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Sample records for semiconducting nanotube junction

  1. Metallic Electrode: Semiconducting Nanotube Junction Model

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryon (Technical Monitor)

    2001-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in an experiment with a scanning tunneling microscope tip and a carbon nanotube [Collins et al., Science 278, 100 ('97)]. We claim that there are two contact modes for a tip (metal) -nanotube semi conductor) junction depending whether the alignment of the metal and semiconductor band structure is (1) variable (vacuum-gap) or (2) fixed (touching) with V. With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube. However, the Schottky mechanism in (2) would result in forward current with V < 0 for an n-nanotube, while with V > 0 for an p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type. We apply this picture to the source-drain I-V characteristics in a long nanotube-channel field-effect-transistor (Zhou et al., Appl. Phys. Lett. 76, 1597 ('00)], and show that two independent metal-semiconductor junctions connected in series are responsible for the observed behavior.

  2. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  3. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  4. Superconducting proximity effect in superconductor / semiconducting-carbon-nanotube / superconductor junctions.

    NASA Astrophysics Data System (ADS)

    Barbara, Paola

    2005-03-01

    We measure the proximity effect in devices made of two superconducting electrodes bridged by a 3-micrometer long semiconducting carbon nanotube. The electrodes are made of a Pd/Nb bilayer and the junctions are fabricated by using standard photolithography [1]. The superconducting proximity effect manifests itself with a peak in the low-bias differential conductance due to Andreev reflection at the superconductor/carbon nanotube interfaces. Application of a gate voltage allows the transparency of the junction to be tuned from high (Andreev reflection) to low (tunneling) [2]. We have studied the temperature dependence of the features in each regime. This work is supported by the NSF (DMR-0239721) and by the Research Corporation. [1] A. Tselev, K. Hatton, M. S. Fuhrer, M. Paranjape and P. Barbara, Nanotechnology 15, 1475 (2004). [2] A. F. Morpurgo, J. Kong, C. M. Marcus, and H. Dai, Science 286, 263 (1999).

  5. Modeling of Schottky Barrier Modulation due to Oxidation at Metallic Electrode and Semiconducting Carbon Nanotube Junction

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2003-01-01

    A model is proposed for the previously reported lower Schottky barrier for holes PHI (sub bH) in air than in vacuum at a metallic electrode - semiconducting carbon nanotube (CNT) junction. We assume that there is a transition region between the electrode and the CNT, and an appreciable potential can drop there. The role of the oxidation is to increase this potential drop with negatively charged oxygen molecules on the CNT, leading to lower PHI(sub Bh) after oxidation. The mechanism prevails in both p- and n-CNTs, and the model consistently explains the key experimental findings.

  6. Carbon nanotube intramolecular junctions

    NASA Astrophysics Data System (ADS)

    Yao, Zhen; Postma, Henk W. Ch.; Balents, Leon; Dekker, Cees

    1999-11-01

    The ultimate device miniaturization would be to use individual molecules as functional devices. Single-wall carbon nanotubes (SWNTs) are promising candidates for achieving this: depending on their diameter and chirality, they are either one-dimensional metals or semiconductors. Single-electron transistors employing metallic nanotubes and field-effect transistors employing semiconducting nanotubes have been demonstrated. Intramolecular devices have also been proposed which should display a range of other device functions. For example, by introducing a pentagon and a heptagon into the hexagonal carbon lattice, two tube segments with different atomic and electronic structures can be seamlessly fused together to create intramolecular metal-metal, metal-semiconductor, or semiconductor-semiconductor junctions. Here we report electrical transport measurements on SWNTs with intramolecular junctions. We find that a metal-semiconductor junction behaves like a rectifying diode with nonlinear transport characteristics that are strongly asymmetric with respect to bias polarity. In the case of a metal-metal junction, the conductance appears to be strongly suppressed and it displays a power-law dependence on temperatures and applied voltage, consistent with tunnelling between the ends of two Luttinger liquids. Our results emphasize the need to consider screening and electron interactions when designing and modelling molecular devices. Realization of carbon-based molecular electronics will require future efforts in the controlled production of these intramolecular nanotube junctions.

  7. Electronic transport, transition-voltage spectroscopy, and the Fano effect in single molecule junctions composed of a biphenyl molecule attached to metallic and semiconducting carbon nanotube electrodes.

    PubMed

    Brito da Silva Júnior, Carlos Alberto; Leal, José Fernando Pereira; Aleixo, Vicente Ferrer Pureza; Pinheiro, Felipe A; Del Nero, Jordan

    2014-09-28

    We have investigated electronic transport in a single-molecule junction composed of a biphenyl molecule attached to a p-doped semiconductor and metallic carbon nanotube leads. We find that the current-voltage characteristics are asymmetric as a result of the different electronic natures of the right and left leads, which are metallic and semiconducting, respectively. We provide an analysis of transition voltage spectroscopy in such a system by means of both Fowler-Nordheim and Lauritsen-Millikan plots; this analysis allows one to identify the positions of resonances and the regions where the negative differential conductance occurs. We show that transmittance curves are well described by the Fano lineshape, for both direct and reverse bias, demonstrating that the frontier molecular orbitals are effectively involved in the transport process. This result gives support to the interpretation of transition voltage spectroscopy based on the coherent transport model. PMID:25109887

  8. Trion electroluminescence from semiconducting carbon nanotubes.

    PubMed

    Jakubka, Florian; Grimm, Stefan B; Zakharko, Yuriy; Gannott, Florentina; Zaumseil, Jana

    2014-08-26

    Near-infrared emission from semiconducting single-walled carbon nanotubes (SWNTs) usually results from radiative relaxation of excitons. By binding an additional electron or hole through chemical or electrochemical doping, charged three-body excitons, so-called trions, are created that emit light at lower energies. The energy difference is large enough to observe weak trion photoluminescence from doped SWNTs even at room temperature. Here, we demonstrate strong trion electroluminescence from electrolyte-gated, light-emitting SWNT transistors with three different polymer-sorted carbon nanotube species, namely, (6,5), (7,5) and (10,5). The red-shifted trion emission is equal to or even stronger than the exciton emission, which is attributed to the high charge carrier density in the transistor channel. The possibility of trions as a radiative relaxation pathway for triplets and dark excitons that are formed in large numbers by electron-hole recombination is discussed. The ratio of trion to exciton emission can be tuned by the applied voltages, enabling voltage-controlled near-infrared light sources with narrow line widths that are solution-processable and operate at low voltages (<3 V). PMID:25029479

  9. Transport in Carbon Nanotube Junctions

    NASA Astrophysics Data System (ADS)

    Khoo, K. H.; Chelikowsky, James R.

    2008-03-01

    There is growing interest in the use of carbon nanotube thin films as transparent electrical conductors and thin-film transistors owing to their high optical transmittance, low sheet resistivity, and ease of fabrication. [1,2] A major contribution to the sheet resistivity originates at nanotube junctions, as electrical contact is typically poor between adjacent nanotubes. It is thus important to characterize carbon nanotube junctions in order to understand the conduction properties of nanotube thin films. To this end, we have performed ab initio density functional theory calculations to investigate the structural, electronic and transport properties of carbon nanotube junctions as a function of nanotube chirality and contact geometry [1] Z. Wu et al., Science 305, 1273 (2004) [2] E. S. Snow, J. P. Novak, P. M. Campbell, and D. Park, Appl. Phys. Lett. 82, 2145 (2003).

  10. Electronic properties of nanotube junctions

    NASA Astrophysics Data System (ADS)

    Lambin, Ph.; Meunier, V.

    1998-08-01

    The possibility of realizing junctions between two different nanotubes has recently attracted a great interest, even though much remains to be done for putting this idea in concrete form. Pentagon-heptagon pair defects in the otherwise perfect graphitic network make such connections possible, with virtually infinite varieties. In this paper, the literature devoted to nanotube junctions is briefly reviewed. A special emphasize is put on the electronic properties of C nanotube junctions, together with an indication on how their current-voltage characteristics may look like.

  11. Process for separating metallic from semiconducting single-walled carbon nanotubes

    NASA Technical Reports Server (NTRS)

    Sun, Ya-Ping (Inventor)

    2008-01-01

    A method for separating semiconducting single-walled carbon nanotubes from metallic single-walled carbon nanotubes is disclosed. The method utilizes separation agents that preferentially associate with semiconducting nanotubes due to the electrical nature of the nanotubes. The separation agents are those that have a planar orientation, .pi.-electrons available for association with the surface of the nanotubes, and also include a soluble portion of the molecule. Following preferential association of the separation agent with the semiconducting nanotubes, the agent/nanotubes complex is soluble and can be solubilized with the solution enriched in semiconducting nanotubes while the residual solid is enriched in metallic nanotubes.

  12. Switching and Rectification in Carbon-Nanotube Junctions

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Andriotis, Antonis N.; Menon, Madhu; Chernozatonskii, Leonid

    2003-01-01

    Multi-terminal carbon-nanotube junctions are under investigation as candidate components of nanoscale electronic devices and circuits. Three-terminal "Y" junctions of carbon nanotubes (see Figure 1) have proven to be especially interesting because (1) it is now possible to synthesize them in high yield in a controlled manner and (2) results of preliminary experimental and theoretical studies suggest that such junctions could exhibit switching and rectification properties. Following the preliminary studies, current-versus-voltage characteristics of a number of different "Y" junctions of single-wall carbon nanotubes connected to metal wires were computed. Both semiconducting and metallic nanotubes of various chiralities were considered. Most of the junctions considered were symmetric. These computations involved modeling of the quantum electrical conductivity of the carbon nanotubes and junctions, taking account of such complicating factors as the topological defects (pentagons, heptagons, and octagons) present in the hexagonal molecular structures at the junctions, and the effects of the nanotube/wire interfaces. A major component of the computational approach was the use of an efficient Green s function embedding scheme. The results of these computations showed that symmetric junctions could be expected to support both rectification and switching. The results also showed that rectification and switching properties of a junction could be expected to depend strongly on its symmetry and, to a lesser degree, on the chirality of the nanotubes. In particular, it was found that a zigzag nanotube branching at a symmetric "Y" junction could exhibit either perfect rectification or partial rectification (asymmetric current-versus-voltage characteristic, as in the example of Figure 2). It was also found that an asymmetric "Y" junction would not exhibit rectification.

  13. Electronic Properties of Carbon Nanotubes and Junctions

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Han, Jie; Yang, Liu; Govindan, T. R.; Jaffe, R.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Metallic and semiconducting Single Wall Carbon Nanotubes (CNT) have recently been characterized using scanning tunneling microscopy (STM) and the manipulation of individual CNT has been demonstrated. These developments make the prospect of using CNT as molecular wires and possibly as electronic devices an even more interesting one. We have been modeling various electronic properties such as the density of states and the transmission coefficient of CNT wires and junctions. These studies involve first calculating the stability of junctions using molecular dynamics simulations and then calculating the electronic properties using a pi-electron tight binding Hamiltonian. We have developed the expertise to calculate the electronic properties of both finite-sized CNT and CNT systems with semi-infinite boundary conditions. In this poster, we will present an overview of some of our results. The electronic application of CNT that is most promising at this time is their use as molecular wires. The conductance can however be greatly reduced because of reflection due to defects and contacts. We have modeled the transmission through CNT in the presence of two types of defects: weak uniform disorder and strong isolated scatterers. We find that the conductance is affected in significantly different manners due to these defects Junctions of CNT have also been imaged using STM. This makes it essential to derive rules for the formation of junctions between tubes of different chirality, study their relative energies and electronic properties. We have generalized the rules for connecting two different CNT and have calculated the transmission and density of states through CNT junctions. Metallic and semiconducting CNT can be joined to form a stable junction and their current versus voltage characteristics are asymmetric. CNT are deformed by the application of external forces including interactions with a substrate or other CNT. In many experiments, these deformation are expected to

  14. Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes.

    PubMed

    Rother, Marcel; Schießl, Stefan P; Zakharko, Yuriy; Gannott, Florentina; Zaumseil, Jana

    2016-03-01

    The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using gate-voltage-dependent electroluminescence, we spatially and spectrally reveal preferential charge transport that does not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification. PMID:26867006

  15. Understanding Charge Transport in Mixed Networks of Semiconducting Carbon Nanotubes

    PubMed Central

    2016-01-01

    The ability to select and enrich semiconducting single-walled carbon nanotubes (SWNT) with high purity has led to a fast rise of solution-processed nanotube network field-effect transistors (FETs) with high carrier mobilities and on/off current ratios. However, it remains an open question whether it is best to use a network of only one nanotube species (monochiral) or whether a mix of purely semiconducting nanotubes but with different bandgaps is sufficient for high performance FETs. For a range of different polymer-sorted semiconducting SWNT networks, we demonstrate that a very small amount of narrow bandgap nanotubes within a dense network of large bandgap nanotubes can dominate the transport and thus severely limit on-currents and effective carrier mobility. Using gate-voltage-dependent electroluminescence, we spatially and spectrally reveal preferential charge transport that does not depend on nominal network density but on the energy level distribution within the network and carrier density. On the basis of these results, we outline rational guidelines for the use of mixed SWNT networks to obtain high performance FETs while reducing the cost for purification. PMID:26867006

  16. Photoexcitation dynamics of coupled semiconducting carbon nanotube thin films.

    PubMed

    Mehlenbacher, Randy D; Wu, Meng-Yin; Grechko, Maksim; Laaser, Jennifer E; Arnold, Michael S; Zanni, Martin T

    2013-04-10

    Carbon nanotubes are a promising means of capturing photons for use in solar cell devices. We time-resolved the photoexcitation dynamics of coupled, bandgap-selected, semiconducting carbon nanotubes in thin films tailored for photovoltaics. Using transient absorption spectroscopy and anisotropy measurements, we found that the photoexcitation evolves by two mechanisms with a fast and long-range component followed by a slow and short-range component. Within 300 fs of optical excitation, 20% of nanotubes transfer their photoexcitation over 5-10 nm into nearby nanotube fibers. After 3 ps, 70% of the photoexcitation resides on the smallest bandgap nanotubes. After this ultrafast process, the photoexcitation continues to transfer on a ~10 ps time scale but to predominantly aligned tubes. Ultimately the photoexcitation hops twice on average between fibers. These results are important for understanding the flow of energy and charge in coupled nanotube materials and light-harvesting devices. PMID:23464618

  17. Electrospun Composite Nanofibers of Semiconductive Polymers for Coaxial PN Junctions

    NASA Astrophysics Data System (ADS)

    Serrano, William; Thomas, Sylvia

    The objective of this research is to investigate the conditions under P3HT and Activink, semiconducting polymers, form 1 dimension (1D) coaxial p-n junctions and to characterize their behavior in the presence of UV radiation and organic gases. For the first time, fabrication and characterization of semiconductor polymeric single fiber coaxial arrangements will be studied. Electrospinning, a low cost, fast and reliable method, with a coaxial syringe arrangement will be used to fabricate these fibers. With the formation of fiber coaxial arrangements, there will be investigations of dimensionality crossovers e.g., from one-dimensional (1D) to two-dimensional (2D). Coaxial core/shell fibers have been realized as seen in a recent publication on an electrospun nanofiber p-n heterojunction of oxides (BiFeO3 and TiO2, respectively) using the electrospinning technique with hydrothermal method. In regards to organic semiconducting coaxial p-n junction nanofibers, no reported studies have been conducted, making this study fundamental and essential for organic semiconducting nano devices for flexible electronics and multi-dimensional integrated circuits.

  18. Optoelectronic Switching of a Carbon Nanotube Chiral Junction Imaged with Nanometer Spatial Resolution.

    PubMed

    Nienhaus, Lea; Wieghold, Sarah; Nguyen, Duc; Lyding, Joseph W; Scott, Gregory E; Gruebele, Martin

    2015-11-24

    Chiral junctions of carbon nanotubes have the potential of serving as optically or electrically controllable switches. To investigate optoelectronic tuning of a chiral junction, we stamp carbon nanotubes onto a transparent gold surface and locate a tube with a semiconducting-metallic junction. We image topography, laser absorption at 532 nm, and measure I-V curves of the junction with nanometer spatial resolution. The bandgaps on both sides of the junction depend on the applied tip field (Stark effect), so the semiconducting-metallic nature of the junction can be tuned by varying the electric field from the STM tip. Although absolute field values can only be estimated because of the unknown tip geometry, the bandgap shifts are larger than expected from the tip field alone, so optical rectification of the laser and carrier generation by the laser must also affect the bandgap switching of the chiral junction. PMID:26348682

  19. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    DOE PAGESBeta

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui -Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; et al

    2016-04-04

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m-1 K-2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, we demonstrate thatmore » phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. As a result, these findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.« less

  20. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui-Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; Kim, Yong-Hyun; Blackburn, Jeffrey L.; Ferguson, Andrew J.

    2016-04-01

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m‑1 K‑2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, we demonstrate that phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. These findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.

  1. Exciton Dynamics in Semiconducting Carbon Nanotubes

    SciTech Connect

    Graham, Matt; Chmeliov, Javgenij; Ma, Yingzhong; Shinohara, Nori; Green, Alexander A.; Hersam, Mark C.; Valkunas, Leonas; Fleming, Graham

    2010-01-01

    We report femtosecond transient absorption spectroscopic study on the (6, 5) single-walled carbon nanotubes and the (7, 5) inner tubes of a dominant double-walled carbon nanotube species. We found that the dynamics of exciton relaxation probed at the first transition-allowed state (E11) of a given tube type exhibits a markedly slower decay when the second transition-allowed state (E22) is excited than that measured by exciting its first transition-allowed state (E11). A linear intensity dependence of the maximal amplitude of the transient absorption signal is found for the E22 excitation, whereas the corresponding amplitude scales linearly with the square root of the E11 excitation intensity. Theoretical modeling of these experimental findings was performed by developing a continuum model and a stochastic model with explicit consideration of the annihilation of coherent excitons. Our detailed numerical simulations show that both models can reproduce reasonably well the initial portion of decay kinetics measured upon the E22 and E11 excitation of the chosen tube species, but the stochastic model gives qualitatively better agreement with the intensity dependence observed experimentally than those obtained with the continuum model.

  2. Octagonal Defects at Carbon Nanotube Junctions

    PubMed Central

    Jaskólski, W.; Pelc, M.; Chico, Leonor; Ayuela, A.

    2013-01-01

    We investigate knee-shaped junctions of semiconductor zigzag carbon nanotubes. Two dissimilar octagons appear at such junctions; one of them can reconstruct into a pair of pentagons. The junction with two octagons presents two degenerate localized states at Fermi energy (EF). The reconstructed junction has only one state near EF, indicating that these localized states are related to the octagonal defects. The inclusion of Coulomb interaction splits the localized states in the junction with two octagons, yielding an antiferromagnetic system. PMID:24089604

  3. Transport Modeling for Metallic Electrode: Semiconducting Nanotube Systems

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryan (Technical Monitor)

    2001-01-01

    Recently, current-voltage (I-V) characteristics have been reported by Collins et al. for a system with a scanning tunneling microscope (STM) tip and a carbon nanotube. The STM tip was driven forward into a film of many entangled nanotubes on a substrate, and then was retracted, so that one of nanotubes bridged the STM and the film. I-V characteristics had two different patterns for different heights. One showed large dI/ dV with V greater than 0, small dI/dV with V less than 0, and I = 0 near V = 0 (type-I), while the other showed rectification, i.e., I does not equal 0 only with V less than 0 (type-II), with the tip grounded. We propose a physical mechanism to explain the observed I-V patterns. We consider that the observed characteristics strongly reflected the nature of the tip (metal) - nanotube (semiconductor) contact. The other end of the nanotube was entangled well in the film, and simply provided a good Ohmic contact. We will argue that there are two different contact modes: vacuum gap and touching modes, depending on the presence or absence of a tiny vacuum gap d approx. 0.1 - 0.2 nm at the junction. These modes may be related to physisorption and chemisorption, respectively. Once admitting their existence, it is naturally shown that I-V characteristics are type-I in the vacuum gap mode, and type-II in the touching mode. We argue that the nanotube had to be an n-type semiconductor judging from the I-V characteristics, contrary to often observed p-type in the transistor applications, where p-type is probably due to the oxidation in air or the trapped charges in the silicon dioxide. Additional information is contained in the original extended abstract.

  4. Preferential syntheses of semiconducting vertically aligned single-walled carbon nanotubes for direct use in FETs.

    PubMed

    Qu, Liangti; Du, Feng; Dai, Liming

    2008-09-01

    We have combined fast heating with plasma enhanced chemical vapor deposition (PECVD) for preferential growth of semiconducting vertically aligned single-walled carbon nanotubes (VA-SWNTs). Raman spectroscopic estimation indicated a high yield of up to 96% semiconducting SWNTs in the VA-SWNT array. The as-synthesized semiconducting SWNTs can be used directly for fabricating FET devices without the need for any postsynthesis purification or separation. PMID:18665651

  5. Below-gap excitation of semiconducting single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Soavi, G.; Grupp, A.; Budweg, A.; Scotognella, F.; Hefner, T.; Hertel, T.; Lanzani, G.; Leitenstorfer, A.; Cerullo, G.; Brida, D.

    2015-10-01

    We investigate the optoelectronic properties of the semiconducting (6,5) species of single-walled carbon nanotubes by measuring ultrafast transient transmission changes with 20 fs time resolution. We demonstrate that photons with energy below the lowest exciton resonance efficiently lead to linear excitation of electronic states. This finding challenges the established picture of a vanishing optical absorption below the fundamental excitonic resonance. Our result points towards below-gap electronic states as an intrinsic property of semiconducting nanotubes.

  6. Transparent Conductive Single-Walled Carbon Nanotube Networks with Precisely Tunable Ratios of Semiconducting and Metallic Nanaotubes

    SciTech Connect

    Blackburn, J. L.; Barnes, T. M.; Beard, M. C.; Kim, Y.-H.; Tenent, R. C.; McDonald, T. J.; To, B.; Coutts, T. J.; Heben, M. J.

    2008-01-01

    We present a comprehensive study of the optical and electrical properties of transparent conductive films made from precisely tuned ratios of metallic and semiconducting single-wall carbon nanotubes. The conductivity and transparency of the SWNT films are controlled by an interplay between localized and delocalized carriers, as determined by the SWNT electronic structure, tube-tube junctions, and intentional and unintentional redox dopants. The results suggest that the main resistance in the SWNT thin films is the resistance associated with tube-tube junctions. Redox dopants are found to increase the delocalized carrier density and transmission probability through intertube junctions more effectively for semiconductor-enriched films than for metal-enriched films. As a result, redox-doped semiconductor-enriched films are more conductive than either intrinsic or redox-doped metal-enriched films.

  7. Uniformly spaced arrays of purely semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Falk, Abram; Kumar, Bharat; Tulevski, George; Farmer, Damon; Hannon, James; Han, Shu-Jen

    Patterning uniformly spaced arrays of carbon nanotubes (CNTs) is a key challenge for carbon electronics. Our group adopts a hybrid approach to meeting this goal. We use top-down lithography to pattern trenches on chips. We then use surface-selective chemical monolayers to facilitate the bottom-up assembly of solution-processed CNTs into these trenches. Previously, we showed large-scale integration of CNTs based on this approach, but modifications to this process have been needed in order to improve the yield and decrease the fraction of non-switching devices. Our latest results show a high degree of selectivity, alignment and yield of successfully placed CNTs at a 100 nm pitch. Electrical measurements confirm that these chemically placed CNTs are nearly 100% semiconducting and of similar quality to randomly dispersed ones. I will then discuss our strategies for increasing the CNT density and extending these results from chip- to wafer-scale electronics. email: alfalk@us.ibm.com.

  8. Single-walled carbon nanotube based molecular switch tunnel junctions.

    PubMed

    Diehl, Michael R; Steuerman, David W; Tseng, Hsian-Rong; Vignon, Scott A; Star, Alexander; Celestre, Paul C; Stoddart, J Fraser; Heath, James R

    2003-12-15

    This article describes two-terminal molecular switch tunnel junctions (MSTJs) which incorporate a semiconducting, single-walled carbon nanotube (SWNT) as the bottom electrode. The nanotube interacts noncovalently with a monolayer of bistable, nondegenerate [2]catenane tetracations, self-organized by their supporting amphiphilic dimyristoylphosphatidyl anions which shield the mechanically switchable tetracations from a two-micrometer wide metallic top electrode. The resulting 0.002 micron 2 area tunnel junction addresses a nanometer wide row of approximately 2000 molecules. Active and remnant current-voltage measurements demonstrated that these devices can be reconfigurably switched and repeatedly cycled between high and low current states under ambient conditions. Control compounds, including a degenerate [2]catenane, were explored in support of the mechanical origin of the switching signature. These SWNT-based MSTJs operate like previously reported silicon-based MSTJs, but differently from similar devices incorporating bottom metal electrodes. The relevance of these results with respect to the choice of electrode materials for molecular electronics devices is discussed. PMID:14714382

  9. Universal empirical formula for optical transition energies of semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jamal, G. R. Ahmed; Mominuzzaman, S. M.

    2016-01-01

    A general empirical relation for calculating first seven optical transition energies of semiconducting single wall carbon nanotubes (SWCNTs) is proposed here for the first time. The proposed formula effectively relates first seven optical transition energies of semiconducting SWCNTs with their chiral indices (n, m) through exponential form containing two specific terms (n+2m) and (2n-m). Both mod 1 and mod 2 types of semiconducting tubes are considered here over a wide diameter range from 0.4 nm to 4.75 nm. It was observed that the proposed empirical relations can predict the recent experimental data of those optical transitions with high accuracy.

  10. Step-edge faceting and local metallization of a single-wall semiconducting carbon nanotube

    NASA Astrophysics Data System (ADS)

    Clair, Sylvain; Kim, Yousoo; Kawai, Maki

    2011-10-01

    The adsorption of a single-wall carbon nanotube on a well-defined metal surface produces substantial mutual interaction that can lead to strong effects both on the nanotube and on the substrate side. We report two kinds of step faceting on Au(111) and Cu(111). We observed local metallization of a semiconducting nanotube induced by the deformation pressure of crossing a step edge on Cu(111). The origin of this effect is discussed. Our results illustrate the complexity and the large number of situations encountered for the nanotube-on-metal system.

  11. Controlled Growth of Semiconducting and Metallic Single-Wall Carbon Nanotubes.

    PubMed

    Liu, Chang; Cheng, Hui-Ming

    2016-06-01

    Single-wall carbon nanotubes (SWCNTs) can be either semiconducting or metallic depending on their chiral angles and diameters. The use of SWCNTs in electronics has long been hindered by the fact that the as-prepared SWCNTs are usually a mixture of semiconducting and metallic ones. Therefore, controlled synthesis of SWCNTs with a uniform electrical type or even predefined chirality has been a focus of carbon nanotube research in recent years. In this Perspective, we summarize recent progress on the controlled growth of semiconducting and metallic SWCNTs by in situ selective etching and by novel catalyst design. The advantages and mechanisms of these approaches are analyzed, and the challenges are discussed. Finally, we predict possible breakthroughs and future trends in the controlled synthesis and applications of SWCNTs. PMID:27149629

  12. Proximity semiconducting nanowire junctions from Josephson to quantum dot regimes

    NASA Astrophysics Data System (ADS)

    Gharavi, Kaveh; Holloway, Gregory; Baugh, Jonathan

    Experimental low-temperature transport results are presented on proximity-effect Josephson junctions made from low bandgap III-V semiconductor nanowires contacted with Nb. Two regimes are explored in terms of the Nb/nanowire interface transparency t. (i) High t allows a supercurrent to flow across the junction with magnitude Ic, which can be modulated using the voltage Vg on a global back gate or a local gate. Relatively high values are obtained for the figure-of-merit parameter IcRN / (eΔ) ~ 0 . 5 , and t ~ 0 . 75 , where RN is the normal state resistance and Δ the superconducting gap of the Nb leads. With the application of an axial magnetic field, Ic decays but exhibits oscillations before being fully suppressed. The period and amplitude of the oscillations depend on Vg. Possible explanations for this behaviour are presented, including Josephson interference of the orbital subbands in the nanowire. (ii) Lower transparency correlates with a spontaneous quantum dot (QD) formed in the nanowire channel. Pairs of Andreev Bound States (ABS) appear at energies | E | < Δ , with one pair unexpectedly pinned at E = 0 for a wide range of Vg. A description of the QD-ABS system beyond the Anderson model is presented to explain the latter results.

  13. Short Channel Field-Effect-Transistors with Inkjet-Printed Semiconducting Carbon Nanotubes.

    PubMed

    Jang, Seonpil; Kim, Bongjun; Geier, Michael L; Hersam, Mark C; Dodabalapur, Ananth

    2015-11-01

    Short channel field-effect-transistors with inkjet-printed semiconducting carbon nanotubes are fabricated using a novel strategy to minimize material consumption, confining the inkjet droplet into the active channel area. This fabrication approach is compatible with roll-to-roll processing and enables the formation of high-performance short channel device arrays based on inkjet printing. PMID:26312458

  14. High-Yield Separation of Metallic and Semiconducting Single-Wall Carbon Nanotubes by Agarose Gel Electrophoresis

    NASA Astrophysics Data System (ADS)

    Tanaka, Takeshi; Jin, Hehua; Miyata, Yasumitsu; Kataura, Hiromichi

    2008-11-01

    We have developed a novel separation method of metallic and semiconducting single-wall carbon nanotubes (SWCNTs) using agarose gel electrophoresis. When the SWCNTs were isolated with sodium dodecyl sulfate (SDS) and embedded in agarose gel, only the metallic SWCNTs separated from the starting gel by an electric field. After 20 min, almost all SWCNTs applied to gel electrophoresis were separated into two fractions, containing ˜95% semiconducting and ˜70% metallic nanotubes. The difference in the response to the electric field between metallic and semiconducting SWCNTs can be explained by the higher affinity of semiconducting SWCNTs to agarose than to SDS.

