plasma during sputtering.

  8. The Structure and Properties of Inductively Coupled Plasma Assisted Magnetron Sputtered Nanocrystalline NbN Coatings in Corrosion Protective Die Casting Molds.

    PubMed

    Chun, Sung-Yong

    2016-02-01

    Niobium nitride coatings for the surface modified die casting molds with various ICP powers have been prepared using ICP assisted magnetron sputtering. The applied ICP power was varied from 0 to 200 W. The deposited coatings were characterized post-deposition using X-ray diffractometry (XRD) and atomic force microscopy (AFM). Single NbN phased coatings with nano-grain sized (<7.6 nm) were identified. The corrosion resistance and hardness of each coating were evaluated from potentiostat and nanoindentator. Superior corrosion protective coatings in excess of 13.9 GPa were deposited with assistance of ICP plasma during sputtering. PMID:27433719

  9. Investigation on hydrogenation performance of Mg{sub 2}Ni+10 wt.% NbN composite

    SciTech Connect

    Zhao, Xin; Han, Shumin; Zhu, Yi; Chen, Xiaocui; Ke, Dandan; Wang, Zhibin; Liu, Ting; Ma, Yufei

    2015-01-15

    The Mg{sub 2}Ni+10 wt.% NbN composite was prepared by mechanical milling and its hydrogen absorption/desorption properties and microstructure were systematically investigated. XRD results indicated that NbN was stable during ball milling process while partly decomposed into NbN{sub 0.95} and NbH during hydriding/dehydriding cycles irreversibly. The composite exhibited excellent hydrogenation/dehydrogenation kinetics performance with 2.71 wt.% hydrogen absorbed in 60 s at 423 K and 0.81 wt.% hydrogen released in 2 h at 523 K, respectively. The H diffusion constant of the composite reached 14.98×10{sup −5} s{sup −1} which was more than twice increased than that of pure Mg{sub 2}Ni powder. The superior hydrogen storage properties of the composite were ascribed to the refined grain size and abundant N-defect points provided by NbN and NbN{sub 0.95} in the composite. - Graphical abstract: The Mg{sub 2}Ni+10 wt.% NbN composite displays improvements on particle size distribution as well as hydrogen storage properties compared with that of pure Mg{sub 2}Ni. - Highlights: • NbN is introduced into Mg{sub 2}Ni hydride by Ar protected ball-milling. • Surfaces of the additive NbN particle are reduced by Mg{sub 2}NiH{sub 4}. • Hydrogenation kinetic property at 423 K is double improved. • Dehydrogenation capacity at 523 K of composites is beyond double improved.

  10. Crosstalk-free operation of multielement superconducting nanowire single-photon detector array integrated with single-flux-quantum circuit in a 0.1 W Gifford-McMahon cryocooler.

    PubMed

    Yamashita, Taro; Miki, Shigehito; Terai, Hirotaka; Makise, Kazumasa; Wang, Zhen

    2012-07-15

    We demonstrate the successful operation of a multielement superconducting nanowire single-photon detector (SSPD) array integrated with a single-flux-quantum (SFQ) readout circuit in a compact 0.1 W Gifford-McMahon cryocooler. A time-resolved readout technique, where output signals from each element enter the SFQ readout circuit with finite time intervals, revealed crosstalk-free operation of the four-element SSPD array connected with the SFQ readout circuit. The timing jitter and the system detection efficiency were measured to be 50 ps and 11.4%, respectively, which were comparable to the performance of practical single-pixel SSPD systems.

  11. Microwave surface resistance of reactively sputtered NbN thin films

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.; Strayer, D. M.

    1987-01-01

    The surface resistance of niobium nitride (NBN) thin films was measured at 7.78 and 10.14 GHz in the temperature range of 1.5 to 4.2 K. The films were reactively sputtered on sapphire substrates to a thickness of approximately 1 micron. The surface resistance was determined by measuring the quality factor (Q) of the TE sub 011 mode of a lead-plated copper cavity where the NbN served as one end-cap of the cavity.

  12. Irreversible evolution of angular-dependent coercivity in Fe80Ni20 nanowire arrays: Detection of a single vortex state

    NASA Astrophysics Data System (ADS)

    Alikhani, M.; Ramazani, A.; Almasi Kashi, M.; Samanifar, S.; Montazer, A. H.

    2016-09-01

    The irreversible evolution of magnetic coercivity in arrays of 75 nm diameter Fe80Ni20 nanowires (NWs) has been explored by means of first-order reversal curve (FORC) analysis as a function of the angle between the magnetic field and the NW axis (0°≤θ≤90°). The Fe80Ni20 NWs with lengths up to 60 μm were fabricated using a pulsed electrodeposition method into hard-anodic aluminum oxide templates with an interpore distance of 275 nm. Investigating the interwire and intrawire magnetostatic interactions, the angular FORC (AFORC) diagrams indicated enhanced intrawire interactions with increasing length and θ (<90°), induced by a magnetization reversal through vortex domain wall (VDW) propagation. Intriguingly, in addition to the VDW mode, a single vortex state with broad irreversible switching of nucleation and annihilation fields was detected at θ=83° for 60 μm long NWs. At θ=90°, the NWs reversed magnetization through transverse domain wall, involving a reversible component by a fraction of 95%. Furthermore, the transition angle between the reversal modes was found to decrease with increasing aspect ratio from 200 to 800. The irreversible angular-dependent coercivity (HcIrrev(θ)) of Fe80Ni20 NWs was extracted from the AFORC measurements and compared with the major angular dependence of coercivity (HcMajor(θ)) obtained from the conventional hysteresis loop measurements. While HcMajor(θ) showed a non-monotonic behavior, HcIrrev(θ) constantly increased with increasing θ (<90°). On the other hand, using analytical models, a 93% agreement was obtained between the theoretical angular-dependent nucleation field and experimental HcIrrev(θ) for irreversible switching of VDW when 0°≤θ≤86°.

  13. Space-and-time resolved spectroscopy of single GaN nanowires

    DOE PAGESBeta

    Upadhya, Prashanth C.; Martinez, Julio A.; Li, Qiming; Wang, George T.; Swartzentruber, Brian S.; Taylor, Antoinette J.; Prasankumar, Rohit P.

    2015-06-30

    Gallium nitridenanowires have garnered much attention in recent years due to their attractive optical and electrical properties. An understanding of carrier transport, relaxation, and recombination in these quasi-one-dimensional nanosystems is therefore important in optimizing them for various applications. We present ultrafast optical microscopic measurements on single GaNnanowires. Furthermore, our experiments, performed while varying the light polarization,excitation fluence, and position, give insight into the mechanisms governing carrier dynamics in these nanosystems.

  14. 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

  15. Superconducting nanowire single-photon detectors integrated with waveguide circuits for quantum information science

    NASA Astrophysics Data System (ADS)

    Gaggero, A.; Sahin, D.; Mattioli, F.; Leoni, R.; Frucci, G.; Jahanmirinejad, S.; Sprengers, J. P.; Beetz, J.; Lermer, M.; Höfling, S.; Kamp, M.; Fiore, A.

    2013-05-01

    We present our progress in the development of an integrated technology suitable for the photonic quantum information processing, showing the first autocorrelator based on two separated detectors integrated on top of the same ridge waveguide. An efficiency of ~1% at 1300 nm for both detectors and independent of the polarization of the incoming photons, is reported. This ultracompact device enables the on-chip measurement of the second-order correlation function g(2)(τ) . We will further discuss ongoing work on the integration of detectors with single-photon sources.

  16. 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

  17. Ultraviolet Raman spectra of single uncoated and SiO2-coated silicon-on-insulator nanowires: Phonon boundary scattering, wave-vector relaxation and stress

    NASA Astrophysics Data System (ADS)

    Poborchii, Vladimir; Tada, Tetsuya; Morita, Yukinori; Kanayama, Toshihiko

    2013-10-01

    We study Raman spectra of single straight Si-on-insulator (SOI) nanowires (NWs) at the 364 nm excitation wavelength. Uncoated SOI NW Raman band downshift and asymmetric broadening appeared to be smaller than those reported for NW ensembles, where these effects are enhanced due to additional wave-vector relaxation associated with NW imperfections. We observe NW-diameter-inversely proportional symmetric Raman band broadening associated with the phonon boundary scattering (PBS). NW longitudinal optical phonon lifetime and mean free path are determined from the PBS band broadening. SiO2-coated NWs display stress transforming from tensile to compressive with a decrease in the NW width.

  18. Generation and the role of dislocations in single-crystalline phase-change In2Se3 nanowires under electrical pulses

    NASA Astrophysics Data System (ADS)

    Mafi, Elham; Tao, Xin; Zhu, Wenguang; Gao, Yanfei; Wang, Chongmin; Gu, Yi

    2016-08-01

    We report the observation of the generation of dislocations in single-crystal phase-change In2Se3 nanowires under electrical pulses and the impact of these dislocations on electrical properties. Particularly, we correlated the atomic-scale structural characteristics with local electrical resistance variations, by performing transmission electron microscopy and scanning Kelvin probe microscopy on the same nanowires. By coupling the experimental results with first-principles density functional theory calculations, we show that the immobile dislocations are generated via vacancy condensations. Importantly, these dislocations lead to several orders of magnitude increase in the electrical resistance, while maintaining the single crystallinity of the lattice. These results significantly advance the fundamental understanding of the structure-property relation in this phase-change material under transient electrical excitations. From a practical perspective, the significant increase in the electrical resistance, driven by the formation of dislocations, can be exploited as a new electronic state in the single-crystalline phase in this phase-change material.

  19. Nano-meter bridge with epitaxially deposited NbN on MgO film

    SciTech Connect

    Yamashita, T.; Hamasaki, K.; Kodaira, Y.; Komata, T.

    1985-03-01

    Nano-meter(nm)-bridges with high-T /SUB c/ materials hold great technological interest because of their smaller capacitance and expected higher I /SUB o/ R /SUB n/ -product. They are promising especially for applications such as high speed logic and high frequency radiation detectors. Also they can operate over a wide temperature range and are stable against thermal cycles as are incorporating the refractory high-T /SUB c/ superconductors. One of the essential ingredient for high quality bridges is to have NbN films. Ultra-thin NbN films have been prepared by rf reactive-sputtering. NbN films deposited epitaxially on rf sputtered MgO films have high superconducting transition temperature T /SUB c/ . T /SUB c/ value of the film with thickness of about 5nm was about 14K, and is much higher than those deposited on Al/sub 2/O/sub 3/ films and Si substrates. Two types of nm-bridges were reproducibly fabricated with NbN films deposited epitaxially on MgO films. The obtained I /SUB o/ R /SUB n/ -products were in a range of 0.5 to 3.6mV. The microwaveinduced voltage steps were observed up to the voltage comparable to I /SUB o/ R /SUB n/ - product. The dc and ac quantum effects of the dc SQUIDS were observed in quite wide range of temperature, 4.2 to 11.4K.

  20. Synthesis and characterization of cadmium telluride nanowire

    NASA Astrophysics Data System (ADS)

    Kum, Maxwell C.; Yoo, Bong Young; Rheem, Young Woo; Bozhilov, Krassimir N.; Chen, Wilfred; Mulchandani, Ashok; Myung, Nosang V.

    2008-08-01

    CdTe nanowires with controlled composition were cathodically electrodeposited using track-etched polycarbonate membrane as scaffolds and their material and electrical properties were systematically investigated. As-deposited CdTe nanowires show nanocrystalline cubic phase structures with grain sizes of up to 60 nm. The dark-field images of nanowires reveal that the crystallinity of nanowires was greatly improved from nanocrystalline to a few single crystals within nanowires upon annealing at 200 °C for 6 h in a reducing environment (5% H2+95% N2). For electrical characterization, a single CdTe nanowire was assembled across microfabricated gold electrodes using the drop-casting method. In addition to an increase in grain size, the electrical resistivity of an annealed single nanowire (a few 105 Ω cm) was one order of magnitude greater than in an as-deposited nanowire, indicating that crystallinity of nanowires improved and defects within nanowires were reduced during annealing. By controlling the dopants levels (e.g. Te content of nanowires), the resistivity of nanowires was varied from 104 to 100 Ω cm. Current-voltage (I-V) characteristics of nanowires indicated the presence of Schottky barriers at both ends of the Au/CdTe interface. Temperature-dependent I-V measurements show that the electron transport mode was determined by a thermally activated component at T>-50 °C and a temperature-independent component below -50 °C. Under optical illumination, the single CdTe nanowire exhibited enhanced conductance.

  1. Characteristics of an Indium Asenide-based nBn photodetectors grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Pedrazzani, Janet Renee

    The nBn photodetector design specifies an n-type absorption layer, a Barrier layer to majority carrier electrons, and an n-type contact layer. The absence of a depletion layer in the lattice-matched nBn photodetector results in substantially reduced levels of Shockley-Read-Hall (SRH) generation current as compared with the competing p-n junction photodiode. The nBn photodetector also suppresses surface leakage current, which is prevalent in cooled, narrow bandgap semiconductor p-n junction photodiodes. Barrier layers consisting of AlAsxSb1-x are used in these InAs-based nBn photodetectors. A zero valance band energy offset exists between the InAs and AlAsxSb1-x layers for a composition in the range 0.14 < x < 0.17, while a composition of x = 0.16 lattice matches InAs. Conduction band energy offsets much greater than kT exist between InAs and all compositions of AlAsxSb1-x, and barrier layers thicker than 100 Angstroms are predicted to attenuate current arising from electron tunnelling to negligible levels. A lattice-matched InAs-based nBn photodetector achieves background limited photodetection (BLIP) operation at 200 K, while surface leakage current prevents two examples of InAs-based photodiodes from achieving BLIP operation. At a temperature of 140 K, this InAs-based nBn photodetector has a measured dark current lower by over 6 orders of magnitude than that of the commercial InAs-based photodiode and 4 orders of magnitude lower than that of an InAs-based photodiode fabricated by the author. Measurements indicate InAs-based nBn photodetectors grown with lattice-mismatched absorption layers have higher dislocation densities and that SRH current is the primary contributor to the dark current. The BLIP temperatures of two nBn photodetectors with InAs absorption layers grown on GaAs substrates are 150 and 160 K. The BLIP temperature of an nBn photodetector with an InAs0.95Sb0.05 absorption layer grown on an InAs substrate is 185 K. Accurate calculation of the thermal

  2. Electrospinning of superconducting YBCO nanowires

    NASA Astrophysics Data System (ADS)

    Duarte, Edgar A.; Rudawski, Nicholas G.; Quintero, Pedro A.; Meisel, Mark W.; Nino, Juan C.

    2015-01-01

    YBa2Cu3O7-δ (YBCO) nanowires with critical transition temperature Tc = 91.7 K were synthesized by an electrospinning process with the use of sol-gel precursors. A homogeneous polymeric solution containing Y, Ba, and Cu acetates was electrospun, resulting in collections of randomly oriented nanowires as well as bundles of aligned nanowires. Fully crystallized YBCO nanowires were obtained after calcination at temperatures as low as 820 °C. The morphology, microstructure, and crystal structure were investigated, and the diameters of the polycrystalline nanowires varied between 120 and 550 nm depending on the viscosity of the precursors. Thinner individual wires, with diameters in the 50-80 nm range, were synthesized with a single grain structure across the entire wire cross-section.

  3. Electrically Injected UV-Visible Nanowire Lasers

    SciTech Connect

    Wang, George T.; Li, Changyi; Li, Qiming; Liu, Sheng; Wright, Jeremy Benjamin; Brener, Igal; Luk, Ting -Shan; Chow, Weng W.; Leung, Benjamin; Figiel, Jeffrey J.; Koleske, Daniel D.; Lu, Tzu-Ming

    2015-09-01

    There is strong interest in minimizing the volume of lasers to enable ultracompact, low-power, coherent light sources. Nanowires represent an ideal candidate for such nanolasers as stand-alone optical cavities and gain media, and optically pumped nanowire lasing has been demonstrated in several semiconductor systems. Electrically injected nanowire lasers are needed to realize actual working devices but have been elusive due to limitations of current methods to address the requirement for nanowire device heterostructures with high material quality, controlled doping and geometry, low optical loss, and efficient carrier injection. In this project we proposed to demonstrate electrically injected single nanowire lasers emitting in the important UV to visible wavelengths. Our approach to simultaneously address these challenges is based on high quality III-nitride nanowire device heterostructures with precisely controlled geometries and strong gain and mode confinement to minimize lasing thresholds, enabled by a unique top-down nanowire fabrication technique.

  4. Fabrication and characterization of porous silicon nanowires

    NASA Astrophysics Data System (ADS)

    Jung, Daeyoon; Cho, Soo Gyeong; Moon, Taeho; Sohn, Honglae

    2016-01-01

    We report the synthesis of porous silicon nanowires through the metalassisted chemical etching of porous silicon in a solution of hydrofluoric acid and hydrogen peroxide. The morphology of porous silicon nanowires was characterized by scanning electron microscopy and transmission electron microscopy. The etch rate of the porous silicon nanowires was faster than that of silicon nanowires, but slower than that of porous silicon. The porous silicon nanowires distributed uniformly on the entire porous silicon layer and the tips of the porous silicon nanowires congregated together. The single crystalline and sponge-like porous structure with the pore diameters of less than 5 nm was confirmed for the porous silicon nanowires. [Figure not available: see fulltext.

  5. High-efficiency second harmonic generation from a single hybrid ZnO nanowire/Au plasmonic nano-oligomer.

    PubMed

    Grinblat, Gustavo; Rahmani, Mohsen; Cortés, Emiliano; Caldarola, Martín; Comedi, David; Maier, Stefan A; Bragas, Andrea V

    2014-11-12

    We introduce a plasmonic-semiconductor hybrid nanosystem, consisting of a ZnO nanowire coupled to a gold pentamer oligomer by crossing the hot-spot. It is demonstrated that the hybrid system exhibits a second harmonic (SH) conversion efficiency of ∼3 × 10(-5)%, which is among the highest values for a nanoscale object at optical frequencies reported so far. The SH intensity was found to be ∼1700 times larger than that from the same nanowire excited outside the hot-spot. Placing high nonlinear susceptibility materials precisely in plasmonic confined-field regions to enhance SH generation opens new perspectives for highly efficient light frequency up-conversion on the nanoscale. PMID:25347036

  6. E{sub 1} Gap of Wurtzite InAs Single Nanowires Measured by Means of Resonant Raman Spectroscopy

    SciTech Connect

    Moeller, M.; Lima, M. M. Jr. de; Cantarero, A.; Dacal, L. C. O.; Iikawa, F.; Chiaramonte, T.; Cotta, M. A.

    2011-12-23

    Indium arsenide nanowires were synthesized with an intermixing of wurtzite and zincblende structure by chemical beam epitaxy with the vapor-liquid-solid mechanism. Resonant Raman spectroscopy of the transverse optical phonon mode at 215 cm{sup -1} reveals an E{sub 1} gap of 2.47 eV which is assigned to the electronic band gap at the A point in the indium arsenide wurtzite phase.

  7. Biomolecule-assisted synthesis of single-crystalline selenium nanowires and nanoribbons via a novel flake-cracking mechanism

    NASA Astrophysics Data System (ADS)

    Zhang, Bin; Ye, Xingchen; Dai, Wei; Hou, Weiyi; Zuo, Fan; Xie, Yi

    2006-01-01

    Recently, the biomolecule-assisted synthesis method has been a new and promising focus in the preparation of various nanomaterials. But current works mainly focus on the synthesis of metal nanoparticles and nanowires using macro-biomolecules (e.g. virus, protein and DNA) as templates in the presence of a reducing agent. Beta-carotene, one of the most common bio-antioxidants, can be oxidized to form species with both hydrophilic and hydrophobic ends, which can provide an in situ soft template for the synthesis of nanomaterials. Herein, a simple beta-carotene-assisted method was developed for the first time to synthesize t-Se nanowires and nanoribbons with high crystallinity. We demonstrate that beta-carotene serves as not only the reducing agent, but also an in situ template in the preparation of Se one-dimensional nanostructures. It is found that the growth mechanism of Se nanomaterials is different from the familiar sphere-wire process. A novel flake-cracking mechanism is proposed. By this biomolecule-assisted route, Te one-dimensional nanostructures and Pd nanowires were also fabricated. The assisted-biomolecule in our method may be spread to carotenoids and other antioxidants, and thus broaden the application fields of biomolecules. Our preliminary investigations have shown that the facile, solution-phase biomolecule-assisted method can be potentially extended to the preparation of other low-dimensional nanostructures. The synthesized t-Se nanowires and nanoribbons may serve as templates to generate other tubular functional nanomaterials and find applications in the studies of structure-property relationships as well as in the fabrication of nanoscale optoelectronic devices.

  8. Low operating voltage single ZnO nanowire field-effect transistors enabled by self-assembled organic gate nanodielectrics.

    PubMed

    Ju, Sanghyun; Lee, Kangho; Janes, David B; Yoon, Myung-Han; Facchetti, Antonio; Marks, Tobin J

    2005-11-01

    The development of nanowire transistors enabled by appropriate dielectrics is of great interest for flexible electronic and display applications. In this study, nanowire field-effect transistors (NW-FETs) composed of individual ZnO nanowires are fabricated using a self-assembled superlattice (SAS) as the gate insulator. The 15-nm SAS film used in this study consists of four interlinked layer-by-layer self-assembled organic monolayers and exhibits excellent insulating properties with a large specific capacitance, 180 nF/cm2, and a low leakage current density, 1 x 10(-8) A/cm2. SAS-based ZnO NW-FETs display excellent drain current saturation at Vds = 0.5 V, a threshold voltage (Vth) of -0.4 V, a channel mobility of approximately 196 cm2/V s, an on-off current ratio of approximately 10(4), and a subthreshold slope of 400 mV/dec. For comparison, ZnO NW-FETs are also fabricated using 70-nm SiO2 as the gate insulator. Implementation of the SAS gate dielectric reduces the NW-FET operating voltage dramatically with more than 1 order of magnitude enhancement of the on-current. These results strongly indicate that SAS-based ZnO NW-FETs are promising candidates for future flexible display and logic technologies.

  9. Hierarchical, ultrathin single-crystal nanowires of CdS conveniently produced in laser-induced thermal field

    DOE PAGESBeta

    Han, Li -Li; Xin, Huolin L.; Kulinich, Sergei A.; Yang, Li -Jun; Du, Xi -Wen

    2015-07-16

    Hierarchical nanowires (HNWs) exhibit unique properties and have wide applications, while often suffering from imperfect structure. We report a facile strategy toward ultrathin CdS HNWs with monocrystal structure, where a continuous-wave (CW) Nd:YAG laser is employed to irradiate an oleic acid (OA) solution containing precursors and a light absorber. The high heating rate and large temperature gradient generated by the CW laser lead to the rapid formation of tiny zinc-blende CdS nanocrystals which then line up into nanowires with the help of OA molecules. Next, the nanowires experience a phase transformation from zinc-blende to wurtzite structure, and the transformation-induced stressmore » creates terraces on their surface, which promotes the growth of side branches and eventually results in monocrystal HNWs with an ultrathin diameter of 24 nm. The one-step synthesis of HNWs is conducted in air and completes in just 40 seconds, thus being very simple and rapid. The prepared CdS HNWs display photocatalytic performance superior to their nanoparticle counterparts, thus showing promise for catalytic applications in the future.« less

  10. Hierarchical, ultrathin single-crystal nanowires of CdS conveniently produced in laser-induced thermal field

    SciTech Connect

    Han, Li -Li; Xin, Huolin L.; Kulinich, Sergei A.; Yang, Li -Jun; Du, Xi -Wen

    2015-07-16

    Hierarchical nanowires (HNWs) exhibit unique properties and have wide applications, while often suffering from imperfect structure. We report a facile strategy toward ultrathin CdS HNWs with monocrystal structure, where a continuous-wave (CW) Nd:YAG laser is employed to irradiate an oleic acid (OA) solution containing precursors and a light absorber. The high heating rate and large temperature gradient generated by the CW laser lead to the rapid formation of tiny zinc-blende CdS nanocrystals which then line up into nanowires with the help of OA molecules. Next, the nanowires experience a phase transformation from zinc-blende to wurtzite structure, and the transformation-induced stress creates terraces on their surface, which promotes the growth of side branches and eventually results in monocrystal HNWs with an ultrathin diameter of 24 nm. The one-step synthesis of HNWs is conducted in air and completes in just 40 seconds, thus being very simple and rapid. The prepared CdS HNWs display photocatalytic performance superior to their nanoparticle counterparts, thus showing promise for catalytic applications in the future.

  11. Superconductor-insulator transition in quasi-one-dimensional single-crystal Nb₂PdS₅ nanowires.

    PubMed

    Ning, Wei; Yu, Hongyan; Liu, Yequn; Han, Yuyan; Wang, Ning; Yang, Jiyong; Du, Haifeng; Zhang, Changjin; Mao, Zhiqiang; Liu, Ying; Tian, Mingliang; Zhang, Yuheng

    2015-02-11

    Superconductor-insulator transition (SIT) in one-dimensional (1D) nanowires attracts great attention in the past decade and remains an open question since contrasting results were reported in nanowires with different morphologies (i.e., granular, polycrystalline, or amorphous) or environments. Nb2PdS5 is a recently discovered low-dimensional superconductor with typical quasi-1D chain structure. By decreasing the wire diameter in the range of 100-300 nm, we observed a clear SIT with a 1D transport character driven by both the cross-sectional area and external magnetic field. We also found that the upper critical magnetic field (Hc2) decreases with the reduction of nanowire cross-sectional area. The temperature dependence of the resistance below Tc can be described by the thermally activated phase slip (TAPS) theory without any signature of quantum phase slips (QPS). These findings demonstrated that the enhanced Coulomb interactions with the shrinkage of the wire diameter competes with the interchain Josephson-like coupling may play a crucial role on the SIT in quasi-1D system. PMID:25575045

  12. Hierarchical, Ultrathin Single-Crystal Nanowires of CdS Conveniently Produced in Laser-Induced Thermal Field.

    PubMed

    Han, Li-Li; Xin, Huolin L; Kulinich, Sergei A; Yang, Li-Jun; Du, Xi-Wen

    2015-07-28

    Hierarchical nanowires (HNWs) exhibit unique properties and have wide applications, while often suffering from imperfect structure. Herein, we report a facile strategy toward ultrathin CdS HNWs with monocrystal structure, where a continuous-wave (CW) Nd:YAG laser is employed to irradiate an oleic acid (OA) solution containing precursors and a light absorber. The high heating rate and large temperature gradient generated by the CW laser lead to the rapid formation of tiny zinc-blende CdS nanocrystals which then line up into nanowires with the help of OA molecules. Next, the nanowires experience a phase transformation from zinc-blende to wurtzite structure, and the transformation-induced stress creates terraces on their surface, which promotes the growth of side branches and eventually results in monocrystal HNWs with an ultrathin diameter of 24 nm. The one-step synthesis of HNWs is conducted in air and completes in just 40 s, thus being very simple and rapid. The prepared CdS HNWs display photocatalytic performance superior to their nanoparticle counterparts, thus showing promise for catalytic applications in the future. PMID:26154589

  13. Superconductor-insulator transition in quasi-one-dimensional single-crystal Nb₂PdS₅ nanowires.

    PubMed

    Ning, Wei; Yu, Hongyan; Liu, Yequn; Han, Yuyan; Wang, Ning; Yang, Jiyong; Du, Haifeng; Zhang, Changjin; Mao, Zhiqiang; Liu, Ying; Tian, Mingliang; Zhang, Yuheng

    2015-02-11

    Superconductor-insulator transition (SIT) in one-dimensional (1D) nanowires attracts great attention in the past decade and remains an open question since contrasting results were reported in nanowires with different morphologies (i.e., granular, polycrystalline, or amorphous) or environments. Nb2PdS5 is a recently discovered low-dimensional superconductor with typical quasi-1D chain structure. By decreasing the wire diameter in the range of 100-300 nm, we observed a clear SIT with a 1D transport character driven by both the cross-sectional area and external magnetic field. We also found that the upper critical magnetic field (Hc2) decreases with the reduction of nanowire cross-sectional area. The temperature dependence of the resistance below Tc can be described by the thermally activated phase slip (TAPS) theory without any signature of quantum phase slips (QPS). These findings demonstrated that the enhanced Coulomb interactions with the shrinkage of the wire diameter competes with the interchain Josephson-like coupling may play a crucial role on the SIT in quasi-1D system.

  14. Improvement of electroluminescence performance by integration of ZnO nanowires and single-crystalline films on ZnO/GaN heterojunction

    SciTech Connect

    Shi, Zhifeng; Zhang, Yuantao Cui, Xijun; Wu, Bin; Zhuang, Shiwei; Yang, Fan; Zhang, Baolin; Du, Guotong; Yang, Xiaotian

    2014-03-31

    Heterojunction light-emitting diodes based on n-ZnO nanowires/ZnO single-crystalline films/p-GaN structure have been demonstrated for an improved electroluminescence performance. A highly efficient ultraviolet emission was observed under forward bias. Compared with conventional n-ZnO/p-GaN structure, high internal quantum efficiency and light extraction efficiency were simultaneously considered in the proposed diode. In addition, the diode can work continuously for ∼10 h with only a slight degradation in harsh environments, indicating its good reliability and application prospect in the future. This route opens possibilities for the development of advanced nanoscale devices in which the advantages of ZnO single-crystalline films and nanostructures can be integrated together.

  15. Confined-space synthesis of single crystal TiO2 nanowires in atmospheric vessel at low temperature: a generalized approach

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoyue; Wang, Hai; Zhou, Yu; Liu, Yong; Li, Baojun; Zhou, Xiang; Shen, Hui

    2015-01-01

    Extensive efforts have been devoted to develop innovative synthesis strategies for nanomaterials in order to exploit the true potential of nanotechnology. However, most approaches require high temperature or high pressure to favor crystallization. Here we highlight an unconventional approach for the confined-space synthesis of the single crystal TiO2 nanowires in the atmospheric vessel at low temperature by cleverly manipulating the unique physical properties of straight-chain saturated fatty acids. Our method also applys to icosane due to its straight-chain saturated hydrocarbon structure and similar physical properties to the saturated fatty acids. Interestingly, we also found that the unsaturated fatty acids can facilitate the crystal growth, but their bent chains lead to the formation of TiO2 particle aggregates. In addition, we demonstrate the growth of TiO2 nanowires on arbitrary substrates, which are of great importance for their wider applications. We thus anticipate our presented method to be a possible starting point for non-classical crystallization strategies and be easily adapted for the fabrication of all other inorganic materials.

  16. Confined-space synthesis of single crystal TiO2 nanowires in atmospheric vessel at low temperature: a generalized approach

    PubMed Central

    Wang, Xiaoyue; Wang, Hai; Zhou, Yu; Liu, Yong; Li, Baojun; Zhou, Xiang; Shen, Hui

    2015-01-01

    Extensive efforts have been devoted to develop innovative synthesis strategies for nanomaterials in order to exploit the true potential of nanotechnology. However, most approaches require high temperature or high pressure to favor crystallization. Here we highlight an unconventional approach for the confined-space synthesis of the single crystal TiO2 nanowires in the atmospheric vessel at low temperature by cleverly manipulating the unique physical properties of straight-chain saturated fatty acids. Our method also applys to icosane due to its straight-chain saturated hydrocarbon structure and similar physical properties to the saturated fatty acids. Interestingly, we also found that the unsaturated fatty acids can facilitate the crystal growth, but their bent chains lead to the formation of TiO2 particle aggregates. In addition, we demonstrate the growth of TiO2 nanowires on arbitrary substrates, which are of great importance for their wider applications. We thus anticipate our presented method to be a possible starting point for non-classical crystallization strategies and be easily adapted for the fabrication of all other inorganic materials. PMID:25634804

  17. Dynamical color-controllable lasing with extremely wide tuning range from red to green in a single alloy nanowire using nanoscale manipulation.

    PubMed

    Liu, Zhicheng; Yin, Leijun; Ning, Hao; Yang, Zongyin; Tong, Limin; Ning, Cun-Zheng

    2013-10-01

    Multicolor lasing and dynamic color-tuning in a wide spectrum range are challenging to realize but critically important in many areas of technology and daily life, such as general lighting, display, multicolor detection, and multiband communication. By exploring nanoscale growth and manipulation, we have demonstrated the first active dynamical color control of multicolor lasing, continuously tunable between red and green colors separated by 107 nm in wavelength. This is achieved in a purposely engineered single CdSSe alloy nanowire with composition varied along the wire axis. By looping the wide-gap end of the alloy nanowire through nanoscale manipulation, two largely independent (only weakly coupled) laser cavities are formed respectively for the green and red color modes. Our approach simultaneously overcomes the two fundamental challenges for multicolor lasing in material growth and cavity design. Such multicolor lasing and continuous color tuning in a wide spectral range represents a new paradigm shift and would eventually enable color-by-design and white-color lasers for lighting, illumination, and many other applications.

  18. Twinning effect on photoluminescence spectra of ZnSe nanowires

    SciTech Connect

    Xu, Jing; Wang, Chunrui Wu, Binhe; Xu, Xiaofeng; Chen, Xiaoshuang; Oh, Hongseok; Baek, Hyeonjun; Yi, Gyu-Chul

    2014-11-07

    Bandgap engineering in a single material along the axial length of nanowires may be realized by arranging periodic twinning, whose twin plane is vertical to the axial length of nanowires. In this paper, we report the effect of twin on photoluminescence of ZnSe nanowires, which refers to the bandgap of it. The exciton-related emission peaks of transverse twinning ZnSe nanowires manifest a 10-meV-blue-shift in comparison with those of longitudinal twinning ZnSe nanowires. The blue-shift is attributed to quantum confinement effect, which is influenced severely by the proportion of wurtzite ZnSe layers in ZnSe nanowires.

  19. Study of phase transitions in NbN ultrathin films under composite ion beam irradiation

    NASA Astrophysics Data System (ADS)

    Prikhodko, K.; Gurovich, B.; Dement'eva, M.

    2016-04-01

    This work demonstrates implementation of Selective Displacement of Atoms (SDA) technique to change the crystal structure and atomic composition of thin superconductive film of NbN under low dose composite ion beam irradiation. All structure investigations were performed using High Resolution Transmission Electron Microscopy (HRTEM) technique by the analysis of Fourier transformation of bright field HRTEM images. It was found that composite ion beam irradiation induces the formation of niobium oxynitrides phases.