  15. Influence of cysteine doping on photoluminescence intensity from semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kurnosov, N. V.; Leontiev, V. S.; Linnik, A. S.; Karachevtsev, V. A.

    2015-03-01

    Photoluminescence (PL) from semiconducting single-walled carbon nanotubes can be applied for detection of cysteine. It is shown that cysteine doping (from 10-8 to 10-3 M) into aqueous suspension of nanotubes with adsorbed DNA leads to increase of PL intensity. The PL intensity was enhanced by 27% at 10-3 M cysteine concentration in suspension. Most likely, the PL intensity increases due to the passivation of p-defects on the nanotube by the cysteine containing reactive thiol group. The effect of doping with other amino acids without this group (methionine, serine, aspartic acid, lysine, proline) on the PL intensity is essentially weaker.

  16. Growth of semiconducting single-wall carbon nanotubes with a narrow band-gap distribution

    PubMed Central

    Zhang, Feng; Hou, Peng-Xiang; Liu, Chang; Wang, Bing-Wei; Jiang, Hua; Chen, Mao-Lin; Sun, Dong-Ming; Li, Jin-Cheng; Cong, Hong-Tao; Kauppinen, Esko I.; Cheng, Hui-Ming

    2016-01-01

    The growth of high-quality semiconducting single-wall carbon nanotubes with a narrow band-gap distribution is crucial for the fabrication of high-performance electronic devices. However, the single-wall carbon nanotubes grown from traditional metal catalysts usually have diversified structures and properties. Here we design and prepare an acorn-like, partially carbon-coated cobalt nanoparticle catalyst with a uniform size and structure by the thermal reduction of a [Co(CN)6]3− precursor adsorbed on a self-assembled block copolymer nanodomain. The inner cobalt nanoparticle functions as active catalytic phase for carbon nanotube growth, whereas the outer carbon layer prevents the aggregation of cobalt nanoparticles and ensures a perpendicular growth mode. The grown single-wall carbon nanotubes have a very narrow diameter distribution centred at 1.7 nm and a high semiconducting content of >95%. These semiconducting single-wall carbon nanotubes have a very small band-gap difference of ∼0.08 eV and show excellent thin-film transistor performance. PMID:27025784

  17. Mechanical and electronic properties at the interface between the Si(100) surface and semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Barraza-Lopez, Salvador

    2007-03-01

    I discuss the ab initio mechanical and electronic properties of semiconducting carbon nanotubes adsorbed on the Si(100) surface. After revising results from nanotubes on the fully unpassivated surface[1], the interaction between a semiconducting nanotube and a fully H-passivated Si(100) surface with dopants is examined[2]. As silicon wafers are ordinarily doped, the model closely resembles experimental onditions[2,3,4], allowing for qualitative comparison. The single H-monolayer prevents electronic states in nanotubes from energetically shifting along with those of the doped supporting substrate, permitting the engineering of the relative positions of the slab and nanotube band edges. Finally, and following experimental work, we study adsorption characteristics of nanotubes on partially passivated surfaces. Surface states in the unpassivated regions modify the electronic structure of the interface and provide for the anchoring of nanotubes, deforming them in some cases. Results with and without dopants will be given[2].1 S. Barraza-Lopez et al. J. Appl. Phys. (in press). 2 Submitted. 3 Appl. Phys. Lett 83, 5029 (2003). 4 P. M. Albrecht and J. W. Lyding, Small (in press).

  18. High purity isolation and quantification of semiconducting carbon nanotubes via column chromatography.

    PubMed

    Tulevski, George S; Franklin, Aaron D; Afzali, Ali

    2013-04-23

    The isolation of semiconducting carbon nanotubes (CNTs) to ultrahigh (ppb) purity is a prerequisite for their integration into high-performance electronic devices. Here, a method employing column chromatography is used to isolate semiconducting nanotubes to 99.9% purity. The study finds that by modifying the solution preparation step, both the metallic and semiconducting fraction are resolved and elute using a single surfactant system, allowing for multiple iterations. Iterative processing enables a far more rapid path to achieving the level of purities needed for high performance computing. After a single iteration, the metallic peak in the absorption spectra is completely attenuated. Although absorption spectroscopy is typically used to characterize CNT purity, it is found to be insufficient in quantifying solutions of high purity (>98 to 99%) due to low signal-to-noise in the metallic region of ultrahigh purity solutions. Therefore, a high throughput electrical testing method was developed to quantify the degree of separation by characterizing ∼4000 field-effect transistors fabricated from the separated nanotubes after multiple iterations of the process. The separation and characterization methods described here provide a path to produce the ultrahigh purity semiconducting CNT solutions needed for high performance electronics. PMID:23484490

  19. High-performance radio frequency transistors based on diameter-separated semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Cao, Yu; Che, Yuchi; Seo, Jung-Woo T.; Gui, Hui; Hersam, Mark C.; Zhou, Chongwu

    2016-06-01

    In this paper, we report the high-performance radio-frequency transistors based on the single-walled semiconducting carbon nanotubes with a refined average diameter of ˜1.6 nm. These diameter-separated carbon nanotube transistors show excellent transconductance of 55 μS/μm and desirable drain current saturation with an output resistance of ˜100 KΩ μm. An exceptional radio-frequency performance is also achieved with current gain and power gain cut-off frequencies of 23 GHz and 20 GHz (extrinsic) and 65 GHz and 35 GHz (intrinsic), respectively. These radio-frequency metrics are among the highest reported for the carbon nanotube thin-film transistors. This study provides demonstration of radio frequency transistors based on carbon nanotubes with tailored diameter distributions, which will guide the future application of carbon nanotubes in radio-frequency electronics.

  20. Characterisation of nanohybrids of porphyrins with metallic and semiconducting carbon nanotubes by EPR and optical spectroscopy.

    PubMed

    Cambré, Sofie; Wenseleers, Wim; Culin, Jelena; Van Doorslaer, Sabine; Fonseca, Antonio; Nagy, Janos B; Goovaerts, Etienne

    2008-09-15

    Single-walled carbon nanotubes (SWCNTs) are noncovalently functionalised with octaethylporphyrins (OEPs) and the resulting nanohybrids are isolated from the free OEPs. Electron paramagnetic resonance (EPR) spectroscopy of cobalt(II)OEP, adsorbed on the nanotube walls by pi-pi-stacking, demonstrates that the CNTs act as electron acceptors. EPR is shown to be very effective in resolving the different interactions for metallic and semiconducting tubes. Moreover, molecular oxygen is shown to bind selectively to nanohybrids with semiconducting tubes. Water solubilisation of the porphyrin/CNT nanohybrids using bile salts, after applying a thorough washing procedure, yields solutions in which at least 99% of the porphyrins are interacting with the CNTs. Due to this purification, we observe, for the first time, the isolated absorption spectrum of the interacting porphyrins, which is strongly red-shifted compared to the free porphyrin absorption. In addition a quasi-complete quenching of the porphyrin fluorescence is also observed. PMID:18712730

  1. Self-Trapping of Charge Carriers in Semiconducting Carbon Nanotubes: Structural Analysis.

    PubMed

    Adamska, Lyudmyla; Nazin, George V; Doorn, Stephen K; Tretiak, Sergei

    2015-10-01

    The spatial extent of charged electronic states in semiconducting carbon nanotubes with indices (6,5) and (7,6) was evaluated using density functional theory. It was observed that electrons and holes self-trap along the nanotube axis on length scales of about 4 and 8 nm, respectively, which localize cations and anions on comparable length scales. Self-trapping is accompanied by local structural distortions showing periodic bond-length alternation. The average lengthening (shortening) of the bonds for anions (cations) is expected to shift the G-mode frequency to lower (higher) values. The smaller-diameter nanotube has reduced structural relaxation due to higher carbon-carbon bond strain. The reorganization energy due to charge-induced deformations in both nanotubes is found to be in the 30-60 meV range. Our results represent the first theoretical simulation of self-trapping of charge carriers in semiconducting nanotubes, and agree with available experimental data. PMID:26722885

  2. Hybrid nanotube-graphene junctions: spin degeneracy breaking and tunable electronic structure.

    PubMed

    Qu, Zhi-bei; Gu, Li; Li, Meina; Shi, Guoyue; Zhuang, Gui-lin

    2013-12-14

    Hybrid carbon nanostructures have attracted enormous interest due to their structural stability and unique physical properties. Geometric and physical properties of a carbon nanotube (CNT)-graphene nanoribbon (GNR) hybrid system were investigated via first-principles density functional theory (DFT) calculations. The nanotube-graphene junction (NTGJ), where the GNR directly links to the CNT by covalent bonds, shows novel electronic dependence on the structural parameters of the building-blocks, such as chirality, nanotube diameter and width of the nanoribbon. For an armchair NTGJ, a small band gap opens up representing asymmetrical spin-up and spin-down bands. However, zig-zag NTGJ shows direct semi-conducting characteristics with a tunable band gap ranging from zero to 0.6 eV. Interestingly, the value of the band gap follows the specific width and diameter dependent oscillations, namely the 3p - 1 principle. Transition-state results reveal the formation of NTGJs is exothermic and has a low energy-barrier. In addition, nanotube-graphene-nanotube junctions or namely dumbbell NTGJs were also studied, which exhibits similar properties with single NTGJ. PMID:24166658

  3. Modeling of Current-Voltage Characteristics in Large Metal-Semiconducting Carbon Nanotube Systems

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryon A. (Technical Monitor)

    2000-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in recent experiment with a scanning tunneling microscope tip and a carbon nanotube [Collins et al., Science 278, 100 (1997)]. We claim that there are two contact modes for a tip (metal)-nanotube (semiconductor) junction depending whether the alignment of the metal and the semiconductor band structures is (1) variable (vacuum-gap) or (2) fixed (touching) with V. With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube. However, the Schottky mechanism in (2) would result in forward current with V < 0 for an n-nanotube, while with V > 0 for an p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type. We apply this model to the source-drain I-V characteristics in a long nanotube-channel field-effect-transistor with metallic electrodes at low temperature [Zhou et al., Appl. Phys. Lett. 76, 1597 (2000)], and show that two independent metal-semiconductor junctions in series are responsible for the observed behavior.

  4. Identifying [corrected] signatures of photothermal current in a double-gated semiconducting nanotube.

    PubMed

    Buchs, G; Bagiante, S; Steele, G A

    2014-01-01

    The remarkable electrical and optical properties of single-walled carbon nanotubes have allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting single-walled carbon nanotube and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from single-walled carbon nanotubes. PMID:25236955

  5. Identifiying signatures of photothermal current in a double-gated semiconducting nanotube

    NASA Astrophysics Data System (ADS)

    Buchs, G.; Bagiante, S.; Steele, G. A.

    2014-09-01

    The remarkable electrical and optical properties of single-walled carbon nanotubes have allowed for engineering device prototypes showing great potential for applications such as photodectors and solar cells. However, any path towards industrial maturity requires a detailed understanding of the fundamental mechanisms governing the process of photocurrent generation. Here we present scanning photocurrent microscopy measurements on a double-gated suspended semiconducting single-walled carbon nanotube and show that both photovoltaic and photothermal mechanisms are relevant for the interpretation of the photocurrent. We find that the dominant or non-dominant character of one or the other processes depends on the doping profile, and that the magnitude of each contribution is strongly influenced by the series resistance from the band alignment with the metal contacts. These results provide new insight into the interpretation of features in scanning photocurrent microscopy and lay the foundation for the understanding of optoelectronic devices made from single-walled carbon nanotubes.

  6. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of electron density for na individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closet neighbors reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  7. Energy Band Gap Study of Semiconducting Single Walled Carbon Nanotube Bundle

    NASA Technical Reports Server (NTRS)

    Elkadi, Asmaa; Decrossas, Emmanuel; El-Ghazaly, Samir

    2013-01-01

    The electronic properties of multiple semiconducting single walled carbon nanotubes (s-SWCNTs) considering various distribution inside a bundle are studied. The model derived from the proposed analytical potential function of the electron density for an individual s-SWCNT is general and can be easily applied to multiple nanotubes. This work demonstrates that regardless the number of carbon nanotubes, the strong coupling occurring between the closest neighbours reduces the energy band gap of the bundle by 10%. As expected, the coupling is strongly dependent on the distance separating the s-SWCNTs. In addition, based on the developed model, it is proposed to enhance this coupling effect by applying an electric field across the bundle to significantly reduce the energy band gap of the bundle by 20%.

  8. Polymer-Sorted Semiconducting Carbon Nanotube Networks for High-Performance Ambipolar Field-Effect Transistors

    PubMed Central

    2014-01-01

    Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm2·V–1·s–1, low ohmic contact resistance, steep subthreshold swings (0.12–0.14 V/dec) and high on/off ratios (106) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61. PMID:25493421

  9. Polymer-sorted semiconducting carbon nanotube networks for high-performance ambipolar field-effect transistors.

    PubMed

    Schiessl, Stefan P; Fröhlich, Nils; Held, Martin; Gannott, Florentina; Schweiger, Manuel; Forster, Michael; Scherf, Ullrich; Zaumseil, Jana

    2015-01-14

    Efficient selection of semiconducting single-walled carbon nanotubes (SWNTs) from as-grown nanotube samples is crucial for their application as printable and flexible semiconductors in field-effect transistors (FETs). In this study, we use atactic poly(9-dodecyl-9-methyl-fluorene) (a-PF-1-12), a polyfluorene derivative with asymmetric side-chains, for the selective dispersion of semiconducting SWNTs with large diameters (>1 nm) from plasma torch-grown SWNTs. Lowering the molecular weight of the dispersing polymer leads to a significant improvement of selectivity. Combining dense semiconducting SWNT networks deposited from an enriched SWNT dispersion with a polymer/metal-oxide hybrid dielectric enables transistors with balanced ambipolar, contact resistance-corrected mobilities of up to 50 cm(2)·V(-1)·s(-1), low ohmic contact resistance, steep subthreshold swings (0.12-0.14 V/dec) and high on/off ratios (10(6)) even for short channel lengths (<10 μm). These FETs operate at low voltages (<3 V) and show almost no current hysteresis. The resulting ambipolar complementary-like inverters exhibit gains up to 61. PMID:25493421

  10. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation.

    PubMed

    Reis, Wieland G; Weitz, R Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-01-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (10(5)) and field-effect mobilities (17 cm(2)/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production. PMID:27188435

  11. Semiconducting polymers with nanocrystallites interconnected via boron-doped carbon nanotubes.

    PubMed

    Yu, Kilho; Lee, Ju Min; Kim, Junghwan; Kim, Geunjin; Kang, Hongkyu; Park, Byoungwook; Ho Kahng, Yung; Kwon, Sooncheol; Lee, Sangchul; Lee, Byoung Hun; Kim, Jehan; Park, Hyung Il; Kim, Sang Ouk; Lee, Kwanghee

    2014-12-10

    Organic semiconductors are key building blocks for future electronic devices that require unprecedented properties of low-weight, flexibility, and portability. However, the low charge-carrier mobility and undesirable processing conditions limit their compatibility with low-cost, flexible, and printable electronics. Here, we present significantly enhanced field-effect mobility (μ(FET)) in semiconducting polymers mixed with boron-doped carbon nanotubes (B-CNTs). In contrast to undoped CNTs, which tend to form undesired aggregates, the B-CNTs exhibit an excellent dispersion in conjugated polymer matrices and improve the charge transport between polymer chains. Consequently, the B-CNT-mixed semiconducting polymers enable the fabrication of high-performance FETs on plastic substrates via a solution process; the μFET of the resulting FETs reaches 7.2 cm(2) V(-1) s(-1), which is the highest value reported for a flexible FET based on a semiconducting polymer. Our approach is applicable to various semiconducting polymers without any additional undesirable processing treatments, indicating its versatility, universality, and potential for high-performance printable electronics. PMID:25372930

  12. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation

    NASA Astrophysics Data System (ADS)

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-05-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production.

  13. Highly Efficient and Scalable Separation of Semiconducting Carbon Nanotubes via Weak Field Centrifugation

    PubMed Central

    Reis, Wieland G.; Weitz, R. Thomas; Kettner, Michel; Kraus, Alexander; Schwab, Matthias Georg; Tomović, Željko; Krupke, Ralph; Mikhael, Jules

    2016-01-01

    The identification of scalable processes that transfer random mixtures of single-walled carbon nanotubes (SWCNTs) into fractions featuring a high content of semiconducting species is crucial for future application of SWCNTs in high-performance electronics. Herein we demonstrate a highly efficient and simple separation method that relies on selective interactions between tailor-made amphiphilic polymers and semiconducting SWCNTs in the presence of low viscosity separation media. High purity individualized semiconducting SWCNTs or even self-organized semiconducting sheets are separated from an as-produced SWCNT dispersion via a single weak field centrifugation run. Absorption and Raman spectroscopy are applied to verify the high purity of the obtained SWCNTs. Furthermore SWCNT - network field-effect transistors were fabricated, which exhibit high ON/OFF ratios (105) and field-effect mobilities (17 cm2/Vs). In addition to demonstrating the feasibility of high purity separation by a novel low complexity process, our method can be readily transferred to large scale production. PMID:27188435

  14. Polychiral semiconducting carbon nanotube-fullerene solar cells.

    PubMed

    Gong, Maogang; Shastry, Tejas A; Xie, Yu; Bernardi, Marco; Jasion, Daniel; Luck, Kyle A; Marks, Tobin J; Grossman, Jeffrey C; Ren, Shenqiang; Hersam, Mark C

    2014-09-10

    Single-walled carbon nanotubes (SWCNTs) have highly desirable attributes for solution-processable thin-film photovoltaics (TFPVs), such as broadband absorption, high carrier mobility, and environmental stability. However, previous TFPVs incorporating photoactive SWCNTs have utilized architectures that have limited current, voltage, and ultimately power conversion efficiency (PCE). Here, we report a solar cell geometry that maximizes photocurrent using polychiral SWCNTs while retaining high photovoltage, leading to record-high efficiency SWCNT-fullerene solar cells with average NREL certified and champion PCEs of 2.5% and 3.1%, respectively. Moreover, these cells show significant absorption in the near-infrared portion of the solar spectrum that is currently inaccessible by many leading TFPV technologies. PMID:25101896

  15. Imaging the formation of a p-n junction in a suspended carbon nanotube with scanning photocurrent microscopy

    NASA Astrophysics Data System (ADS)

    Buchs, Gilles; Barkelid, Maria; Bagiante, Salvatore; Steele, Gary A.; Zwiller, Val

    2011-10-01

    We use scanning photocurrent microscopy (SPCM) to investigate individual suspended semiconducting carbon nanotube devices where the potential profile is engineered by means of local gates. In situ tunable p-n junctions can be generated at any position along the nanotube axis. Combining SPCM with transport measurements allows a detailed microscopic study of the evolution of the band profiles as a function of the gates voltage. Here we study the emergence of a p-n and a n-p junctions out of a n-type transistor channel using two local gates. In both cases the I - V curves recorded for gate configurations corresponding to the formation of the p-n or n-p junction in the SPCM measurements reveal a clear transition from resistive to rectification regimes. The rectification curves can be fitted well to the Shockley diode model with a series resistor and reveal a clear ideal diode behavior.

  16. Carbon nanotube- MoS2 p-n junction: Fabrication and transport properties

    NASA Astrophysics Data System (ADS)

    Bhanu, Udai; Islam, Muahmmad; Khondaker, Saiful

    2014-03-01

    Integrating two different nanoscale semicondcutors of opposite carrier types are of great interest for many electronic and optical applications. Few layers molybdenum disulfide (MoS2) is an n-type semiconductor while semiconductoing single walled carbon nanotubes (SWNT) show p-type behavior. In this work, we demonstrate a simple technique for integrating these two semiconductors for fabricating a p-n junction. Few layers MoS2 device were mechanically exfoliated from a single crystal of MoS2 and making electrical contact via electron beam lithography. Another pair of electrodes, which are orthogonal to MoS2 device, is deposited and semiconducting reach SWNT(s-SWNT) solution was dielectrophoretically assembled between the second pair of electrodes. The s-SWNT goes over the MoS2 and fabricates two p-n junctions. We will discuss the electronic transport properties of the fabricated devices.

  17. Indentation Tests Reveal Geometry-Regulated Stiffening of Nanotube Junctions.

    PubMed

    Ozden, Sehmus; Yang, Yang; Tiwary, Chandra Sekhar; Bhowmick, Sanjit; Asif, Syed; Penev, Evgeni S; Yakobson, Boris I; Ajayan, Pulickel M

    2016-01-13

    Here we report a unique method to locally determine the mechanical response of individual covalent junctions between carbon nanotubes (CNTs), in various configurations such as "X", "Y", and "Λ"-like. The setup is based on in situ indentation using a picoindenter integrated within a scanning electron microscope. This allows for precise mapping between junction geometry and mechanical behavior and uncovers geometry-regulated junction stiffening. Molecular dynamics simulations reveal that the dominant contribution to the nanoindentation response is due to the CNT walls stretching at the junction. Targeted synthesis of desired junction geometries can therefore provide a "structural alphabet" for construction of macroscopic CNT networks with tunable mechanical response. PMID:26618517

  18. Direct observation of hole transfer from semiconducting polymer to carbon nanotubes.

    PubMed

    Lan, Fei; Li, Guangyong

    2013-05-01

    Carbon nanotubes have been proven to play significant roles in polymer-based solar cells. However, there is intensive debate on whether carbon nanotube behaves as a donor or acceptor in the semiconducting polymer:carbon nanotube composite. In this paper, we report a direct observation via Kelvin probe force microscopy (KPFM) that single walled carbon nanotubes (SWNTs) behave as hole transporting channels in poly(3-hexylthiophene-2,5-diyl) (P3HT)/SWNT heterojunctions. By comparing the surface potential (SP) change of SWNT in dark and under illumination, we observed that electrons are blocked from SWNT while holes are transferred to SWNT. This observation can be well-explained by our proposed band alignment model of P3HT/SWNT heterojunction. The finding is further verified by hole mobility measurement using the space charge limited current (SCLC) method. SCLC results indicate that the existence of small amount of SWNT (wt 0.5%) promotes device hole mobility to around 15-fold, indicating SWNT act as hole transfer channel. Our finding of hole transporting behavior of SWNT in P3HT/SWNT blend will provide a useful guidance for enhancing the performance of polymer solar cells by carbon nanotubes. PMID:23574570

  19. Diffusion-assisted photoexcitation transfer in coupled semiconducting carbon nanotube thin films.

    PubMed

    Grechko, Maksim; Ye, Yumin; Mehlenbacher, Randy D; McDonough, Thomas J; Wu, Meng-Yin; Jacobberger, Robert M; Arnold, Michael S; Zanni, Martin T

    2014-06-24

    We utilize femtosecond transient absorption spectroscopy to study dynamics of photoexcitation migration in films of semiconducting single-wall carbon nanotubes. Films of nanotubes in close contact enable energy migration such as needed in photovoltaic and electroluminescent devices. Two types of films composed of nanotube fibers are utilized in this study: densely packed and very porous. By comparing exciton kinetics in these films, we characterize excitation transfer between carbon nanotubes inside fibers versus between fibers. We find that intrafiber transfer takes place in both types of films, whereas interfiber transfer is greatly suppressed in the porous one. Using films with different nanotube composition, we are able to test several models of exciton transfer. The data are inconsistent with models that rely on through-space interfiber energy transfer. A model that fits the experimental results postulates that interfiber transfer occurs only at intersections between fibers, and the excitons reach the intersections by diffusing along the long-axis of the tubes. We find that time constants for the inter- and intrafiber transfers are 0.2-0.4 and 7 ps, respectively. In total, hopping between fibers accounts for about 60% of all exciton downhill transfer prior to 4 ps in the dense film. The results are discussed with regards to transmission electron micrographs of the films. This study provides a rigorous analysis of the photophysics in this new class of promising materials for photovoltaics and other technologies. PMID:24806792

  20. Growth of semiconducting single-walled carbon nanotubes by using ceria as catalyst supports.

    PubMed

    Qin, Xiaojun; Peng, Fei; Yang, Feng; He, Xiaohui; Huang, Huixin; Luo, Da; Yang, Juan; Wang, Sheng; Liu, Haichao; Peng, Lianmao; Li, Yan

    2014-02-12

    The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors. PMID:24392872

  1. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes.

    PubMed

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  2. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Comfort, Everett; Lee, Ji Ung

    2016-06-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range.

  3. Detection of a biexciton in semiconducting carbon nanotubes using nonlinear optical spectroscopy.

    PubMed

    Colombier, L; Selles, J; Rousseau, E; Lauret, J S; Vialla, F; Voisin, C; Cassabois, G

    2012-11-01

    We report the observation of the biexciton in semiconducting single-wall carbon nanotubes by means of nonlinear optical spectroscopy. Our measurements reveal the universal asymmetric line shape of the Fano resonance intrinsic to the biexciton transition. For nanotubes of the (9,7) chirality, we find a biexciton binding energy of 106 meV. From the calculation of the χ((3)) nonlinear response, we provide a quantitative interpretation of our measurements, leading to an estimation of the characteristic Fano factor q of 7 ± 3. This value allows us to extract the first experimental information on the biexciton stability and we obtain a biexciton annihilation rate comparable to the exciton-exciton annihilation one. PMID:23215424

  4. Large Bandgap Shrinkage from Doping and Dielectric Interface in Semiconducting Carbon Nanotubes

    PubMed Central

    Comfort, Everett; Lee, Ji Ung

    2016-01-01

    The bandgap of a semiconductor is one of its most important electronic properties. It is often considered to be a fixed property of the semiconductor. As the dimensions of semiconductors reduce, however, many-body effects become dominant. Here, we show that doping and dielectric, two critical features of semiconductor device manufacturing, can dramatically shrink (renormalize) the bandgap. We demonstrate this in quasi-one-dimensional semiconducting carbon nanotubes. Specifically, we use a four-gated device, configured as a p-n diode, to investigate the fundamental electronic structure of individual, partially supported nanotubes of varying diameter. The four-gated construction allows us to combine both electrical and optical spectroscopic techniques to measure the bandgap over a wide doping range. PMID:27339272

  5. Semiconductive Nanotube Array Constructed from Giant [Pb(II)18I54(I2)9] Wheel Clusters.

    PubMed

    Wang, Guan-E; Xu, Gang; Liu, Bin-Wen; Wang, Ming-Sheng; Yao, Ming-Shui; Guo, Guo-Cong

    2016-01-11

    Crystalline nanotube array would create great opportunity for novel electrical application. Herein we report the first example of a metal halide based crystalline nanotube array which is constructed from an unprecedented giant [Pb(II)18I54(I2)9] wheel cluster, as determined by synchrotron X-ray diffraction. The electrical properties of the single crystal were studied and the present compound shows typical semiconductivity and highly anisotropic conductivity. PMID:26549327

  6. Dielectrophoretic Assembly of Semiconducting Carbon Nanotubes Separated and Enriched by Spin Column Chromatography and Its Application to Gas Sensing

    NASA Astrophysics Data System (ADS)

    Nakano, Michihiko; Fujioka, Masahiro; Mai, Kaori; Watanabe, Hideaki; Martin, Yul; Suehiro, Junya

    2012-04-01

    The present authors have previously demonstrated the electrokinetic fabrication of a single-walled carbon nanotube (SWCNT) gas sensor by employing dielectrophoresis. Because this method employs mass-produced SWCNTs, it can realize cheaper and more flexible SWCNT gas sensor fabrication than that based on the on-site synthesis of SWCNTs. In this study, a new protocol was proposed and tested for the separation and enrichment of semiconducting SWCNTs, aiming to improve the SWCNT gas sensor sensitivity. The protocol employed a spin column filled with size-exclusion dextran-based gel beads as well as two surfactants (sodium dodecyl sulfate and sodium deoxycholate), which had different affinities to metallic and semiconducting SWCNTs. The separation and enrichment of the semiconducting SWCNTs were confirmed by measuring their optical and electrical properties. The CNT gas sensor fabricated using enriched semiconducting SWCNTs was highly sensitive to nitrogen dioxide (NO2) gas, - more sensitive by 10 times than that fabricated using the pristine SWCNT mixture.

  7. Room temperature infrared imaging sensors based on highly purified semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Wei, Nan; Zhao, Qingliang; Zhang, Dehui; Wang, Sheng; Peng, Lian-Mao

    2015-04-01

    High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a single chip, each consists of 3 × 3 pixel arrays. The demonstrated advantages of constructing a high performance IR system using purified semiconducting CNT aligned films include, among other things, fast response, excellent stability and uniformity, ideal linear photocurrent response, high imaging polarization sensitivity and low power consumption.High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a

  8. Thin film transistors using preferentially grown semiconducting single-walled carbon nanotube networks by water-assisted plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Kim, Un Jeong; Lee, Eun Hong; Kim, Jong Min; Min, Yo-Sep; Kim, Eunseong; Park, Wanjun

    2009-07-01

    Nearly perfect semiconducting single-walled carbon nanotube random network thin film transistors were fabricated and their reproducible transport properties were investigated. The networked single-walled carbon nanotubes were directly grown by water-assisted plasma-enhanced chemical vapor deposition. Optical analysis confirmed that the nanotubes were mostly semiconductors without clear metallic resonances in both the Raman and the UV-vis-IR spectroscopy. The transistors made by the nanotube networks whose density was much larger than the percolation threshold also showed no metallic paths. Estimation based on the conductance change of semiconducting nanotubes in the SWNT network due to applied gate voltage difference (conductance difference for on and off state) indicated a preferential growth of semiconducting nanotubes with an advantage of water-assisted PECVD. The nanotube transistors showed 10-5 of on/off ratio and ~8 cm2 V-1 s-1 of field effect mobility.