  20. MWIR InSb detector with nBn architecture for high operating temperature

    NASA Astrophysics Data System (ADS)

    Perez, J.-P.; Evirgen, A.; Abautret, J.; Christol, P.; Cordat, A.; Nedelcu, A.

    2015-01-01

    In this communication, we report results obtained on a new InSb/InAlSb/InSb `bariode', grown by MBE on (100)- oriented InSb substrate. Because of a very weak valence band offset with InSb (~ 25meV), InAlSb is a good candidate as a barrier layer for electrons. However, due to lattice mismatch with the InSb substrate, careful growth study of InAlSb was made to insure high crystal quality. As a result, InSb-based nBn detector device exhibits dark current density equals to 1x10-9A.cm-2 at 77K: two decades lower than Insb standard pin photodiode with similar cut-off wavelength. Moreover, compared to standard pn (or pin) InSb-based photodetectors fabricated by implanted planar process or by molecular beam epitaxy (MBE), we demonstrate that the reachable working temperature, around 120 K, of the InSbbased nBn detector is respectively higher than 40 K and 20 K than the previous. Such result demonstrates the potentiality of Insb detectors with nBn architecture to reach the high operating temperature.

  1. Identification of the Interactors of Human Nibrin (NBN) and of Its 26 kDa and 70 kDa Fragments Arising from the NBN 657del5 Founder Mutation

    PubMed Central

    Pennisi, Rosa; Pallotta, Valeria; D'Alessandro, Angelo; Antoccia, Antonio; Zolla, Lello; Ascenzi, Paolo; di Masi, Alessandra

    2014-01-01

    Nibrin (also named NBN or NBS1) is a component of the MRE11/RAD50/NBN complex, which is involved in early steps of DNA double strand breaks sensing and repair. Mutations within the NBN gene are responsible for the Nijmegen breakage syndrome (NBS). The 90% of NBS patients are homozygous for the 657del5 mutation, which determines the synthesis of two truncated proteins of 26 kDa (p26) and 70 kDa (p70). Here, HEK293 cells have been exploited to transiently express either the full-length NBN protein or the p26 or p70 fragments, followed by affinity chromatography enrichment of the eluates. The application of an unsupervised proteomics approach, based upon SDS-PAGE separation and shotgun digestion of protein bands followed by MS/MS protein identification, indicates the occurrence of previously unreported protein interacting partners of the full-length NBN protein and the p26 fragment containing the FHA/BRCT1 domains, especially after cell irradiation. In particular, results obtained shed light on new possible roles of NBN and of the p26 fragment in ROS scavenging, in the DNA damage response, and in protein folding and degradation. In particular, here we show that p26 interacts with PARP1 after irradiation, and this interaction exerts an inhibitory effect on PARP1 activity as measured by NAD+ levels. Furthermore, the p26-PARP1 interaction seems to be responsible for the persistence of ROS, and in turn of DSBs, at 24 h from IR. Since some of the newly identified interactors of the p26 and p70 fragments have not been found to interact with the full-length NBN, these interactions may somehow contribute to the key biological phenomena underpinning NBS. PMID:25485873

  2. Superconducting nanowire single photon detectors fabricated from an amorphous Mo{sub 0.75}Ge{sub 0.25} thin film

    SciTech Connect

    Verma, V. B.; Lita, A. E.; Vissers, M. R.; Marsili, F.; Pappas, D. P.; Mirin, R. P.; Nam, S. W.

    2014-07-14

    We present the characteristics of superconducting nanowire single photon detectors (SNSPDs) fabricated from amorphous Mo{sub 0.75}Ge{sub 0.25} thin-films. Fabricated devices show a saturation of the internal detection efficiency at temperatures below 1 K, with system dark count rates below 500 cps. Operation in a closed-cycle cryocooler at 2.5 K is possible with system detection efficiencies exceeding 20% for SNSPDs which have not been optimized for high detection efficiency. Jitter is observed to vary between 69 ps at 250 mK and 187 ps at 2.5 K using room temperature amplifiers.

  3. The light-matter interaction of a single semiconducting AlGaN nanowire and noble metal Au nanoparticles in the sub-diffraction limit.

    PubMed

    Sivadasan, A K; Madapu, Kishore K; Dhara, Sandip

    2016-08-24

    Near field scanning optical microscopy (NSOM) is not only a tool for imaging of sub-diffraction limited objects but also a prominent characteristic tool for understanding the intrinsic properties of nanostructures. In order to understand light-matter interactions in the near field regime using a NSOM technique with an excitation of 532 nm (2.33 eV), we selected an isolated single semiconducting AlGaN nanowire (NW) of diameter ∼120 nm grown via a vapor liquid solid (VLS) mechanism along with a metallic Au nanoparticle (NP) catalyst. The role of electronic transitions from different native defect related energy states of AlGaN is discussed in understanding the NSOM images for the semiconducting NW. The effect of strong surface plasmon resonance absorption of an excitation laser on the NSOM images for Au NPs, involved in the VLS growth mechanism of NWs, is also observed. PMID:27511614

  4. A hierarchical nanostructure consisting of amorphous MnO 2, Mn 3O 4 nanocrystallites, and single-crystalline MnOOH nanowires for supercapacitors

    NASA Astrophysics Data System (ADS)

    Hu, Chi-Chang; Hung, Ching-Yun; Chang, Kuo-Hsin; Yang, Yi-Lin

    In this communication, a porous hierarchical nanostructure consisting of amorphous MnO 2 (a-MnO 2), Mn 3O 4 nanocrystals, and single-crystalline MnOOH nanowires is designed for the supercapacitor application, which is prepared by a simple two-step electrochemical deposition process. Because of the gradual co-transformation of Mn 3O 4 nanocrystals and a-MnO 2 nanorods into an amorphous manganese oxide, the cycle stability of a-MnO 2 is obviously enhanced by adding Mn 3O 4. This unique ternary oxide nanocomposite with 100-cycle CV activation exhibits excellent capacitive performances, i.e., excellent reversibility, high specific capacitances (470 F g -1 in CaCl 2), high power property, and outstanding cycle stability. The highly porous microstructures of this composite before and after the 10,000-cycle CV test are examined by means of scanning electron microscopy (SEM) and transmission electron microscopy (TEM).

  5. The light-matter interaction of a single semiconducting AlGaN nanowire and noble metal Au nanoparticles in the sub-diffraction limit.

    PubMed

    Sivadasan, A K; Madapu, Kishore K; Dhara, Sandip

    2016-08-24

    Near field scanning optical microscopy (NSOM) is not only a tool for imaging of sub-diffraction limited objects but also a prominent characteristic tool for understanding the intrinsic properties of nanostructures. In order to understand light-matter interactions in the near field regime using a NSOM technique with an excitation of 532 nm (2.33 eV), we selected an isolated single semiconducting AlGaN nanowire (NW) of diameter ∼120 nm grown via a vapor liquid solid (VLS) mechanism along with a metallic Au nanoparticle (NP) catalyst. The role of electronic transitions from different native defect related energy states of AlGaN is discussed in understanding the NSOM images for the semiconducting NW. The effect of strong surface plasmon resonance absorption of an excitation laser on the NSOM images for Au NPs, involved in the VLS growth mechanism of NWs, is also observed.

  6. ZnO nanowire lasers.

    PubMed

    Vanmaekelbergh, Daniël; van Vugt, Lambert K

    2011-07-01

    The pathway towards the realization of optical solid-state lasers was gradual and slow. After Einstein's paper on absorption and stimulated emission of light in 1917 it took until 1960 for the first solid state laser device to see the light. Not much later, the first semiconductor laser was demonstrated and lasing in the near UV spectral range from ZnO was reported as early as 1966. The research on the optical properties of ZnO showed a remarkable revival since 1995 with the demonstration of room temperature lasing, which was further enhanced by the first report of lasing by a single nanowire in 2001. Since then, the research focussed increasingly on one-dimensional nanowires of ZnO. We start this review with a brief description of the opto-electronic properties of ZnO that are related to the wurtzite crystal structure. How these properties are modified by the nanowire geometry is discussed in the subsequent sections, in which we present the confined photon and/or polariton modes and how these can be investigated experimentally. Next, we review experimental studies of laser emission from single ZnO nanowires under different experimental conditions. We emphasize the special features resulting from the sub-wavelength dimensions by presenting our results on single ZnO nanowires lying on a substrate. At present, the mechanism of lasing in ZnO (nanowires) is the subject of a strong debate that is considered at the end of this review. PMID:21552596

  7. Nanowires, nanostructures and devices fabricated therefrom

    DOEpatents

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2005-04-19

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  8. Room-temperature near-infrared up-conversion lasing in single-crystal Er-Y chloride silicate nanowires

    NASA Astrophysics Data System (ADS)

    Ye, Rui; Xu, Chao; Wang, Xingjun; Cui, Jishi; Zhou, Zhiping

    2016-10-01

    Near-infrared up-conversion lasing in erbium(Er)-yttrium(Y) chloride silicate nanowires was demonstrated when pumped by 1476 nm laser at room temperature. The emission covers a very wide wavelength range (400–1000 nm). A clear threshold for 985 nm peak was observed at a launched average pump power of approximately 7 mW. Above threshold, the intensity increases linearly when turning up the pump power. The full width at half maximum at 985 nm decreases from 1.25 nm to 0.25 nm when reducing the measurement temperature from 30 K to 7 K, which is the narrowest linewidth of 980 nm micro-lasers to date. Our demonstration presents a possible novel method of utilizing up-conversion mechanism in Er-Y nanowire to achieve tunable near-infrared laser, which breaks new ground in the exploration of nanoscale optoelectronic devices operating at near-infrared wavelength.

  9. Room-temperature near-infrared up-conversion lasing in single-crystal Er-Y chloride silicate nanowires

    PubMed Central

    Ye, Rui; Xu, Chao; Wang, Xingjun; Cui, Jishi; Zhou, Zhiping

    2016-01-01

    Near-infrared up-conversion lasing in erbium(Er)-yttrium(Y) chloride silicate nanowires was demonstrated when pumped by 1476 nm laser at room temperature. The emission covers a very wide wavelength range (400–1000 nm). A clear threshold for 985 nm peak was observed at a launched average pump power of approximately 7 mW. Above threshold, the intensity increases linearly when turning up the pump power. The full width at half maximum at 985 nm decreases from 1.25 nm to 0.25 nm when reducing the measurement temperature from 30 K to 7 K, which is the narrowest linewidth of 980 nm micro-lasers to date. Our demonstration presents a possible novel method of utilizing up-conversion mechanism in Er-Y nanowire to achieve tunable near-infrared laser, which breaks new ground in the exploration of nanoscale optoelectronic devices operating at near-infrared wavelength. PMID:27703180

  10. Single-step electropolymerization patterning of a polypyrrole nanowire by ultra-short pulses via an AFM cantilever.

    PubMed

    Nam, Kihwan; Lee, Gyudo; Jung, Huihun; Park, Jinsung; Kim, Chi Hyun; Seo, Jongbum; Yoon, Dae Sung; Lee, Sang Woo; Kwon, Taeyun

    2011-06-01

    Conducting polymers (CPs) have attracted a great deal of attention due to their unique properties; these properties are useful in implementing various functional devices, such as memory, and chemical and biological sensors. In particular, the nanopatterning of CPs is a key technology that will accelerate the adoption of CPs in fabricating nanoscaled multifunctional devices. This paper presents an innovative technique for forming polypyrrole nanowire (PPy-NW) patterns, without any additional pretreatment on the gold surface, using atomic force microscopy (AFM) and ultra-short pulse voltage. Applying the ultra-short pulse voltage to the AFM tip has the following advantage: since the electrochemical current is extremely localized around the tip, the successful formation of CP nanowires results. This is because the pulse width is much shorter than the resistor-capacitor (RC) time constant of the equivalent electrochemical circuit of our experimental set-up. This paper provides systematic results regarding the dimensional variation of the PPy-NW patterns produced by varying the electrical conditions of the ultra-short pulse, such as the pulse amplitude, width, and frequency. The results show that use of an ultra-short pulse is essential in fabricating PPy-NW patterns. Additionally, an ultra-short pulse offers excellent pattern controllability for both width (353 nm ∼ 3.37 µm) and height (2.0 ∼ 88.3 nm).

  11. Catalyzed oxidation for nanowire growth

    NASA Astrophysics Data System (ADS)

    Tai, Kaiping; Sun, Ke; Huang, Bo; Dillon, Shen J.

    2014-04-01

    A simple, low-cost and scalable route to substrate-supported nanowire growth is reported based on catalyzed oxidation. The process shares common features with popular catalyzed nanowire growth techniques such as vapor-liquid-solid (VLS), vapor-solid-solid (VSS), or vapor-quasi-solid (VQS) that use catalyst nanoparticles to direct the deposition of reactants from the vapor phase. Catalyzed oxidation for nanowire growth (CONG) utilizes catalyzed anion (e.g. O2) reduction from the vapor phase and metal (e.g. Fe) oxidation from the substrate to produce oxide nanowires (e.g. Fe3O4). The approach represents a new class of nanowire growth methodology that may be applied to a broad range of systems. CONG does not require expensive chemical vapor deposition or physical vapor deposition equipment and can be implemented at intermediate temperatures (400-600 °C) in a standard laboratory furnace. This work also demonstrates a passive approach to catalyst deposition that allows the process to be implemented simply with no lithography or physical vapor deposition steps. This effort validates the general approach by synthesizing MnO, Fe3O4, WO3, MgO, TiO2, ZnO, ReO3, and NiO nanowires via CONG. The process produces single crystalline nanowires that can be grown to high aspect ratio and as high-density nanowire forests. Applications of the as-grown Fe3O4 and ReO3 nanowires for lithium ion battery systems are demonstrated to display high areal energy density and power.

  12. Catalyzed oxidation for nanowire growth.

    PubMed

    Tai, Kaiping; Sun, Ke; Huang, Bo; Dillon, Shen J

    2014-04-11

    A simple, low-cost and scalable route to substrate-supported nanowire growth is reported based on catalyzed oxidation. The process shares common features with popular catalyzed nanowire growth techniques such as vapor-liquid-solid (VLS), vapor-solid-solid (VSS), or vapor-quasi-solid (VQS) that use catalyst nanoparticles to direct the deposition of reactants from the vapor phase. Catalyzed oxidation for nanowire growth (CONG) utilizes catalyzed anion (e.g. O2) reduction from the vapor phase and metal (e.g. Fe) oxidation from the substrate to produce oxide nanowires (e.g. Fe3O4). The approach represents a new class of nanowire growth methodology that may be applied to a broad range of systems. CONG does not require expensive chemical vapor deposition or physical vapor deposition equipment and can be implemented at intermediate temperatures (400-600 °C) in a standard laboratory furnace. This work also demonstrates a passive approach to catalyst deposition that allows the process to be implemented simply with no lithography or physical vapor deposition steps. This effort validates the general approach by synthesizing MnO, Fe3O4, WO3, MgO, TiO2, ZnO, ReO3, and NiO nanowires via CONG. The process produces single crystalline nanowires that can be grown to high aspect ratio and as high-density nanowire forests. Applications of the as-grown Fe3O4 and ReO3 nanowires for lithium ion battery systems are demonstrated to display high areal energy density and power.

  13. Lithographically patterned nanowire electrodeposition

    NASA Astrophysics Data System (ADS)

    Xiang, Chengxiang

    Lithographically patterned nanowire electrodeposition (LPNE) is a new method for fabricating polycrystalline metal nanowires using electrodeposition. In LPNE, a sacrificial metal (M1 = silver or nickel) layer, 5 - 100 nm in thickness, is first vapor deposited onto a glass, oxidized silicon, or Kapton polymer film. A photoresist (PR) layer is then deposited, photopatterned, and the exposed Ag or Ni is removed by wet etching. The etching duration is adjusted to produce an undercut ≈300 nm in width at the edges of the exposed PR. This undercut produces a horizontal trench with a precisely defined height equal to the thickness of theM1 layer. Within this trench, a nanowire of metal M2 is electrodeposited (M2 = gold, platinum, palladium, or bismuth). Finally the PR layer and M1 layer are removed. The nanowire height and width can be independently controlled down to minimum dimensions of 5 nm (h) and 11 nm (w), for example, in the case of platinum. These nanowires can be 1 cm in total length. We measure the temperature-dependent resistance of 100 um sections of Au and Pd wires in order to estimate an electrical grain size for comparison with measurements by X-ray diffraction and transmission electron microscopy. Nanowire arrays can be postpatterned to produce two-dimensional arrays of nanorods. Nanowire patterns can also be overlaid one on top of another by repeating the LPNE process twice in succession to produce, for example, arrays of low-impedance, nanowirenanowire junctions. The resistance, R, of single gold nanowires was measured in situ during electrooxidation in aqueous 0.10 M sulfuric acid. Electrooxidation caused the formation of a gold oxide that is approximately 0.8 monolayers (ML) in thickness at +1.1 V vs saturated mercurous sulfate reference electrode (MSE) based upon coulometry and ex situ X-ray photoelectron spectroscopic analysis. As the gold nanowires were electrooxidized, R increased by an amount that depended on the wire thickness, ranging from

  14. Maskless electrodeposited contact for conducting polymer nanowires

    NASA Astrophysics Data System (ADS)

    Hangarter, Carlos M.; Bangar, Mangesh; Hernandez, Sandra C.; Chen, Wilfred; Deshusses, Marc A.; Mulchandani, Ashok; Myung, Nosang V.

    2008-02-01

    This letter reports a simple and scalable method to create mechanical joints and electrical contacts of conducting polymer nanowires to electrodes by selective maskless metal electrodeposition on electrodes. This is an attractive route for contacting nanowires as it bypasses harsh processing conditions of conventional methods. The electrodeposition conditions and initial resistance of the nanowires were found to have a significant impact on the selective maskless deposition. Different dopants were also investigated to understand the polymer reduction during cathodic deposition of metal. A single dodecyl sulfate doped polypyrrole nanowire with maskless electrodeposited nickel contacts was shown to have improved sensitivity toward ammonia gas.

  15. Diluted magnetic semiconductor nanowires exhibiting magnetoresistance

    DOEpatents

    Yang, Peidong; Choi, Heonjin; Lee, Sangkwon; He, Rongrui; Zhang, Yanfeng; Kuykendal, Tevye; Pauzauskie, Peter

    2011-08-23

    A method for is disclosed for fabricating diluted magnetic semiconductor (DMS) nanowires by providing a catalyst-coated substrate and subjecting at least a portion of the substrate to a semiconductor, and dopant via chloride-based vapor transport to synthesize the nanowires. Using this novel chloride-based chemical vapor transport process, single crystalline diluted magnetic semiconductor nanowires Ga.sub.1-xMn.sub.xN (x=0.07) were synthesized. The nanowires, which have diameters of .about.10 nm to 100 nm and lengths of up to tens of micrometers, show ferromagnetism with Curie temperature above room temperature, and magnetoresistance up to 250 Kelvin.

  16. Surface Passivation of Germanium Nanowires

    SciTech Connect

    Adhikari, Hemant; Sun, Shiyu; Pianetta, Piero; Chidsey, Chirstopher E.D.; McIntyre, Paul C.; /SLAC, SSRL

    2005-05-13

    The surface of single crystal, cold-wall CVD-grown germanium nanowires was studied by synchrotron radiation photoemission spectroscopy (SR-PES) and also by conventional XPS. The as-grown germanium nanowires seem to be hydrogen terminated. Exposure to laboratory atmosphere leads to germanium oxide growth with oxidation states of Ge{sup 1+}, Ge{sup 2+}, Ge{sup 3+}, while exposure to UV light leads to a predominance of the Ge{sup 4+} oxidation state. Most of the surface oxide could be removed readily by aqueous HF treatment which putatively leaves the nanowire surface hydrogen terminated with limited stability in air. Alternatively, chlorine termination could be achieved by aq. HCl treatment of the native oxide-coated nanowires. Chlorine termination was found to be relatively more stable than the HF-last hydrogen termination.

  17. Functional deficiency of NBN, the Nijmegen breakage syndrome protein, in a p.R215W mutant breast cancer cell line

    PubMed Central

    2014-01-01

    Background Mutations in NBN, the gene for Nijmegen Breakage Syndrome (NBS), are thought to predispose women to developing breast cancer, but a breast cancer cell line containing mutations in NBN has not yet been described. The p.R215W missense mutation occurs at sub-polymorphic frequencies in several populations. We aimed to investigate its functional impact in breast cancer cells from a carrier of this NBN mutation. Methods Breast cancer cell lines were screened by immunoblotting for NBN protein levels, and the NBN coding region was sequenced for mutation analysis. Radiosensitivity assays and functional studies were performed through immunocytochemistry and immunoblotting, and flow cytometry was employed to assess cell cycle progression. Impedance measurements were used to study the consequences of PARP1 inhibition. Statistical comparisons between cell lines were performed using t-tests. Results HCC1395 breast cancer cells exhibited reduced NBN protein levels. Direct sequencing identified the NBN p.R215W mutation in the hemizygous state, in addition to a truncation in BRCA1. Mutations in both genes were already present in the heterozygous state in the patient’s germline. HCC1395 cells were highly radiosensitive, susceptible to apoptosis and were deficient in the formation of NBN foci. There was also evidence for some impairment in the formation of γH2AX, MDC1, and 53BP1 foci after irradiation; these foci appeared smaller and irregular compared with repair foci in wild-type cells, although ATM signalling was largely unaffected. In line with their deficiency in NBN and BRCA1, HCC1395 cells were particularly sensitive to PARP1 inhibition. Conclusion Our results indicate that the p.R215W mutation in the HCC1395 breast cancer cell line impairs NBN function, making this cell line a potentially useful cellular model for studying defective NBN protein within a mutant BRCA1 background. PMID:24928521

  18. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance.

    PubMed

    Ghobadi, Amir; Ulusoy, T Gamze; Garifullin, Ruslan; Guler, Mustafa O; Okyay, Ali K

    2016-01-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed. PMID:27464476

  19. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance

    NASA Astrophysics Data System (ADS)

    Ghobadi, Amir; Ulusoy, T. Gamze; Garifullin, Ruslan; Guler, Mustafa O.; Okyay, Ali K.

    2016-07-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed.

  20. Effects of the single-ion anisotropy on magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) cylindrical Ising nanowire

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Bi, Jiang-lin; Liu, Rui-jia; Chen, Xu; Liu, Jin-ping

    2016-10-01

    Monte Carlo simulation has been performed in detail to study magnetic and thermodynamic properties of a ferrimagnetic mixed-spin (1, 3/2) cylindrical Ising nanowire with core-shell structure. The ground phase diagrams are obtained for different single-ion anisotropies. The system can display rich phase transitions such as the second- and first-order phase transitions, the tricritical points and the compensation points. Especially, emphasis has been given to the effects of the single-ion anisotropy and the temperate on the magnetization, the internal energy, the specific heat, the compensation points and hysteresis loops of the system as well as two sublattices. A number of characteristic phenomena such as such as various types of magnetization curves and triple, duadruple as well as quintuple hysteresis loops behaviors have been observed for certain physical parameters, originating from the competitions among the anisotropies, temperature and the longitudinal magnetic field. It is found that the single-ion anisotropy and the temperature strongly affect the coercivity and the remanence of the system. A satisfactory agreement can be achieved from comparisons between our results and previous theoretical and experimental works.

  1. A Heterojunction Design of Single Layer Hole Tunneling ZnO Passivation Wrapping around TiO2Nanowires for Superior Photocatalytic Performance

    PubMed Central

    Ghobadi, Amir; Ulusoy, T. Gamze; Garifullin, Ruslan; Guler, Mustafa O.; Okyay, Ali K.

    2016-01-01

    Nanostructured hybrid heterojunctions have been studied widely for photocatalytic applications due to their superior optical and structural properties. In this work, the impact of angstrom thick atomic layer deposited (ALD) ZnO shell layer on photocatalytic activity (PCA) of hydrothermal grown single crystalline TiO2 nanowires (NWs) is systematically explored. We showed that a single cycle of ALD ZnO layer wrapped around TiO2 NWs, considerably boosts the PCA of the heterostructure. Subsequent cycles, however, gradually hinder the photocatalytic activity (PCA) of the TiO2 NWs. Various structural, optical, and transient characterizations are employed to scrutinize this unprecedented change. We show that a single atomic layer of ZnO shell not only increases light harvesting capability of the heterostructure via extension of the absorption toward visible wavelengths, but also mitigates recombination probability of carriers through reduction of surface defects density and introduction of proper charge separation along the core-shell interface. Furthermore, the ultrathin ZnO shell layer allows a strong contribution of the core (TiO2) valence band holes through tunneling across the ultrathin interface. All mechanisms responsible for this enhanced PCA of heterostructure are elucidated and corresponding models are proposed. PMID:27464476

  2. Superconducting properties of very high quality NbN thin films grown by high temperature chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Hazra, D.; Tsavdaris, N.; Jebari, S.; Grimm, A.; Blanchet, F.; Mercier, F.; Blanquet, E.; Chapelier, C.; Hofheinz, M.

    2016-10-01

    Niobium nitride (NbN) is widely used in high-frequency superconducting electronics circuits because it has one of the highest superconducting transition temperatures ({T}{{c}}˜ 16.5 {{K}}) and largest gap among conventional superconductors. In its thin-film form, the T c of NbN is very sensitive to growth conditions and it still remains a challenge to grow NbN thin films (below 50 nm) with high T c. Here, we report on the superconducting properties of NbN thin films grown by high-temperature chemical vapor deposition (HTCVD). Transport measurements reveal significantly lower disorder than previously reported, characterized by a Ioffe-Regel parameter ({k}{{F}}{\\ell }) ˜ 12. Accordingly we observe {T}{{c}}˜ 17.06 {{K}} (point of 50% of normal state resistance), the highest value reported so far for films of thickness 50 nm or less, indicating that HTCVD could be particularly useful for growing high quality NbN thin films.

  3. CdTe nBn photodetectors with ZnTe barrier layer grown on InSb substrates

    NASA Astrophysics Data System (ADS)

    He, Zhao-Yu; Campbell, Calli M.; Lassise, Maxwell B.; Lin, Zhi-Yuan; Becker, Jacob J.; Zhao, Yuan; Boccard, Mathieu; Holman, Zachary; Zhang, Yong-Hang

    2016-09-01

    We have demonstrated an 820 nm cutoff CdTe nBn photodetector with ZnTe barrier layer grown on an InSb substrate. At room temperature, under a bias of -0.1 V, the photodetector shows Johnson and shot noise limited specific detectivity (D*) of 3 × 1013 cm Hz1/2/W at a wavelength of 800 nm and 2 × 1012 cm Hz1/2/W at 200 nm. The D* is optimized by using a top contact design of ITO/undoped-CdTe. This device not only possesses nBn advantageous characteristics, such as generation-recombination dark current suppression and voltage-bias-addressed two-color photodetection, but also offers features including responsivity enhancements by deep-depletion and by using a heterostructure ZnTe barrier layer. In addition, this device provides a platform to study nBn device physics at room temperature, which will help us to understand more sophisticated properties of infrared nBn photodetectors that may possess a large band-to-band tunneling current at a high voltage bias, because this current is greatly suppressed in the large-bandgap CdTe nBn photodetector.

  4. Free-standing and single-crystalline Fe(1-x)Mn(x)Si nanowires with room-temperature ferromagnetism and excellent magnetic response.

    PubMed

    Hung, Min-Hsiu; Wang, Chiu-Yen; Tang, Jianshi; Lin, Ching-Chun; Hou, Te-Chien; Jiang, Xiaowei; Wang, Kang L; Chen, Lih-Juann

    2012-06-26

    High-aspect-ratio Fe(1-x)Mn(x)Si nanowires with room-temperature ferromagnetism were synthesized by a chemical vapor deposition (CVD) method in one step. This is the first report of ternary silicide nanowires using magnetic Mn ions to partially replace metal sites in the host matrix. Here we report the excellent magnetic characteristics of Fe(1-x)Mn(x)Si nanowires, which exhibit strong ferromagnetism at room temperature and high magnetoresistance (MR) variation. As-synthesized Fe(1-x)Mn(x)Si nanowires show a hyperbranched morphology and a spin-disorder behavior. The strong spin interaction in Fe(1-x)Mn(x)Si nanowires, induced by the substitution of Fe sublattices for magnetic Mn ions, was revealed in the hysteresis loops. The magnetization versus magnetic field (M-H) curves of Fe(1-x)Mn(x)Si nanowires are much less sensitive to the temperature variation from 10 to 300 K than those of FeSi nanowires. Remarkably, the excellent MR performance, -41.6% at 25 K with a magnetic field of 9 T, was demonstrated in an individual Fe(0.88)Mn(0.12)Si nanowire.

  5. Theoretical Study of Midwave Infrared HgCdTe nBn Detectors Operating at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Akhavan, Nima Dehdashti; Jolley, Gregory; Umana-Membreno, Gilberto A.; Antoszewski, Jarek; Faraone, Lorenzo

    2015-09-01

    We report a theoretical study of mercury cadmium telluride (HgCdTe) unipolar n-type/barrier/ n-type (nBn) detectors for midwave infrared (MWIR) applications at elevated temperatures. The results obtained indicate that the composition, doping, and thickness of the barrier layer in MWIR HgCdTe nBn detectors can be optimized to yield performance levels comparable with those of ideal HgCdTe p- n photodiodes. It is also shown that introduction of an additional barrier at the back contact layer of the detector structure (nBnn+) leads to substantial suppression of the Auger generation-recombination (GR) mechanism; this results in an order-of-magnitude reduction in the dark current level compared with conventional nBn or p- n junction-based detectors, thus enabling background-limited detector operation above 200 K.

  6. Angle dependence on the anisotropic magnetoresistance amplitude of a single-contacted Ni nanowire subjected to a thermo-mechanical strain

    NASA Astrophysics Data System (ADS)

    Melilli, G.; Madon, B.; Wegrowe, J.-E.; Clochard, M.-C.

    2015-12-01

    The effects of thermoelastic and piezoelectric strain of an active track-etched β-PVDF polymer matrix on an electrodeposited single-contacted Ni nanowire (NW) are investigated at the nanoscale by measuring the change of magnetization (i.e. using the inverse magnetostriction effect). The magnetization state is measured locally by anisotropic magnetoresistance (AMR). The ferromagnetic NW plays thus the role of a mechanical probe that allows the effects of mechanical strain to be characterized and described qualitatively and quantitatively. The inverse magnetostriction was found to be responsible for a quasi-disappearance of the AMR signal for a variation of the order of ΔT ≈ 10 K. In other terms, the variation of the magnetization due to the stress compensates the effect of external magnetic field applied on the NW resistance. The induced stress field in a single Ni NW was found 1000 time higher than the bulk stress field (due to thermal expansion measured on the PVDF). This amplification could be attributed to three nanoscopic effects: (1) a stress mismatch between the Ni NW and the membrane, (2) a non-negligible role of the surface tension on Ni NW Young modulus, and (3) the possibility of non-linear stress-strain law. We investigate here the role of these different contributions using track-etched polymer membranes irradiated at various angles (αirrad) leading to, after electrodeposition, embedded Ni NWs of different orientations.

  7. Highly ordered large-scale neuronal networks of individual cells - toward single cell to 3D nanowire intracellular interfaces.

    PubMed

    Kwiat, Moria; Elnathan, Roey; Pevzner, Alexander; Peretz, Asher; Barak, Boaz; Peretz, Hagit; Ducobni, Tamir; Stein, Daniel; Mittelman, Leonid; Ashery, Uri; Patolsky, Fernando

    2012-07-25

    The use of artificial, prepatterned neuronal networks in vitro is a promising approach for studying the development and dynamics of small neural systems in order to understand the basic functionality of neurons and later on of the brain. The present work presents a high fidelity and robust procedure for controlling neuronal growth on substrates such as silicon wafers and glass, enabling us to obtain mature and durable neural networks of individual cells at designed geometries. It offers several advantages compared to other related techniques that have been reported in recent years mainly because of its high yield and reproducibility. The procedure is based on surface chemistry that allows the formation of functional, tailormade neural architectures with a micrometer high-resolution partition, that has the ability to promote or repel cells attachment. The main achievements of this work are deemed to be the creation of a large scale neuronal network at low density down to individual cells, that develop intact typical neurites and synapses without any glia-supportive cells straight from the plating stage and with a relatively long term survival rate, up to 4 weeks. An important application of this method is its use on 3D nanopillars and 3D nanowire-device arrays, enabling not only the cell bodies, but also their neurites to be positioned directly on electrical devices and grow with registration to the recording elements underneath.

  8. Terahertz Direct Detection Characteristics of a Superconducting NbN Bolometer

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Miao, Wei; Yao, Qi-Jun; Zhang, Wen; Shi, Sheng-Cai

    2011-01-01

    We report the terahertz direct detection characteristics of a spiral antenna coupled NbN superconducting hot-electron bolometer (HEB) at a bath temperature of 4.2 K. Thermal conductance determined from resistance transition curves with different bias currents is found to be 3 × 10-7 W/K. The device shows a read-out circuit limited noise equivalent power (NEP) of 4.5 × 10-12 W/Hz1/2 at 4.2 K with a home-made transimpedance amplifier operating at room temperature.

  9. NbN A/D Conversion of IR Focal Plane Sensor Signal at 10 K

    NASA Technical Reports Server (NTRS)

    Eaton, L.; Durand, D.; Sandell, R.; Spargo, J.; Krabach, T.

    1994-01-01

    We are implementing a 12 bit SFQ counting ADC with parallel-to-serial readout using our established 10 K NbN capability. This circuit provides a key element of the analog signal processor (ASP) used in large infrared focal plane arrays. The circuit processes the signal data stream from a Si:As BIB detector array. A 10 mega samples per second (MSPS) pixel data stream flows from the chip at a 120 megabit bit rate in a format that is compatible with other superconductive time dependent processor (TDP) circuits being developed. We will discuss our planned ASP demonstration, the circuit design, and test results.