  9. Thin film transistors using preferentially grown semiconducting single-walled carbon nanotube networks by water-assisted plasma-enhanced chemical vapor deposition.

    PubMed

    Kim, Un Jeong; Lee, Eun Hong; Kim, Jong Min; Min, Yo-Sep; Kim, Eunseong; Park, Wanjun

    2009-07-22

    Nearly perfect semiconducting single-walled carbon nanotube random network thin film transistors were fabricated and their reproducible transport properties were investigated. The networked single-walled carbon nanotubes were directly grown by water-assisted plasma-enhanced chemical vapor deposition. Optical analysis confirmed that the nanotubes were mostly semiconductors without clear metallic resonances in both the Raman and the UV-vis-IR spectroscopy. The transistors made by the nanotube networks whose density was much larger than the percolation threshold also showed no metallic paths. Estimation based on the conductance change of semiconducting nanotubes in the SWNT network due to applied gate voltage difference (conductance difference for on and off state) indicated a preferential growth of semiconducting nanotubes with an advantage of water-assisted PECVD. The nanotube transistors showed 10(-5) of on/off ratio and approximately 8 cm2 V(-1) s(-1) of field effect mobility. PMID:19567966

  10. Vacuum filtration based formation of liquid crystal films of semiconducting carbon nanotubes and high performance transistor devices

    NASA Astrophysics Data System (ADS)

    King, Benjamin; Panchapakesan, Balaji

    2014-05-01

    In this paper, we report ultra-thin liquid crystal films of semiconducting carbon nanotubes using a simple vacuum filtration process. Vacuum filtration of nanotubes in aqueous surfactant solution formed nematic domains on the filter membrane surface and exhibited local ordering. A 2D fast Fourier transform was used to calculate the order parameters from scanning electron microscopy images. The order parameter was observed to be sensitive to the filtration time demonstrating different regions of transformation namely nucleation of nematic domains, nanotube accumulation and large domain growth.Transmittance versus sheet resistance measurements of such films resulted in optical to dc conductivity of σ opt/σ dc = 9.01 indicative of purely semiconducting nanotube liquid crystal network.Thin films of nanotube liquid crystals with order parameters ranging from S = 0.1-0.5 were patterned into conducting channels of transistor devices which showed high I on/I off ratios from 10-19 800 and electron mobility values μ e = 0.3-78.8 cm2 (V-s)-1, hole mobility values μ h = 0.4-287 cm2 (V-s)-1. High I on/I off ratios were observed at low order parameters and film mass. A Schottky barrier transistor model is consistent with the observed transistor characteristics. Electron and hole mobilities were seen to increase with order parameters and carbon nanotube mass fractions. A fundamental tradeoff between decreasing on/off ratio and increasing mobility with increasing nanotube film mass and order parameter is therefore concluded. Increase in order parameters of nanotubes liquid crystals improved the electronic transport properties as witnessed by the increase in σ dc/σ opt values on macroscopic films and high mobilities in microscopic transistors. Liquid crystal networks of semiconducting nanotubes as demonstrated here are simple to fabricate, transparent, scalable and could find wide ranging device applications.

  11. Reflectance modulation by free-carrier exciton screening in semiconducting nanotubes

    NASA Astrophysics Data System (ADS)

    Pinto, Fabrizio

    2013-07-01

    A model of exciton screening by photo-generated free charges in semiconducting single-walled carbon nanotubes is considered to interpret recent data from the only experiment on this phenomenon reported in the literature. The potential of electron-hole interactions on the nanotube surface is computed starting from the derived full two-dimensional expression. The error of screened potential numerical computations is analyzed in detail by also including strategies for convergence acceleration and computing time optimization. The two-dimensional Wannier equation on the nanotube surface is solved by means of variational methods and convergence to published results in the unscreened case is demonstrated. The effect of screening charges on the exciton energy is estimated numerically by taking advantage of memoization algorithms. We show that a firm connection can be made between the present description and data readily available from future similar reflectivity experiments to constrain the linear density of photo-generated carriers. Applications of dielectric function modulation to dispersion force manipulation and nanodevice actuation are briefly discussed.

  12. Tunable spin-polaron state in a singly clamped semiconducting carbon nanotube

    NASA Astrophysics Data System (ADS)

    Pistolesi, F.; Shekhter, R.

    2015-07-01

    We consider a semiconducting carbon nanotube (CNT) lying on a ferromagnetic insulating substrate with one end passing the substrate and suspended over a metallic gate. We assume that the polarized substrate induces an exchange interaction acting as a local magnetic field for the electrons in the nonsuspended CNT side. Generalizing the approach of I. Snyman and Yu.V. Nazarov [Phys. Rev. Lett. 108, 076805 (2012), 10.1103/PhysRevLett.108.076805], we show that one can generate electrostatically a tunable spin-polarized polaronic state localized at the bending end of the CNT. We argue that at low temperatures manipulation and detection of the localized quantum spin state are possible.

  13. A photodegradable hexaaza-pentacene molecule for selective dispersion of large-diameter semiconducting carbon nanotubes.

    PubMed

    Han, Jie; Ji, Qiyan; Li, Hongbo; Li, Gang; Qiu, Song; Li, Hai-Bei; Zhang, Qichun; Jin, Hehua; Li, Qingwen; Zhang, Jin

    2016-06-01

    Harvesting high-purity semiconducting single-walled carbon nanotubes (s-SWCNTs) with removable dispersants remains a challenge. In this work, we demonstrate that small heteroacene derivatives may serve as promising selective dispersants for sorting s-SWCNTs. A rich N "doped" and thiophene-substituted hexaazapentacene molecule, denoted as 4HP, was found to be more favorable for high-purity s-SWCNTs with large diameters. Importantly, 4HP is photodegradable under 365 nm or blue light, which enables a simple deposition approach for the formation of clean s-SWCNT networks. The as-fabricated thin film transistors show excellent performance with a charge-mobility of 30-80 cm(2) V(-1) s(-1) and an on-off ratio of 10(4)-10(6). PMID:27230421

  14. Controlled defects in semiconducting carbon nanotubes promote efficient generation and luminescence of trions.

    PubMed

    Brozena, Alexandra H; Leeds, Jarrett D; Zhang, Yin; Fourkas, John T; Wang, YuHuang

    2014-05-27

    We demonstrate efficient creation of defect-bound trions through chemical doping of controlled sp(3) defect sites in semiconducting, single-walled carbon nanotubes. These tricarrier quasi-particles luminesce almost as brightly as their parent excitons, indicating a remarkably efficient conversion of excitons into trions. Substantial populations of trions can be generated at low excitation intensities, even months after a sample has been prepared. Photoluminescence spectroscopy reveals a trion binding energy as high as 262 meV, which is substantially larger than any previously reported values. This discovery may have important ramifications not only for studying the basic physics of trions but also for the application of these species in fields such as photonics, electronics, and bioimaging. PMID:24669843

  15. Recent Progress in Obtaining Semiconducting Single-Walled Carbon Nanotubes for Transistor Applications.

    PubMed

    Islam, Ahmad E; Rogers, John A; Alam, Muhammad A

    2015-12-22

    High purity semiconducting single-walled carbon nanotubes (s-SWCNTs) with a narrow diameter distribution are required for high-performance transistors. Achieving this goal is extremely challenging because the as-grown material contains mixtures of s-SWCNTs and metallic- (m-) SWCNTs with wide diameter distributions, typically inadequate for integrated circuits. Since 2000, numerous ex situ methods have been proposed to improve the purity of the s-SWCNTs. The majority of these techniques fail to maintain the quality and integrity of the s-SWCNTs with a few notable exceptions. Here, the progress in realizing high purity s-SWCNTs in as-grown and post-processed materials is highlighted. A comparison of transistor parameters (such as on/off ratio and field-effect mobility) obtained from test structures establishes the effectiveness of various methods and suggests opportunities for future improvements. PMID:26540144

  16. Exciton-exciton annihilation and relaxation pathways in semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chmeliov, Jevgenij; Narkeliunas, Jonas; Graham, Matt W.; Fleming, Graham R.; Valkunas, Leonas

    2016-01-01

    We present a thorough analysis of one- and two-color transient absorption measurements performed on single- and double-walled semiconducting carbon nanotubes. By combining the currently existing models describing exciton-exciton annihilation--the coherent and the diffusion-limited ones--we are able to simultaneously reproduce excitation kinetics following both E11 and E22 pump conditions. Our simulations revealed the fundamental photophysical behavior of one-dimensional coherent excitons and non-trivial excitation relaxation pathways. In particular, we found that after non-linear annihilation a doubly-excited exciton relaxes directly to its E11 state bypassing the intermediate E22 manifold, so that after excitation resonant with the E11 transition, the E22 state remains unpopulated. A quantitative explanation for the observed much faster excitation kinetics probed at E22 manifold, comparing to those probed at the E11 band, is also provided.

  17. Selective Growth of Metallic and Semiconducting Single Walled Carbon Nanotubes on Textured Silicon.

    PubMed

    Jang, Mira; Lee, Jongtaek; Park, Teahee; Lee, Junyoung; Yang, Jonghee; Yi, Whikun

    2016-03-01

    We fabricated the etched Si substrate having the pyramidal pattern size from 0.5 to 4.2 μm by changing the texturing process parameters, i.e., KOH concentration, etching time, and temperature. Single walled carbon nanotubes (SWNTs) were then synthesized on the etched Si substrates with different pyramidal pattern by chemical vapor deposition. We investigated the optical and electronic properties of SWNT film grown on the etched Si substrates of different morphology by using scanning electron microscopy, Raman spectroscopy and conducting probe atomic force microscopy. We confirmed that the morphology of substrate strongly affected the selective growth of the SWNT film. Semiconducting SWNTs were formed on larger pyramidal sized Si wafer with higher ratio compared with SWNTs on smaller pyramidal sized Si. PMID:27455748

  18. Room temperature infrared imaging sensors based on highly purified semiconducting carbon nanotubes.

    PubMed

    Liu, Yang; Wei, Nan; Zhao, Qingliang; Zhang, Dehui; Wang, Sheng; Peng, Lian-Mao

    2015-04-21

    High performance infrared (IR) imaging systems usually require expensive cooling systems, which are highly undesirable. Here we report the fabrication and performance characteristics of room temperature carbon nanotube (CNT) IR imaging sensors. The CNT IR imaging sensor is based on aligned semiconducting CNT films with 99% purity, and each pixel or device of the imaging sensor consists of aligned strips of CNT asymmetrically contacted by Sc and Pd. We found that the performance of the device is dependent on the CNT channel length. While short channel devices provide a large photocurrent and a rapid response of about 110 μs, long channel length devices exhibit a low dark current and a high signal-to-noise ratio which are critical for obtaining high detectivity. In total, 36 CNT IR imagers are constructed on a single chip, each consists of 3 × 3 pixel arrays. The demonstrated advantages of constructing a high performance IR system using purified semiconducting CNT aligned films include, among other things, fast response, excellent stability and uniformity, ideal linear photocurrent response, high imaging polarization sensitivity and low power consumption. PMID:25807291

  19. Angular momentum and topology in semiconducting single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Izumida, W.; Okuyama, R.; Yamakage, A.; Saito, R.

    2016-05-01

    Semiconducting single-wall carbon nanotubes are classified into two types by means of the orbital angular momentum of the valley state, which is useful to study their low-energy electronic properties in finite length. The classification is given by an integer d , which is the greatest common divisor of two integers n and m specifying the chirality of nanotubes, by analyzing cutting lines. For the case that d is greater than or equal to four, the two lowest subbands from two valleys have different angular momenta with respect to the nanotube axis. Reflecting the decoupling of two valleys, discrete energy levels in finite-length nanotubes exhibit fourfold degeneracy and small lift of fourfold degeneracy by the spin-orbit interaction. For the case that d is less than or equal to two, in which the two lowest subbands from two valleys have the same angular momentum, discrete levels exhibit a lift of fourfold degeneracy reflecting the coupling of two valleys. Especially, two valleys are strongly coupled when the chirality is close to the armchair chirality. An effective one-dimensional lattice model is derived by extracting states with relevant angular momentum, which reveals the valley coupling in the eigenstates. A bulk-edge correspondence, which is a relationship between the number of edge states and the winding number calculated in the corresponding bulk system, is analytically shown by using the argument principle, and this enables us to estimate the number of edge states from the bulk property. The number of edge states depends not only on the chirality but also on the shape of boundary.

  20. Semiconducting single-walled carbon nanotubes sorting with a removable solubilizer based on dynamic supramolecular coordination chemistry

    NASA Astrophysics Data System (ADS)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2014-10-01

    Highly pure semiconducting single-walled carbon nanotubes (SWNTs) are essential for the next generation of electronic devices, such as field-effect transistors and photovoltaic applications; however, contamination by metallic SWNTs reduces the efficiency of their associated devices. Here we report a simple and efficient method for the separation of semiconducting- and metallic SWNTs based on supramolecular complex chemistry. We here describe the synthesis of metal-coordination polymers (CP-Ms) composed of a fluorene-bridged bis-phenanthroline ligand and metal ions. On the basis of a difference in the ‘solubility product’ of CP-M-solubilized semiconducting SWNTs and metallic SWNTs, we readily separated semiconducting SWNTs. Furthermore, the CP-M polymers on the SWNTs were simply removed by adding a protic acid and inducing depolymerization to the monomer components. We also describe molecular mechanics calculations to reveal the difference of binding and wrapping mode between CP-M/semiconducting SWNTs and CP-M/metallic SWNTs. This study opens a new stage for the use of such highly pure semiconducting SWNTs in many possible applications.

  1. Preferential Growth of Semiconducting Single-Walled Carbon Nanotubes on Substrate by Europium Oxide

    PubMed Central

    2010-01-01

    In this paper, we have demonstrated that europium oxide (Eu2O3) is a new type of active catalyst for single-walled carbon nanotubes (SWNTs) growth under suitable conditions. Both random SWNT networks and horizontally aligned SWNT arrays are efficiently grown on silicon wafers. The density of the SWNT arrays can be altered by the CVD conditions. This result further provides the experimental evidence that the efficient catalyst for SWNT growth is more size dependent than the catalysts themselves. Furthermore, the SWNTs from europium sesquioxides have compatibly higher quality than that from Fe/Mo catalyst. More importantly, over 80% of the nanotubes from Eu2O3 are semiconducting SWNTs (s-SWNTs), indicating the preferential growth of s-SWNTs from Eu2O3. This new finding could open a way for selective growth of s-SWNTs, which can be used as high-current nanoFETs and sensors. Moreover, the successful growth of SWNTs by Eu2O3 catalyst provides new experimental information for understanding the preferential growth of s-SWNTs from Eu2O3, which may be helpful for their controllable synthesis. PMID:21076709

  2. Gate-tuned spin to charge conversion in semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Shigematsu, Ei; Nagano, Hiroshi; Dushenko, Sergey; Ando, Yuichiro; Tsuda, Tetsuya; Kuwabata, Susumu; Takenobu, Taishi; Tanaka, Takeshi; Kataura, Hiromichi; Shinjo, Teruya; Shiraishi, Masashi

    Interconversion of spin and charge current is a hot topic in the molecular spintronics. It was achieved for the first time in a conducting conjugated polymer 1, and shortly followed by spin-charge conversion in graphene. However, control over carrier type has not been shown yet. In this study we focused on single-walled carbon nanotubes (SWNT). Spin injection into semiconductor from metal ferromagnet is challenging due to the presence of Schottky barrier and conductance mismatch problem. To bypass it, we used ionic liquid electric gate and ferrimagnetic insulator. We prepared SWNT layer on top of ferrimagnetic yttrium iron garnet substrate. Using spin pumping we successfully observed spin-charge conversion in metallic SWNT. As for a semiconducting SWNT, we applied a top gate using ionic liquid. The drain-source current vs. gate voltage dependence showed tuning of the Fermi level and changing of carrier type. Under gate voltage application we measured electromotive force induced by spin pumping. Detected voltage changed its sign together with carrier type. This is first evidence of spin-charge conversion in carbon nanotubes 2. 1 K. Ando et al., Nature Mater. 12, 622 (2013). 2 E. Shigematsu et al., submitted.

  3. Ultrafast Exciton Hopping Observed in Bare Semiconducting Carbon Nanotube Thin Films with Two-Dimensional White-Light Spectroscopy.

    PubMed

    Mehlenbacher, Randy D; Wang, Jialiang; Kearns, Nicholas M; Shea, Matthew J; Flach, Jessica T; McDonough, Thomas J; Wu, Meng-Yin; Arnold, Michael S; Zanni, Martin T

    2016-06-01

    We observe ultrafast energy transfer between bare carbon nanotubes in a thin film using two-dimensional (2D) white-light spectroscopy. Using aqueous two-phase separation, semiconducting carbon nanotubes are purified from their metallic counterparts and condensed into a 10 nm thin film with no residual surfactant. Cross peak intensities put the time scale for energy transfer at <60 fs, and 2D anisotropy measurements determine that energy transfer is most efficient between parallel nanotubes, thus favoring directional energy flow. Lifetimes are about 300 fs. Thus, these results are in sharp contrast to thin films prepared from nanotubes that are wrapped by polymers, which exhibit picosecond energy transfer and randomize the direction of energy flow. Ultrafast energy flow and directionality are exciting properties for next-generation photovoltaics, photodetectors, and other devices. PMID:27182690

  4. Thermoelectric Detection of Multi-Subband Density of States in Semiconducting and Metallic Single-Walled Carbon Nanotubes.

    PubMed

    Shimizu, Sunao; Iizuka, Takahiko; Kanahashi, Kaito; Pu, Jiang; Yanagi, Kazuhiro; Takenobu, Taishi; Iwasa, Yoshihiro

    2016-07-01

    Thermoelectric detection of a multi-subband density of states in semiconducting and metallic single-walled carbon nanotubes is demonstrated by scanning the Fermi energy from electron-doped to hole-doped regions. The Fermi energy is systematically controlled by utilizing the strong electric field induced in electric-double-layer transistor configurations, resulting in the optimization of the thermoelectric power factor. PMID:27191367

  5. Mechanical deformations of boron nitride nanotubes in crossed junctions

    SciTech Connect

    Zhao, Yadong; Chen, Xiaoming; Ke, Changhong; Park, Cheol; Fay, Catharine C.; Stupkiewicz, Stanislaw

    2014-04-28

    We present a study of the mechanical deformations of boron nitride nanotubes (BNNTs) in crossed junctions. The structure and deformation of the crossed tubes in the junction are characterized by using atomic force microscopy. Our results show that the total tube heights are reduced by 20%–33% at the crossed junctions formed by double-walled BNNTs with outer diameters in the range of 2.21–4.67 nm. The measured tube height reduction is found to be in a nearly linear relationship with the summation of the outer diameters of the two tubes forming the junction. The contact force between the two tubes in the junction is estimated based on contact mechanics theories and found to be within the range of 4.2–7.6 nN. The Young's modulus of BNNTs and their binding strengths with the substrate are quantified, based on the deformation profile of the upper tube in the junction, and are found to be 1.07 ± 0.11 TPa and 0.18–0.29 nJ/m, respectively. Finally, we perform finite element simulations on the mechanical deformations of the crossed BNNT junctions. The numerical simulation results are consistent with both the experimental measurements and the analytical analysis. The results reported in this paper contribute to a better understanding of the structural and mechanical properties of BNNTs and to the pursuit of their applications.

  6. Mechanical deformations of boron nitride nanotubes in crossed junctions

    NASA Astrophysics Data System (ADS)

    Zhao, Yadong; Chen, Xiaoming; Park, Cheol; Fay, Catharine C.; Stupkiewicz, Stanislaw; Ke, Changhong

    2014-04-01

    We present a study of the mechanical deformations of boron nitride nanotubes (BNNTs) in crossed junctions. The structure and deformation of the crossed tubes in the junction are characterized by using atomic force microscopy. Our results show that the total tube heights are reduced by 20%-33% at the crossed junctions formed by double-walled BNNTs with outer diameters in the range of 2.21-4.67 nm. The measured tube height reduction is found to be in a nearly linear relationship with the summation of the outer diameters of the two tubes forming the junction. The contact force between the two tubes in the junction is estimated based on contact mechanics theories and found to be within the range of 4.2-7.6 nN. The Young's modulus of BNNTs and their binding strengths with the substrate are quantified, based on the deformation profile of the upper tube in the junction, and are found to be 1.07 ± 0.11 TPa and 0.18-0.29 nJ/m, respectively. Finally, we perform finite element simulations on the mechanical deformations of the crossed BNNT junctions. The numerical simulation results are consistent with both the experimental measurements and the analytical analysis. The results reported in this paper contribute to a better understanding of the structural and mechanical properties of BNNTs and to the pursuit of their applications.

  7. Pure Optical Dephasing Dynamics in Semiconducting Single-Walled Carbon Nanotubes

    SciTech Connect

    Graham, Matt; Fleming, Graham; Ma, Yingzhong; Green, Alexander A.; Hersam, Mark C.

    2011-01-01

    We report a detailed study of ultrafast exciton dephasing processes in semiconducting single-walled carbon nanotubes (SWNTs) employing a sample highly enriched in a single tube species, the (6,5) tube. Systematic measurements of femtosecond pump-probe, two-pulse photon echo and three-pulse photon echo peak shift over a broad range of excitation intensities and lattice temperature (from 4.4 to 292 K) enable us to quantify the timescales of pure optical dephasing (T 2 ), along with exciton-exciton and exciton-phonon scattering, environmental effects as well as spectral diffusion. While the exciton dephasing time (T2 ) increases from 205 fs at room temperature to 320 fs at 70 K, we found that further decrease of the lattice temperature leads to a shortening of the T2 times. This complex temperature dependence was found to arise from an enhanced relaxation of exciton population at lattice temperatures below 80 K. By quantitatively accounting the contribution from the population relaxation, the corresponding pure optical dephasing times increase monotonically from 225 fs at room temperature to 508 fs at 4.4 K. We further found that below 180 K, the inverse of the pure dephasing time (1/T 2 ) scales linearly with temperature with a slope of 6.7 0.6 eV/K, which suggests dephasing arising from one-phonon scattering (i.e. acoustic phonons). In view ofthe large dynamic disorder of the surrounding environment, the origin of the long room temperature pure dephasing time is proposed to result from reduced strength of exciton-phonon coupling by motional narrowing over nuclear fluctuations. This consideration further suggests the occurrence of remarkable initial exciton delocalization, and makes nanotubes ideal to study many-body effects in spatially confined systems.

  8. InAs/Si Hetero-Junction Nanotube Tunnel Transistors

    PubMed Central

    Hanna, Amir N.; Fahad, Hossain M.; Hussain, Muhammad M.

    2015-01-01

    Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ‘ON’ state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunneling area while achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. Numerical simulations has shown that a 10 nm thin nanotube TFET with a 100 nm core gate has a 5×normalized output current compared to a 10 nm diameter GAA NW TFET. PMID:25923104

  9. Multimodal probing of oxygen and water interaction with metallic and semiconducting carbon nanotube networks under ultraviolet irradiation

    DOE PAGESBeta

    Nelson, Anthony J.; Ivanov, Ilia N.; Muckley, Eric S.; Jacobs, Christopher B.

    2016-06-01

    In this study, carbon nanotube (CNT) networks composed of semiconducting single wall nanotubes (s-SWNTs), metallic single wall nanotubes (m-SWNTs), and multiwall nanotubes (MWNTs) were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in film resistance and mass were measured in situ. In the dark, resistance of metallic nanotube networks increases in the presence of O2 and H2O, whereas resistance of s-SWNT networks decreases. We find that UV irradiation increases the sensitivity of CNT networks to O2 and H2O by more than an order of magnitude. Under UV irradiation, the resistance of metallic nanotube networksmore » decreases in the presence of O2 and H2O likely through the generation of free charge carriers. UV irradiation increases the gas/vapor sensitivity of s-SWNT networks by nearly a factor of 2 compared to metallic nanotube networks. Networks of s-SWNTs show evidence of delamination from the gold-plated QCM crystal, possibly due to preferential adsorption of O2 and H2O on gold.« less

  10. Multimodal probing of oxygen and water interaction with metallic and semiconducting carbon nanotube networks under ultraviolet irradiation

    NASA Astrophysics Data System (ADS)

    Muckley, Eric S.; Nelson, Anthony J.; Jacobs, Christopher B.; Ivanov, Ilia N.

    2016-04-01

    Interaction between ultraviolet (UV) light and carbon nanotube (CNT) networks plays a central role in gas adsorption, sensor sensitivity, and stability of CNT-based electronic devices. To determine the effect of UV light on sorption kinetics and resistive gas/vapor response of different CNT networks, films of semiconducting single-wall nanotubes (s-SWNTs), metallic single-wall nanotubes, and multiwall nanotubes were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in film resistance and mass were measured in situ. In the dark, resistance of metallic nanotube networks increases in the presence of O2 and H2O, whereas resistance of s-SWNT networks decreases. UV irradiation decreases the resistance of metallic nanotube networks in the presence of O2 and H2O and increases the gas/vapor sensitivity of s-SWNT networks by nearly a factor of 2 compared to metallic nanotube networks. s-SWNT networks show evidence of delamination from the gold-plated quartz crystal microbalance crystal, possibly due to preferential adsorption of O2 and H2O on gold. UV irradiation increases the sensitivity of all CNT networks to O2 and H2O by an order of magnitude, which demonstrates the importance of UV light for enhancing response and lowering detection limits in CNT-based gas/vapor sensors.

  11. Selective Synthesis of Subnanometer Diameter Semiconducting Single-Walled Carbon Nanotubes

    SciTech Connect

    Loebick, C.; Podila, R; Reppert, J; Chudow, J; Ren, F; Haller, G; Rao, A; Pfefferle, L

    2010-01-01

    Subnanometer single-walled carbon nanotubes (sub-nm SWNTs) were synthesized at different temperatures (600, 700, and 800 C) using CoMn bimetallic catalysts supported on MCM-41 silica templates. The state of the catalyst was investigated using X-ray absorption, and the (n,m) indices of the sub-nm SWNTs were determined from Raman spectroscopy and photoluminescence measurements. We find that the size of the metallic particles that seed the growth of sub-nm SWNTs (diameter {approx}0.5-1.0 nm) is highly sensitive to the reaction temperature. Low reaction temperature (600 C) favors the growth of semiconducting tubes whose diameters range from 0.5 to 0.7 nm. These results were also confirmed by electrical transport measurements. Interestingly, dominant intermediate frequency modes on the same intensity scale as the Raman breathing modes were observed. An unusual 'S-like' dispersion of the G-band was present in the Raman spectra of sub-nm SWNTs with diameters <0.7 nm.

  12. Surfactant free fractions of metallic and semiconducting single-walled carbon nanotubes via optimised gel chromatography

    SciTech Connect

    Lukaszczuk, Pawel; Ruemmeli, Mark H.; Knupfer, Martin; Kalenczuk, Ryszard J.; Borowiak-Palen, Ewa

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer The application of gel permeation chromatography technique in a field of SWCNT separation. Black-Right-Pointing-Pointer Non-commercial agarose gel used as a column filling. Black-Right-Pointing-Pointer Purification route is presented, quality and quantity estimation is shown. Black-Right-Pointing-Pointer Process is ready for high-scale separation of SWCNTs. -- Abstract: We report the procedure of sorting/purification of carbon nanotubes by electronic type using chromatographic column with sodium dodecylsulfate (SDS) and sodium deoxycholate (DOC) solutions as the eluents. The non-commercial agarose gel in different concentrations has been tested in the process. It was found that in optimal gel concentration the fractionation resulted in {approx}96.2% yield of semiconducting species. Importantly, to get surfactant-free fractions the post-separation purification procedure has been carried out. The UV-vis-NIR and Raman spectroscopy have been utilised for the samples analysis. High resolution transmission microscopy and thermogravimetric analysis allowed to study the sample morphology and purity, respectively.

  13. H-bonded supramolecular polymer for the selective dispersion and subsequent release of large-diameter semiconducting single-walled carbon nanotubes.