  10. A superconducting NbN detector for neutral nanoparticles

    NASA Astrophysics Data System (ADS)

    Marksteiner, Markus; Divochiy, Alexander; Sclafani, Michele; Haslinger, Philipp; Ulbricht, Hendrik; Korneev, Alexander; Semenov, Alexander; Gol'tsman, Gregory; Arndt, Markus

    2009-11-01

    We present a proof-of-principle study of superconducting single photon detectors (SSPD) for the detection of individual neutral molecules/nanoparticles at low energies. The new detector is applied to characterize a laser desorption source for biomolecules and allows retrieval of the arrival time distribution of a pulsed molecular beam containing the amino acid tryptophan, the polypeptide gramicidin as well as insulin, myoglobin and hemoglobin. We discuss the experimental evidence that the detector is actually sensitive to isolated neutral particles.

  11. Optical absorption of silicon nanowires

    SciTech Connect

    Xu, T.; Lambert, Y.; Krzeminski, C.; Grandidier, B.; Stievenard, D.; Leveque, G.; Akjouj, A.; Pennec, Y.; Djafari-Rouhani, B.

    2012-08-01

    We report on simulations and measurements of the optical absorption of silicon nanowires (NWs) versus their diameter. We first address the simulation of the optical absorption based on two different theoretical methods: the first one, based on the Green function formalism, is useful to calculate the scattering and absorption properties of a single or a finite set of NWs. The second one, based on the finite difference time domain (FDTD) method, is well-adapted to deal with a periodic set of NWs. In both cases, an increase of the onset energy for the absorption is found with increasing diameter. Such effect is experimentally illustrated, when photoconductivity measurements are performed on single tapered Si nanowires connected between a set of several electrodes. An increase of the nanowire diameter reveals a spectral shift of the photocurrent intensity peak towards lower photon energies that allow to tune the absorption onset from the ultraviolet radiations to the visible light spectrum.

  12. Large area fabrication of vertical silicon nanowire arrays by silver-assisted single-step chemical etching and their formation kinetics

    NASA Astrophysics Data System (ADS)

    Srivastava, Sanjay K.; Kumar, Dinesh; Schmitt, S. W.; Sood, K. N.; Christiansen, S. H.; Singh, P. K.

    2014-05-01

    Vertically aligned silicon nanowire (SiNW) arrays have been fabricated over a large area using a silver-assisted single-step electroless wet chemical etching (EWCE) method, which involves the etching of silicon wafers in aqueous hydrofluoric acid (HF) and silver nitrate (AgNO3) solution. A comprehensive systematic investigation on the influence of different parameters, such as the etching time (up to 15 h), solution temperature (10-80 °C), AgNO3 (5-200 mM) and HF (2-22 M) concentrations, and properties of the multi-crystalline silicon (mc-Si) wafers, is presented to establish a relationship of these parameters with the SiNW morphology. A linear dependence of the NW length on the etch time is obtained even at higher temperature (10-50 °C). The activation energy for the formation of SiNWs on Si(100) has been found to be equal to ˜0.51 eV . It has been shown for the first time that the surface area of the Si wafer exposed to the etching solution is an important parameter in determining the etching kinetics in the single-step process. Our results establish that single-step EWCE offers a wide range of parameters by means of which high quality vertical SiNWs can be produced in a very simple and controlled manner. A mechanism for explaining the influence of various parameters on the evolution of the NW structure is discussed. Furthermore, the SiNW arrays have extremely low reflectance (as low as <3% for Si(100) NWs and <12% for mc-Si NWs) compared to ˜35% for the polished surface in the 350-1000 nm wavelength range. The remarkably low reflection surface of SiNW arrays has great potential for use as an effective light absorber material in novel photovoltaic architectures, and other optoelectronic and photonic devices.

  13. 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.

  14. Room temperature performance of mid-wavelength infrared InAsSb nBn detectors

    SciTech Connect

    Soibel, Alexander; Hill, Cory J.; Keo, Sam A.; Hoglund, Linda; Rosenberg, Robert; Kowalczyk, Robert; Khoshakhlagh, Arezou; Fisher, Anita; Ting, David Z.-Y.; Gunapala, Sarath D.

    2014-07-14

    In this work, we investigate the high temperature performance of mid-wavelength infrared InAsSb-AlAsSb nBn detectors with cut-off wavelengths near 4.5 μm. The quantum efficiency of these devices is 35% without antireflection coatings and does not change with temperature in the 77–325 K temperature range, indicating potential for room temperature operation. The current generation of nBn detectors shows an increase of operational bias with temperature, which is attributed to a shift in the Fermi energy level in the absorber. Analysis of the device performance shows that operational bias and quantum efficiency of these detectors can be further improved. The device dark current stays diffusion limited in the 150 K–325 K temperature range and becomes dominated by generation-recombination processes at lower temperatures. Detector detectivities are D*(λ) = 1 × 10{sup 9} (cm Hz{sup 0.5}/W) at T = 300 K and D*(λ) = 5 × 10{sup 9} (cm Hz{sup 0.5}/W) at T = 250 K, which is easily achievable with a one stage TE cooler.

  15. IF impedance and mixer gain of NbN hot electron bolometers

    NASA Astrophysics Data System (ADS)

    Kooi, J. W.; Baselmans, J. J. A.; Hajenius, M.; Gao, J. R.; Klapwijk, T. M.; Dieleman, P.; Baryshev, A.; de Lange, G.

    2007-02-01

    The intermediate frequency (IF) characteristics, the frequency dependent IF impedance, and the mixer conversion gain of a small area hot electron bolometer (HEB) have been measured and modeled. The device used is a twin slot antenna coupled NbN HEB mixer with a bridge area of 1×0.15μm2, and a critical temperature of 8.3K. In the experiment the local oscillator frequency was 1.300THz, and the (IF) 0.05-10GHz. We find that the measured data can be described in a self-consistent manner with a thin film model presented by Nebosis et al. [Proceedings of the Seventh International Symposium on Space Terahertz Technology, Charlottesville, VA, 1996 (unpublished), pp. 601-613], that is based on the two temperature electron-phonon heat balance equations of Perrin-Vanneste [J. Phys. (Paris) 48, 1311 (1987)]. From these results the thermal time constant, governing the gain bandwidth of HEB mixers, is observed to be a function of the electron-phonon scattering time, phonon escape time, and the electron temperature. From the developed theory the maximum predicted gain bandwidth for a NbN HEB is found to be 5.5-6GHz. In contrast, the gain bandwidth of the device under discussion was measured to be ˜2.3GHz which, consistent with the outlined theory, is attributed to a somewhat low critical temperature and nonoptimal film thickness (6nm).

  16. 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.

  17. High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

    PubMed

    An, Qinwei; Meng, Xianquan; Sun, Pan

    2015-10-21

    Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells.

  18. Patterned growth of single-crystal 3, 4, 9, 10-perylenetetracarboxylic dianhydride nanowire arrays for field-emission and optoelectronic devices.

    PubMed

    Pan, Huanhuan; Zhang, Xiujuan; Yang, Yang; Shao, Zhibin; Deng, Wei; Ding, Ke; Zhang, Yu; Jie, Jiansheng

    2015-07-24

    3, 4, 9, 10-perylenetetracarboxylic dianhydride (PTCDA) organic nanostructures possess extraordinary electronic and optoelectronic properties. However, it remains a challenge to achieve patterned growth of PTCDA nanowire (NW) arrays for integrated device applications. Here, we demonstrated the high-density, large-area, uniform, and cross-aligned growth of single-crystalline PTCDA NW arrays by using Au nanoparticles (NPs) as the growth templates. The high surface energy of Au NPs led to the cross-aligned growth of organic NWs, enabling the growth of PTCDA NW arrays with any desirable patterns by pre-patterning the Au films on a Si substrate. The PTCDA NW arrays as field emitters show good performance with a large emission current density and high emission stability. Furthermore, photodetectors based on PTCDA NW arrays were constructed via a simple in-situ growth approach, which exhibited high sensitivity to a wideband light ranging from 400-800 nm and surpassed the individual NW-based photodetectors in terms of higher photocurrent and faster response speed. Successful applications of PTCDA NW arrays in field emission and photodetectors show a great potential application of organic NW arrays in future efficient electronic and optoelectronic devices. PMID:26135069

  19. Heterojunction nanowires having high activity and stability for the reduction of oxygen: formation by self-assembly of iron phthalocyanine with single walled carbon nanotubes (FePc/SWNTs).

    PubMed

    Zhu, Jia; Jia, Nana; Yang, Lijun; Su, Dong; Park, Jinseong; Choi, YongMan; Gong, Kuanping

    2014-04-01

    A self-assembly approach to preparing iron phthalocyanine/single-walled carbon nanotube (FePc/SWNT) heterojunction nanowires as a new oxygen reduction reaction (ORR) electrocatalyst has been developed by virtue of water-adjusted dispersing in 1-cyclohexyl-pyrrolidone (CHP) of the two components. The FePc/SWNT nanowires have a higher Fermi level compared to pure FePc (d-band center, DFT=-0.69 eV versus -0.87 eV, respectively). Consequently, an efficient channel for transferring electron to the FePc surface is readily created, facilitating the interaction between FePc and oxygen, so enhancing the ORR kinetics. This heterojunction-determined activity in ORR illustrates a new stratagem to preparing non-noble ORR electrocatalysts of significant importance in constructing real-world fuel cells. PMID:24491331

  20. Facile synthesis of vanadium oxide nanowires

    NASA Astrophysics Data System (ADS)

    Kysar, Jesse; Sekhar, Praveen Kumar

    2016-10-01

    A simple growth process is reported for the synthesis of vanadium (II) oxide nanowires with an average width of 65 nm and up to 5 μm in length for growth at 1000 °C for 3 h. The vanadium (II) oxide nanowires were grown on a gold-coated silicon substrate at ambient pressure using a single heat zone furnace with Ar as the carrier gas. Gold was utilized as a catalyst for the growth of the nanowires. The growth temperature and heating time were varied to observe the nanowire morphology. An increase in nanowire width was observed with an increase in the heating temperature. A ninefold increase in the number density of the nanowires was observed when the heating time was changed from 30 min to 3 h. This is the first time a simple growth process for producing VO nanowires at ambient pressure has been demonstrated. Such a scheme enables wider use of VO nanowires in critical applications such as energy storage, gas sensors, and optical devices.

  1. Broad Wavelength Tunable Robust Lasing from Single-Crystal Nanowires of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

    PubMed

    Fu, Yongping; Zhu, Haiming; Stoumpos, Constantinos C; Ding, Qi; Wang, Jue; Kanatzidis, Mercouri G; Zhu, Xiaoyang; Jin, Song

    2016-08-23

    Lead halide perovskite nanowires (NWs) are emerging as a class of inexpensive semiconductors with broad bandgap tunability for optoelectronics, such as tunable NW lasers. Despite exciting progress, the current organic-inorganic hybrid perovskite NW lasers suffer from limited tunable wavelength range and poor material stability. Herein, we report facile solution growth of single-crystal NWs of inorganic perovskite CsPbX3 (X = Br, Cl) and their alloys [CsPb(Br,Cl)3] and a low-temperature vapor-phase halide exchange method to convert CsPbBr3 NWs into perovskite phase CsPb(Br,I)3 alloys and metastable CsPbI3 with well-preserved perovskite crystal lattice and NW morphology. These single crystalline NWs with smooth end facets and subwavelength dimensions are ideal Fabry-Perot cavities for NW lasers. Optically pumped tunable lasing across the entire visible spectrum (420-710 nm) is demonstrated at room temperature from these NWs with low lasing thresholds and high-quality factors. Such highly efficient lasing similar to what can be achieved with organic-inorganic hybrid perovskites indicates that organic cation is not essential for light emission application from these lead halide perovskite materials. Furthermore, the CsPbBr3 NW lasers show stable lasing emission with no measurable degradation after at least 8 h or 7.2 × 10(9) laser shots under continuous illumination, which are substantially more robust than their organic-inorganic counterparts. The Cs-based perovskites offer a stable material platform for tunable NW lasers and other nanoscale optoelectronic devices. PMID:27437566

  2. Broad Wavelength Tunable Robust Lasing from Single-Crystal Nanowires of Cesium Lead Halide Perovskites (CsPbX3, X = Cl, Br, I).

    PubMed

    Fu, Yongping; Zhu, Haiming; Stoumpos, Constantinos C; Ding, Qi; Wang, Jue; Kanatzidis, Mercouri G; Zhu, Xiaoyang; Jin, Song

    2016-08-23

    Lead halide perovskite nanowires (NWs) are emerging as a class of inexpensive semiconductors with broad bandgap tunability for optoelectronics, such as tunable NW lasers. Despite exciting progress, the current organic-inorganic hybrid perovskite NW lasers suffer from limited tunable wavelength range and poor material stability. Herein, we report facile solution growth of single-crystal NWs of inorganic perovskite CsPbX3 (X = Br, Cl) and their alloys [CsPb(Br,Cl)3] and a low-temperature vapor-phase halide exchange method to convert CsPbBr3 NWs into perovskite phase CsPb(Br,I)3 alloys and metastable CsPbI3 with well-preserved perovskite crystal lattice and NW morphology. These single crystalline NWs with smooth end facets and subwavelength dimensions are ideal Fabry-Perot cavities for NW lasers. Optically pumped tunable lasing across the entire visible spectrum (420-710 nm) is demonstrated at room temperature from these NWs with low lasing thresholds and high-quality factors. Such highly efficient lasing similar to what can be achieved with organic-inorganic hybrid perovskites indicates that organic cation is not essential for light emission application from these lead halide perovskite materials. Furthermore, the CsPbBr3 NW lasers show stable lasing emission with no measurable degradation after at least 8 h or 7.2 × 10(9) laser shots under continuous illumination, which are substantially more robust than their organic-inorganic counterparts. The Cs-based perovskites offer a stable material platform for tunable NW lasers and other nanoscale optoelectronic devices.

  3. Manganese oxide nanowires, films, and membranes and methods of making

    DOEpatents

    Suib, Steven Lawrence; Yuan, Jikang

    2008-10-21

    Nanowires, films, and membranes comprising ordered porous manganese oxide-based octahedral molecular sieves, and methods of making, are disclosed. A single crystal ultra-long nanowire includes an ordered porous manganese oxide-based octahedral molecular sieve, and has an average length greater than about 10 micrometers and an average diameter of about 5 nanometers to about 100 nanometers. A film comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is stacked on a surface of a substrate, wherein the nanowires of each layer are substantially axially aligned. A free standing membrane comprises a microporous network comprising a plurality of single crystal nanowires in the form of a layer, wherein a plurality of layers is aggregately stacked, and wherein the nanowires of each layer are substantially axially aligned.

  4. Real-time monitoring of auxin vesicular exocytotic efflux from single plant protoplasts by amperometry at microelectrodes decorated with nanowires.

    PubMed

    Liu, Jun-Tao; Hu, Liang-Sheng; Liu, Yan-Ling; Chen, Rong-Sheng; Cheng, Zhi; Chen, Shi-Jing; Amatore, Christian; Huang, Wei-Hua; Huo, Kai-Fu

    2014-03-01

    Recent biochemical results suggest that auxin (IAA) efflux is mediated by a vesicular cycling mechanism, but no direct detection of vesicular IAA release from single plant cells in real-time has been possible up to now. A TiC@C/Pt-QANFA micro-electrochemical sensor has been developed with high sensitivity in detection of IAA, and it allows real-time monitoring and quantification of the quantal release of auxin from single plant protoplast by exocytosis.

  5. Synthesis of nanostructures in nanowires using sequential catalyst reactions

    SciTech Connect

    Panciera, F.; Chou, Y. -C.; Reuter, M. C.; Zakharov, D.; Stach, E. A.; Hofmann, S.; Ross, F. M.

    2015-07-13

    Nanowire growth by the vapour–liquid–solid (VLS) process enables a high level of control over nanowire composition, diameter, growth direction, branching and kinking, periodic twinning, and crystal structure. The tremendous impact of VLS-grown nanowires is due to this structural versatility, generating applications ranging from solid-state lighting and single-photon sources to thermoelectric devices. Here, we show that the morphology of these nanostructures can be further tailored by using the liquid droplets that catalyse nanowire growth as a ‘mixing bowl’, in which growth materials are sequentially supplied to nucleate new phases. Growing within the liquid, these phases adopt the shape of faceted nanocrystals that are then incorporated into the nanowires by further growth. Furthermore, we demonstrate this concept by epitaxially incorporating metal-silicide nanocrystals into Si nanowires with defect-free interfaces, and discuss how this process can be generalized to create complex nanowire-based heterostructures.

  6. Synthesis of nanostructures in nanowires using sequential catalyst reactions

    DOE PAGESBeta

    Panciera, F.; Chou, Y. -C.; Reuter, M. C.; Zakharov, D.; Stach, E. A.; Hofmann, S.; Ross, F. M.

    2015-07-13

    Nanowire growth by the vapour–liquid–solid (VLS) process enables a high level of control over nanowire composition, diameter, growth direction, branching and kinking, periodic twinning, and crystal structure. The tremendous impact of VLS-grown nanowires is due to this structural versatility, generating applications ranging from solid-state lighting and single-photon sources to thermoelectric devices. Here, we show that the morphology of these nanostructures can be further tailored by using the liquid droplets that catalyse nanowire growth as a ‘mixing bowl’, in which growth materials are sequentially supplied to nucleate new phases. Growing within the liquid, these phases adopt the shape of faceted nanocrystalsmore » that are then incorporated into the nanowires by further growth. Furthermore, we demonstrate this concept by epitaxially incorporating metal-silicide nanocrystals into Si nanowires with defect-free interfaces, and discuss how this process can be generalized to create complex nanowire-based heterostructures.« less

  7. Synthesis of nanostructures in nanowires using sequential catalyst reactions

    PubMed Central

    Panciera, F.; Chou, Y.-C.; Reuter, M.C.; Zakharov, D.; Stach, E.A.; Hofmann, S.; Ross, F.M.

    2016-01-01

    Nanowire growth by the vapor-liquid-solid process enables a high level of control over nanowire composition, diameter, growth direction, branching and kinking, periodic twinning, and crystal structure. The tremendous impact of VLS-grown nanowires is due to this structural versatility, generating applications ranging from solid state lighting and single photon sources to thermoelectric devices. Here we show that the morphology of these nanostructures can be further tailored by using the liquid droplets that catalyze nanowire growth as a “mixing bowl”, in which growth materials are sequentially supplied to nucleate new phases. Growing within the liquid, these phases adopt the shape of faceted nanocrystals that are then incorporated into the nanowires by further growth. We demonstrate this concept by epitaxially incorporating metal silicide nanocrystals into Si nanowires with defect-free interfaces, and discuss how this process can be generalized to create complex nanowire-based heterostructures. PMID:26168344

  8. Tunable magnetic nanowires for biomedical and harsh environment applications

    PubMed Central

    Ivanov, Yurii P.; Alfadhel, Ahmed; Alnassar, Mohammed; Perez, Jose E.; Vazquez, Manuel; Chuvilin, Andrey; Kosel, Jürgen

    2016-01-01

    We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires. PMID:27072595

  9. A detailed study of magnetization reversal in individual Ni nanowires

    SciTech Connect

    Vilanova Vidal, Enrique; Ivanov, Yurii P.; Mohammed, Hanan; Kosel, Jürgen

    2015-01-19

    Magnetic nanowires have emerged as essential components for a broad range of applications. In many cases, a key property of these components is the switching field, which is studied as a function of the angle between the field and the nanowire. We found remarkable differences of up to 100% between the switching fields of different nanowires from the same fabrication batch. Our experimental results and micromagnetic simulations indicate that the nanowires exhibit a single domain behavior and that the switching mechanism includes vortex domain wall motion across the nanowire. The differences between the switching fields are attributed to different cross-sections of the nanowires, as found by electron microscopy. While a circular cross-section yields the smallest switching field values, any deviation from this shape results in an increase of the switching field. The shape of the nanowires' cross-sections is thus a critical parameter that has not been previously taken into account.

  10. Tunable magnetic nanowires for biomedical and harsh environment applications

    NASA Astrophysics Data System (ADS)

    Ivanov, Yurii P.; Alfadhel, Ahmed; Alnassar, Mohammed; Perez, Jose E.; Vazquez, Manuel; Chuvilin, Andrey; Kosel, Jürgen

    2016-04-01

    We have synthesized nanowires with an iron core and an iron oxide (magnetite) shell by a facile low-cost fabrication process. The magnetic properties of the nanowires can be tuned by changing shell thicknesses to yield remarkable new properties and multi-functionality. A multi-domain state at remanence can be obtained, which is an attractive feature for biomedical applications, where a low remanence is desirable. The nanowires can also be encoded with different remanence values. Notably, the oxidation process of single-crystal iron nanowires halts at a shell thickness of 10 nm. The oxide shell of these nanowires acts as a passivation layer, retaining the magnetic properties of the iron core even during high-temperature operations. This property renders these core-shell nanowires attractive materials for application to harsh environments. A cell viability study reveals a high degree of biocompatibility of the core-shell nanowires.

  11. Silicon nanowire circuits fabricated by AFM oxidation nanolithography.

    PubMed

    Martínez, Ramses V; Martínez, Javier; Garcia, Ricardo

    2010-06-18

    We report a top-down process for the fabrication of single-crystalline silicon nanowire circuits and devices. Local oxidation nanolithography is applied to define very narrow oxide masks on top of a silicon-on-insulator substrate. In a plasma etching, the nano-oxide mask generates a nanowire with a rectangular section. The nanowire width coincides with the lateral size of the mask. In this way, uniform and well-defined transistors with channel widths in the 10-20 nm range have been fabricated. The nanowires can be positioned with sub-100 nm lateral accuracy. The transistors exhibit an on/off current ratio of 10(5). The atomic force microscope nanolithography offers full control of the nanowire's shape from straight to circular or a combination of them. It also enables the integration of several nanowires within the same circuit. The nanowire transistors have been applied to detect immunological processes.

  12. 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.

  13. III-Nitride nanowire optoelectronics

    NASA Astrophysics Data System (ADS)

    Zhao, Songrui; Nguyen, Hieu P. T.; Kibria, Md. G.; Mi, Zetian

    2015-11-01

    Group-III nitride nanowire structures, including GaN, InN, AlN and their alloys, have been intensively studied in the past decade. Unique to this material system is that its energy bandgap can be tuned from the deep ultraviolet (~6.2 eV for AlN) to the near infrared (~0.65 eV for InN). In this article, we provide an overview on the recent progress made in III-nitride nanowire optoelectronic devices, including light emitting diodes, lasers, photodetectors, single photon sources, intraband devices, solar cells, and artificial photosynthesis. The present challenges and future prospects of III-nitride nanowire optoelectronic devices are also discussed.

  14. Nanowires for thermal energy conversion and management

    NASA Astrophysics Data System (ADS)

    Chen, Renkun

    This dissertation presents the application of nanowires in two aspects of thermal energy conversion and management: (i) silicon (Si) nanowires as efficient and scalable thermoelectric materials due to the reduced thermal conductivity (k), and (ii) Si and copper (Cu) nanowire arrays for enhanced phase change heat transfer including boiling and evaporation and their applications in thermal management of microelectronics. In the first half of the thesis (chapter 2 and 3), we describe thermal and thermoelectric measurements of individual Si nanowires for studying phonon transport properties and their potential application in thermoelectrics. A theoretical model based on coherent phonon scattering was developed to explain the experiemental data, which suggests that phonon-boundary scattering is highly frequency dependent. For low frequency (long wavelength) phonons, the transport is nearly ballistic, whereas high frequency or short wavelength phonons scatter diffusively at nanowire boundary. The competition between the two phonon transmission regimes results in the unusual linear behavior of the thermal conductance of thin VLS Si nanowires at low temperature. Next, the thermal conductivity of EE Si nanowires, which have much rougher surface compared to VLS nanowires, was measured and found to be five-eight times lower than that of VLS counterparts with similar diameters. The substantial reduction in k is presumably due to the higher surface roughness, since both types of nanowires have single crystalline cores. In particular, for ˜ 50 nm EE Si nanowires etched from 0.1 O-cm B-doped p-Si <111> (˜2 x 1017 cm-3 dopant concentration), the k is around 1.6 Wm-1K-1 and the kL is ˜1.2 Wm-1 K-1 at room temperature, approaching that of amorphous Si. The single nanowire measurements show the great promise of using Si nanowire arrays as high-performance, scalable thermoelectric materials. As the second focus of the thesis (chapter 4 and 5), nanowire arrays were used for enhanced

  15. Single nanowire light-emitting diodes using uniaxial and coaxial InGaN/GaN multiple quantum wells synthesized by metalorganic chemical vapor deposition.

    PubMed

    Ra, Yong-Ho; Navamathavan, Rangaswamy; Yoo, Hee-Il; Lee, Cheul-Ro

    2014-03-12

    We report the controlled synthesis of InGaN/GaN multiple quantum well (MQW) uniaxial (c-plane) and coaxial (m-plane) nanowire (NW) heterostructures by metalorganic chemical vapor deposition. Two kinds of heterostructure NW light-emitting diodes (LEDs) have been fabricated: (1) 10 pairs of InGaN/GaN MQW layers in the c-plane on the top of n-GaN NWs where Mg-doped p-GaN NW is axially grown (2) p-GaN/10 pairs of InGaN/GaN shell structure were surrounded by n-GaN core. Here, we discuss a comparative analysis based on the m-plane and the c-plane oriented InGaN/GaN MQW NW arrays. High-resolution transmission electron microscopy studies revealed that the barrier and the well structures of MQW were observed to be substantially clear with regular intervals while the interface regions were extremely sharp. The c-plane and m-plane oriented MQW single NW was utilized for the parallel assembly fabrication of the LEDs via a focused ion beam. The polarization induced effects on the c-plane and m-plane oriented MQW NWs were precisely compared via power dependence electroluminescence. The electrical properties of m-plane NWs exhibited superior characteristics than that of c-plane NWs owing to the absence of piezoelectric polarization fields. According to this study, high-quality m-plane coaxial NWs can be utilized for the realization of high-brightness LEDs.

  16. Room temperature performance of mid-wavelength infrared InAsSb nBn detectors

    NASA Astrophysics Data System (ADS)

    Soibel, Alexander; Hill, Cory J.; Keo, Sam A.; Hoglund, Linda; Rosenberg, Robert; Kowalczyk, Robert; Khoshakhlagh, Arezou; Fisher, Anita; Ting, David Z.-Y.; Gunapala, Sarath D.

    2015-05-01

    In this work we investigate the high temperature performance of mid-wavelength infrared InAsSb-AlAsSb nBn detectors with cut-off wavelengths near 4.5 μm. The quantum efficiency of these devices is 35% without antireflection coatings and does not change with temperature in the 77-325 K temperature range, indicating potential for room temperature operation. The device dark current stays diffusion limited in the 150-325 K temperature range and becomes dominated by generation-recombination processes at lower temperatures. Detector detectivities of D*(λ) = 1 × 109 (cm Hz0.5/W) at T = 300 K and D*(λ) = 5 × 109 (cm Hz0.5/W) at T = 250 K, which is easily achievable with a one stage TE cooler.

  17. Minority carrier lifetime and dark current measurements in mid-wavelength infrared InAs0.91Sb0.09 alloy nBn photodetectors

    DOE PAGESBeta

    Olson, B. V.; Kim, J. K.; Kadlec, E. A.; Klem, J. F.; Hawkins, S. D.; Leonhardt, D.; Coon, W. T.; Fortune, T. R.; Cavaliere, M. A.; Tauke-Pedretti, A.; et al

    2015-11-03

    Carrier lifetime and dark current measurements are reported for a mid-wavelength infrared InAs 0.91Sb0.09 alloy nBn photodetector. Minority carrier lifetimes are measured using a non-contact time-resolved microwave technique on unprocessed portions of the nBn wafer and the Auger recombination Bloch function parameter is determined to be |F1F2|=0.292. Moreover, the measured lifetimes are also used to calculate the expected diffusion dark current of the nBn devices and are compared with the experimental dark current measured in processed photodetector pixels from the same wafer. As a result, excellent agreement is found between the two, highlighting the important relationship between lifetimes and diffusionmore » currents in nBn photodetectors.« less

  18. Chemical Sensing with Nanowires

    NASA Astrophysics Data System (ADS)

    Penner, Reginald M.

    2012-07-01

    Transformational advances in the performance of nanowire-based chemical sensors and biosensors have been achieved over the past two to three years. These advances have arisen from a better understanding of the mechanisms of transduction operating in these devices, innovations in nanowire fabrication, and improved methods for incorporating receptors into or onto nanowires. Nanowire-based biosensors have detected DNA in undiluted physiological saline. For silicon nanowire nucleic acid sensors, higher sensitivities have been obtained by eliminating the passivating oxide layer on the nanowire surface and by substituting uncharged protein nucleic acids for DNA as the capture strands. Biosensors for peptide and protein cancer markers, based on both semiconductor nanowires and nanowires of conductive polymers, have detected these targets at physiologically relevant concentrations in both blood plasma and whole blood. Nanowire chemical sensors have also detected several gases at the parts-per-million level. This review discusses these and other recent advances, concentrating on work published in the past three years.

  19. Scaling laws for the critical current density of NbN films in high magnetic fields

    SciTech Connect

    Hampshire, D.P. . Dept. of Physics); Gray, K.E.; Kampwirth, R.T. )

    1992-08-01

    We have measured the critical current density (Jc) of two NbN films (500 {Angstrom} and 1550 {Angstrom} thick) as a function of temperature in magnetic fields up to 25 Tesla using transport measurements. In both films, the functional form of the volume pinning force F{sub p} obeys the Fietz - Webb scaling law throughout the entire magnetic field and temperature range such that: F{sub p}=J{sub c} {times} B= {alpha}B{sub c2}{sup m}(T)b{sup {1/2}} (1-b){sup 2} = {alpha}*(1-T/T{sub c}){sup m}b{sup {1/2}}(1-b){sup 2} where {alpha} and {alpha}* are constants dependent on the film, B{sub c2}(T) is the upper critical field, b = B/B{sub c2}(T) is the reduced magnetic field, {Tc} is the critical temperature and we find m = 2.7 {plus minus} 0.1. Over a limited range of magnetic fields close to B{sub c2}(T), we can approximate this functional form by: F{sub p} = {Beta}B{sub c2}{sup M}(T)b(1-b){sup 2}={Beta}*(1-T/{Tc}){sup M}b(1-b){sup 2} where {Beta} and {Beta}* are constants and we find M = 2.6{plus minus}0.2. Values of J{sub c} derived from D.C. magnetisation data obtained using Bean's model show qualitative agreement with the transport measurements throughout the superconducting phase. Despite the marked granularity in the microstructure of these films, we interpret our results as evidence that a flux pinning mechanism determines the transport current density in NbN films in high magnetic fields.

  20. Scaling laws for the critical current density of NbN films in high magnetic fields

    SciTech Connect

    Hampshire, D.P.; Gray, K.E.; Kampwirth, R.T.

    1992-08-01

    We have measured the critical current density (Jc) of two NbN films (500 {Angstrom} and 1550 {Angstrom} thick) as a function of temperature in magnetic fields up to 25 Tesla using transport measurements. In both films, the functional form of the volume pinning force F{sub p} obeys the Fietz - Webb scaling law throughout the entire magnetic field and temperature range such that: F{sub p}=J{sub c} {times} B= {alpha}B{sub c2}{sup m}(T)b{sup {1/2}} (1-b){sup 2} = {alpha}*(1-T/T{sub c}){sup m}b{sup {1/2}}(1-b){sup 2} where {alpha} and {alpha}* are constants dependent on the film, B{sub c2}(T) is the upper critical field, b = B/B{sub c2}(T) is the reduced magnetic field, {Tc} is the critical temperature and we find m = 2.7 {plus_minus} 0.1. Over a limited range of magnetic fields close to B{sub c2}(T), we can approximate this functional form by: F{sub p} = {Beta}B{sub c2}{sup M}(T)b(1-b){sup 2}={Beta}*(1-T/{Tc}){sup M}b(1-b){sup 2} where {Beta} and {Beta}* are constants and we find M = 2.6{plus_minus}0.2. Values of J{sub c} derived from D.C. magnetisation data obtained using Bean`s model show qualitative agreement with the transport measurements throughout the superconducting phase. Despite the marked granularity in the microstructure of these films, we interpret our results as evidence that a flux pinning mechanism determines the transport current density in NbN films in high magnetic fields.

  1. Photocurrent enhancement of an individual gallium nitride nanowire decorated with gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Sundararajan, Jency Pricilla; Sargent, Meredith; McIlroy, David N.

    2011-03-01

    Variation in electron transport properties of individual n-type gallium nitride (GaN) nanowire and gold decorated gallium nitride (Au-GaN) nanowire were studied with respect to laser exposure of different wavelength and intensity. Single nanowire devices were manufactured by photolithography process in nanotechnology cleanroom, were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). A drop in electrical conductivity of Au-GaN nanowire was observed relative to bare GaN nanowire. Under laser illumination, we noticed an enhancement in photocurrent in Au-GaN nanowire, which increased with increase in excitation power at ambient conditions. We present a comparative study of the opto-electrical behavior of bare GaN nanowire vs Au-GaN nanowire and explain the IV characteristics and FET characteristics with respect to the length and diameter of nanowire. USDA, UI-BANTech.

  2. Fabrication of highly-ordered nanopatterned copper nanowire arrays by photolithography.

    PubMed

    Li, Xiaoru; Wang, Yiqian; Song, Guojun; She, Xilin; Peng, Zhi; Wang, Shulong; Li, Jianjiang

    2010-07-01

    Two different patterns, one being circular and the other being QDU, of copper (Cu) nanowire arrays were successfully produced by electrochemical deposition and photolithography. The highly-ordered patterns of Cu nanowire arrays were observed to stand freely on the substrate using scanning electron microscopy (SEM). Chemical analyses have been performed on Cu nanowires using energy dispersive X-ray spectroscopy (EDS). The results confirmed that it is mainly composed of Cu. Selected-area electron diffraction (SAED) pattern indicated the nanowires are single crystalline and the growth direction of the nanowires is along the [220] direction. With the deposition time increasing, the length of Cu nanowires increaseed.

  3. Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif.

    PubMed

    Wang, Xinyang; Zhang, Fan; Schellhammer, Karl Sebastian; Machata, Peter; Ortmann, Frank; Cuniberti, Gianaurelio; Fu, Yubin; Hunger, Jens; Tang, Ruizhi; Popov, Alexey A; Berger, Reinhard; Müllen, Klaus; Feng, Xinliang

    2016-09-14

    A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen-boron-nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV-vis-NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2(•+). Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons. PMID:27541867

  4. 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.