    PubMed

    Pochorovski, Igor; Wang, Huiliang; Feldblyum, Jeremy I; Zhang, Xiaodong; Antaris, Alexander L; Bao, Zhenan

    2015-04-01

    Semiconducting, single-walled carbon nanotubes (SWNTs) are promising candidates for applications in thin-film transistors, solar cells, and biological imaging. To harness their full potential, however, it is necessary to separate the semiconducting from the metallic SWNTs present in the as-synthesized SWNT mixture. While various polymers are able to selectively disperse semiconducting SWNTs, the subsequent removal of the polymer is challenging. However, many applications require semiconducting SWNTs in their pure form. Toward this goal, we have designed a 2-ureido-6[1H]-pyrimidinone (UPy)-based H-bonded supramolecular polymer that can selectively disperse semiconducting SWNTs. The dispersion purity is inversely related to the dispersion yield. In contrast to conventional polymers, the polymer described herein was shown to disassemble into monomeric units upon addition of an H-bond-disrupting agent, enabling isolation of dispersant-free, semiconducting SWNTs. PMID:25815604

  14. Novel Electrical and Optoelectronic Characterization Methods for Semiconducting Nanowires and Nanotubes

    NASA Astrophysics Data System (ADS)

    Katzenmeyer, Aaron Michael

    As technology journalist David Pogue recounted, "If everything we own had improved over the last 25 years as much as electronics have, the average family car would travel four times faster than the space shuttle; houses would cost 200 bucks." The electronics industry is one which, through Moore's Law, created a self-fulfilling prophecy of exponential advancement. This progress has made unforeseen technologies commonplace and revealed new physical understanding of the world in which we live. It is in keeping with these trends that the current work is motivated. This dissertation focuses on the advancement of electrical and optoelectronic characterization techniques suitable for understanding the underlying physics and applications of nanoscopic devices, in particular semiconducting nanowires and nanotubes. In this work an in situ measurement platform based on a field-emission scanning electron microscope fitted with an electrical nanoprobe is shown to be a robust instrument for determining fundamental aspects of nanowire systems (i.e. the dominant mode of carrier transport and the nature of the electrical contacts to the nanowire). The platform is used to fully classify two distinct systems. In one instance it is found that indium arsenide nanowires display space-charge-limited transport and are contacted Ohmically. In the other, gallium arsenide nanowires are found to sequentially show the trap-mediated transport regimes of Poole-Frenkel effect and phonon-assisted tunneling. The contacts in this system are resolved to be asymmetric -- one is Ohmic while the other is a Schottky barrier. Additionally scanning photocurrent microscopy is used to spatially resolve optoelectronic nanowire and nanotube devices. In core/shell gallium arsenide nanowire solar cell arrays it is shown that each individual nanowire functions as a standalone solar cell. Nanotube photodiodes are mapped by scanning photocurrent microscopy to confirm an optimal current collection scheme has been

  15. Semiconducting ZnSnN2 thin films for Si/ZnSnN2 p-n junctions

    NASA Astrophysics Data System (ADS)

    Qin, Ruifeng; Cao, Hongtao; Liang, Lingyan; Xie, Yufang; Zhuge, Fei; Zhang, Hongliang; Gao, Junhua; Javaid, Kashif; Liu, Caichi; Sun, Weizhong

    2016-04-01

    ZnSnN2 is regarded as a promising photovoltaic absorber candidate due to earth-abundance, non-toxicity, and high absorption coefficient. However, it is still a great challenge to synthesize ZnSnN2 films with a low electron concentration, in order to promote the applications of ZnSnN2 as the core active layer in optoelectronic devices. In this work, polycrystalline and high resistance ZnSnN2 films were fabricated by magnetron sputtering technique, then semiconducting films were achieved after post-annealing, and finally Si/ZnSnN2 p-n junctions were constructed. The electron concentration and Hall mobility were enhanced from 2.77 × 1017 to 6.78 × 1017 cm-3 and from 0.37 to 2.07 cm2 V-1 s-1, corresponding to the annealing temperature from 200 to 350 °C. After annealing at 300 °C, the p-n junction exhibited the optimum rectifying characteristics, with a forward-to-reverse ratio over 103. The achievement of this ZnSnN2-based p-n junction makes an opening step forward to realize the practical application of the ZnSnN2 material. In addition, the nonideal behaviors of the p-n junctions under both positive and negative voltages are discussed, in hope of suggesting some ideas to further improve the rectifying characteristics.

  16. Giant piezoresistivity in aligned carbon nanotube nanocomposite: account for nanotube structural distortion at crossed tunnel junctions.

    PubMed

    Gong, S; Zhu, Z H

    2015-01-28

    High piezoresistivity is critical for multifunctional carbon nanotube polymer composites with sensing capability. By developing a new percolation network model, this work reveals theoretically that a giant piezoresistivity in the composites can be potentially achieved by controlled nanotube alignment resulting from field based alignment techniques. The tube-tube and/or tube-matrix interaction in conjunction with the aligned carbon nanotube networks are fully considered in the newly proposed model. The structural distortion of nanotubes is determined self-consistently by minimizing the pseudo-potential energy at crossed-tube junctions based on the Lennard-Jones potential and simulation of coarse grain molecular dynamics. The tunneling transport through crossed-tube junctions is calculated by the Landauer-Büttiker formula with empirical fitting by first-principle calculation. The simulation results also reveal that the piezoresistivity can be further improved by using low carbon nanotube loadings near the percolation threshold, carbon nanotubes with a small aspect ratio, high intrinsic conductivity and polymers with a small Poisson's ratio. This giant piezoresistive effect offers a tremendously promising future, which needs further thorough exploration. PMID:25492244

  17. Separation of single-walled carbon nanotubes into metallic and semiconducting groups: a simple and large-scale method

    NASA Astrophysics Data System (ADS)

    Lu, Jing; Maeda, Y.

    2006-03-01

    Separation of a large number of single-walled carbon nanotubes (SWNTs) into groups each with specifically metallic and semiconducting properties is an extremely important task for technology application. Even though effective methods (1, 2) have been devised, they suffer from drawbacks such as either the yield is low (3) or expense is high (4). In this work, we study the problem from a theoretical approach, we notice that based on the first principles calculations the binding strengths of methylamine to the semiconducting [13, 0] SWNT are only 36˜61% of that to the metallic [7, 7] SWNT, which suggests that the amines is much more attractive toward the pure metallic than the semiconducting SWNTs. Therefore starting from as-prepared SWNTs and with the assistance of amines, we achieved SWNTs with enriched metallic properties over semiconducting in a convenient and large-scale manner. References: (1) D. Chattopadhyay, L. Galeska, F. Papadimitrakopoulos, Journal of the American Chemical Society 125, 3370 (MAR 19, 2003). (2) H. P. Li et al., Journal of the American Chemical Society 126, 1014 (FEB 4, 2004). (3) R. Krupke, F. Hennrich, H. von Lohneysen, M. Kappes, SCIENCE 301, 344 (JUL 18, 2003). (4) M. Zheng et al., Science 302, 1545 (NOV 28, 2003).

  18. Nearly exclusive growth of small diameter semiconducting single-wall carbon nanotubes from organic chemistry synthetic end-cap molecules.

    PubMed

    Liu, Bilu; Liu, Jia; Li, Hai-Bei; Bhola, Radha; Jackson, Edward A; Scott, Lawrence T; Page, Alister; Irle, Stephan; Morokuma, Keiji; Zhou, Chongwu

    2015-01-14

    The inability to synthesize single-wall carbon nanotubes (SWCNTs) possessing uniform electronic properties and chirality represents the major impediment to their widespread applications. Recently, there is growing interest to explore and synthesize well-defined carbon nanostructures, including fullerenes, short nanotubes, and sidewalls of nanotubes, aiming for controlled synthesis of SWCNTs. One noticeable advantage of such processes is that no metal catalysts are used, and the produced nanotubes will be free of metal contamination. Many of these methods, however, suffer shortcomings of either low yield or poor controllability of nanotube uniformity. Here, we report a brand new approach to achieve high-efficiency metal-free growth of nearly pure SWCNT semiconductors, as supported by extensive spectroscopic characterization, electrical transport measurements, and density functional theory calculations. Our strategy combines bottom-up organic chemistry synthesis with vapor phase epitaxy elongation. We identify a strong correlation between the electronic properties of SWCNTs and their diameters in nanotube growth. This study not only provides material platforms for electronic applications of semiconducting SWCNTs but also contributes to fundamental understanding of the growth mechanism and controlled synthesis of SWCNTs. PMID:25521257

  19. Quantitative analysis of the oxidation effects on the electrical characteristics of high-purity, large-diameter semiconducting carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Gao, Jia; Loo, Yueh-Lin

    2014-03-01

    Many attempts have been made to utilize carbon nanotubes for chemical, biological and gas sensing applications. Previous studies show that adsorbed ozone (O3) on carbon nanotubes can drastically influence their electrical characteristics. On the one hand, ozone act as p dopants; exposure thus leads to an increase in electrical conductivity. On the other hand, ozone readily oxidizes carbon nanotubes; this chemical reaction results in a decrease in conductivity. It remains ambiguous which process dominates and quantitative evaluation of these two effects is lacking. In this study, we elucidate the interaction between ozone and carbon nanotubes by evaluating the field-effect mobilities of polymer-sorted large diameter semiconducting carbon nanotubes based transistors. Upon exposure to ozone, we observe a positive shift in the threshold voltage from -0.7 to 11.7 V and a concurrent decrease of hole mobility from 2.5 to 0.5 cm2/Vs. Accordingly, the source-drain current exhibits a non-monotonic dependence on ozone exposure time. This dependence reveals that doping dominates the electrical characteristics of carbon nanotube transistors initially. Beyond 3-minutes of ozone exposure, chemical oxidation dominates, resulting in a progressive decrease in source-drain current.

  20. Observation and Modeling of Single Wall Carbon Nanotube Bend Junctions

    NASA Technical Reports Server (NTRS)

    Han, Jie; Anantram, M. P.; Jaffe, R. L.; Kong, J.; Dai, H.; Saini, Subhash (Technical Monitor)

    1998-01-01

    Single wall carbon nanotube (SWNT) bends, with diameters from approx. 1.0 to 2.5 nm and bend angles from 18 deg. to 34 deg., are observed in catalytic decomposition of hydrocarbons at 600 - 1200 C. An algorithm using molecular dynamics simulation (MD) techniques is developed to model these structures that are considered to be SWNT junctions formed by topological defects (i.e. pentagon-heptagon pairs). The algorithm is used to predict the tube helicities and defect configurations for bend junctions using the observed tube diameters and bend angles. The number and arrangement of the defects at the junction interfaces are found to depend on the tube helicities and bend angle. The structural and energetic calculations using the Brenner potential show a number of stable junction configurations for each bend angle with the 34 deg. bends being more stable than the others. Tight binding calculations for local density of state (LDOS) and transmission coefficients are carried out to investigate electrical properties of the bend junctions.

  1. Band structure and optical transitions in semiconducting double-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Makaev, D. V.; D'Yachkov, P. N.

    2006-11-01

    The electronic structure of semiconducting double-wall carbon nanotubes (CNTs) is calculated using the linearized augmented cylindrical wave method. The consideration is performed in the framework of the local density functional theory and the muffin-tin (MT) approximation for the one-electron Hamiltonian. The electronic spectrum of a double-wall CNT is determined by the free motion of electrons in the interatomic space of the two cylindrical layers, scattering by the MT spheres, and tunneling through the classically impenetrable region. Calculated results for double-wall CNTs of the ( n, 0)@( n', 0) zigzag type indicate that the shift of the band-gap width depends on whether n and n' are divided by 3 with a remainder of 1 or 2. It is found that, regardless of the type of the inner tube, the energy gap E g of the outer tube decreases by 0.15-0.22 eV if the tube belongs to the sequence n = 2 (mod 3). For the outer tubes of the sequence n = 1 (mod 3), the shifts of the band gap Δ E g are always negative -0.15 ≤ Δ E g ≤ -0.05 eV. In both cases, the shifts Δ E g weakly oscillate rather than decrease in going to tubes of a larger diameter d. For the inner tubes, the changes in the band gap Δ E g are more sensitive to the diameter. At 10 ≤ n ≤ 16, the shifts Δ E g are positive and the maximum value of Δ E g equals 0.39 and 0.32 for the sequences n = 2 (mod 3) and n = 1 (mod 3), respectively. In going to the inner tubes of a larger diameter, Δ E g rapidly drops and then oscillates in the range from -0.05 to 0.06 eV. The calculated results indicate that the shifts of the optical band gaps in core and shell tubes upon the formation of double-wall CNTs are significant, which must hinder the identification of double-wall CNTs by optical methods. On the other hand, the obtained results open up possibilities for a more detailed classification of double-wall nanotubes.

  2. Exciton annihilation and dephasing dynamics in semiconducting single-walled carbon nanotubes

    SciTech Connect

    Graham, Matt; Ma, Yingzhong; Green, Alexander A.; Hersam, Mark C.; Fleming, Graham

    2010-01-01

    Semiconducting single-walled carbon nanotubes (SWNTs) are one of the most intriguing nanomaterials due to their large aspect ratios, size tunable properties, and dominant many body interactions. While the dynamics of exciton population relaxation have been well characterized, optical dephasing processes have only been exam- ined indirectly through steady-state measurements such as single-molecule spectroscopy that can yield highly variable estimates of the homogeneous linewidth. To bring clarity to these conflicting estimates, a time-domain measurement of exciton dephasing at an ensemble level is necessary. Using two-pulse photon echo (2PE) spec- troscopy, comparatively long dephasing times approaching 200 fs are extracted for the (6,5) tube species at room temperature. In this contribution, we extend our previous study of 2PE and pump-probe spectroscopy to low temperatures to investigate inelastic exciton-exciton scattering. In contrast to the population kinetics observed upon excitation of the second transition-allowed excitonic state (E22 ), our one-color pump-probe data instead shows faster relaxation upon cooling to 60 K when the lowest transition-allowed state (E11 ) is directly excited for the (6,5) tube species. Analysis of the kinetics obtained suggests that the observed acceleration of kinetic decay at low temperature originates from an increasing rate of exciton-exciton annihilation. In order to directly probe exciton-exciton scattering processes, femtosecond 2PE signal is measured as a function of excitation fluence and temperature. Consistent with the observed enhancement of exciton-exciton scattering and annihilation at low temperatures, the dephasing rates show a correlated trend with the temperature dependence of the population lifetimes extracted from one-color pump-probe measurements.

  3. Scalable and selective dispersion of semiconducting arc-discharged carbon nanotubes by dithiafulvalene/thiophene copolymers for thin film transistors.

    PubMed

    Wang, Huiliang; Mei, Jianguo; Liu, Peng; Schmidt, Kristin; Jiménez-Osés, Gonzalo; Osuna, Sílvia; Fang, Lei; Tassone, Christopher J; Zoombelt, Arjan Pieter; Sokolov, Anatoliy N; Houk, Kendall N; Toney, Michael F; Bao, Zhenan

    2013-03-26

    We report a simple and scalable method to enrich large quantities of semiconducting arc-discharged single-walled carbon nanotubes (SWNTs) with diameters of 1.1-1.8 nm using dithiafulvalene/thiophene copolymers. Stable solutions of highly individualized and highly enriched semiconducting SWNTs were obtained after a simple sonication and centrifuge process. Molecular dynamics (MD) simulations of polymer backbone interactions with and without side chains indicated that the presence of long alkyl side chains gave rise to the selectivity toward semiconducting tubes, indicating the importance of the roles of the side chains to both solubilize and confer selectivity to the polymers. We found that, by increasing the ratio of thiophene to dithiafulvalene units in the polymer backbone (from pDTFF-1T to pDTFF-3T), we can slightly improve the selectivity toward semiconducting SWNTs. This is likely due to the more flexible backbone of pDTFF-3T that allows the favorable wrapping of SWNTs with certain chirality as characterized by small-angle X-ray scattering. However, the dispersion yield was reduced from pDTFF-1T to pDTFF-3T. MD simulations showed that the reduction is due to the smaller polymer/SWNT contact area, which reduces the dispersion ability of pDTFF-3T. These experimental and modeling results provide a better understanding for future rational design of polymers for sorting SWNTs. Finally, high on/off ratio solution-processed thin film transistors were fabricated from the sorted SWNTs to confirm the selective dispersion of semiconducting arc-discharge SWNTs. PMID:23402644

  4. Photocurrent generation efficiency of a carbon nanotube pn junction

    NASA Astrophysics Data System (ADS)

    McCulley, Daniel; Aspitarte, Lee; Minot, Ethan

    Carrier multiplication effects can enhance the quantum efficiency of photovoltaic devices. For example, quantum dot solar cells have demonstrated photon-to-electron conversion efficiencies greater than 100% when photon energies exceed twice the band gap. Carbon nanotube photodiodes exhibit carrier multiplication effects (Gabor et al., Science 2009), but the quantum efficiency of such photodiodes has not previously been characterized. We have reproduced the carrier multiplication phenomena in individual CNT pn junctions and investigated the conditions under which it occurs. We will present early results quantifying the internal quantum efficiency of the process.

  5. Water flow through carbon nanotube junctions as molecular convergent nozzles

    NASA Astrophysics Data System (ADS)

    Hanasaki, Itsuo; Nakatani, Akihiro

    2006-06-01

    Molecular dynamics (MD) simulations are conducted for water flow through carbon nanotube (CNT) junctions as molecular nozzles. The fluidized piston model (FPM) is employed to drive the inlet flow at streaming velocities of 25 and 50 m s-1. Water flow through the CNT junctions is found to undergo an increase in streaming velocity, a decrease in pressure, and an increase in temperature. Although the difference of the upstream velocities does not generally lead to an appreciable density difference in the downstream CNT, the higher streaming velocity causes the upstream density to increase. The streaming velocity remains almost constant in the upstream CNT, but increases dramatically in the junction region. The ratio of downstream to upstream streaming velocities increases with the ratio of upstream to downstream cross section. A higher inlet velocity results in larger acceleration, which is generally more noticeable at larger cross-sectional ratios, and less prominent in junctions with smaller cross-sectional ratios. The cross-sectional ratio calculated from the internal radii of the CNTs based on the oxygen atomic density profile of water is closer to the ratio of downstream to upstream streaming velocities than the cross-sectional ratio calculated from the radii given by the carbon atomic centres.

  6. The computational design of junctions between carbon nanotubes and graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Li, Ye-Fei; Li, Bing-Rui; Zhang, Hao-Li

    2009-06-01

    Using first-principles density functional theory calculations, various junction models constructed from different carbon nanotube and graphene nanoribbon units via covalent linkage have been envisioned. These models consist of linear, T- and H-shaped junctions within the connection modes between carbon nanotube and graphene nanoribbon units. The electronic transport properties of different junctions have been systematically investigated by using the non-equilibrium Green's function. The simulation results suggested that the proposed models are promising for future applications in novel nanoelectronics.

  7. Printed thin film transistors and CMOS inverters based on semiconducting carbon nanotube ink purified by a nonlinear conjugated copolymer

    NASA Astrophysics Data System (ADS)

    Xu, Wenya; Dou, Junyan; Zhao, Jianwen; Tan, Hongwei; Ye, Jun; Tange, Masayoshi; Gao, Wei; Xu, Weiwei; Zhang, Xiang; Guo, Wenrui; Ma, Changqi; Okazaki, Toshiya; Zhang, Kai; Cui, Zheng

    2016-02-01

    Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (+/-2 V) and subthreshold swing (SS) (122-161 mV dec-1), high effective mobility (up to 17.6-37.7 cm2 V-1 s-1) and high on/off ratio (104-107). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption.Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge

  8. Enhanced ambipolar charge injection with semiconducting polymer/carbon nanotube thin films for light-emitting transistors.

    PubMed

    Gwinner, Michael C; Jakubka, Florian; Gannott, Florentina; Sirringhaus, Henning; Zaumseil, Jana

    2012-01-24

    We investigate the influence of small amounts of semiconducting single-walled carbon nanotubes (SWNTs) dispersed in polyfluorenes such as poly(9,9-di-n-octylfluorene-alt-benzothiadiazole (F8BT) and poly(9,9-dioctylfluorene) (F8) on device characteristics of bottom contact/top gate ambipolar light-emitting field-effect transistors (LEFETs) based on these conjugated polymers. We find that the presence of SWNTs within the semiconducting layer at concentrations below the percolation limit significantly increases both hole and electron injection, even for a large band gap semiconductor like F8, without leading to significant luminescence quenching of the conjugated polymer. As a result of the reduced contact resistance and lower threshold voltages, larger ambipolar currents and thus brighter light emission are observed. We examine possible mechanisms of this effect such as energy level alignment, reduced bulk resistance above the contacts, and field-enhanced injection at the nanotube tips. The observed ambipolar injection improvement is applicable to most conjugated polymers in staggered transistor configurations or similar organic electronic devices where injection barriers are an issue. PMID:22142143

  9. Effect of ozone exposure on the electrical characteristics of high-purity, large-diameter semiconducting carbon nanotubes.

    PubMed

    Gao, Jia; Loo, Yueh-Lin

    2014-06-14

    In this study, we have elucidated the interactions between ozone and carbon nanotubes by monitoring the characteristics of field-effect transistors based on polymer-sorted, large-diameter semiconducting carbon nanotubes. The drain-source current of these transistors initially increases with ozone exposure and then it progressively decreases with increasing exposure beyond 3 min. This non-monotonic dependence of the drain-source current can be ascribed to two competing processes. At short ozone exposure, p-doping of carbon nanotubes dominates; the drain-source current thus increases as a result of increasing hole concentration. This effect is most evidenced in a progressive threshold voltage shift towards positive voltages with increasing exposure to ozone. At extended ozone exposure, chemical oxidation of carbon nanotubes instead dominates. The drain-source current decreases as a result of decreasing hole mobility. This effect manifests itself in a monotonic decrease in the mobility of these devices as a function of ozone exposure. PMID:24760174

  10. Printed thin film transistors and CMOS inverters based on semiconducting carbon nanotube ink purified by a nonlinear conjugated copolymer.

    PubMed

    Xu, Wenya; Dou, Junyan; Zhao, Jianwen; Tan, Hongwei; Ye, Jun; Tange, Masayoshi; Gao, Wei; Xu, Weiwei; Zhang, Xiang; Guo, Wenrui; Ma, Changqi; Okazaki, Toshiya; Zhang, Kai; Cui, Zheng

    2016-02-28

    Two innovative research studies are reported in this paper. One is the sorting of semiconducting carbon nanotubes and ink formulation by a novel semiconductor copolymer and second is the development of CMOS inverters using not the p-type and n-type transistors but a printed p-type transistor and a printed ambipolar transistor. A new semiconducting copolymer (named P-DPPb5T) was designed and synthesized with a special nonlinear structure and more condensed conjugation surfaces, which can separate large diameter semiconducting single-walled carbon nanotubes (sc-SWCNTs) from arc discharge SWCNTs according to their chiralities with high selectivity. With the sorted sc-SWCNTs ink, thin film transistors (TFTs) have been fabricated by aerosol jet printing. The TFTs displayed good uniformity, low operating voltage (±2 V) and subthreshold swing (SS) (122-161 mV dec(-1)), high effective mobility (up to 17.6-37.7 cm(2) V(-1) s(-1)) and high on/off ratio (10(4)-10(7)). With the printed TFTs, a CMOS inverter was constructed, which is based on the p-type TFT and ambipolar TFT instead of the conventional p-type and n-type TFTs. Compared with other recently reported inverters fabricated by printing, the printed CMOS inverters demonstrated a better noise margin (74% 1/2 Vdd) and was hysteresis free. The inverter has a voltage gain of up to 16 at an applied voltage of only 1 V and low static power consumption. PMID:26847814

  11. Photoresponse of a Single Y-Junction Carbon Nanotube.

    PubMed

    Samanta, Sudeshna; Saini, Deepika; Singha, Achintya; Das, Kaustuv; Bandaru, Prabhakar R; Rao, Apparao M; Raychaudhuri, Arup Kumar

    2016-07-27

    We report investigation of optical response in a single strand of a branched carbon nanotube (CNT), a Y-junction CNT composed of multiwalled CNTs. The experiment was performed by connecting a pair of branches while grounding the remaining one. Of the three branch combinations, only one combination is optically active which also shows a nonlinear semiconductor-like I-V curve, while the other two branch combinations are optically inactive and show linear ohmic I-V curves. The photoresponse includes a zero-bias photocurrent from the active branch combination. Responsivity of ≈1.6 mA/W has been observed from a single Y-CNT at a moderate bias of 150 mV with an illumination of wavelength 488 nm. The photoresponse experiment allows us to understand the nature of internal connections in the Y-CNT. Analysis of data locates the region of photoactivity at the junction of only two branches and only the combination of these two branches (and not individual branches) exhibits photoresponse upon illumination. A model calculation based on back-to-back Schottky-type junctions at the branch connection explains the I-V data in the dark and shows that under illumination the barriers at the contacts become lowered due to the presence of photogenerated carriers. PMID:27379988

  12. A phenomenological model for selective growth of semiconducting single-walled carbon nanotubes based on catalyst deactivation

    NASA Astrophysics Data System (ADS)

    Sakurai, Shunsuke; Yamada, Maho; Sakurai, Hiroko; Sekiguchi, Atsuko; Futaba, Don N.; Hata, Kenji

    2015-12-01

    A method for the selective semiconducting single-walled carbon nanotube (SWCNT) growth over a continuous range from 67% to 98%, within the diameter range of 0.8-1.2 nm, by the use of a ``catalyst conditioning process'' prior to growth is reported. Continuous control revealed an inverse relationship between the selectivity and the yield as evidenced by a 1000-times difference in yield between the highest selectivity and non-selectivity. Further, these results show that the selectivity is highly sensitive to the presence of a precise concentration of oxidative and reductive gases (i.e. water and hydrogen), and the highest selectivity occurred along the border between the conditions suitable for high yield and no-growth. Through these results, a phenomenological model has been constructed to explain the inverse relationship between yield and selectivity based on catalyst deactivation. We believe our model to be general, as the fundamental mechanisms limiting selective semiconducting SWCNT growth are common to the previous reports of limited yield.A method for the selective semiconducting single-walled carbon nanotube (SWCNT) growth over a continuous range from 67% to 98%, within the diameter range of 0.8-1.2 nm, by the use of a ``catalyst conditioning process'' prior to growth is reported. Continuous control revealed an inverse relationship between the selectivity and the yield as evidenced by a 1000-times difference in yield between the highest selectivity and non-selectivity. Further, these results show that the selectivity is highly sensitive to the presence of a precise concentration of oxidative and reductive gases (i.e. water and hydrogen), and the highest selectivity occurred along the border between the conditions suitable for high yield and no-growth. Through these results, a phenomenological model has been constructed to explain the inverse relationship between yield and selectivity based on catalyst deactivation. We believe our model to be general, as the

  13. Thin-film transistors using DNA-wrapped semiconducting single-wall carbon nanotubes with selected chiralities

    NASA Astrophysics Data System (ADS)

    Kuwahara, Yuki; Nihey, Fumiyuki; Ohmori, Shigekazu; Saito, Takeshi

    2015-10-01

    Selected semiconducting chiralities, (7,5), (7,6), and (8,4), of DNA-wrapped single-wall carbon nanotubes (DNA-SWCNTs) were used for thin-film transistors (TFTs). Chirality separation was carried out by ion exchange chromatography (IEX) with the ssDNA of the (TAT)4 sequence. An on/off ratio of 3.8 × 106 with a carrier mobility of 11 cm2/(V·s) was successfully achieved in the fabricated SWCNT-TFTs. The comparison between the on/off ratios obtained before (101-102) and after IEX (104-107) indicated that the IEX separation process sufficiently improves the performance of SWCNT-TFTs because of the reducing metallic SWCNT pathways in the TFT channel.

  14. A phenomenological model for selective growth of semiconducting single-walled carbon nanotubes based on catalyst deactivation.

    PubMed

    Sakurai, Shunsuke; Yamada, Maho; Sakurai, Hiroko; Sekiguchi, Atsuko; Futaba, Don N; Hata, Kenji

    2016-01-14

    A method for the selective semiconducting single-walled carbon nanotube (SWCNT) growth over a continuous range from 67% to 98%, within the diameter range of 0.8-1.2 nm, by the use of a "catalyst conditioning process" prior to growth is reported. Continuous control revealed an inverse relationship between the selectivity and the yield as evidenced by a 1000-times difference in yield between the highest selectivity and non-selectivity. Further, these results show that the selectivity is highly sensitive to the presence of a precise concentration of oxidative and reductive gases (i.e. water and hydrogen), and the highest selectivity occurred along the border between the conditions suitable for high yield and no-growth. Through these results, a phenomenological model has been constructed to explain the inverse relationship between yield and selectivity based on catalyst deactivation. We believe our model to be general, as the fundamental mechanisms limiting selective semiconducting SWCNT growth are common to the previous reports of limited yield. PMID:26660858

  15. A study of preferential growth of carbon nanotubes with semiconducting behavior grown by plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Mizutani, Takashi; Ohnaka, Hirofumi; Okigawa, Yuki; Kishimoto, Shigeru; Ohno, Yutaka

    2009-10-01

    The electrical properties of carbon nanotubes (CNTs) grown by plasma-enhanced chemical vapor deposition (PECVD) have been studied by measuring the I-V characteristics of many CNT-field effect transistors. The ratio of modulation current to total current was as high as 97%, with a small nondepletable OFF current component. This suggests that CNTs with semiconducting behavior were preferentially grown in the PECVD process. Raman scattering spectroscopy of the PECVD-grown CNTs, however, revealed several peaks of the radial breezing mode, which correspond to the presence of metallic CNTs. Scanning gate microscopy measurement of the CNT-FET with an ON/OFF ratio of 100 revealed the existence of a potential barrier in the metallic CNTs. These results suggest that observation of the preferential growth of CNTs with semiconducting behavior in the CNT-FETs fabricated via the present PECVD process results from the opening of the band gap due to defects caused by irradiation damage during the PECVD growth.

  16. Determination of the metallic/semiconducting ratio in bulk single-wall carbon nanotube samples by cobalt porphyrin probe electron paramagnetic resonance spectroscopy.

    PubMed

    Cambré, Sofie; Wenseleers, Wim; Goovaerts, Etienne; Resasco, Daniel E

    2010-11-23

    A simple and quantitative, self-calibrating spectroscopic technique for the determination of the ratio of metallic to semiconducting single-wall carbon nanotubes (SWCNTs) in a bulk sample is presented. The technique is based on the measurement of the electron paramagnetic resonance (EPR) spectrum of the SWCNT sample to which cobalt(II)octaethylporphyrin (CoOEP) probe molecules have been added. This yields signals from both CoOEP molecules on metallic and on semiconducting tubes, which are easily distinguished and accurately characterized in this work. By applying this technique to a variety of SWCNT samples produced by different synthesis methods, it is shown that these signals for metallic and semiconducting tubes are independent of other factors such as tube length, defect density, and diameter, allowing the intensities of both signals for arbitrary samples to be retrieved by a straightforward least-squares regression. The technique is self-calibrating in that the EPR intensity can be directly related to the number of spins (number of CoOEP probe molecules), and as the adsorption of the CoOEP molecules is itself found to be unbiased toward metallic or semiconducting tubes, the measured intensities can be directly related to the mass percentage of metallic and semiconducting tubes in the bulk SWCNT sample. With the use of this method it was found that for some samples the metallic/semiconducting ratios strongly differed from the usual 1:2 ratio. PMID:20958073

  17. Effect of selectively intercalated polyiodide on the electric transports of metallic- and semiconducting-enriched single-wall carbon nanotube networks

    NASA Astrophysics Data System (ADS)

    Fujimori, Toshihiko; Urita, Koki

    2016-06-01

    We report the selective intercalation of polyiodide chains (I5-) inside the interstitial sites of single-wall carbon nanotube (SWCNT) bundles of which internal sites are pre-encapsulated with monatomic sulfur chains. By using metallic- and semiconducting-enriched SWCNTs with diameter of ˜1 nm, our direct-current electric transport measurements reveal that the I5- intercalation on the metallic- and semiconducting-enriched SWCNT networks exhibits an opposite trend on the temperature dependence of the electric resistance at cryogenic temperature. Based on our analysis using the fluctuation-induced tunneling conduction model, the intercalation of I5- chains into the semiconducting-SWCNTs leads to the increase in energy barriers required for tunneling processes. Since the charge transfer is negligible between I5- chains and the semiconducting-SWCNTs, the main effect of the intercalated I5- on the semiconducting-SWCNTs is to behave as a scattering center below 50 K. In contrast to the semiconducting-SWCNTs, the intercalation of I5- chains into the metallic-SWCNTs results in the suppression of tunneling barriers due to the charge transfer interaction. The energy barrier is further reduced by the encapsulation of I5- chains inside the metallic-SWCNT, implying that the doping effect could be more effectively enhanced by the interaction through the inner spaces of SWCNTs.

  18. Heat welding of non-orthogonal X-junction of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, Xueming; Han, Zhonghe; Li, Yonghua; Chen, Dongci; Zhang, Pu; To, Albert C.

    2012-09-01

    Though X-junctions of single-walled carbon nanotubes (SWCNTs) have been intensively studied, studies concerning non-orthogonal X-junctions are still very rare. In this paper, the heat welding of defect-free non-orthogonal X-junctions with different crossed angles are investigated by molecular dynamics simulations. The difference between the heat welding of non-orthogonal and orthogonal X-junctions is described, and the angle effect on the configuration and stability of the heat welded non-orthogonal X-junctions is discussed. Compared with the orthogonal X-junction, two crossed SWCNTs with a smaller non-orthogonal angle are easier to join by heat welding, and this may be an important reason why the large tubes are difficult to join, whereas large nanotube bundles are easier to observe in experiments.

  19. Temperature Behavior of the Photoluminescence Decay of Semiconducting Carbon Nanotubes: The Effective Lifetime

    SciTech Connect

    Karaiskaj, D.; Mascarenhas, A.; Choi, J. H.; Graff, R.; Strano, M. S.

    2007-01-01

    The temperature dependence of the photoluminescence decay of excitons in single-walled carbon nanotubes was measured for two nanotube species, (7,6) and (7,5), representative of the two nanotube (n-m)mod 3 families. A monotonic increase of the photoluminescence lifetime with decreasing temperature is observed. The external strain induced by lowering the temperature below the freezing point of the solution leads to an overall lowering of the photoluminescence lifetime. This effect indicates that the measured lifetime is defined by the intrinsic electronic properties of carbon nanotubes and could be understood as an exchange interaction between bright and dark excitonic states. We find the lifetime to vary between 223 and 319 ps between 290 and 5 K, obtained by a multiexponential fit, well in agreement with previous experiments.

  20. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review

    NASA Astrophysics Data System (ADS)

    Tang, Malcolm S. Y.; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Loke Show, Pau

    2016-08-01

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology.

  1. Metallic and semiconducting carbon nanotubes separation using an aqueous two-phase separation technique: a review.

    PubMed

    Tang, Malcolm S Y; Ng, Eng-Poh; Juan, Joon Ching; Ooi, Chien Wei; Ling, Tau Chuan; Woon, Kai Lin; Show, Pau Loke

    2016-08-19

    It is known that carbon nanotubes show desirable physical and chemical properties with a wide array of potential applications. Nonetheless, their potential has been hampered by the difficulties in acquiring high purity, chiral-specific tubes. Considerable advancement has been made in terms of the purification of carbon nanotubes, for instance chemical oxidation, physical separation, and myriad combinations of physical and chemical methods. The aqueous two-phase separation technique has recently been demonstrated to be able to sort carbon nanotubes based on their chirality. The technique requires low cost polymers and salt, and is able to sort the tubes based on their diameter as well as metallicity. In this review, we aim to provide a review that could stimulate innovative thought on the progress of a carbon nanotubes sorting method using the aqueous two-phase separation method, and present possible future work and an outlook that could enhance the methodology. PMID:27396920

  2. Photoinduced Spontaneous Free-Carrier Generation in Semiconducting Single-Walled Carbon Nanotubes

    SciTech Connect

    Park, Jaehong; Reid, Obadiah G.; Blackburn, Jeffrey L.; Rumbles, Garry

    2015-11-04

    The strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Despite these large binding energies, reported photoluminescence quantum yields are typically low and some studies suggest that photoexcitation of carbon nanotube excitonic transitions can produce free charge carriers. Here we report the direct measurement of long-lived free-carrier generation in chirality-pure, single-walled carbon nanotubes in a low dielectric solvent. Time-resolved microwave conductivity enables contactless and quantitative measurement of the real and imaginary photoconductance of individually suspended nanotubes. We found that the conditions of the microwave conductivity measurement allow us to avoid the complications of most previous measurements of nanotube free-carrier generation, including tube–tube/tube–electrode contact, dielectric screening by nearby excitons and many-body interactions. At low photon fluence (approximately 0.05 excitons per μm length of tubes), we directly observe free carriers on excitation of the first and second carbon nanotube exciton transitions.

  3. Photoinduced spontaneous free-carrier generation in semiconducting single-walled carbon nanotubes

    PubMed Central

    Park, Jaehong; Reid, Obadiah G.; Blackburn, Jeffrey L.; Rumbles, Garry

    2015-01-01

    Strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Despite these large binding energies, reported photoluminescence quantum yields are typically low and some studies suggest that photoexcitation of carbon nanotube excitonic transitions can produce free charge carriers. Here we report the direct measurement of long-lived free-carrier generation in chirality-pure, single-walled carbon nanotubes in a low dielectric solvent. Time-resolved microwave conductivity enables contactless and quantitative measurement of the real and imaginary photoconductance of individually suspended nanotubes. The conditions of the microwave conductivity measurement allow us to avoid the complications of most previous measurements of nanotube free-carrier generation, including tube–tube/tube–electrode contact, dielectric screening by nearby excitons and many-body interactions. Even at low photon fluence (approximately 0.05 excitons per μm length of tubes), we directly observe free carriers on excitation of the first and second carbon nanotube exciton transitions. PMID:26531728

  4. Photoinduced Spontaneous Free-Carrier Generation in Semiconducting Single-Walled Carbon Nanotubes

    DOE PAGESBeta

    Park, Jaehong; Reid, Obadiah G.; Blackburn, Jeffrey L.; Rumbles, Garry

    2015-11-04

    The strong quantum confinement and low dielectric screening impart single-walled carbon nanotubes with exciton-binding energies substantially exceeding kBT at room temperature. Despite these large binding energies, reported photoluminescence quantum yields are typically low and some studies suggest that photoexcitation of carbon nanotube excitonic transitions can produce free charge carriers. Here we report the direct measurement of long-lived free-carrier generation in chirality-pure, single-walled carbon nanotubes in a low dielectric solvent. Time-resolved microwave conductivity enables contactless and quantitative measurement of the real and imaginary photoconductance of individually suspended nanotubes. We found that the conditions of the microwave conductivity measurement allow us tomore » avoid the complications of most previous measurements of nanotube free-carrier generation, including tube–tube/tube–electrode contact, dielectric screening by nearby excitons and many-body interactions. At low photon fluence (approximately 0.05 excitons per μm length of tubes), we directly observe free carriers on excitation of the first and second carbon nanotube exciton transitions.« less

  5. Transition from direct tunneling to field emission in carbon nanotube intramolecular junctions

    NASA Astrophysics Data System (ADS)

    Chiu, Po-Wen; Roth, Siegmar

    2008-01-01

    Transport measurements through metal-semiconductor carbon nanotube intramolecular junctions were carried out at high gate voltages in which regime the influence of Schottky barrier to charge transport is weak. The I-Vds curves exhibit an inflection point in the form of ln(I /Vds2)-1/Vds, showing a transition of transport mechanism from direct tunneling to field emission. The findings are interpreted in terms of quantum tunneling through a rectanglelike barrier at the junction, with a barrier width of ˜4nm, in good agreement with that observed on pentagon-heptagon defects at nanotube junctions via scanning tunneling spectroscopy.

  6. Realistic-contact-induced enhancement of rectifying in carbon-nanotube/graphene-nanoribbon junctions

    SciTech Connect

    Zhang, Xiang-Hua; Li, Xiao-Fei; Wang, Ling-Ling Xu, Liang; Luo, Kai-Wu

    2014-03-10

    Carbon-nanotube/graphene-nanoribbon junctions were recently fabricated by the controllable etching of single-walled carbon-nanotubes [Wei et al., Nat. Commun. 4, 1374 (2013)] and their electronic transport properties were studied here. First principles results reveal that the transmission function of the junctions show a heavy dependence on the shape of contacts, but rectifying is an inherent property which is insensitive to the details of contacts. Interestingly, the rectifying ratio is largely enhanced in the junction with a realistic contact and the enhancement is insensitive to the details of contact structures. The stability of rectifying suggests a significant feasibility to manufacture realistic all-carbon rectifiers in nanoelectronics.

  7. Effect of Alignment on Transport Properties of Carbon Nanotube/Metallic Junctions

    NASA Technical Reports Server (NTRS)

    Wincheski, Buzz; Namkung, Min; Smits, Jan; Williams, Phillip; Harvey, Robert

    2003-01-01

    Ballistic and spin coherent transport in single walled carbon nanotubes (SWCNT) are predicted to enable high sensitivity single-nanotube devices for strain and magnetic field sensing. Based upon these phenomena, electron beam lithography procedures have been developed to study the transport properties of purified HiPCO single walled carbon nanotubes for development into sensory materials for nondestructive evaluation. Purified nanotubes are dispersed in solvent suspension and then deposited on the device substrate before metallic contacts are defined and deposited through electron beam lithography. This procedure produces randomly dispersed ropes, typically 2 - 20 nm in diameter, of single walled carbon nanotubes. Transport and scanning probe microscopy studies have shown a good correlation between the junction resistance and tube density, alignment, and contact quality. In order to improve transport properties of the junctions a technique has been developed to align and concentrate nanotubes at specific locations on the substrate surface. Lithographic techniques are used to define local areas where high frequency electric fields are to be concentrated. Application of the fields while the substrate is exposed to nanotube-containing solution results in nanotube arrays aligned with the electric field lines. A second electron beam lithography layer is then used to deposit metallic contacts across the aligned tubes. Experimental measurements are presented showing the increased tube alignment and improvement in the transport properties of the junctions.

  8. Toxicological Profiling of Highly Purified Metallic and Semiconducting Single-Walled Carbon Nanotubes in the Rodent Lung and E. coli.

    PubMed

    Wang, Xiang; Mansukhani, Nikhita D; Guiney, Linda M; Lee, Jae-Hyeok; Li, Ruibin; Sun, Bingbing; Liao, Yu-Pei; Chang, Chong Hyun; Ji, Zhaoxia; Xia, Tian; Hersam, Mark C; Nel, André E

    2016-06-28

    The electronic properties of single-walled carbon nanotubes (SWCNTs) are potentially useful for electronics, optics, and sensing applications. Depending on the chirality and diameter, individual SWCNTs can be classified as semiconducting (S-SWCNT) or metallic (M-SWCNT). From a biological perspective, the hazard profiling of purified metallic versus semiconducting SWCNTs has been pursued only in bacteria, with the conclusion that aggregated M-SWCNTs are more damaging to bacterial membranes than S-SWCNTs. However, no comparative studies have been performed in a mammalian system, where most toxicity studies have been undertaken using relatively crude SWCNTs that include a M:S mix at 1:2 ratio. In order to compare the toxicological impact of SWCNTs sorted to enrich them for each of the chirality on pulmonary cells and the intact lung, we used density gradient ultracentrifugation and extensive rinsing to prepare S- and M-SWCNTs that are >98% purified. In vitro screening showed that both tube variants trigger similar amounts of interleukin 1β (IL-1β) and transforming growth factor (TGF-β1) production in THP-1 and BEAS-2B cells, without cytotoxicity. Oropharyngeal aspiration confirmed that both SWCNT variants induce comparable fibrotic effects in the lung and abundance of IL-1β and TGF-β1 release in the bronchoalveolar lavage fluid. There was also no change in the morphology, membrane integrity, and viability of E. coli, in contradistinction to the previously published effects of aggregated tubes on the bacterial membrane. Collectively, these data indicate that the electronic properties and chirality do not independently impact SWCNT toxicological impact in the lung, which is of significance to the safety assessment and incremental use of purified tubes by industry. PMID:27159184

  9. Sorting of large-diameter semiconducting carbon nanotube and printed flexible driving circuit for organic light emitting diode (OLED)

    NASA Astrophysics Data System (ADS)

    Xu, Wenya; Zhao, Jianwen; Qian, Long; Han, Xianying; Wu, Liangzhuan; Wu, Weichen; Song, Minshun; Zhou, Lu; Su, Wenming; Wang, Chao; Nie, Shuhong; Cui, Zheng

    2014-01-01

    A novel approach was developed to sort a large-diameter semiconducting single-walled carbon nanotube (sc-SWCNT) based on copolyfluorene derivative with high yield. High purity sc-SWCNTs inks were obtained by wrapping arc-discharge SWCNTs with poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) aided by sonication and centrifugation in tetrahydrofuran (THF). The sorted sc-SWCNT inks and nanosilver inks were used to print top-gated thin-film transistors (TFTs) on flexible substrates with an aerosol jet printer. The printed TFTs demonstrated low operating voltage, small hysteresis, high on-state current (up to 10-3 A), high mobility and on-off ratio. An organic light emitting diode (OLED) driving circuit was constructed based on the printed TFTs, which exhibited high on-off ratio up to 104 and output current up to 3.5 × 10-4 A at Vscan = -4.5 V and Vdd = 0.8 V. A single OLED was switched on with the driving circuit, showing the potential as backplanes for active matrix OLED applications.A novel approach was developed to sort a large-diameter semiconducting single-walled carbon nanotube (sc-SWCNT) based on copolyfluorene derivative with high yield. High purity sc-SWCNTs inks were obtained by wrapping arc-discharge SWCNTs with poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) aided by sonication and centrifugation in tetrahydrofuran (THF). The sorted sc-SWCNT inks and nanosilver inks were used to print top-gated thin-film transistors (TFTs) on flexible substrates with an aerosol jet printer. The printed TFTs demonstrated low operating voltage, small hysteresis, high on-state current (up to 10-3 A), high mobility and on-off ratio. An organic light emitting diode (OLED) driving circuit was constructed based on the printed TFTs, which exhibited high on-off ratio up to 104 and output current up to 3.5 × 10-4 A at Vscan = -4.5 V and Vdd = 0.8 V. A single OLED was switched on with the driving

  10. CoPt/CeO2 catalysts for the growth of narrow diameter semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Tang, Lei; Li, Taotao; Li, Chaowei; Ling, Lin; Zhang, Kai; Yao, Yagang

    2015-11-01

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 +/- 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition, electronic transport measurements also confirm that the Ion/Ioff ratio is mainly in the order of ~103. This work provides an effective strategy for the facile fabrication of narrow diameter distributed s-SWNTs, which will be beneficial to fundamental research and the broad application of SWNTs for future nanoelectronics.For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 +/- 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition

  11. A rational design for the separation of metallic and semiconducting single-walled carbon nanotubes using a magnetic field

    NASA Astrophysics Data System (ADS)

    Luo, Chengzhi; Wan, Da; Jia, Junji; Li, Delong; Pan, Chunxu; Liao, Lei

    2016-06-01

    The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm2 V-1 s-1 and an on/off ratio of 106. We also established a model to quantitatively calculate the percentage of m-SWNTs on the substrate and this model shows a good match with the experimental data. Furthermore, our rational design also provides a new avenue for the growth of SWNTs with specific chirality and manipulated arrangement due to the difference of magnetic susceptibilities between different diameters, chiralities, and types.The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm2 V-1 s-1 and an on/off ratio of 106. We also established a model to quantitatively calculate the percentage of m

  12. Resonant transport through a carbon nanotube junction exposed to an ac field.

    PubMed

    Shafranjuk, S E

    2011-12-14

    The electron transport through a carbon nanotube (CNT) double barrier junction exposed to an external electromagnetic field is studied. The electron spectrum in the quantum well (QW) formed by the junction bears relativistic features. We examine how the ac field affects the level quantization versus the ac field parameters and chirality. We find that the transport through the junction changes dramatically versus the ac field frequency and amplitude. These changes are pronounced in the junction's differential conductance, which allows judgment about the role of relativistic effects in the CNT QW structures. PMID:22109843

  13. CoPt/CeO2 catalysts for the growth of narrow diameter semiconducting single-walled carbon nanotubes.

    PubMed

    Tang, Lei; Li, Taotao; Li, Chaowei; Ling, Lin; Zhang, Kai; Yao, Yagang

    2015-12-14

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, effective techniques for the growth of semiconducting SWNTs (s-SWNTs) with a specific diameter are still a great challenge. Herein, we report a facile strategy for the selective growth of narrow diameter distributed s-SWNTs using CoPt/CeO2 catalysts. The addition of Pt into a Co catalyst dramatically reduces the diameter distributions and even the chirality distributions of the as-grown SWNTs. Oxygen vacancies that are provided by mesoporous CeO2 are responsible for creating an oxidative environment to in situ etch metallic SWNTs (m-SWNTs). Atomic force microscope (AFM) and Raman spectroscopy characterizations indicate a narrow diameter distribution of 1.32 ± 0.03 nm and the selective growth of s-SWNTs to 93%, respectively. In addition, electronic transport measurements also confirm that the Ion/Ioff ratio is mainly in the order of ∼10(3). This work provides an effective strategy for the facile fabrication of narrow diameter distributed s-SWNTs, which will be beneficial to fundamental research and the broad application of SWNTs for future nanoelectronics. PMID:26553394

  14. Intra- and inter-tube exciton relaxation dynamics in high purity semiconducting and metallic single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ichida, Masao; Saito, Shingo; Miyata, Yasumitsu; Yanagi, Kazuhiro; Kataura, Hiromichi; Ando, Hiroaki

    2013-02-01

    We have measured the exciton and carrier dynamics in the high purity semiconducting (S-) and metallic (M-) single-walled carbon nanotubes (SWNTs) in the isolated and aggregated (bundled) forms. The exciton relaxation decay times are measured by using the pump-probe spectroscopy. For bundled samples, the relaxation time becomes shorter than that for isolated SWNTs sample, because of the existence of inter-tube relaxation. We estimate the relaxation rates from S-SWNT to S-SWNT and S-SWNT to M-SWNT using the decay times for isolated SWNTs, high purity S-SWNTs bundle, and doped S-SWNTs in high purity M-SWNTs bundle. For S-SWNTs, inter-tube relaxation plays an important role in the relaxation dynamics. However, for M-SWNTs, the inter-tube relaxation is not so important, and the transition energy and intensity of exciton in M-SWNTs is strongly affected by the photoexcited carriers which plays like as photo doping.

  15. Separation of the semiconducting and the metallic types of single-wall carbon nanotube by electrophoresis method

    NASA Astrophysics Data System (ADS)

    Chen, Hsi-Chao; Yen, Chih-Feng; Chen, Guan-Jhen; Hsiao, Tzu-Ti; Zhou, Yang; Huang, Kuo-Ting; Lee, Hsin-Ta; Yang, Wan-Ting

    2014-09-01

    This study was to separate the semiconducting and the metallic types of single-wall carbon nanotubes (SWNTs) by electrophoresis with the different dispersants that are deoxyribonucleic acid (DNA), Triton X-100 and sodium dodecyl sulfate (SDS), respectively. The dispersants modify the surface of SWNTs and disperse in the de-ionized water. and used electric power supply 100V to electrophoresis. However, the different dispersants such as DNA, Triton X-100 and SDS coated on SWNTs have different property of electronic field. Hence, in the same power of electrophoresis was applied to separate out s-SWNT and m-SWNT from the raw-SWNT. In addition, the DNA base pair and quantitative can be determine by electrophoresis with standard mark. The electrophoresis has features that low sample need, low energy required and efficiently for this fabrication. The results of Raman spectrum could verify the separation efficiency and determine the electrical of the samples with the radial breathing mode (RBM, 100-400cm-1) of SWNT. After the dispersion process with DNA, a new peak (~1450 cm-1) has been observed between D-band (~1350cm-1) and G-band (~1550cm-1) that also can identify s-SWNT and m-SWNT.

  16. Selective Dispersion of Highly Pure Large-Diameter Semiconducting Carbon Nanotubes by a Flavin for Thin-Film Transistors.

    PubMed

    Park, Minsuk; Kim, Somin; Kwon, Hyeokjae; Hong, Sukhyun; Im, Seongil; Ju, Sang-Yong

    2016-09-01

    Scalable and simple methods for selective extraction of pure, semiconducting (s) single-walled carbon nanotubes (SWNTs) is of profound importance for electronic and photovoltaic applications. We report a new, one-step procedure to obtain respective large-diameter s- and metallic (m)-SWNT enrichment purity in excess of 99% and 78%, respectively, via interaction between the aromatic dispersing agent and SWNTs. The approach utilizes N-dodecyl isoalloxazine (FC12) as a surfactant in conjunction with sonication and benchtop centrifugation methods. After centrifugation, the supernatant is enriched in s-SWNTs with less carbonaceous impurities, whereas precipitate is enhanced in m-SWNTs. In addition, the use of an increased centrifugal force enhances both the purity and population of larger diameter s-SWNTs. Photoinduced energy transfer from FC12 to SWNTs is facilitated by respective electronic level alignment. Owing to its peculiar photoreduction capability, FC12 can be employed to precipitate SWNTs upon UV irradiation and observe absorption of higher optical transitions of SWNTs. A thin-film transistor prepared from a dispersion of enriched s-SWNTs was fabricated to verify electrical performance of the sorted sample and was observed to display p-type conductance with an average on/off ratio over 10(6) and an average mobility over 10 cm(2)/V·s. PMID:27538495

  17. A rational design for the separation of metallic and semiconducting single-walled carbon nanotubes using a magnetic field.

    PubMed

    Luo, Chengzhi; Wan, Da; Jia, Junji; Li, Delong; Pan, Chunxu; Liao, Lei

    2016-07-14

    The separation of metallic (m-) and semiconducting (s-) single-walled carbon nanotubes (SWNTs) without causing contamination and damage is a major challenge for SWNT-based devices. As a facile and nondestructive tool, the use of a magnetic field could be an ideal strategy to separate m-/s-SWNTs, based on the difference of magnetic susceptibilities. Here, we designed a novel magnetic field-assisted floating catalyst chemical vapor deposition system to separate m-/s-SWNTs. Briefly, m-SWNTs are attracted toward the magnetic pole, leaving s-SWNTs on the substrate. By using this strategy, s-SWNTs with a purity of 99% could be obtained, which is enough to construct high-performance transistors with a mobility of 230 cm(2) V(-1) s(-1) and an on/off ratio of 10(6). We also established a model to quantitatively calculate the percentage of m-SWNTs on the substrate and this model shows a good match with the experimental data. Furthermore, our rational design also provides a new avenue for the growth of SWNTs with specific chirality and manipulated arrangement due to the difference of magnetic susceptibilities between different diameters, chiralities, and types. PMID:27315328

  18. Radio Frequency Transistors Using Aligned Semiconducting Carbon Nanotubes with Current-Gain Cutoff Frequency and Maximum Oscillation Frequency Simultaneously Greater than 70 GHz.

    PubMed

    Cao, Yu; Brady, Gerald J; Gui, Hui; Rutherglen, Chris; Arnold, Michael S; Zhou, Chongwu

    2016-07-26

    In this paper, we report record radio frequency (RF) performance of carbon nanotube transistors based on combined use of a self-aligned T-shape gate structure, and well-aligned, high-semiconducting-purity, high-density polyfluorene-sorted semiconducting carbon nanotubes, which were deposited using dose-controlled, floating evaporative self-assembly method. These transistors show outstanding direct current (DC) performance with on-current density of 350 μA/μm, transconductance as high as 310 μS/μm, and superior current saturation with normalized output resistance greater than 100 kΩ·μm. These transistors create a record as carbon nanotube RF transistors that demonstrate both the current-gain cutoff frequency (ft) and the maximum oscillation frequency (fmax) greater than 70 GHz. Furthermore, these transistors exhibit good linearity performance with 1 dB gain compression point (P1dB) of 14 dBm and input third-order intercept point (IIP3) of 22 dBm. Our study advances state-of-the-art of carbon nanotube RF electronics, which have the potential to be made flexible and may find broad applications for signal amplification, wireless communication, and wearable/flexible electronics. PMID:27327074

  19. A Comprehensive Numerical Investigation on the Mechanical Properties of Hetero-Junction Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ali, Ghavamian; Andreas, Öchsner

    2015-08-01

    A set of forty-three hetero-junction CNTs, made of forty-four homogeneous carbon nanotubes of different chiralities and configurations with all possible hetero-connection types, were numerically simulated, based on the finite element method in a commercial finite element software and their Young's and shear moduli, and critical buckling loads were obtained and evaluated under the tensile, torsional and buckling loads with an assumption of linear elastic deformation and also compared with each other. The comparison of the linear elastic behavior of hetero-junction CNTs and their corresponding fundamental tubes revealed that the size, type of the connection, and the bending angle in the structure of hetero-junction CNTs considerably influences the mechanical properties of these hetero-structures. It was also discovered that the Stone-Wales defect leads to lower elastic and torsional strength of hetero-junction CNTs when compared to homogeneous CNTs. However, the buckling strength of the hetero-junction CNTs was found to lie in the range of the buckling strength of their corresponding fundamental tubes. It was also determined that the shear modulus of hetero-junction carbon nanotubes generally tends to be closer to the shear modulus of their wider fundamental tubes while critical buckling loads of these heterostructures seem to be closer to critical buckling loads of their thinner fundamental tubes. The evaluation of the elastic properties of hetero-junction carbon nanotubes showed that among the hetero-junction models, those with armchair-armchair and zigzag-zigzag kinks have the highest elastic modulus while the models with armchair-zigzag connections show the lowest elastic stiffness. The results from torsion tests also revealed the fact that zigzag-zigzag and armchair-zigzag hetero-junction carbon nanotubes have the highest and the lowest shear modulus, respectively. Finally, it was observed that the highest critical buckling loads belong to armchair

  20. Predicting excitonic gaps of semiconducting single-walled carbon nanotubes from a field theoretic analysis

    DOE PAGESBeta

    Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.

    2015-02-17

    We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. Asmore » a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.« less

  1. Predicting excitonic gaps of semiconducting single-walled carbon nanotubes from a field theoretic analysis

    NASA Astrophysics Data System (ADS)

    Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.

    2015-02-01

    We demonstrate that a nonperturbative framework for the treatment of the excitations of single-walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. We test this theory explicitly on the data reported by Dukovic et al. [Nano Lett. 5, 2314 (2005), 10.1021/nl0518122] and Sfeir et al. [Phys. Rev. B 82, 195424 (2010), 10.1103/PhysRevB.82.195424] and so demonstrate the method works over a wide range of reported excitonic spectra.

  2. Predicting excitonic gaps of semiconducting single-walled carbon nanotubes from a field theoretic analysis

    SciTech Connect

    Konik, Robert M.; Sfeir, Matthew Y.; Misewich, James A.

    2015-02-17

    We demonstrate that a non-perturbative framework for the treatment of the excitations of single walled carbon nanotubes based upon a field theoretic reduction is able to accurately describe experiment observations of the absolute values of excitonic energies. This theoretical framework yields a simple scaling function from which the excitonic energies can be read off. This scaling function is primarily determined by a single parameter, the charge Luttinger parameter of the tube, which is in turn a function of the tube chirality, dielectric environment, and the tube's dimensions, thus expressing disparate influences on the excitonic energies in a unified fashion. As a result, we test this theory explicitly on the data reported in [NanoLetters 5, 2314 (2005)] and [Phys. Rev. B 82, 195424 (2010)] and so demonstrate the method works over a wide range of reported excitonic spectra.