  5. Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

    DOEpatents

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2009-08-04

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  6. Methods of fabricating nanostructures and nanowires and devices fabricated therefrom

    DOEpatents

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2010-11-16

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  7. Methods Of Fabricating Nanosturctures And Nanowires And Devices Fabricated Therefrom

    DOEpatents

    Majumdar, Arun; Shakouri, Ali; Sands, Timothy D.; Yang, Peidong; Mao, Samuel S.; Russo, Richard E.; Feick, Henning; Weber, Eicke R.; Kind, Hannes; Huang, Michael; Yan, Haoquan; Wu, Yiying; Fan, Rong

    2006-02-07

    One-dimensional nanostructures having uniform diameters of less than approximately 200 nm. These inventive nanostructures, which we refer to as "nanowires", include single-crystalline homostructures as well as heterostructures of at least two single-crystalline materials having different chemical compositions. Because single-crystalline materials are used to form the heterostructure, the resultant heterostructure will be single-crystalline as well. The nanowire heterostructures are generally based on a semiconducting wire wherein the doping and composition are controlled in either the longitudinal or radial directions, or in both directions, to yield a wire that comprises different materials. Examples of resulting nanowire heterostructures include a longitudinal heterostructure nanowire (LOHN) and a coaxial heterostructure nanowire (COHN).

  8. Controllable positioning and alignment of silver nanowires by tunable hydrodynamic focusing

    NASA Astrophysics Data System (ADS)

    Liu, Mei; Chen, Ying; Guo, Qiuquan; Li, Ruying; Sun, Xueliang; Yang, Jun

    2011-03-01

    Assembly and alignment of nanowires or nanotubes are critical steps for integrating functional nanodevices by the bottom-up strategy. However, it is still challenging to manipulate either an array of nanowires or individual nanowires in a controllable manner. Here we present a simple but versatile method of positioning and aligning nanowires by hydrodynamic focusing that functions as 'hydro-tweezers'. By adjusting the flow duration and flow rates of the sheath flows and sample flow, the density, width and position of the nanowire arrays, as building blocks of nanodevices, can be readily tuned in the hydrodynamic focusing process. This approach exhibits great potentials in the assembly of an array of functional nanodevices. With this method, multiple nanowire arrays can be positioned and aligned on predefined locations. Further focusing the sample flow, nanowires flow in single file. Thus single nanowires can also be lined up and located to desired positions.

  9. Semiconductor Nanowires for Photoelectrochemical Water Splitting

    NASA Astrophysics Data System (ADS)

    Hwang, Yun Jeong

    Photolysis of water with semiconductor materials has been investigated intensely as a clean and renewable energy resource by storing solar energy in chemical bonds such as hydrogen. One-dimensional (1D) nanostructures such as nanowires can provide several advantages for photoelectrochemical (PEC) water splitting due to their high surface areas and excellent charge transport and collection efficiency. This dissertation discusses various nanowire photoelectrodes for single or dual semiconductor systems, and their linked PEC cells for self-driven water splitting. After an introduction of solar water splitting in the first chapter, the second chapter demonstrates water oxidative activities of hydrothermally grown TiO2 nanowire arrays depending on their length and surface properties. The photocurrents with TiO2 nanowire arrays approach saturation due to their poor charge collection efficiency with longer nanowires despite increased photon absorption efficiency. Epitaxial grains of rutile atomic layer deposition (ALD) shell on TiO2 nanowire increase the photocurrent density by 1.5 times due to improved charge collection efficiency especially in the short wavelength region. Chapter three compares the photocurrent density of the planar Si and Si nanowire arrays coated by anatase ALD TiO 2 thin film as a model system of a dual bandgap system. The electroless etched Si nanowire coated by ALD TiO2 (Si EENW/TiO2) shows 2.5 times higher photocurrent density due to lower reflectance and higher surface area. Also, this chapter illustrates that n-Si/n-TiO2 heterojunction is a promising structure for the photoanode application of a dual semiconductor system, since it can enhance the photocurrent density compared to p-Si/n-TiO 2 junction with the assistance of bend banding at the interface. Chapter four demonstrates the charge separation and transport of photogenerated electrons and holes within a single asymmetric Si/TiO2 nanowire. Kelvin probe force microscopy measurements show

  10. Tunable electric and magnetic properties of CoxZn1-xS nanowires

    NASA Astrophysics Data System (ADS)

    Lu, Ming-Yen; Chen, Lih-Juann; Mai, Wenjie; Wang, Zhong Lin

    2008-12-01

    We report the growth of ZnS nanowires doped with cobalt using a one-step thermal evaporation method. The magnetism of the nanowires was maintained at room temperature, and the saturated magnetization increased with cobalt contents. Current-voltage measurements of a single nanowire showed not only a linear relationship, which implies Ohmic contacts of nanowire devices, but also tunable conductivities by doping concentration.

  11. Electrical breakdown of nanowires.

    PubMed

    Zhao, Jiong; Sun, Hongyu; Dai, Sheng; Wang, Yan; Zhu, Jing

    2011-11-01

    Instantaneous electrical breakdown measurements of GaN and Ag nanowires are performed by an in situ transmission electron microscopy method. Our results directly reveal the mechanism that typical thermally heated semiconductor nanowires break at the midpoint, while metallic nanowires breakdown near the two ends due to the stress induced by electromigration. The different breakdown mechanisms for the nanowires are caused by the different thermal and electrical properties of the materials.

  12. Ferroelectric phase transition of individual barium titanate nanowires

    NASA Astrophysics Data System (ADS)

    Spanier, Jonathan E.; Urban, Jeffrey J.; Yun, Wan Soo; Park, Hongkun

    2003-03-01

    Ferroelectric phase transition temperatures (T_c) of individual, single-crystalline barium titanate (BaTiO_3) nanowires are measured as a function of nanowire diameter, and the results are analyzed using a theoretical model based on the Landau-Ginzburg-Devonshire theory. The measurements show that Tc is depressed as the nanowire diameter gets smaller, approaching room temperature when the diameter reaches 3 nm. The theoretical analysis reproduces the scaling relation between the Tc depression and nanowire diameter and provides information about the stability difference between the surface and bulk polarization. This work is supported by NSF.

  13. Permanent bending and alignment of ZnO nanowires.

    PubMed

    Borschel, Christian; Spindler, Susann; Lerose, Damiana; Bochmann, Arne; Christiansen, Silke H; Nietzsche, Sandor; Oertel, Michael; Ronning, Carsten

    2011-05-01

    Ion beams can be used to permanently bend and re-align nanowires after growth. We have irradiated ZnO nanowires with energetic ions, achieving bending and alignment in different directions. Not only the bending of single nanowires is studied in detail, but also the simultaneous alignment of large ensembles of ZnO nanowires. Computer simulations reveal how the bending is initiated by ion beam induced damage. Detailed structural characterization identifies dislocations to relax stresses and make the bending and alignment permanent, even surviving annealing procedures.

  14. Whole-exome sequencing identifies a somatic missense mutation of NBN in clear cell sarcoma of the salivary gland.

    PubMed

    Zhang, Lei; Jia, Zhen; Mao, Fengbiao; Shi, Yueyi; Bu, Rong Fa; Zhang, Baorong

    2016-06-01

    Clear cell sarcoma (CCS) is a rare, low-grade carcinoma commonly located in the distal extremities of young adults involving tendons and aponeuroses. CCS is characterized by its poor prognosis due to late diagnosis, multiple local recurrence, propensity to late metastases, and a high rate of tumor-related mortality. The genetic cause for CCS is thought to be EWSR1 gene translocation. However, CCS lacking a translocation may have other, as yet uncharacterized, genetic mutations that can cause the same pathological effect. A combination of whole‑exome sequencing and Sanger sequencing of cancer tissue and venous blood from a patient diagnosed with CCS of the salivary gland revealed a somatic missense mutation, c.1061C>T (p.P354L), in exon 9 of the Nibrin gene (NBN). This somatic missense mutation led to the conversion of proline to leucine (p.P354L), resulting in deleterious effects for the NBN protein. Multiple-sequence alignments showed that codon 354, where the mutation (c.1061C>T) occurs, is located within a phylogenetically conserved region. In conclusion, we here report a somatic missense mutation c.1061C>T (p.P354L) in the NBN gene in a patient with CCS lacking an EWSR1-ATF1 fusion. Our findings broaden the genotypic spectrum of CCS and provide new molecular insight that should prove useful in the future clinical genetic diagnosis of CCS. PMID:27109316

  15. Twin plane re-entrant mechanism for catalytic nanowire growth.

    PubMed

    Gamalski, Andrew D; Voorhees, Peter W; Ducati, Caterina; Sharma, Renu; Hofmann, Stephan

    2014-03-12

    A twin-plane based nanowire growth mechanism is established using Au catalyzed Ge nanowire growth as a model system. Video-rate lattice-resolved environmental transmission electron microscopy shows a convex, V-shaped liquid catalyst-nanowire growth interface for a ⟨112⟩ growth direction that is composed of two Ge {111} planes that meet at a twin boundary. Unlike bulk crystals, the nanowire geometry allows steady-state growth with a single twin boundary at the nanowire center. We suggest that the nucleation barrier at the twin-plane re-entrant groove is effectively reduced by the line energy, and hence the twin acts as a preferential nucleation site that dictates the lateral step flow cycle which constitutes nanowire growth.

  16. Characterization of Co2FeAl nanowires

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.; Pegg, I. L.; Philip, J.

    2011-03-01

    Heusler alloy, Co 2 FeAl (CFA) is a potentially useful material in the field of spintronics due to its high spin polarization. The CFA nanowires are grown for the first time by the electrospinning method. The diameters of the wires formed are ranging from 80 -- 100 nm. The structural characterization of the nanowires is done using X-Ray diffraction and Raman spectroscopy. The nanowires exhibit cubic structure with a lattice constant, a = 2.44 Å. Parallel arrays of nanowires are grown for magnetic characterization using electric field applied at the collector plate. The nanowires exhibit ferromagnetic behavior with a Curie temperature higher than 400 K. Nanoscale devices are fabricated with single CFA nanowire to understand the magnetotransport properties. This work has been supported by funding from NSF under CAREER Grant No. ECCS-0845501 and NSF-MRI, DMR-0922997.

  17. SiC nanowires: A photocatalytic nanomaterial

    SciTech Connect

    Zhou Weimin; Yan Lijun; Wang Ying; Zhang Yafei

    2006-07-03

    Single-crystal {beta}-SiC nanowires coated with amorphous SiO{sub 2} were synthesized by a simple thermal evaporation technique. The photocatalytic activity of the SiC nanowires was characterized by measuring the photodegradation rate of acetaldehyde catalyzed by SiC as a function of UV irradiation time. It exhibited excellent photocatalytic activity, leading to the efficient decomposition of acetaldehyde by irradiation with UV light. The progress of the photocatalytic reaction can be monitored by the evolution of one of the products, CO{sub 2}. It has been observed that the as-synthesized SiC nanowires (with the SiO{sub 2} coating) have higher catalytic activity than the HF-etched, oxide-free SiC nanowires.

  18. Enhanced Thermoelectric Performance in Rough Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Renkun; Hochbaum, Allon I.; Diaz Delgado, Raul; Liang, Wenjie; Garnett, Erik C.; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-03-01

    Due to the disparity between electron (<10 nm) and phonon ( ˜100 nm) mean free paths in silicon, nanostructured Si could effectively block phonon transport by boundary scattering while maintaining electron transport, thereby enhancing thermoelectric figure of merit, ZT. Here we report the wafer-scale electrochemical synthesis and thermoelectric characterization of rough Si nanowires with enhanced ZT, relative to the bulk material. Single nanowire measurements show that their electrical resistivity and Seebeck coefficient are similar to those of bulk Si with similar dopant concentration. Thin nanowires, however, exhibit a 100-fold reduction in thermal conductivity (k), yielding a large ZT = 0.6 at room temperature. Although bulk Si is a poor thermoelectric material, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

  19. Mode Switching and Filtering in Nanowire Lasers.

    PubMed

    Röder, Robert; Sidiropoulos, Themistoklis P H; Buschlinger, Robert; Riediger, Max; Peschel, Ulf; Oulton, Rupert F; Ronning, Carsten

    2016-04-13

    Coherent light sources confining the light below the vacuum wavelength barrier will drive future concepts of nanosensing, nanospectroscopy, and photonic circuits. Here, we directly image the angular emission of such a light source based on single semiconductor nanowire lasers. It is confirmed that the lasing switches from the fundamental mode in a thin ZnO nanowire to an admixture of several transverse modes in thicker nanowires approximately at the multimode cutoff. The mode competition with higher order modes substantially slows down the laser dynamics. We show that efficient photonic mode filtering in tapered nanowires selects the desired fundamental mode for lasing with improved performance including power, efficiency, and directionality important for an optimal coupling between adjacent nanophotonic waveguides. PMID:27007261

  20. Deformation mechanisms of Cu nanowires with planar defects

    SciTech Connect

    Tian, Xia Yang, Haixia; Wan, Rui; Cui, Junzhi; Yu, Xingang

    2015-01-21

    Molecular dynamics simulations are used to investigate the mechanical behavior of Cu nanowires (NWs) with planar defects such as grain boundaries (GBs), twin boundaries (TBs), stacking faults (SFs), etc. To investigate how the planar defects affect the deformation and fracture mechanisms of naowires, three types of nanowires are considered in this paper: (1) polycrystalline Cu nanowire; (2) single-crystalline Cu nanowire with twin boundaries; and (3) single-crystalline Cu nanowire with stacking faults. Because of the large fraction of atoms at grain boundaries, the energy of grain boundaries is higher than that of the grains. Thus, grain boundaries are proved to be the preferred sites for dislocations to nucleate. Moreover, necking and fracture prefer to occur at the grain boundary interface owing to the weakness of grain boundaries. For Cu nanowires in the presence of twin boundaries, it is found that twin boundaries can strength nanowires due to the restriction of the movement of dislocations. The pile up of dislocations on twin boundaries makes them rough, inducing high energy in twin boundaries. Hence, twin boundaries can emit dislocations, and necking initiates at twin boundaries. In the case of Cu nanowires with stacking faults, all pre-existing stacking faults in the nanowires are observed to disappear during deformation, giving rise to a fracture process resembling the samples without stacking fault.

  1. Fabrication of multilayer nanowires

    NASA Astrophysics Data System (ADS)

    Kaur, Jasveer; Singh, Avtar; Kumar, Davinder; Thakur, Anup; Kaur, Raminder

    2016-05-01

    Multilayer nanowires were fabricated by potentiostate ectrodeposition template synthesis method into the pores of polycarbonate membrane. In present work layer by layer deposition of two different metals Ni and Cu in polycarbonate membrane having pore size of 600 nm were carried out. It is found that the growth of nanowires is not constant, it varies with deposition time. Scanning electron microscopy (SEM) is used to study the morphology of fabricated multilayer nanowires. An energy dispersive X-ray spectroscopy (EDS) results confirm the composition of multilayer nanowires. The result shows that multilayer nanowires formed is dense.

  2. Electro-triggering and electrochemical monitoring of dopamine exocytosis from a single cell by using ultrathin electrodes based on Au nanowires

    NASA Astrophysics Data System (ADS)

    Kang, Mijeong; Yoo, Seung Min; Gwak, Raekeun; Eom, Gayoung; Kim, Jihwan; Lee, Sang Yup; Kim, Bongsoo

    2015-12-01

    A sophisticated set of an Au nanowire (NW) stimulator-Au NW detector system is developed for electrical cell stimulation and electrochemical analysis of subsequent exocytosis with very high spatial resolution. Dopamine release from a rat pheochromocytoma cell is more stimulated by a more negative voltage pulse. This system could help to improve the therapeutic efficacy of electrotherapies by providing valuable information on their healing mechanism.A sophisticated set of an Au nanowire (NW) stimulator-Au NW detector system is developed for electrical cell stimulation and electrochemical analysis of subsequent exocytosis with very high spatial resolution. Dopamine release from a rat pheochromocytoma cell is more stimulated by a more negative voltage pulse. This system could help to improve the therapeutic efficacy of electrotherapies by providing valuable information on their healing mechanism. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06021d

  3. Gold-platinum alloy nanowires as highly sensitive materials for electrochemical detection of hydrogen peroxide.

    PubMed

    Zhou, Yibo; Yu, Gang; Chang, Fangfang; Hu, Bonian; Zhong, Chuan-Jian

    2012-12-13

    The exploitation of the unique electrical properties of nanowires requires an effective assembly of nanowires as functional materials on a signal transduction platform. This paper describes a new strategy to assemble gold-platinum alloy nanowires on microelectrode devices and demonstrates the sensing characteristics to hydrogen peroxide. The alloy nanowires have been controllably electrodeposited on microelectrodes by applying an alternating current. The composition, morphology and alloying structures of the nanowires were characterized, revealing a single-phase alloy characteristic, highly monodispersed morphology, and controllable bimetallic compositions. The alloy nanowires were shown to exhibit electrocatalytic response characteristics for the detection of hydrogen peroxide, exhibiting a high sensitivity, low detection limit, and fast response time. The nanowire's response mechanism to hydrogen peroxide is also discussed in terms of the synergistic activity of the bimetallic binding sites, which has important implications for a better design of functional nanowires as sensing materials for a wide range of applications.