  3. Intensity Ratio of Resonant Raman Modes for (n , m) Enriched Semiconducting Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Piao, Yanmei; Simpson, Jeffrey; Streit, Jason; Ao, Geyou; Fagan, Jeffrey; Hight Walker, Angela

    Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of eleven, chirality-enriched, single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation. The results demonstrate a significantly under-recognized complexity in the evaluation of Raman spectra for the assignment of (n , m) population distributions. Strong chiral angle and mod dependencies affect the intensity ratio of the RBM to G modes and can result in misleading interpretations. Furthermore, we report five additional values for chirality dependent G+ and G- Raman peak positions and intensities, supporting accuracy in literature values, and extending the available data to cover more of the small diameter regime by including the first (5,4) second-order, resonance Raman spectra. Together, the Raman spectral library is demonstrated to be sufficient for decoupling multiple species via a spectral fitting process, and enable fundamental characterization even in mixed chiral population samples.

  4. Interaction of Nucleobases with Semiconducting Nanotubes and Nanocages: Does the Solvent Matter?

    NASA Astrophysics Data System (ADS)

    Wang, Zhoufei; Slough, William; He, Haiying; Pandey, Ravindra; Karna, Shashi

    2013-03-01

    The tremendous advancement in nanotechnology has brought great promise in the area of bio-applications. Nanoscale materials and structures have attracted a lot of interest for their potential applications in biosensing, biorecognition, luminescent probes for DNA, biomedical labeling, drug delivery etc. Gaining fundamental understanding of the interaction of bio-systems with nanomaterials is critical in putting all these applications into full play. Despite the fact that most of these interactions appear in aqueous environment, the solvent effect has often been neglected in previous computational studies. In this talk, we will report our comparison study of nucleobases interacting with BN nanotubes and chalcogenide nanocages with/without considering the aqueous solution, based on first-principles calculations. The results reveal a significant effect from the water solution, which may largely reduce the interaction energy due to the polarization of the dielectric solvent medium.

  5. Intensity Ratio of Resonant Raman Modes for (n,m) Enriched Semiconducting Carbon Nanotubes.

    PubMed

    Piao, Yanmei; Simpson, Jeffrey R; Streit, Jason K; Ao, Geyou; Zheng, Ming; Fagan, Jeffrey A; Hight Walker, Angela R

    2016-05-24

    Relative intensities of resonant Raman spectral features, specifically the radial breathing mode (RBM) and G modes, of 11, chirality-enriched, single-wall carbon nanotube (SWCNT) species were established under second-order optical transition excitation. The results demonstrate an under-recognized complexity in the evaluation of Raman spectra for the assignment of (n,m) population distributions. Strong chiral angle and mod dependencies affect the intensity ratio of the RBM to G modes and can result in misleading interpretations. Furthermore, we report five additional (n,m) values for the chirality-dependent G(+) and G(-) Raman peak positions and intensity ratios; thereby extending the available data to cover more of the smaller diameter regime by including the (5,4) second-order, resonance Raman spectra. Together, the Raman spectral library is demonstrated to be sufficient for decoupling G peaks from multiple species via a spectral fitting process, and enables fundamental characterization even in mixed chiral population samples. PMID:27128733

  6. Is there a Difference in Van Der Waals Interactions between Rare Gas Atoms Adsorbed on Metallic and Semiconducting Single-Walled Carbon Nanotubes?

    SciTech Connect

    Chen, De-Li; Mandeltort, Lynn; Saidi, Wissam A.; Yates, John T.; Cole, Milton W.; Johnson, J. Karl

    2013-03-01

    Differences in polarizabilities of metallic (M) and semiconducting (S) single-walled carbon nanotubes (SWNTs) might give rise to differences in adsorption potentials. We show from experiments and van der Waals-corrected density functional theory (DFT) that binding energies of Xe adsorbed on M- and S-SWNTs are nearly identical. Temperature programmed desorption of Xe on purified M- and S-SWNTs give similar peak temperatures, indicating that desorption kinetics and binding energies are independent of the type of SWNT. Binding energies computed from vdW-corrected DFT are in good agreement with experiments.

  7. Role of inter-tube coupling and quantum interference on electrical transport in carbon nanotube junctions

    NASA Astrophysics Data System (ADS)

    Tripathy, Srijeet; Bhattacharyya, Tarun Kanti

    2016-09-01

    Due to excellent transport properties, Carbon nanotubes (CNTs) show a lot of promise in sensor and interconnect technology. However, recent studies indicate that the conductance in CNT/CNT junctions are strongly affected by the morphology and orientation between the tubes. For proper utilization of such junctions in the development of CNT based technology, it is essential to study the electronic properties of such junctions. This work presents a theoretical study of the electrical transport properties of metallic Carbon nanotube homo-junctions. The study focuses on discerning the role of inter-tube interactions, quantum interference and scattering on the transport properties on junctions between identical tubes. The electronic structure and transport calculations are conducted with an Extended Hückel Theory-Non Equilibrium Green's Function based model. The calculations indicate conductance to be varying with a changing crossing angle, with maximum conductance corresponding to lattice registry, i.e. parallel configuration between the two tubes. Further calculations for such parallel configurations indicate onset of short and long range oscillations in conductance with respect to changing overlap length. These oscillations are attributed to inter-tube coupling effects owing to changing π orbital overlap, carrier scattering and quantum interference of the incident, transmitted and reflected waves at the inter-tube junction.

  8. Large magnetoresistance in Heusler-alloy-based epitaxial magnetic junctions with semiconducting Cu(In0.8Ga0.2)Se2 spacer

    NASA Astrophysics Data System (ADS)

    Kasai, S.; Takahashi, Y. K.; Cheng, P.-H.; Ikhtiar, Ohkubo, T.; Kondou, K.; Otani, Y.; Mitani, S.; Hono, K.

    2016-07-01

    We investigated the structure and magneto-transport properties of magnetic junctions using a Co2Fe(Ga0.5Ge0.5) Heusler alloy as ferromagnetic electrodes and a Cu(In0.8Ga0.2)Se2 (CIGS) semiconductor as spacers. Owing to the semiconducting nature of the CIGS spacer, large magnetoresistance (MR) ratios of 40% at room temperature and 100% at 8 K were obtained for low resistance-area product (RA) values between 0.3 and 3 Ω μm2. Transmission electron microscopy observations confirmed the fully epitaxial growth of the chalcopyrite CIGS layer, and the temperature dependence of RA indicated that the large MR was due to spin dependent tunneling.

  9. Room-temperature resonant tunneling of electrons in carbon nanotube junction quantum wells

    NASA Astrophysics Data System (ADS)

    Biswas, Sujit K.; Schowalter, Leo J.; Jung, Yung Joon; Vijayaraghavan, Aravind; Ajayan, Pulickel M.; Vajtai, Robert

    2005-05-01

    Resonant tunneling structures [M. Bockrath, W. Liang, D. Bozovic, J. H. Hafner, C. B. Lieber, M. Tinkham, and H. Park, Science 291, 283 (2001)], formed between the junction of two single walled nanotubes and the conductive atomic force microscopy tip contact were investigated using current sensing atomic force microscopy. Oscillations in the current voltage characteristics were measured at several positions of the investigated nanotube. The oscillatory behavior is shown to follow a simple quantum mechanical model, dependent on the energy separation in the quantum well formed within the two junctions. Our model shows that these observations seen over several hundreds of nanometers, are possible only if the scattering cross section at defects is small resulting in long phase coherence length, and if the effective mass of the carrier electrons is small. We have calculated the approximate mass of the conduction electrons to be 0.003me.

  10. Photocurrent Quantum Yield in Suspended Carbon Nanotube p-n Junctions.

    PubMed

    Aspitarte, Lee; McCulley, Daniel R; Minot, Ethan D

    2016-09-14

    We study photocurrent generation in individual suspended carbon nanotube p-n junctions using spectrally resolved scanning photocurrent microscopy. Spatial maps of the photocurrent allow us to determine the length of the p-n junction intrinsic region, as well as the role of the n-type Schottky barrier. We show that reverse-bias operation eliminates complications caused by the n-type Schottky barrier and increases the length of the intrinsic region. The absorption cross-section of the CNT is calculated using an empirically verified model, and the effect of substrate reflection is determined using FDTD simulations. We find that the room temperature photocurrent quantum yield is approximately 30% when exciting the carbon nanotube at the S44 and S55 excitonic transitions. The quantum yield value is an order of magnitude larger than previous estimates. PMID:27575386

  11. Landauer-Type Transport Theory for Interacting Quantum Wires: Application to Carbon Nanotube Y Junctions

    NASA Astrophysics Data System (ADS)

    Chen, S.; Trauzettel, B.; Egger, R.

    2002-11-01

    We propose a Landauerlike theory for nonlinear transport in networks of one-dimensional interacting quantum wires (Luttinger liquids). A concrete example of current experimental focus is given by carbon nanotube Y junctions. Our theory has three basic ingredients that allow one to explicitly solve this transport problem: (i) radiative boundary conditions to describe the coupling to external leads, (ii) the Kirchhoff node rule describing charge conservation, and (iii) density matching conditions at every node.

  12. Landauer-type transport theory for interacting quantum wires: application to carbon nanotube y junctions.

    PubMed

    Chen, S; Trauzettel, B; Egger, R

    2002-11-25

    We propose a Landauerlike theory for nonlinear transport in networks of one-dimensional interacting quantum wires (Luttinger liquids). A concrete example of current experimental focus is given by carbon nanotube Y junctions. Our theory has three basic ingredients that allow one to explicitly solve this transport problem: (i) radiative boundary conditions to describe the coupling to external leads, (ii) the Kirchhoff node rule describing charge conservation, and (iii) density matching conditions at every node. PMID:12485088

  13. Multiwall nanotubes with intramolecular junctions (CNx/C): Preparation, rectification, logic gates, and application

    NASA Astrophysics Data System (ADS)

    Hu, Ping'an; Xiao, Kai; Liu, Yunqi; Yu, Gui; Wang, Xianbao; Fu, Lei; Cui, Guanglei; Zhu, Daoben

    2004-06-01

    We prepared a large quantity of multiwall nanotubes with intramolecular junctions (CNx/C) by pyrolysis of iron phthalocyanine with or without an inlet of ammonia gas. The nanotubes consist of two sections, one section made of carbon nitride featuring bamboo-like structure and the other one made of carbon featuring empty hollow cylinder structure, and thus the intramolecular junctions were formed in the middle as a result of being doped or undoped with nitrogen. Nanodiode based on a single CNx/C junction shows reproducible rectifying behavior with a rectification ratio of 1.3×103 at ±2 V. In addition, the nanodiode demonstrated as a half-wave rectifier worked at an input sine wave of 1 kHz. Two CNx/C junctions were configured together to exhibit functions of OR and AND logic gates. Moreover, after substituting the wave-detection silicon diode in common transistor radio set with our nanodiode, the radio set still worked normally, representing an important step toward the potential application for nano-scale devices.

  14. Junction-Controlled Elasticity of Single-Walled Carbon Nanotube Dispersions in Acrylic Copolymer Gels and Solutions

    SciTech Connect

    Schoch, Andrew B.; Shull, Kenneth R.; Brinson, L. Catherine

    2008-08-26

    Oscillatory shear rheometry is used to study the mechanical response of single-walled carbon nanotubes dispersed in solutions of acrylic diblock or triblock copolymers in 2-ethyl-1-hexanol. Thermal transitions in the copolymer solutions provide a route for the easy processing of these composite materials, with excellent dispersion of the nanotubes as verified by near-infrared photoluminescence spectroscopy. The nanotube dispersions form elastic networks with properties that are controlled by the junction points between nanotubes, featuring a temperature-dependent elastic response that is controlled by the dynamic properties of the matrix copolymer solution. The data are consistent with the formation of micelle-like aggregates around the nanotubes. At low temperatures the core-forming poly(methyl methacrylate) blocks are glassy, and the overall mechanical response of the composite does not evolve with time. At higher temperatures the enhanced mobility of the core-forming blocks enables the junctions to achieve more intimate nanotube-nanotube contact, and the composite modulus increases with time. These aging effects are observed in both diblock and triblock copolymer solutions but are partially reversed in the triblock solutions by cooling through the gel transition of the triblock copolymer. This result is attributed to the generation of internal stresses during gelation and the ability of these stresses to break or weaken the nanotube junctions.

  15. Self-formation of highly aligned metallic, semiconducting and single chiral single-walled carbon nanotubes assemblies via a crystal template method

    SciTech Connect

    Kawai, Hideki; Hasegawa, Kai; Yanagi, Kazuhiro; Oyane, Ayako; Naitoh, Yasuhisa

    2014-09-01

    The fabrication of an aligned array of single-walled carbon nanotubes (SWCNTs) with a single chiral state has been a significant challenge for SWCNT applications as well as for basic science research. Here, we developed a simple, unique technique to produce assemblies in which metallic, semiconducting, and single chiral state SWCNTs were densely and highly aligned. We utilized a crystal of surfactant as a template on which mono-dispersed SWCNTs in solution self-assembled. Micro-Raman measurements and scanning electron microscopy measurements clearly showed that the SWCNTs were highly and densely aligned parallel to the crystal axis, indicating that approximately 70% of the SWCNTs were within 7° of being parallel. Moreover, the assemblies exhibited good field effect transistor characteristics with an on/off ratio of 1.3 × 10{sup 5}.

  16. Photocurrent spectroscopy of exciton and free particle optical transitions in suspended carbon nanotube pn-junctions

    SciTech Connect

    Chang, Shun-Wen; Theiss, Jesse; Hazra, Jubin; Aykol, Mehmet; Kapadia, Rehan; Cronin, Stephen B.

    2015-08-03

    We study photocurrent generation in individual, suspended carbon nanotube pn-junction diodes formed by electrostatic doping using two gate electrodes. Photocurrent spectra collected under various electrostatic doping concentrations reveal distinctive behaviors for free particle optical transitions and excitonic transitions. In particular, the photocurrent generated by excitonic transitions exhibits a strong gate doping dependence, while that of the free particle transitions is gate independent. Here, the built-in potential of the pn-junction is required to separate the strongly bound electron-hole pairs of the excitons, while free particle excitations do not require this field-assisted charge separation. We observe a sharp, well defined E{sub 11} free particle interband transition in contrast with previous photocurrent studies. Several steps are taken to ensure that the active charge separating region of these pn-junctions is suspended off the substrate in a suspended region that is substantially longer than the exciton diffusion length and, therefore, the photocurrent does not originate from a Schottky junction. We present a detailed model of the built-in fields in these pn-junctions, which, together with phonon-assistant exciton dissociation, predicts photocurrents on the same order of those observed experimentally.

  17. Nanomanipulation and Lithography: The Building (and Modeling) of Carbon Nanotube Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Louie, Richard Nam

    2002-12-01

    Aircraft fuselages suffer alternating stress during takeoffs and landings, and fatigue cracks begin to grow, usually at rivet holes. The detection of these fatigue cracks under installed fasteners in aging aircraft is a major goal of the nondestructive evaluation (NDE) community. The use of giant magnetoresistance (GMR) sensors in electromagnetic (EM) NDE has been increasing rapidly. For example, here at Langley Research Center, a Rotating Probe System (RPS) containing a GMR element has been incorporated into a product to detect deeply buried flaws in aerospace structures. In order to advance this eddy current probe application and many similar ones, research to create smaller, more sensitive and energy-efficient EM sensors has been aggressively pursued. Recent theoretical and experimental work on spin coherent transport supports the feasibility of carbon nanotube (CNT) based magnetic tunnel junctions. In this study, a spatial filtering scheme is presented that improves the signal to noise ratio of the RPS and does not significantly impact the number of false alarms. Signals due to buried flaws occur at higher frequencies than do signals due to rivet tilt or probe misalignment, and the strategy purposefully targets this fact. Furthermore, the spatial filtering scheme exploits decreases in the probe output that are observed immediately preceding and following the peak in output due to a fatigue crack. Using the new filters, an enhanced probability of flaw detection is expected. In the future, even tinier, more sensitive, low-power sensors are envisioned for the rotating probe and other nondestructive inspection systems. These may be comprised of single-walled carbon nanotubes (SWCNTs) that connect two ferromagnetic (FM) electrodes. Theoretical work has been done at Langley to model the electrical and magnetoconductance behavior of such junctions, for systems containing short "armchair" nanotubes. The present work facilitates the modeling of more realistic system

  18. Hetero-junctions of Boron Nitride and Carbon Nanotubes: Synthesis and Characterization

    SciTech Connect

    Yap, Yoke Khin

    2013-03-14

    Hetero-junctions of boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs) are expected to have appealing new properties that are not available from pure BNNTs and CNTs. Theoretical studies indicate that BNNT/CNT junctions could be multifunctional and applicable as memory, spintronic, electronic, and photonics devices with tunable band structures. This will lead to energy and material efficient multifunctional devices that will be beneficial to the society. However, experimental realization of BNNT/CNT junctions was hindered by the absent of a common growth technique for BNNTs and CNTs. In fact, the synthesis of BNNTs was very challenging and may involve high temperatures (up to 3000 degree Celsius by laser ablation) and explosive chemicals. During the award period, we have successfully developed a simple chemical vapor deposition (CVD) technique to grow BNNTs at 1100-1200 degree Celsius without using dangerous chemicals. A series of common catalyst have then been identified for the synthesis of BNNTs and CNTs. Both of these breakthroughs have led to our preliminary success in growing two types of BNNT/CNT junctions and two additional new nanostructures: 1) branching BNNT/CNT junctions and 2) co-axial BNNT/CNT junctions, 3) quantum dots functionalized BNNTs (QDs-BNNTs), 4) BNNT/graphene junctions. We have started to understand their structural, compositional, and electronic properties. Latest results indicate that the branching BNNT/CNT junctions and QDs-BNNTs are functional as room-temperature tunneling devices. We have submitted the application of a renewal grant to continue the study of these new energy efficient materials. Finally, this project has also strengthened our collaborations with multiple Department of Energy's Nanoscale Science Research Centers (NSRCs), including the Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory, and the Center for Integrated Nanotechnologies (CINTs) at Sandia National Laboratories and Los

  19. Nanosoldering carbon nanotube junctions by local chemical vapor deposition for improved device performance.

    PubMed

    Do, Jae-Won; Estrada, David; Xie, Xu; Chang, Noel N; Mallek, Justin; Girolami, Gregory S; Rogers, John A; Pop, Eric; Lyding, Joseph W

    2013-01-01

    The performance of carbon nanotube network (CNN) devices is usually limited by the high resistance of individual nanotube junctions (NJs). We present a novel method to reduce this resistance through a nanoscale chemical vapor deposition (CVD) process. By passing current through the devices in the presence of a gaseous CVD precursor, localized nanoscale Joule heating induced at the NJs stimulates the selective and self-limiting deposition of metallic nanosolder. The effectiveness of this nanosoldering process depends on the work function of the deposited metal (here Pd or HfB2), and it can improve the on/off current ratio of a CNN device by nearly an order of magnitude. This nanosoldering technique could also be applied to other device types where nanoscale resistance components limit overall device performance. PMID:24215439

  20. Facile Isolation of Adsorbent-Free Long and Highly-Pure Chirality-Selected Semiconducting Single-Walled Carbon Nanotubes Using A Hydrogen-bonding Supramolecular Polymer

    PubMed Central

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2015-01-01

    The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only the chiral- or chemically-purity while sacrificing the sem-SWNT intrinsic structural identities by applying strong ultra-sonication and/or chemical modifications. Toward the ultimate purification of the sem-SWNTs, here we report a mild-conditioned extraction of the sem-SWNTs using removable supramolecular hydrogen-bonding polymers (HBPs) that are composed of dicarboxylic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selective extraction. Replacing conventional strong sonication techniques by a simple shaking using HPBs was found to provide long sem-SWNTs (>2.0 μm) with a very high D/G ratio, which was determined by atomic force microscopy observations. The HBPs were readily removed from the nanotube surfaces by an outer stimulus, such as a change in the solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to propose possible structures for the HBP-wrapped sem-SWNTs, furthermore, the mechanism of the chiral selectivity for the sorted sem-SWNTs is well explained by the relationship between the molecular surface area and mass of the HBP/SWNT composites. PMID:26658356

  1. Facile Isolation of Adsorbent-Free Long and Highly-Pure Chirality-Selected Semiconducting Single-Walled Carbon Nanotubes Using A Hydrogen-bonding Supramolecular Polymer

    NASA Astrophysics Data System (ADS)

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2015-12-01

    The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only the chiral- or chemically-purity while sacrificing the sem-SWNT intrinsic structural identities by applying strong ultra-sonication and/or chemical modifications. Toward the ultimate purification of the sem-SWNTs, here we report a mild-conditioned extraction of the sem-SWNTs using removable supramolecular hydrogen-bonding polymers (HBPs) that are composed of dicarboxylic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selective extraction. Replacing conventional strong sonication techniques by a simple shaking using HPBs was found to provide long sem-SWNTs (>2.0 μm) with a very high D/G ratio, which was determined by atomic force microscopy observations. The HBPs were readily removed from the nanotube surfaces by an outer stimulus, such as a change in the solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to propose possible structures for the HBP-wrapped sem-SWNTs, furthermore, the mechanism of the chiral selectivity for the sorted sem-SWNTs is well explained by the relationship between the molecular surface area and mass of the HBP/SWNT composites.

  2. Facile Isolation of Adsorbent-Free Long and Highly-Pure Chirality-Selected Semiconducting Single-Walled Carbon Nanotubes Using A Hydrogen-bonding Supramolecular Polymer.

    PubMed

    Toshimitsu, Fumiyuki; Nakashima, Naotoshi

    2015-01-01

    The ideal form of semiconducting-single-walled carbon nanotubes (sem-SWNTs) for science and technology is long, defect-free, chirality pure and chemically pure isolated narrow diameter tubes. While various techniques to solubilize and purify sem-SWNTs have been developed, many of them targeted only the chiral- or chemically-purity while sacrificing the sem-SWNT intrinsic structural identities by applying strong ultra-sonication and/or chemical modifications. Toward the ultimate purification of the sem-SWNTs, here we report a mild-conditioned extraction of the sem-SWNTs using removable supramolecular hydrogen-bonding polymers (HBPs) that are composed of dicarboxylic- or diaminopyridyl-fluorenes with ~70%-(8,6)SWNT selective extraction. Replacing conventional strong sonication techniques by a simple shaking using HPBs was found to provide long sem-SWNTs (>2.0 μm) with a very high D/G ratio, which was determined by atomic force microscopy observations. The HBPs were readily removed from the nanotube surfaces by an outer stimulus, such as a change in the solvent polarities, to provide chemically pure (8,6)-enriched sem-SWNTs. We also describe molecular mechanics calculations to propose possible structures for the HBP-wrapped sem-SWNTs, furthermore, the mechanism of the chiral selectivity for the sorted sem-SWNTs is well explained by the relationship between the molecular surface area and mass of the HBP/SWNT composites. PMID:26658356

  3. Flexible infrared detectors based on p-n junctions of multi-walled carbon nanotubes.

    PubMed

    Huang, Zhenlong; Gao, Min; Yan, Zhuocheng; Pan, Taisong; Liao, Feiyi; Lin, Yuan

    2016-05-14

    Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm(-2) even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors. PMID:27101973

  4. Electron Transport through Polyene Junctions in between Carbon Nanotubes: an Ab Initio Realization

    NASA Astrophysics Data System (ADS)

    Chen, Yiing-Rei; Chen, Kai-Yu; Dou, Kun-Peng; Tai, Jung-Shen; Lee, Hsin-Han; Kaun, Chao-Cheng

    With both ab initio and tight-binding model calculations, we study a system of polyene bridged armchair carbon nanotube electrodes, considering one-polyene and two-polyene cases, to address aspects of quantum transport through junctions with multiple conjugated molecules. The ab initio results of the two-polyene cases not only show the interference effect in transmission, but also the sensitive dependence of such effect on the combination of relative contact sites, which agrees nicely with the tight-binding model. Moreover, we show that the discrepancy mainly brought by ab initio relaxation provides an insight into the influence upon transmission spectra, from the junction's geometry, bonding and effective potential. This work was supported by the Ministry of Science and Technology of the Republic of China under Grant Nos. 99-2112-M-003-012-MY2 and 103-2622-E-002-031, and the National Center for Theoretical Sciences of Taiwan.

  5. Electronic transport in biphenyl single-molecule junctions with carbon nanotubes electrodes: The role of molecular conformation and chirality

    SciTech Connect

    Brito Silva, C. A. Jr.; Granhen, E. R.; Silva, S. J. S. da; Leal, J. F. P.; Del Nero, J.; Pinheiro, F. A.

    2010-08-15

    We investigate, by means of ab initio calculations, electronic transport in molecular junctions composed of a biphenyl molecule attached to metallic carbon nanotubes. We find that the conductance is proportional to cos{sup 2} {theta}, with {theta} the angle between phenyl rings, when the Fermi level of the contacts lies within the frontier molecular orbitals energy gap. This result, which agrees with experiments in biphenyl junctions with nonorganic contacts, suggests that the cos{sup 2} {theta} law has a more general applicability, irrespective of the nature of the electrodes. We calculate the geometrical degree of chirality of the junction, which only depends on the atomic positions, and demonstrate that it is not only proportional to cos{sup 2} {theta} but also is strongly correlated with the current through the system. These results indicate that molecular conformation plays the preponderant role in determining transport properties of biphenyl-carbon nanotubes molecular junctions.

  6. Role of pH controlled DNA secondary structures in the reversible dispersion/precipitation and separation of metallic and semiconducting single-walled carbon nanotubes.

    PubMed

    Maji, Basudeb; Samanta, Suman K; Bhattacharya, Santanu

    2014-04-01

    Single-stranded DNA (ss-DNA) oligomers (dA20, d[(C3TA2)3C3] or dT20) are able to disperse single-walled carbon nanotubes (SWNTs) in water at pH 7 through non-covalent wrapping on the nanotube surface. At lower pH, an alteration of the DNA secondary structure leads to precipitation of the SWNTs from the dispersion. The structural change of dA20 takes place from the single-stranded to the A-motif form at pH 3.5 while in case of d[(C3TA2)3C3] the change occurs from the single-stranded to the i-motif form at pH 5. Due to this structural change, the DNA is no longer able to bind the nanotube and hence the SWNT precipitates from its well-dispersed state. However, this could be reversed on restoring the pH to 7, where the DNA again relaxes in the single-stranded form. In this way the dispersion and precipitation process could be repeated over and over again. Variable temperature UV-Vis-NIR and CD spectroscopy studies showed that the DNA-SWNT complexes were thermally stable even at ∼90 °C at pH 7. Broadband NIR laser (1064 nm) irradiation also demonstrated the stability of the DNA-SWNT complex against local heating introduced through excitation of the carbon nanotubes. Electrophoretic mobility shift assay confirmed the formation of a stable DNA-SWNT complex at pH 7 and also the generation of DNA secondary structures (A/i-motif) upon acidification. The interactions of ss-DNA with SWNTs cause debundling of the nanotubes from its assembly. Selective affinity of the semiconducting SWNTs towards DNA than the metallic ones enables separation of the two as evident from spectroscopic as well as electrical conductivity studies. PMID:24569668

  7. Flexible infrared detectors based on p-n junctions of multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Huang, Zhenlong; Gao, Min; Yan, Zhuocheng; Pan, Taisong; Liao, Feiyi; Lin, Yuan

    2016-05-01

    Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm-2 even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors.Different types of multi-walled carbon nanotubes (CNTs), synthesized by chemical vapor deposition, are used to fabricate infrared (IR) detectors on flexible substrates based on CNT p-n junctions. It is found that this kind of detector is sensitive to infrared signals with a power density as low as 90 μW mm-2 even at room temperature. Besides, unlike other devices, the detector with this unique structure can be bent for 100 cycles without any damage and its functionality does not degenerate once it recovers to the initial state. The results give a good reference for developing efficient, low-cost, and flexible IR detectors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08791k

  8. Role of pH controlled DNA secondary structures in the reversible dispersion/precipitation and separation of metallic and semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Maji, Basudeb; Samanta, Suman K.; Bhattacharya, Santanu

    2014-03-01

    Single-stranded DNA (ss-DNA) oligomers (dA20, d[(C3TA2)3C3] or dT20) are able to disperse single-walled carbon nanotubes (SWNTs) in water at pH 7 through non-covalent wrapping on the nanotube surface. At lower pH, an alteration of the DNA secondary structure leads to precipitation of the SWNTs from the dispersion. The structural change of dA20 takes place from the single-stranded to the A-motif form at pH 3.5 while in case of d[(C3TA2)3C3] the change occurs from the single-stranded to the i-motif form at pH 5. Due to this structural change, the DNA is no longer able to bind the nanotube and hence the SWNT precipitates from its well-dispersed state. However, this could be reversed on restoring the pH to 7, where the DNA again relaxes in the single-stranded form. In this way the dispersion and precipitation process could be repeated over and over again. Variable temperature UV-Vis-NIR and CD spectroscopy studies showed that the DNA-SWNT complexes were thermally stable even at ~90 °C at pH 7. Broadband NIR laser (1064 nm) irradiation also demonstrated the stability of the DNA-SWNT complex against local heating introduced through excitation of the carbon nanotubes. Electrophoretic mobility shift assay confirmed the formation of a stable DNA-SWNT complex at pH 7 and also the generation of DNA secondary structures (A/i-motif) upon acidification. The interactions of ss-DNA with SWNTs cause debundling of the nanotubes from its assembly. Selective affinity of the semiconducting SWNTs towards DNA than the metallic ones enables separation of the two as evident from spectroscopic as well as electrical conductivity studies.Single-stranded DNA (ss-DNA) oligomers (dA20, d[(C3TA2)3C3] or dT20) are able to disperse single-walled carbon nanotubes (SWNTs) in water at pH 7 through non-covalent wrapping on the nanotube surface. At lower pH, an alteration of the DNA secondary structure leads to precipitation of the SWNTs from the dispersion. The structural change of dA20 takes place

  9. Single Walled Carbon Nanotube-Based Junction Biosensor for Detection of Escherichia coli

    PubMed Central

    Yamada, Kara; Kim, Chong-Tai; Kim, Jong-Hoon; Chung, Jae-Hyun; Lee, Hyeon Gyu; Jun, Soojin

    2014-01-01

    Foodborne pathogen detection using biomolecules and nanomaterials may lead to platforms for rapid and simple electronic biosensing. Integration of single walled carbon nanotubes (SWCNTs) and immobilized antibodies into a disposable bio-nano combinatorial junction sensor was fabricated for detection of Escherichia coli K-12. Gold tungsten wires (50 µm diameter) coated with polyethylenimine (PEI) and SWCNTs were aligned to form a crossbar junction, which was functionalized with streptavidin and biotinylated antibodies to allow for enhanced specificity towards targeted microbes. In this study, changes in electrical current (ΔI) after bioaffinity reactions between bacterial cells (E. coli K-12) and antibodies on the SWCNT surface were monitored to evaluate the sensor's performance. The averaged ΔI increased from 33.13 nA to 290.9 nA with the presence of SWCNTs in a 108 CFU/mL concentration of E. coli, thus showing an improvement in sensing magnitude. Electrical current measurements demonstrated a linear relationship (R2 = 0.973) between the changes in current and concentrations of bacterial suspension in range of 102–105 CFU/mL. Current decreased as cell concentrations increased, due to increased bacterial resistance on the bio-nano modified surface. The detection limit of the developed sensor was 102 CFU/mL with a detection time of less than 5 min with nanotubes. Therefore, the fabricated disposable junction biosensor with a functionalized SWCNT platform shows potential for high-performance biosensing and application as a detection device for foodborne pathogens. PMID:25233366

  10. Geometric and electronic structure of carbon nanotube networks: 'super'-carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Coluci, V. R.; Galvão, D. S.; Jorio, A.