  4. Silicon Nanowire Devices

    NASA Astrophysics Data System (ADS)

    Kamins, Theodore

    2006-03-01

    Metal-catalyzed, self-assembled, one-dimensional semiconductor nanowires are being considered as possible device elements to augment and supplant conventional electronics and to extend the use of CMOS beyond the physical and economic limits of conventional technology. Such nanowires can create nanostructures without the complexity and cost of extremely fine scale lithography. The well-known and controllable properties of silicon make silicon nanowires especially attractive. Easy integration with conventional electronics will aid their acceptance and incorporation. For example, connections can be formed to both ends of a nanowire by growing it laterally from a vertical surface formed by etching the top silicon layer of a silicon-on-insulator structure into isolated electrodes. Field-effect structures are one class of devices that can be readily built in silicon nanowires. Because the ratio of surface to volume in a thin nanowire is high, conduction through the nanowire is very sensitive to surface conditions, making it effective as the channel of a field-effect transistor or as the transducing element of a gas or chemical sensor. As the nanowire diameter decreases, a greater fraction of the mobile charge can be modulated by a given external charge, increasing the sensitivity. Having the gate of a nanowire transistor completely surround the nanowire also enhances the sensitivity. For a field-effect sensor to be effective, the charge must be physically close to the nanowire so that the majority of the compensating charge is induced in the nanowire and so that ions in solution do not screen the charge. Because only induced charge is being sensed, a coating that selectively binds the target species should be added to the nanowire surface to distinguish between different species in the analyte. The nanowire work at Hewlett-Packard Laboratories was supported in part by the Defense Advanced Research Projects Agency.

  5. Superconducting NbN Coplanar Switch Driven by DC Current for CMB Instruments

    NASA Astrophysics Data System (ADS)

    Bordier, G.; Cammilleri, V. D.; Bélier, B.; Bleurvacq, N.; Ghribi, A.; Piat, M.; Tartari, A.; Zannoni, M.

    2014-09-01

    The next generations of cosmic microwave background (CMB) instruments will be dedicated to the detection and characterisation of CMB B-modes. To measure this tiny signal, instruments need to control and minimise systematics. Signal modulation is one way to achieve such a control. New generation of focal planes will include the entire detection chain on chip. In this context, we present a superconducting coplanar switch driven by DC current. It consists of a superconducting micro-bridge which commutes between its on (superconducting) and off (normal metal) states, depending on the amplitude of the current injection. To be effective, we have to use a high normal state resistivity superconducting material with a gap frequency higher than the frequencies of operation (millimeter waves). Several measurements were made at low temperature on NbN and yielded very high resistivities. Preliminary results of components dc behavior is shown. Thanks to its low power consumption, fast modulation and low weight, this component is a perfect candidate for future CMB space missions.

  6. Study of the effect of NbN on microwave Niobium cavities for gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Liccardo, V.; França, E. K.; Aguiar, O. D.; Oliveira, R. M.; Ribeiro, K. L.; Silva, M. M. N. F.

    2016-07-01

    Superconducting reentrant cavities may be used in parametric transducers for resonant-mass gravitational wave detectors. When coupled to a spherical resonant antenna, transducers will monitor its mechanical quadrupolar modes, working as a mass-spring system. In this paper we will investigate the effect of the Niobium Nitride (NbN), produced through plasma immersion ion implantation (PIII), on the quality factor of reentrant Niobium (Nb) cavities. With the PIII surface treatment unloaded electrical Q-factors (Q0) of the order of 105 were obtained in cryogenic conditions. These results indicated a significant increase in the effect of superconductivity after the cavity surfaces have been heavily attacked by a concentrated acid mixture and after suffering successive PIII processes. Q0's ~ 3.0 × 105 at 4.2 K are expected to be obtained using Nb RRR399 with a suitable surface treatment. These cavities, with high Q0, are already installed and being tested in the Gravitational Wave Detector Mario Schenberg. The experimental tests have been carried out at the laboratories of the National Institute for Space Research (INPE).

  7. Solvothermal synthesis of strontium phosphate chloride nanowire

    NASA Astrophysics Data System (ADS)

    Lam, W. M.; Wong, C. T.; Li, Z. Y.; Luk, K. D. K.; Chan, W. K.; Yang, C.; Chiu, K. Y.; Xu, B.; Lu, W. W.

    2007-08-01

    Strontium phosphate chloride nanowire was synthesized via a solvothermal treatment of strontium tri-polyphosphate and Collin salt in 1,4-dioxane at 150 °C. The effects of 1,4-dioxane concentration on particle morphology, crystallinity and phase purity were investigated in this study. The specimen morphology was analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When the concentration of 1,4-dioxane was below 10%, micron-sized whisker was the dominant form. At 20-25% concentration of 1,4-dioxane, strontium phosphate chloride single-crystalline nanowire was 31±12 nm in diameter and 1.43±0.6 μm in length with an aspect ratio of 52.28±29.41. X-ray diffraction (XRD) pattern of this nanowire matched with that of strontium phosphate chloride (JCPDS #083-0973). When 1,4-dioxane concentration exceeded 25%, nanorod aggregate was the dominant form instead of nanowire. At 20-25% 1,4-dioxane concentration suitable strontium concentration combine with high chemical potential environment favors the formation of nanowires. By adding 1,4-dioxane impure phase such as β-strontium hydrogen phosphate, nanorod formation was suppressed. This method provides an efficient way to synthesize high aspect ratio strontium phosphate chloride nanowire. It has potential bioactive nanocomposite, high mechanical performance bioactive bone cement filler and fluorescent material applications.

  8. Semiconductor nanowires and nanowire heterostructures: Fundamental transport phenomena and application in nanoelectronics

    NASA Astrophysics Data System (ADS)

    Xiang, Jie

    Semiconductor nanowires are emerging among the most promising family of materials to impact future electronics owing to the highly controlled growth, which has enabled predictable variation of structure and composition on multiple length scales. This thesis presents study on two critical scientific areas: understanding the potentially unique nature of 1D electrical transport in nanowires and corresponding enhancements in device performance. First, we describe using solid state reaction to transform single crystal silicon nanowires into metallic nickel silicide nanowires, which possess low resistivity and high current density. NiSi/Si nanowire heterostructures were also created with atomically sharp metal/semiconductor interface and shown to enable FETs with outstanding performance. Next we will focus on exploring the unique physics of 1D transport. Inspired by band structure engineering in planar 2D electron gas systems, we have designed and synthesized undoped Ge/Si core/shell nanowire heterostructures using the CVD method. Transport measurements on individual nanowire confirmed the formation of a hole gas and an absence of Schottky barrier at the metal contacts. Significantly, conductance quantization was observed at low temperature suggestive of ballistic transport through discrete 1D subbands. This 1D hole gas has created a new platform for studies in low-dimensional physics. Here we show studies of mesoscopic Josephson junctions using Ge/Si core/shell nanowires with superconducting contacts, which exhibit a dissipationless supercurrent. A systematic investigation of the multiple Andreev reflection phenomena as well as supercurrent quantization from quantum confinement effect in the narrow nanowire channel will be presented. Furthermore, we have utilized the 1D hole gas and incorporated high-kappa dielectrics using atomic layer deposition and metal top-gate to fabricate high performance Ge/Si nanowire FETs with scaled transconductance and on-current values 3

  9. Aluminum-catalyzed silicon nanowires: Growth methods, properties, and applications

    NASA Astrophysics Data System (ADS)

    Hainey, Mel F.; Redwing, Joan M.

    2016-12-01

    Metal-mediated vapor-liquid-solid (VLS) growth is a promising approach for the fabrication of silicon nanowires, although residual metal incorporation into the nanowires during growth can adversely impact electronic properties particularly when metals such as gold and copper are utilized. Aluminum, which acts as a shallow acceptor in silicon, is therefore of significant interest for the growth of p-type silicon nanowires but has presented challenges due to its propensity for oxidation. This paper summarizes the key aspects of aluminum-catalyzed nanowire growth along with wire properties and device results. In the first section, aluminum-catalyzed nanowire growth is discussed with a specific emphasis on methods to mitigate aluminum oxide formation. Next, the influence of growth parameters such as growth temperature, precursor partial pressure, and hydrogen partial pressure on nanowire morphology is discussed, followed by a brief review of the growth of templated and patterned arrays of nanowires. Aluminum incorporation into the nanowires is then discussed in detail, including measurements of the aluminum concentration within wires using atom probe tomography and assessment of electrical properties by four point resistance measurements. Finally, the use of aluminum-catalyzed VLS growth for device fabrication is reviewed including results on single-wire radial p-n junction solar cells and planar solar cells fabricated with nanowire/nanopyramid texturing.

  10. High-performance laterally-arranged multiple-bandgap solar cells using spatially composition-graded CdxPb1-xS nanowires on a single substrate: a design study.

    PubMed

    Caselli, D A; Ning, C Z

    2011-07-01

    In this paper, laterally arranged multiple bandgap (LAMB) solar cells based on CdxPb1-xS alloy nanowires of varying composition on a single substrate are designed to be used together with a dispersive concentrator. Simulation results for a design with six subcells in series connection are presented. The design is based on a unique materials capability achieved in our recent research. An efficiency of 34.9% was obtained for operation without solar concentration, which increased to 40.5%, 41.7%, and 42.7% for concentration ratios of 25, 100, and 240 respectively. The device was also simulated with decreased carrier mobilities to model the possible reduction in absorber conductivity, depending on the nanowire geometry and configuration. For a concentration ratio of unity, decreasing the mobilities to 25% of their original values caused less than a 2.5% absolute drop in efficiency. The LAMB design offers the advantages of an integrated cell platform and the potential for low-cost, high efficiency photovoltaic systems.

  11. Burnout current density of bismuth nanowires

    NASA Astrophysics Data System (ADS)

    Cornelius, T. W.; Picht, O.; Müller, S.; Neumann, R.; Völklein, F.; Karim, S.; Duan, J. L.

    2008-05-01

    Single bismuth nanowires with diameters ranging from 100nmto1μm were electrochemically deposited in ion track-etched single-pore polycarbonate membranes. The maximum current density the wires are able to carry was investigated by ramping up the current until failure occurred. It increases by three to four orders of magnitude for nanowires embedded in the template compared to bulk bismuth and rises with diminishing diameter. Simulations show that the wires are heated up electrically to the melting temperature. Since the surface-to-volume ratio rises with diminishing diameter, thinner wires dissipate the heat more efficiently to the surrounding polymer matrix and, thus, can tolerate larger current densities.

  12. 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

  13. From nanodiamond to nanowires.

    SciTech Connect

    Barnard, A.; Materials Science Division

    2005-01-01

    Recent advances in the fabrication and characterization of semiconductor and metallic nanowires are proving very successful in meeting the high expectations of nanotechnologists. Although the nanoscience surrounding sp{sup 3} bonded carbon nanotubes has continued to flourish over recent years the successful synthesis of the sp{sup 3} analogue, diamond nanowires, has been limited. This prompts questions as to whether diamond nanowires are fundamentally unstable. By applying knowledge obtained from examining the structural transformations in nanodiamond, a framework for analyzing the structure and stability of diamond nanowires may be established. One possible framework will be discussed here, supported by results of ab initio density functional theory calculations used to study the structural relaxation of nanodiamond and diamond nanowires. The results show that the structural stability and electronic properties of diamond nanowires are dependent on the surface morphology, crystallographic direction of the principal axis, and the degree of surface hydrogenation.

  14. 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.

  15. Thermoelectric Properties of Higher Manganese Silicide Nanowires

    NASA Astrophysics Data System (ADS)

    Moore, Arden; Higgins, Jeremy; Zhou, Feng; Jin, Song; Shi, Li

    2009-03-01

    Higher manganese silicides (HMS) have a relatively high thermoelectric figure of merit (ZT) of about 0.7. HMS nanowires have been synthesized using a chemical vapor deposition method. In this work, the thermoelectric properties of individual HMS nanowires are measured and analyzed to determine the role of size effects on electron and phonon transport as well as potential ZT enhancement. Measurements of Seebeck coefficient, electrical conductivity, and thermal conductivity were performed using both suspended and substrate-based microdevices. Results show that the Seebeck coefficient of two as-synthesized 60 nm diameter nanowires between 300-400K is about 25-50% lower than that of single crystal bulk parallel to the c-axis, while the electrical conductivity values are about 25% lower than bulk single crystal in the same direction. The thermal conductivity of one 60 nm diameter nanowire at room temperature was found to be four times smaller than the bulk value along the c-axis. The large reduction in thermal conductivity and small to moderate impact on electrical transport may lead to HMS nanowires with enhanced ZT.

  16. Fourier Transform Emission Spectroscopy of the Low-Lying Electronic States of NbN

    NASA Astrophysics Data System (ADS)

    Ram, R. S.; Bernath, P. F.

    2000-06-01

    The high-resolution spectrum of NbN has been investigated in emission in the 3000-15 000 cm-1 region using a Fourier transform spectrometer. The bands were excited in a microwave discharge through a mixture of NbCl5 vapor, ∼5 mTorr of N2, and 3 Torr of He. Numerous bands observed in the near-infrared region have been classified into the following transitions: f1Φ-c1Γ, e1Π-a1Δ, C3Π0+-A3Σ-1, C3Π0--A3Σ-1, C3Π1-a1Δ, C3Π1-A3Σ-0, d1Σ+-A3Σ-0, and d1Σ+-b1Σ+. These observations are consistent with the energy level diagram provided by laser excitation and emission spectroscopy [Y. Azuma, G. Huang, M. P. J. Lyne, A. J. Merer, and V. I. Srdanov, J. Chem. Phys. 100, 4138-4155 (1993)]. The missing d1Σ+ state has been observed for the first time and its spectroscopic parameters are consistent with the theoretical predictions of S. R. Langhoff and W. Bauschlicher, Jr. [J. Mol. Spectrosc. 143, 169-179 (1990)]. Rotational analysis of a number of bands has been obtained and improved spectroscopic parameters have been extracted for the low-lying electronic states. The observation of several vibrational bands with v = 1 has enabled us to determine the vibrational intervals and equilibrium bond lengths for the A3Σ-0, a1Δ, b1Σ+, d1Σ+, and C3Π1 states.

  17. Elastic properties of nanowires

    NASA Astrophysics Data System (ADS)

    da Fonseca, Alexandre F.; Malta, C. P.; Galva~O, Douglas S.

    2006-05-01

    We present a model to study Young's modulus and Poisson's ratio of the composite material of amorphous nanowires. It is an extension of the model derived by two of us [da Fonseca and Galva~o, Phys. Rev. Lett. 92, 175502 (2004)] to study the elastic properties of amorphous nanosprings. The model is based on twisting and tensioning a straight nanowire and we propose an experimental setup to obtain the elastic parameters of the nanowire. We used the Kirchhoff rod model to obtain the expressions for the elastic constants of the nanowire.

  18. Understanding hydrothermal transformation from Mn2O3 particles to Na0.55Mn2O4·1.5H2O nanosheets, nanobelts, and single crystalline ultra-long Na4Mn9O18 nanowires

    PubMed Central

    Park, Yohan; Woo Lee, Sung; Kim, Ki Hyeon; Min, Bong-Ki; Kumar Nayak, Arpan; Pradhan, Debabrata; Sohn, Youngku

    2015-01-01

    Manganese oxides are one of the most valuable materials for batteries, fuel cells and catalysis. Herein, we report the change in morphology and phase of as-synthesized Mn2O3 by inserting Na+ ions. In particular, Mn2O3 nanoparticles were first transformed to 2 nm thin Na0.55Mn2O4·1.5H2O nanosheets and nanobelts via hydrothermal exfoliation and Na cation intercalation, and finally to sub-mm ultra-long single crystalline Na4Mn9O18 nanowires. This paper reports the morphology and phase-dependent magnetic and catalytic (CO oxidation) properties of the as-synthesized nanostructured Na intercalated Mn-based materials. PMID:26667348

  19. Self-Assembled PbSe Nanowire:Perovskite Hybrids.

    PubMed

    Yang, Zhenyu; Yassitepe, Emre; Voznyy, Oleksandr; Janmohamed, Alyf; Lan, Xinzheng; Levina, Larissa; Comin, Riccardo; Sargent, Edward H

    2015-12-01

    Inorganic semiconductor nanowires are of interest in nano- and microscale photonic and electronic applications. Here we report the formation of PbSe nanowires based on directional quantum dot alignment and fusion regulated by hybrid organic-inorganic perovskite surface ligands. All material synthesis is carried out at mild temperatures. Passivation of PbSe quantum dots was achieved via a new perovskite ligand exchange. Subsequent in situ ammonium/amine substitution by butylamine enables quantum dots to be capped by butylammonium lead iodide, and this further drives the formation of a PbSe nanowire superlattice in a two-dimensional (2D) perovskite matrix. The average spacing between two adjacent nanowires agrees well with the thickness of single atomic layer of 2D perovskite, consistent with the formation of a new self-assembled semiconductor nanowire:perovskite heterocrystal hybrid.

  20. Super-Joule heating in graphene and silver nanowire network

    NASA Astrophysics Data System (ADS)

    Maize, Kerry; Das, Suprem R.; Sadeque, Sajia; Mohammed, Amr M. S.; Shakouri, Ali; Janes, David B.; Alam, Muhammad A.

    2015-04-01

    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.