    2006-02-01

    Structures of the so-called super-carbon nanotubes are proposed. These structures are built from single walled carbon nanotubes connected by Y-like junctions forming a 'super'-sheet that is then rolled into a seamless cylinder. Such a procedure can be repeated several times, generating a fractal structure. This procedure is not limited to carbon nanotubes, and can be easily modified for application to other systems. Tight binding total energy and density of states calculations showed that the 'super'-sheets and tubes are stable and predicted to present metallic and semiconducting behaviour.

  11. Carbon nanotube intramolecular p-i-n junction diodes with symmetric and asymmetric contacts

    PubMed Central

    Chen, Changxin; Liao, Chenghao; Wei, Liangming; Zhong, Hanqing; He, Rong; Liu, Qinran; Liu, Xiaodong; Lai, Yunfeng; Song, Chuanjuan; Jin, Tiening; Zhang, Yafei

    2016-01-01

    A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~102 for the device with the Au/Au symmetric contact to >103 for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current. PMID:26915400

  12. A p-i-n junction diode based on locally doped carbon nanotube network

    PubMed Central

    Liu, Xiaodong; Chen, Changxin; Wei, Liangming; Hu, Nantao; Song, Chuanjuan; Liao, Chenghao; He, Rong; Dong, Xusheng; Wang, Ying; Liu, Qinran; Zhang, Yafei

    2016-01-01

    A p-i-n junction diode constructed by the locally doped network of single-walled carbon nanotubes (SWNTs) was investigated. In this diode, the two opposite ends of the SWNT-network channel were selectively doped by triethyloxonium hexachloroantimonate (OA) and polyethylenimine (PEI) to obtain the air-stable p- and n-type SWNTs respectively while the central area of the SWNT-network remained intrinsic state, resulting in the formation of a p-i-n junction with a strong built-in electronic field in the SWNTs. The results showed that the forward current and the rectification ratio of the diode increased as the doping degree increased. The forward current of the device could also be increased by decreasing the channel length. A high-performance p-i-n junction diode with a high rectification ratio (~104), large forward current (~12.2 μA) and low reverse saturated current (~1.8 nA) was achieved with the OA and PEI doping time of 5 h and 18 h for a channel length of ~6 μm. PMID:26996610

  13. Carbon nanotube intramolecular p-i-n junction diodes with symmetric and asymmetric contacts.

    PubMed

    Chen, Changxin; Liao, Chenghao; Wei, Liangming; Zhong, Hanqing; He, Rong; Liu, Qinran; Liu, Xiaodong; Lai, Yunfeng; Song, Chuanjuan; Jin, Tiening; Zhang, Yafei

    2016-01-01

    A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~10(2) for the device with the Au/Au symmetric contact to >10(3) for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current. PMID:26915400

  14. A p-i-n junction diode based on locally doped carbon nanotube network

    NASA Astrophysics Data System (ADS)

    Liu, Xiaodong; Chen, Changxin; Wei, Liangming; Hu, Nantao; Song, Chuanjuan; Liao, Chenghao; He, Rong; Dong, Xusheng; Wang, Ying; Liu, Qinran; Zhang, Yafei

    2016-03-01

    A p-i-n junction diode constructed by the locally doped network of single-walled carbon nanotubes (SWNTs) was investigated. In this diode, the two opposite ends of the SWNT-network channel were selectively doped by triethyloxonium hexachloroantimonate (OA) and polyethylenimine (PEI) to obtain the air-stable p- and n-type SWNTs respectively while the central area of the SWNT-network remained intrinsic state, resulting in the formation of a p-i-n junction with a strong built-in electronic field in the SWNTs. The results showed that the forward current and the rectification ratio of the diode increased as the doping degree increased. The forward current of the device could also be increased by decreasing the channel length. A high-performance p-i-n junction diode with a high rectification ratio (~104), large forward current (~12.2 μA) and low reverse saturated current (~1.8 nA) was achieved with the OA and PEI doping time of 5 h and 18 h for a channel length of ~6 μm.

  15. Carbon nanotube intramolecular p-i-n junction diodes with symmetric and asymmetric contacts

    NASA Astrophysics Data System (ADS)

    Chen, Changxin; Liao, Chenghao; Wei, Liangming; Zhong, Hanqing; He, Rong; Liu, Qinran; Liu, Xiaodong; Lai, Yunfeng; Song, Chuanjuan; Jin, Tiening; Zhang, Yafei

    2016-02-01

    A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~102 for the device with the Au/Au symmetric contact to >103 for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current.

  16. Mechanics of lipid bilayer junctions affecting the size of a connecting lipid nanotube

    NASA Astrophysics Data System (ADS)

    Karlsson, Roger; Kurczy, Michael; Grzhibovskis, Richards; Adams, Kelly L.; Ewing, Andrew G.; Cans, Ann-Sofie; Voinova, Marina V.

    2011-06-01

    In this study we report a physical analysis of the membrane mechanics affecting the size of the highly curved region of a lipid nanotube (LNT) that is either connected between a lipid bilayer vesicle and the tip of a glass microinjection pipette (tube-only) or between a lipid bilayer vesicle and a vesicle that is attached to the tip of a glass microinjection pipette (two-vesicle). For the tube-only configuration (TOC), a micropipette is used to pull a LNT into the interior of a surface-immobilized vesicle, where the length of the tube L is determined by the distance of the micropipette to the vesicle wall. For the two-vesicle configuration (TVC), a small vesicle is inflated at the tip of the micropipette tip and the length of the tube L is in this case determined by the distance between the two interconnected vesicles. An electrochemical method monitoring diffusion of electroactive molecules through the nanotube has been used to determine the radius of the nanotube R as a function of nanotube length L for the two configurations. The data show that the LNT connected in the TVC constricts to a smaller radius in comparison to the tube-only mode and that tube radius shrinks at shorter tube lengths. To explain these electrochemical data, we developed a theoretical model taking into account the free energy of the membrane regions of the vesicles, the LNT and the high curvature junctions. In particular, this model allows us to estimate the surface tension coefficients from R( L) measurements.

  17. Growth of close-packed semiconducting single-walled carbon nanotube arrays using oxygen-deficient TiO2 nanoparticles as catalysts.

    PubMed

    Kang, Lixing; Hu, Yue; Liu, Lili; Wu, Juanxia; Zhang, Shuchen; Zhao, Qiuchen; Ding, Feng; Li, Qingwen; Zhang, Jin

    2015-01-14

    For the application of single-walled carbon nanotubes (SWNTs) in nanoelectronic devices, techniques to obtain horizontally aligned semiconducting SWNTs (s-SWNTs) with higher densities are still in their infancy. We reported herein a rational approach for the preferential growth of densely packed and well-aligned s-SWNTs arrays using oxygen-deficient TiO2 nanoparticles as catalysts. Using this approach, a suitable concentration of oxygen vacancies in TiO2 nanoparticles could form by optimizing the flow rate of hydrogen and carbon sources during the process of SWNT growth, and then horizontally aligned SWNTs with the density of ∼ 10 tubes/μm and the s-SWNT percentage above 95% were successfully obtained on ST-cut quartz substrates. Theoretical calculations indicated that TiO2 nanoparticles with a certain concentration of oxygen vacancies have a lower formation energy between s-SWNT than metallic SWNT (m-SWNT), thus realizing the preferential growth of s-SWNT arrays. Furthermore, this method can also be extended to other semiconductor oxide nanoparticles (i.e., ZnO, ZrO2 and Cr2O3) for the selective growth of s-SWNTs, showing clear potential to the future applications in nanoelectronics. PMID:25539021

  18. Carbon-Nanotube Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Wong, Eric; Schlecht, Erich; Hunt, Brian; Siegel, Peter

    2006-01-01

    Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid

  19. 0-π quantum transition in a carbon nanotube Josephson junction: Universal phase dependence and orbital degeneracy

    NASA Astrophysics Data System (ADS)

    Delagrange, R.; Weil, R.; Kasumov, A.; Ferrier, M.; Bouchiat, H.; Deblock, R.

    2016-05-01

    In a π -Josephson junction, the supercurrent's sign is reversed due to the dephasing of superconducting pairs upon their traversal of the nonsuperconducting part. 0-π quantum transitions are extremely sensitive to electronic and magnetic correlations, providing powerful exploration tools of competing orders. In a quantum dot connected to superconducting reservoirs, the transition is governed by gate voltage. As shown recently, it can also be controlled by the superconducting phase in the case of strong competition between the superconducting proximity effect and Kondo correlations. We investigated here the current-phase relation in a clean carbon nanotube quantum dot, close to orbital degeneracy, in a regime of strong competition between local electronic correlations and superconducting proximity effect. We show that the nature of the transition depends crucially on the occupation and the width of the orbital levels, which determine their respective contribution to transport. When the transport of Cooper pairs takes place through only one of these levels, we find that the phase diagram of the phase-dependent 0-π transition is a universal characteristic of a discontinuous level-crossing quantum transition at zero temperature. In the case where the two levels are involved, the nanotube Josephson current exhibits a continuous 0-π transition, independent of the superconducting phase, revealing a different physical mechanism of the transition.

  20. The computational design of junctions by carbon nanotube insertion into a graphene matrix

    NASA Astrophysics Data System (ADS)

    Mao, Yuliang; Zhong, Jianxin

    2009-09-01

    Using first-principles density functional theory calculations, two types of junction models constructed from armchair and zigzag carbon nanotube (CNT) insertion into a graphene matrix have been envisioned. It has been found that the insertion of the CNT into the graphene matrix leads to the formation of C-C covalent bonds between graphene and the CNT that distort the CNT geometry. However, the hydrogenation of the suspended carbon bonds on the graphene resumes the graphene-like structure of the pristine tube. The calculated band structure of armchair CNT insertion into graphene or hydrogenation graphene opens up a band gap and converts the metallic CNT into a semiconductor. For the zigzag CNT, the sp3 hybridization between the graphene and nanotube alters the band structure of the tube significantly, whereas saturating the dangling bonds of terminal carbon atoms of graphene makes the CNT almost keep the same character of the bands as that in the pristine tube. The synthesis of our designed hybrid structures must be increasingly driven by an interest in molecules that not only have intriguing structures but also have special functions such as hydrogen storage.

  1. Electronically Pure Single-Chirality Semiconducting Single-Walled Carbon Nanotube for Large-Scale Electronic Devices.

    PubMed

    Li, Huaping; Liu, Hongyu; Tang, Yifan; Guo, Wenmin; Zhou, Lili; Smolinski, Nina

    2016-08-17

    Single-walled carbon nanotube (SWCNT) networks deposited from a purple single chirality (6,5) SWCNT aqueous solution were electrically characterized as pure semiconductors based on metal/semiconductor/metal Schottky contacts using both complex instruments and a portable device. Both air-stable PMOS (p-type metal-oxide-semiconductor) and NMOS (n-type metal-oxide-semiconductor, resembling amorphous silicon) thin film transistors were fabricated on (6,5) SWCNT in large scale showing the characteristics of fA off current and ION/IOFF ratio of >1 × 10(8). CMOS (complementary metal-oxide-semiconductor) SWCNT inverter was demonstrated by wire-bonding PMOS (6,5) SWCNT TFT and NMOS (6,5) SWCNT TFT together to achieve the voltage gain as large as 52. PMID:27487382

  2. Ultrafast Terahertz Probes of Interacting Dark Excitons in Chirality-Specific Semiconducting Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Luo, Liang; Chatzakis, Ioannis; Patz, Aaron; Wang, Jigang

    2015-03-01

    Ultrafast terahertz spectroscopy accesses the dark excitonic ground state in resonantly excited (6,5) single-walled carbon nanotubes via internal, direct dipole-allowed transitions between the lowest-lying dark-bright pair state of ˜6 meV . An analytical model reproduces the response that enables the quantitative analysis of transient densities of dark excitons and e -h plasma, oscillator strength, transition energy renormalization, and dynamics. Nonequilibrium, yet stable, quasi-one-dimensional quantum states with dark excitonic correlations rapidly emerge even with increasing off-resonance photoexcitation and experience a unique crossover to complex phase-space filling of both dark and bright pair states, different from dense two- and three-dimensional excitons influenced by the thermalization, cooling, and ionization to free carriers.

  3. Unambiguous Diagnosis of Photoinduced Charge Carrier Signatures in a Stoichiometrically Controlled Semiconducting Polymer-Wrapped Carbon Nanotube Assembly.

    PubMed

    Olivier, Jean-Hubert; Park, Jaehong; Deria, Pravas; Rawson, Jeff; Bai, Yusong; Kumbhar, Amar S; Therien, Michael J

    2015-07-01

    Single-walled carbon nanotube (SWNT)-based nanohybrid compositions based on (6,5) chirality-enriched SWNTs ([(6,5) SWNTs]) and a chiral n-type polymer (S-PBN(b)-Ph4 PDI) that exploits a perylenediimide (PDI)-containing repeat unit are reported; S-PBN(b)-Ph4 PDI-[(6,5) SWNT] superstructures feature a PDI electron acceptor unit positioned at 3 nm intervals along the nanotube surface, thus controlling rigorously SWNT-electron acceptor stoichiometry and organization. Potentiometric studies and redox-titration experiments determine driving forces for photoinduced charge separation (CS) and thermal charge recombination (CR) reactions, as well as spectroscopic signatures of SWNT hole polaron and PDI radical anion (PDI(-.) ) states. Time-resolved pump-probe spectroscopic studies demonstrate that S-PBN(b)-Ph4 PDI-[(6,5) SWNT] electronic excitation generates PDI(-.) via a photoinduced CS reaction (τCS ≈0.4 ps, ΦCS ≈0.97). These experiments highlight the concomitant rise and decay of transient absorption spectroscopic signatures characteristic of the SWNT hole polaron and PDI(-.) states. Multiwavelength global analysis of these data provide two charge-recombination time constants (τCR ≈31.8 and 250 ps) that likely reflect CR dynamics involving both an intimately associated SWNT hole polaron and PDI(-.) charge-separated state, and a related charge-separated state involving PDI(-.) and a hole polaron site produced via hole migration along the SWNT backbone that occurs over this timescale. PMID:26014277

  4. Analysis of longitudinal vibration band gaps in periodic carbon nanotube intramolecular junctions using finite element method

    NASA Astrophysics Data System (ADS)

    Li, Jiaqian; Shen, Haijun

    2015-12-01

    The longitudinal vibration band gaps in periodic (n, 0)-(2n, 0) single-walled carbon nanotube(SWCNT) intramolecular junctions(IMJs) are investigated based on the finite element calculation. The frequency ranges of band gaps in frequency response functions(FRF) simulated by finite element method (FEM) show good agreement with those in band structure obtained by simple spring-mass model. Moreover, a comprehensive parametric study is also conducted to highlight the influences of the geometrical parameters such as the size of unit cell, component ratios of the IMJs and diameters of the CNT segments as well as geometric imperfections on the first band gap. The results show that the frequency ranges and the bandwidth of the gap strongly depend on the geometrical parameters. Furthermore, the influences of geometrical parameters on gaps are nuanced in IMJs with different topological defects. The existence of vibration band gaps in periodic IMJs lends a new insight into the development of CNT-based nano-devices in application of vibration isolation.

  5. A novel nanopin model based on a Y-junction carbon nanotube

    NASA Astrophysics Data System (ADS)

    Zhang, Zhong-Qiang; Zhong, Jun; Ye, Hong-Fei; Liu, Zhen; Cheng, Guang-Gui; Ding, Jian-Ning

    2016-08-01

    A prototype of nanopin based on a Y-junction carbon nanotube (CNT) is first proposed. The loading and unloading processes are investigated by using classical molecular dynamics, considering the influences of the fit dimension, positioning error, thermal effect, and the loading/unloading velocity on the performance of the proposed nanopin. The optimum size of the gap between the nanopin and the through hole in a silicon component is obtained, which is responsible for a desired fixity with the acceptable install resistance. It is found that a proper positioning error in a certain direction associated with the branched structure of the nanopin will facilitate the installation process. The performance of the proposed nanopin is not sensitive to thermal and normal axial velocity of the nanopin, while the unloading direction affects appreciably on the service performance of the nanopin attributed to the orientation of the branched CNT. Particularly, the service performance of the proposed nanopin considerably depends on several special deforming configurations in the loading and unloading processes.

  6. Controlling the magnetic state of a carbon nanotube Josephson junction with the superconducting phase

    NASA Astrophysics Data System (ADS)

    Delagrange, Raphaelle; Weil, R.; Kasumov, A.; Bouchiat, H.; Deblock, R.; Luitz, D. J.; Meden, V.

    The Kondo effect is a many-body phenomenon that screens the magnetic moment of an impurity in a metal. The associated singlet state can be probed in a single impurity by electronic transport in a quantum dot (QD), here made of a carbon nanotube (CNT), which provides a localized electron between the two contacts. Using superconducting leads, one can investigate the competition between the Kondo effect and the superconductivity induced in the CNT. The superconductivity can destroy the Kondo singlet in favor of a magnetic doublet, leading to a sign reversal of the supercurrent in the S-CNT-S junction. This singlet-doublet transition depends on the Kondo temperature and the superconducting gap, as well as the position of the impurity level. We demonstrate experimentally that the superconducting phase difference across the QD can also control this magnetic transition. We use the measurement of the relation between the supercurrent and this superconducting phase as a tool to probe the transition. We show that it has a distinctly anharmonic behavior, that reveals the phase-mediated singlet to doublet transition, in good agreement with finite temperature quantum Monte Carlo calculations. We extract as well a phase diagram of the phase-controlled quantum transition at zero temperature.

  7. p-n junction photodetectors based on macroscopic single-walled carbon nanotube films

    NASA Astrophysics Data System (ADS)

    He, Xiaowei; Nanot, Sébastien; Hauge, Robert H.; Kono, Junichiro

    2013-03-01

    Single-Wall carbon nanotubes (SWCNTs) are promising in use of solar technology and photodetection. There have been many reports about photovoltaic effect in nanoelectronic devices based on individual SWCNTs, but they are limited by miniscule absorption. There has been a growing trend for merging SWNTs into mico- and macroscopic devices to provide more practical applications. Here we report p-n junction photodetectors based on macroscopic SWCNTs film. Factors affecting the PV amplitude and response time have been studied, including substrates, doping level. The maximal responsivity ~ 1 V/W was observed with samples on Teflon tapes, while a fast response time ~ 80 μs was observed with samples on AlN substrates. Hence an optimal combination of photoresponse time and amplitude can be found by choosing proper substrates. We found that the PV amplitude increases nonlinearly with increasing n-doping concentration, indicating the existence of an optimal doping concentration. Finally, we checked photoresponse in a wide wavelength range (360 to 900 nm), and PV was observed throughout, indicating that the device could potential be used as a broadband photodetector.

  8. Nanotechnology with Carbon Nanotubes: Mechanics, Chemistry, and Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak

    2003-01-01

    This viewgraph presentation reviews the Nanotechnology of carbon nanotubes. The contents include: 1) Nanomechanics examples; 2) Experimental validation of nanotubes in composites; 3) Anisotropic plastic collapse; 4) Spatio-temporal scales, yielding single-wall nanotubes; 5) Side-wall functionalization of nanotubes; 6) multi-wall Y junction carbon nanotubes; 7) Molecular electronics with Nanotube junctions; 8) Single-wall carbon nanotube junctions; welding; 9) biomimetic dendritic neurons: Carbon nanotube, nanotube electronics (basics), and nanotube junctions for Devices,

  9. Flexible high-performance carbon nanotube integrated circuits.

    PubMed

    Sun, Dong-ming; Timmermans, Marina Y; Tian, Ying; Nasibulin, Albert G; Kauppinen, Esko I; Kishimoto, Shigeru; Mizutani, Takashi; Ohno, Yutaka

    2011-03-01

    Carbon nanotube thin-film transistors are expected to enable the fabrication of high-performance, flexible and transparent devices using relatively simple techniques. However, as-grown nanotube networks usually contain both metallic and semiconducting nanotubes, which leads to a trade-off between charge-carrier mobility (which increases with greater metallic tube content) and on/off ratio (which decreases). Many approaches to separating metallic nanotubes from semiconducting nanotubes have been investigated, but most lead to contamination and shortening of the nanotubes, thus reducing performance. Here, we report the fabrication of high-performance thin-film transistors and integrated circuits on flexible and transparent substrates using floating-catalyst chemical vapour deposition followed by a simple gas-phase filtration and transfer process. The resulting nanotube network has a well-controlled density and a unique morphology, consisting of long (~10 µm) nanotubes connected by low-resistance Y-shaped junctions. The transistors simultaneously demonstrate a mobility of 35 cm(2) V(-1) s(-1) and an on/off ratio of 6 × 10(6). We also demonstrate flexible integrated circuits, including a 21-stage ring oscillator and master-slave delay flip-flops that are capable of sequential logic. Our fabrication procedure should prove to be scalable, for example, by using high-throughput printing techniques. PMID:21297625

  10. Transport Properties of p-n Junctions Formed in Boron/Nitrogen Doped Carbon Nanotubes and Graphene Nanoribbons

    NASA Astrophysics Data System (ADS)

    Hammouri, Mahmoud; Vasiliev, Igor

    2014-03-01

    We apply ab initio computational methods based on density functional theory to study the transport properties of p-n junctions made of single-walled carbon nanotubes and graphene nanoribbons. The p-n junctions are formed by doping the opposite ends of carbon nanostructures with boron and nitrogen atoms. Our calculations are carried out using the SIESTA electronic structure code combined with the generalized gradient approximation for the exchange-correlation functional. The transport properties are calculated using a self-consistent nonequilibrium Green's function method implemented in the TranSIESTA package. The modeled nanoscale p-n junctions exhibit linear I-V characteristics in the forward bias and nonlinear I-V characteristics with a negative differential resistance in the reverse bias. The computed transmission spectra and the I-V characteristics of the p-n junctions are compared to the results of other theoretical studies and to the available experimental data. Supported by NMSU GREG Award and by NSF CHE-1112388.

  11. PREFACE: Semiconducting oxides Semiconducting oxides

    NASA Astrophysics Data System (ADS)

    Catlow, Richard; Walsh, Aron

    2011-08-01

    Semiconducting oxides are amongst the most widely studied and topical materials in contemporary condensed matter science, with interest being driven both by the fundamental challenges posed by their electronic and magnetic structures and properties, and by the wide range of applications, including those in catalysis and electronic devices. This special section aims to highlight recent developments in the physics of these materials, and to show the link between developing fundamental understanding and key application areas of oxide semiconductors. Several aspects of the physics of this wide and expanding range of materials are explored in this special section. Transparent semiconducting oxides have a growing role in several technologies, but challenges remain in understanding their electronic structure and the physics of charge carriers. A related problem concerns the nature of redox processes and the reactions which interconvert defects and charge carriers—a key issue which may limit the extent to which doping strategies may be used to alter electronic properties. The magnetic structures of the materials pose several challenges, while surface structures and properties are vital in controlling catalytic properties, including photochemical processes. The field profits from and exploits a wide range of contemporary physical techniques—both experimental and theoretical. Indeed, the interplay between experiment and computation is a key aspect of contemporary work. A number of articles describe applications of computational methods whose use, especially in modelling properties of defects in these materials, has a long and successful history. Several papers in this special section relate to work presented at a symposium within the European Materials Research Society (EMRS) meeting held in Warsaw in September 2010, and we are grateful to the EMRS for supporting this symposium. We would also like to thank the editorial staff of Journal of Physics: Condensed Matter for

  12. PREFACE: Semiconducting oxides Semiconducting oxides

    NASA Astrophysics Data System (ADS)

    Catlow, Richard; Walsh, Aron

    2011-08-01

    Semiconducting oxides are amongst the most widely studied and topical materials in contemporary condensed matter science, with interest being driven both by the fundamental challenges posed by their electronic and magnetic structures and properties, and by the wide range of applications, including those in catalysis and electronic devices. This special section aims to highlight recent developments in the physics of these materials, and to show the link between developing fundamental understanding and key application areas of oxide semiconductors. Several aspects of the physics of this wide and expanding range of materials are explored in this special section. Transparent semiconducting oxides have a growing role in several technologies, but challenges remain in understanding their electronic structure and the physics of charge carriers. A related problem concerns the nature of redox processes and the reactions which interconvert defects and charge carriers—a key issue which may limit the extent to which doping strategies may be used to alter electronic properties. The magnetic structures of the materials pose several challenges, while surface structures and properties are vital in controlling catalytic properties, including photochemical processes. The field profits from and exploits a wide range of contemporary physical techniques—both experimental and theoretical. Indeed, the interplay between experiment and computation is a key aspect of contemporary work. A number of articles describe applications of computational methods whose use, especially in modelling properties of defects in these materials, has a long and successful history. Several papers in this special section relate to work presented at a symposium within the European Materials Research Society (EMRS) meeting held in Warsaw in September 2010, and we are grateful to the EMRS for supporting this symposium. We would also like to thank the editorial staff of Journal of Physics: Condensed Matter for

  13. Charge transfer at junctions of a single layer of graphene and a metallic single walled carbon nanotube.

    PubMed

    Paulus, Geraldine L C; Wang, Qing Hua; Ulissi, Zachary W; McNicholas, Thomas P; Vijayaraghavan, Aravind; Shih, Chih-Jen; Jin, Zhong; Strano, Michael S

    2013-06-10

    Junctions between a single walled carbon nanotube (SWNT) and a monolayer of graphene are fabricated and studied for the first time. A single layer graphene (SLG) sheet grown by chemical vapor deposition (CVD) is transferred onto a SiO₂/Si wafer with aligned CVD-grown SWNTs. Raman spectroscopy is used to identify metallic-SWNT/SLG junctions, and a method for spectroscopic deconvolution of the overlapping G peaks of the SWNT and the SLG is reported, making use of the polarization dependence of the SWNT. A comparison of the Raman peak positions and intensities of the individual SWNT and graphene to those of the SWNT-graphene junction indicates an electron transfer of 1.12 × 10¹³ cm⁻² from the SWNT to the graphene. This direction of charge transfer is in agreement with the work functions of the SWNT and graphene. The compression of the SWNT by the graphene increases the broadening of the radial breathing mode (RBM) peak from 3.6 ± 0.3 to 4.6 ± 0.5 cm⁻¹ and of the G peak from 13 ± 1 to 18 ± 1 cm⁻¹, in reasonable agreement with molecular dynamics simulations. However, the RBM and G peak position shifts are primarily due to charge transfer with minimal contributions from strain. With this method, the ability to dope graphene with nanometer resolution is demonstrated. PMID:23281165

  14. Electronic transport in oligo-para-phenylene junctions attached to carbon nanotube electrodes: Transition-voltage spectroscopy and chirality

    SciTech Connect

    Brito Silva, C. A. Jr.; Silva, S. J. S. da; Leal, J. F. P.; Pinheiro, F. A.; Del Nero, J.

    2011-06-15

    We have investigated, by means of a nonequilibrium Green's function method coupled to density functional theory, the electronic transport properties of molecular junctions composed of oligo-para-phenylene (with two, three, four, and five phenyl rings) covalently bridging the gap between metallic carbon nanotubes electrodes. We have found that the current is strongly correlated to a purely geometrical chiral parameter, both on-resonance and off-resonance. The Fowler-Nordheim plot exhibits minima, V{sub min}, that occur whenever the tail of a resonant transmission peak enters in the bias window. This result corroborates the scenario in which the coherent transport model gives the correct interpretation to transition voltage spectroscopy (TVS). We have shown that V{sub min} corresponds to voltages where a negative differential resistance (NDR) occurs. The finding that V{sub min} corresponds to voltages that exhibit NDR, which can be explained only in single-molecule junctions within the coherent transport model, further confirms the applicability of such models to adequately interpret TVS. The fact that the electrodes are organic is at the origin of differences in the behavior of V{sub min} if compared to the case of molecular junctions with nonorganic contacts treated so far.

  15. Mechanical behavior of carbon nanotube and graphene junction as a building block for 3D carbon nanostructures

    NASA Astrophysics Data System (ADS)

    Moradi, Mina; Aghazadeh Mohandesi, Jamshid

    2015-11-01

    The incorporation of defects in junction area of 1D and 2D carbon nanostructures has a major impact on properties of their 3D structures. In the present study, molecular dynamics simulation is utilized to examine the mechanical behavior of graphene sheet (GS) in carbon nanotube (CNT)-GS junctions. The tensile load was applied along the GS in connection with CNTs of different chiralities. The adaptive intermolecular reactive empirical bond order potential was chosen to model C-C interactions. It provided a reliable model for CNT, GS and their junctions. The results revealed that the connection of CNT to the GS with a hole could improve the mechanical properties of defective GS, which appeared to be independent of CNT type. It was found that the high strength C-C bonds postpone the crack propagation and motivates new crack nucleation. When a hole or CNT placed on the GS, it caused stress concentration, exactly along a line on its side. The lower mechanical properties were consequently associated with crack nucleation and propagation on both sides in a way that cracks encountered each other during the failure; while, the cracks in pristine GS propagate parallel to each other and could not encounter each other.

  16. Characterization of the flow of the CO/CO 2 gases through carbon nanotube junctions using molecular dynamic simulations

    NASA Astrophysics Data System (ADS)

    Sabzyan, Hassan; Tavangar, Zahra

    2009-08-01

    A detailed study of the gas flow in carbon nanotubes (CNT) and carbon nanotube junctions (CNTJ) can open the way towards the study of the reaction mixture flow in prospective nano-reactors. In this work, flow of the pure and mixed CO/CO 2 gases through some selected CNTs and three types of CNT1- J-CNT2 CNTJs, ( 12, 12)- J-( 3, 8), ( 12, 8)- J-( 8, 12) and ( 8, 8)- J-( 13, 0), are studied using molecular dynamic simulations. Results of this study show that regardless of the diameter and helicity type of the CNT1 and CNT2, when the flow starts with the molecules in the CNT1, the number density of molecules in the CNT2 is higher than that in the CNT1. Projected radial distribution of the molecules are calculated and analyzed in terms of the molecule-molecule and molecule-wall interactions. The well-structured projected radial distribution results show that the CNT radius and helicity as well as the type of molecules determine the lateral distribution of the gas molecules along the flow.

  17. Length-Sorted, Large-Diameter, Polyfluorene-Wrapped Semiconducting Single-Walled Carbon Nanotubes for High-Density, Short-Channel Transistors.

    PubMed

    Hennrich, Frank; Li, Wenshan; Fischer, Regina; Lebedkin, Sergei; Krupke, Ralph; Kappes, Manfred M

    2016-02-23

    Samples of highly enriched semiconducting SWCNTs with average diameters of 1.35 nm have been prepared by combining PODOF polymer wrapping with size-exclusion chromatography. The purity of the material was determined to be >99.7% from the transfer characteristics of short-channel transistors comprising densely aligned sc-SWCNTs. The transistors have a hole mobility of up to 297 cm(2)V(-1) s(-1) and an On/Off ratio as high as 2 × 10(8). PMID:26792404

  18. Carbon Nanotube Based Molecular Electronics and Motors: A View from Classical and Quantum Dynamics Simulations

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash (Technical Monitor)

    1998-01-01

    The tubular forms of fullerenes popularly known as carbon nanotubes are experimentally produced as single-, multiwall, and rope configurations. The nanotubes and nanoropes have shown to exhibit unusual mechanical and electronic properties. The single wall nanotubes exhibit both semiconducting and metallic behavior. In short undefected lengths they are the known strongest fibers which are unbreakable even when bent in half. Grown in ropes their tensile strength is approximately 100 times greater than steel at only one sixth the weight. Employing large scale classical and quantum molecular dynamics simulations we will explore the use of carbon nanotubes and carbon nanotube junctions in 2-, 3-, and 4-point molecular electronic device components, dynamic strength characterization for compressive, bending and torsional strains, and chemical functionalization for possible use in a nanoscale molecular motor. The above is an unclassified material produced for non-competitive basic research in the nanotechnology area.

  19. Change in Chirality of Semiconducting Single-Walled Carbon Nanotubes Can Overcome Anionic Surfactant Stabilization: A Systematic Study of Aggregation Kinetics

    PubMed Central

    Khan, Iftheker A.; Flora, Joseph R. V.; Nabiul Afrooz, A. R. M.; Aich, Nirupam; Schierz, P. Ariette; Ferguson, P. Lee; Sabo-Attwood, Tara; Saleh, Navid B.

    2015-01-01

    Single-walled carbon nanotubes’ (SWNT) effectiveness in applications is enhanced by debundling or stabilization. Anionic surfactants are known to effectively stabilize SWNTs. However, the role of specific chirality on surfactant-stabilized SWNT aggregation has not been studied to date. The aggregation behavior of chirally enriched (6,5) and (7,6) semiconducting SWNTs, functionalized with three anionic surfactants—sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium deoxycholate (SDOCO)—was evaluated with time-resolved dynamic light scattering. A wide range of mono- (NaCl) and di-valent (CaCl2) electrolytes as well as a 2.5 mg TOC/L Suwannee River humic acid (SRHA) were used as background chemistry. Overall, SDBS showed the most effectiveness in SWNT stability, followed by SDOCO and SDS. However, the relatively larger diameter (7,6) chiral tubes compromised the surfactant stability, compared to (6,5) chiral enrichment, due to enhanced van der Waals interaction. The presence of di-valent electrolytes overshadowed the chirality effects and resulted in similar aggregation behavior for both the SWNT samples. Molecular modeling results enumerated key differences in surfactant conformation on SWNT surfaces and identified interaction energy changes between the two chiralities to delineate aggregation mechanisms. The stability of SWNTs increased in the presence of SRHA under 10 mM monovalent and mixed electrolyte conditions. The results suggest that change in chirality can overcome surfactant stabilization of semiconducting SWNTs. SWNT stability can also be strongly influenced by the anionic surfactant structure. PMID:26855611

  20. Hetero-junction carbon nanotube FET with lightly doped drain and source regions

    NASA Astrophysics Data System (ADS)

    Yousefi, Reza; Doorzad, Leila

    2016-01-01

    In this paper, a new structure was introduced for carbon nanotube (CNT) MOSFET transistors. The proposed structure was composed of two different nanotubes for the source/drain and channel regions. Electrical characteristics of this structure were investigated using nonequilibrium Green’s function approach. Results of the simulations demonstrated that the proposed hetero-structure had almost the same ON-current and much less OFF-current and as a result higher ION/IOFF ratio than the conventional homo-structure. Results of the comparison between switching behavior in equal ION/IOFF ratio showed that, although the proposed structure had longer delay, its power dissipation for every switching event was less than that of the conventional structure. A further comparison of the switching characteristic in equal ON-current values showed that the proposed structure enjoys from shorter delay and also consumes less power-delay product (PDP) when compared to the LDDS structure.

  1. High performance thin film transistors based on regioregular poly(3-dodecylthiophene)-sorted large diameter semiconducting single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Chao; Qian, Long; Xu, Wenya; Nie, Shuhong; Gu, Weibing; Zhang, Jianhui; Zhao, Jianwen; Lin, Jian; Chen, Zheng; Cui, Zheng

    2013-05-01

    In this work, a simple and rapid method to selectively sort semiconducting-SWCNTs (sc-SWCNTs) with large diameters using regioregular poly(3-dodecylthiophene) (rr-P3DDT) is presented. The absorption spectra and Raman spectra demonstrated that metallic species of arc discharge SWCNTs were effectively removed after interaction with rr-P3DDT in toluene with the aid of sonication and centrifugation. The sorted sc-SWCNT inks have been directly used to fabricate thin film transistors (TFTs) by dip-coating, drop-casting and inkjet printing. TFTs with an effective mobility of ~34 cm2 V-1 s-1 and on-off ratios of ~107 have been achieved by dip coating and drop casting the ink on SiO2/Si substrates with pre-patterned interdigitated gold electrode arrays. The printed devices also showed excellent electrical properties with a mobility of up to 6.6 cm2 V-1 s-1 and on-off ratios of up to 105. Printed inverters based on the TFTs have been constructed on glass substrates, showing a maximum voltage gain of 112 at a Vdd of -5 V. This work paves the way for making printable logic circuits for real applications.In this work, a simple and rapid method to selectively sort semiconducting-SWCNTs (sc-SWCNTs) with large diameters using regioregular poly(3-dodecylthiophene) (rr-P3DDT) is presented. The absorption spectra and Raman spectra demonstrated that metallic species of arc discharge SWCNTs were effectively removed after interaction with rr-P3DDT in toluene with the aid of sonication and centrifugation. The sorted sc-SWCNT inks have been directly used to fabricate thin film transistors (TFTs) by dip-coating, drop-casting and inkjet printing. TFTs with an effective mobility of ~34 cm2 V-1 s-1 and on-off ratios of ~107 have been achieved by dip coating and drop casting the ink on SiO2/Si substrates with pre-patterned interdigitated gold electrode arrays. The printed devices also showed excellent electrical properties with a mobility of up to 6.6 cm2 V-1 s-1 and on-off ratios of up to 105

  2. Rectifying performance and negative differential behavior in graphite—chain—carbon nanotube junctions

    SciTech Connect

    Qiu, Ming; Li, Jiangfan; Liew, K. M.; Yuan, Chris

    2014-01-13

    In this paper, the (5, 5) capped carbon nanotubes (CNTs) in contact with different lengths of sp monoatomic chains grown on the surface of graphite substrate are fabricated and its electronic transport properties sandwiched between CNT and graphite electrodes are investigated. The first-principles calculations based on nonequilibrium Green's function in combination with density-functional theory show that their rectifying performance and negative differential resistance behavior are observed under very low biases and obviously are enhanced when the length increases. From our analysis, the charge transfer, transmission spectra, projected density of states and evolutions of molecular orbitals are responsible for these phenomena.

  3. Rectifying performance and negative differential behavior in graphite—chain—carbon nanotube junctions

    NASA Astrophysics Data System (ADS)

    Qiu, Ming; Li, Jiangfan; Liew, K. M.; Yuan, Chris

    2014-01-01

    In this paper, the (5, 5) capped carbon nanotubes (CNTs) in contact with different lengths of sp monoatomic chains grown on the surface of graphite substrate are fabricated and its electronic transport properties sandwiched between CNT and graphite electrodes are investigated. The first-principles calculations based on nonequilibrium Green's function in combination with density-functional theory show that their rectifying performance and negative differential resistance behavior are observed under very low biases and obviously are enhanced when the length increases. From our analysis, the charge transfer, transmission spectra, projected density of states and evolutions of molecular orbitals are responsible for these phenomena.

  4. Ultrafast charge separation at a polymer-single-walled carbon nanotube molecular junction.

    PubMed

    Stranks, Samuel D; Weisspfennig, Christian; Parkinson, Patrick; Johnston, Michael B; Herz, Laura M; Nicholas, Robin J

    2011-01-12

    We have investigated the charge photogeneration dynamics at the interface formed between single-walled carbon nanotubes (SWNTs) and poly(3-hexylthiophene) (P3HT) using a combination of femtosecond spectroscopic techniques. We demonstrate that photoexcitation of P3HT forming a single molecular layer around a SWNT leads to an ultrafast (∼430 fs) charge transfer between the materials. The addition of excess P3HT leads to long-term charge separation in which free polarons remain separated at room temperature. Our results suggest that SWNT-P3HT blends incorporating only small fractions (1%) of SWNTs allow photon-to-charge conversion with efficiencies comparable to those for conventional (60:40) P3HT-fullerene blends, provided that small-diameter tubes are individually embedded in the P3HT matrix. PMID:21105722

  5. Thermionic energy conversion in carbon nanotube networks

    NASA Astrophysics Data System (ADS)

    Li, Chen; Pipe, Kevin; Kevin Pipe's Group Team

    We investigate whether efficient carrier ballistic transport in CNT networks can overcome the parasitic effects of high CNT thermal conductance to yield thermionic (TI) devices with high energy conversion efficiency and/or high cooling power density. We simulate semiconducting single-walled carbon nanotube (SWCNT) structures in which inter-tube junctions provide the necessary filtering of high-energy electrons. Using energy-dependent transmission functions, we compare the performances of various junction types in selective filtering, and then perform Monte Carlo (MC) simulations to study the subsequent relaxation of hot electrons within the SWCNTs. Finally, we examine the parasitic effects of high thermal conductance, accounting for reductions in phonon mean free path due to scattering at inter-tube junctions. The results of the junction transmission, MC, and phonon transport simulations suggest optimal CNT types, junction types, and inter-junction spacings that maximize energy conversion metrics such as efficiency and cooling power density. While certain aspects of electron transport and phonon transport in CNT networks remain unresolved, our simulations suggest that CNT-based networks show promise for TI energy conversion.

  6. Nanotube

    Energy Science and Technology Software Center (ESTSC)

    2007-09-13

    This is a source code to calculate the current-voltage characteristics, the charge distribution and the electrostatic potential in carbon nanotube devices. The code utilizes the non-equilibrium Green's function method, implemented in a tight-binding scheme, to calculate the charge distribution and the energy-dependent transmission function, from which the current or the conductance are obtained. The electrostatic potential is obtained by solving Poisson's equation on a grid with boundary conditions on the electrodes, and at other interfaces.more » Self-consistency between the charge and the electrostatic potential is achieved using a linear mixing method. Different versions of the code allow the modeling of different types of nanotube devices: Version 1.0: Modeling of carbon nanotube electronic devices with cylindrical symmetry Version 1.1: Modeling of planar carbon nanotube electronic devices Version 1.2: Modeling of photocurrent in carbon nanotube devices« less

  7. Revisiting the laser dye Styryl-13 as a reference near-infrared fluorophore: implications for the photoluminescence quantum yields of semiconducting single-walled carbon nanotubes.

    PubMed

    Stürzl, Ninette; Lebedkin, Sergei; Kappes, Manfred M

    2009-09-24

    The near-infrared (NIR) polymethine dye Styryl-13 emitting at approximately 925 nm has recently been suggested as a reference fluorophore for determining the quantum yield (QY) of the NIR photoluminescence of dispersed single-walled carbon nanotubes (SWNTs). Ju et al. reported the QY for SWNTs to be as high as 20% on the basis of 11% QY for Styryl-13 in methanol (Science 2009, 323, 1319). We directly compared the fluorescence of Styryl-13 and Styryl-20 (emitting at approximately 945 nm) with that of the standard fluorophore Rhodamine 6G using a spectrometer with a broad visible-NIR detection range. QYs of 2.0 (4.5) and 0.52 (0.80)% were determined for Styryl-13 and Styryl-20 in methanol (propylene carbonate), respectively. Correspondingly, the above-mentioned photoluminescence efficiency of SWNTs appears to be strongly overestimated. We also discuss singlet oxygen as an alternative NIR reference. A total QY of 1.4% was measured for the emission of singlet oxygen at 1275 nm, as photosensitized by C70 fullerene in air-saturated carbon tetrachloride. PMID:19757846

  8. Revisiting the Laser Dye Styryl-13 As a Reference Near-Infrared Fluorophore: Implications for the Photoluminescence Quantum Yields of Semiconducting Single-Walled Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Stürzl, Ninette; Lebedkin, Sergei; Kappes, Manfred M.

    2009-08-01

    The near-infrared (NIR) polymethine dye Styryl-13 emitting at ˜925 nm has recently been suggested as a reference fluorophore for determining the quantum yield (QY) of the NIR photoluminescence of dispersed single-walled carbon nanotubes (SWNTs). Ju et al. reported the QY for SWNTs to be as high as 20% on the basis of 11% QY for Styryl-13 in methanol (Science 2009, 323, 1319). We directly compared the fluorescence of Styryl-13 and Styryl-20 (emitting at ˜945 nm) with that of the standard fluorophore Rhodamine 6G using a spectrometer with a broad visible-NIR detection range. QYs of 2.0 (4.5) and 0.52 (0.80)% were determined for Styryl-13 and Styryl-20 in methanol (propylene carbonate), respectively. Correspondingly, the above-mentioned photoluminescence efficiency of SWNTs appears to be strongly overestimated. We also discuss singlet oxygen as an alternative NIR reference. A total QY of 1.4% was measured for the emission of singlet oxygen at 1275 nm, as photosensitized by C70 fullerene in air-saturated carbon tetrachloride.

  9. Solar cells composed of semiconductive materials

    SciTech Connect

    Hezel, R.

    1981-03-03

    A solar cell is composed of a semiconductive material having an active zone in which charge carriers are produced by photons which strike and penetrate into the solar cell. The cell is comprised of a semiconductive body having an electrically insulating laminate with metal contacts therein positioned on the semiconductor body in the active zone thereof. The insulating laminate is composed of a double layer of insulating material, with the layer in direct contact with the semiconductive surface being composed of SiO2 which is either natural or is produced at temperatures below 800/sup 0/ C. And the layer superimposed above the SiO2 layer being composed of a different insulating material, such as plasma-produced Si3N4. In certain embodiments of the invention, a whole-area pn-junction is provided parallel to the semiconductive surface. The solar cells of the invention exhibit a higher degree of efficiency due to a higher fixed interface charged density, and low surface recombination velocity, an increased UV sensitivity, improved surface protection and passivation and improved anti-reflection characteristics relative to prior art solar cell devices.

  10. Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage

    PubMed Central

    Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

    2015-01-01

    One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm2 and length-specific capacitance up to 23.9 mF/cm, — one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources. PMID:26601246

  11. Rationally designed graphene-nanotube 3D architectures with a seamless nodal junction for efficient energy conversion and storage.

    PubMed

    Xue, Yuhua; Ding, Yong; Niu, Jianbing; Xia, Zhenhai; Roy, Ajit; Chen, Hao; Qu, Jia; Wang, Zhong Lin; Dai, Liming

    2015-09-01

    One-dimensional (1D) carbon nanotubes (CNTs) and 2D single-atomic layer graphene have superior thermal, electrical, and mechanical properties. However, these nanomaterials exhibit poor out-of-plane properties due to the weak van der Waals interaction in the transverse direction between graphitic layers. Recent theoretical studies indicate that rationally designed 3D architectures could have desirable out-of-plane properties while maintaining in-plane properties by growing CNTs and graphene into 3D architectures with a seamless nodal junction. However, the experimental realization of seamlessly-bonded architectures remains a challenge. We developed a strategy of creating 3D graphene-CNT hollow fibers with radially aligned CNTs (RACNTs) seamlessly sheathed by a cylindrical graphene layer through a one-step chemical vapor deposition using an anodized aluminum wire template. By controlling the aluminum wire diameter and anodization time, the length of the RACNTs and diameter of the graphene hollow fiber can be tuned, enabling efficient energy conversion and storage. These fibers, with a controllable surface area, meso-/micropores, and superior electrical properties, are excellent electrode materials for all-solid-state wire-shaped supercapacitors with poly(vinyl alcohol)/H2SO4 as the electrolyte and binder, exhibiting a surface-specific capacitance of 89.4 mF/cm(2) and length-specific capacitance up to 23.9 mF/cm, - one to four times the corresponding record-high capacities reported for other fiber-like supercapacitors. Dye-sensitized solar cells, fabricated using the fiber as a counter electrode, showed a power conversion efficiency of 6.8% and outperformed their counterparts with an expensive Pt wire counter electrode by a factor of 2.5. These novel fiber-shaped graphene-RACNT energy conversion and storage devices are so flexible they can be woven into fabrics as power sources. PMID:26601246

  12. A study of junction effect transistors and their roles in carbon nanotube field emission cathodes in compact pulsed power applications

    NASA Astrophysics Data System (ADS)

    Shui, Qiong

    This thesis is focusing on a study of junction effect transistors (JFETs) in compact pulsed power applications. Pulsed power usually requires switches with high hold-off voltage, high current, low forward voltage drop, and fast switching speed. 4H-SiC, with a bandgap of 3.26 eV (The bandgap of Si is 1.12eV) and other physical and electrical superior properties, has gained much attention in high power, high temperature and high frequency applications. One topic of this thesis is to evaluate if 4H-SiC JFETs have a potential to replace gas phase switches to make pulsed power system compact and portable. Some other pulsed power applications require cathodes of providing stable, uniform, high electron-beam current. So the other topic of this research is to evaluate if Si JFET-controlled carbon nanotube field emitter cold cathode will provide the necessary e-beam source. In the topic of "4H-SiC JFETs", it focuses on the design and simulation of a novel 4H-SiC normally-off VJFET with high breakdown voltage using the 2-D simulator ATLAS. To ensure realistic simulations, we utilized reasonable physical models and the established parameters as the input into these models. The influence of key design parameters were investigated which would extend pulsed power limitations. After optimizing the key design parameters, with a 50-mum drift region, the predicted breakdown voltage for the VJFET is above 8kV at a leakage current of 1x10-5A/cm2 . The specific on-state resistance is 35 mO·cm 2 at VGS = 2.7 V, and the switching speed is several ns. The simulation results suggest that the 4H-SiC VJFET is a potential candidate for improving switching performance in repetitive pulsed power applications. To evaluate the 4H-SiC VJFETs in pulsed power circuits, we extracted some circuit model parameters from the simulated I-V curves. Those parameters are necessary for circuit simulation program such as SPICE. This method could be used as a test bench without fabricating the devices to

  13. Strain Sensitivity in Single Walled Carbon Nanotubes for Multifunctional Materials

    NASA Technical Reports Server (NTRS)

    Heath, D. M. (Technical Monitor); Smits, Jan M., VI

    2005-01-01

    Single walled carbon nanotubes represent the future of structural aerospace vehicle systems due to their unparalleled strength characteristics and demonstrated multifunctionality. This multifunctionality rises from the CNT's unique capabilities for both metallic and semiconducting electron transport, electron spin polarizability, and band gap modulation under strain. By incorporating the use of electric field alignment and various lithography techniques, a single wall carbon nanotube (SWNT) test bed for measurement of conductivity/strain relationships has been developed. Nanotubes are deposited at specified locations through dielectrophoresis. The circuit is designed such that the central, current carrying section of the nanotube is exposed to enable atomic force microscopy and manipulation in situ while the transport properties of the junction are monitored. By applying this methodology to sensor development a flexible single wall carbon nanotube (SWNT) based strain sensitive device has been developed. Studies of tensile testing of the flexible SWNT device vs conductivity are also presented, demonstrating the feasibility of using single walled HiPCO (high-pressure carbon monoxide) carbon nanotubes as strain sensing agents in a multi-functional materials system.

  14. A novel investigation on carbon nanotube/ZnO, Ag/ZnO and Ag/carbon nanotube/ZnO nanowires junctions for harvesting piezoelectric potential on textile

    SciTech Connect

    Khan, Azam Edberg, Jesper; Nur, Omer; Willander, Magnus

    2014-07-21

    In the present work, three junctions were fabricated on textile fabric as an alternative substrate for harvesting piezoelectric potential. First junction was formed on ordinary textile as (textile/multi-walled carbon nanotube film/zinc oxide nanowires (S1: T/CNTs/ZnO NWs)) and the other two were formed on conductive textile with the following layer sequence: conductive textile/zinc oxide nanowires (S2: CT/ZnO NWs) and conductive textile/multi-walled carbon nanotubes film/zinc oxide nanowires (S3: CT/CNTs/ZnO NWs). Piezoelectric potential was harvested by using atomic force microscopy in contact mode for the comparative analysis of the generated piezoelectric potential. ZnO NWs were synthesized by using the aqueous chemical growth method. Surface analysis of the grown nanostructures was performed by using scanning electron microscopy and transmission electron microscopy. The growth orientation and crystalline size were studied by using X-ray diffraction technique. This study reveals that textile as an alternative substrate have many features like cost effective, highly flexible, nontoxic, light weight, soft, recyclable, reproducible, portable, wearable, and washable for nanogenerators fabrication with acceptable performance and with a wide choice of modification for obtaining large amount of piezoelectric potential.

  15. A novel investigation on carbon nanotube/ZnO, Ag/ZnO and Ag/carbon nanotube/ZnO nanowires junctions for harvesting piezoelectric potential on textile

    NASA Astrophysics Data System (ADS)

    Khan, Azam; Edberg, Jesper; Nur, Omer; Willander, Magnus

    2014-07-01

    In the present work, three junctions were fabricated on textile fabric as an alternative substrate for harvesting piezoelectric potential. First junction was formed on ordinary textile as (textile/multi-walled carbon nanotube film/zinc oxide nanowires (S1: T/CNTs/ZnO NWs)) and the other two were formed on conductive textile with the following layer sequence: conductive textile/zinc oxide nanowires (S2: CT/ZnO NWs) and conductive textile/multi-walled carbon nanotubes film/zinc oxide nanowires (S3: CT/CNTs/ZnO NWs). Piezoelectric potential was harvested by using atomic force microscopy in contact mode for the comparative analysis of the generated piezoelectric potential. ZnO NWs were synthesized by using the aqueous chemical growth method. Surface analysis of the grown nanostructures was performed by using scanning electron microscopy and transmission electron microscopy. The growth orientation and crystalline size were studied by using X-ray diffraction technique. This study reveals that textile as an alternative substrate have many features like cost effective, highly flexible, nontoxic, light weight, soft, recyclable, reproducible, portable, wearable, and washable for nanogenerators fabrication with acceptable performance and with a wide choice of modification for obtaining large amount of piezoelectric potential.

  16. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency.

    PubMed

    Funde, Adinath M; Nasibulin, Albert G; Syed, Hashmi Gufran; Anisimov, Anton S; Tsapenko, Alexey; Lund, Peter; Santos, J D; Torres, I; Gandía, J J; Cárabe, J; Rozenberg, A D; Levitsky, Igor A

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics. PMID:27005494

  17. Carbon nanotube-amorphous silicon hybrid solar cell with improved conversion efficiency

    NASA Astrophysics Data System (ADS)

    Funde, Adinath M.; Nasibulin, Albert G.; Gufran Syed, Hashmi; Anisimov, Anton S.; Tsapenko, Alexey; Lund, Peter; Santos, J. D.; Torres, I.; Gandía, J. J.; Cárabe, J.; Rozenberg, A. D.; Levitsky, Igor A.

    2016-05-01

    We report a hybrid solar cell based on single walled carbon nanotubes (SWNTs) interfaced with amorphous silicon (a-Si). The high quality carbon nanotube network was dry transferred onto intrinsic a-Si forming Schottky junction for metallic SWNT bundles and heterojunctions for semiconducting SWNT bundles. The nanotube chemical doping and a-Si surface treatment minimized the hysteresis effect in current-voltage characteristics allowing an increase in the conversion efficiency to 1.5% under an air mass 1.5 solar spectrum simulator. We demonstrated that the thin SWNT film is able to replace a simultaneously p-doped a-Si layer and transparent conductive electrode in conventional amorphous silicon thin film photovoltaics.

  18. Carbon Nanotubes for Space Photovoltaic Applications

    NASA Technical Reports Server (NTRS)

    Efstathiadis, Harry; Haldar, Pradeep; Landi, Brian J.; Denno, Patrick L.; DiLeo, Roberta A.; VanDerveer, William; Raffaelle, Ryne P.

    2007-01-01

    Carbon nanotubes (CNTs) can be envisioned as an individual graphene sheet rolled into a seamless cylinder (single-walled, SWNT), or concentric sheets as in the case of a multi-walled carbon nanotube (MWNT) (1). The role-up vector will determine the hexagonal arrangement and "chirality" of the graphene sheet, which will establish the nanotube to be metallic or semiconducting. The optoelectronic properties will depend directly on this chiral angle and the diameter of the SWNT, with semiconductor types exhibiting a band gap energy (2). Characteristic of MWNTs are the concentric graphene layers spaced 0.34 nm apart, with diameters from 10-200 nm and lengths up to hundreds of microns (2). In the case of SWNTs, the diameters range from 0.4 - 2 nm and lengths have been reported up to 1.5 cm (3). SWNTs have the distinguishable property of "bundling" together due to van der Waal's attractions to form "ropes." A comparison of these different structural types is shown in Figure 1. The use of SWNTS in space photovoltaic (PV) applications is attractive for a variety of reasons. Carbon nanotubes as a class of materials exhibit unprecedented optical, electrical, mechanical properties, with the added benefit of being nanoscale in size which fosters ideal interaction in nanomaterial-based devices like polymeric solar cells. The optical bandgap of semiconducting SWNTs can be varied from approx. 0.4 - 1.5 eV, with this property being inversely proportional to the nanotube diameter. Recent work at GE Global Research has shown where a single nanotube device can behave as an "ideal" pn diode (5). The SWNT was bridged over a SiO2 channel between Mo contacts and exhibited an ideality factor of 1, based on a fit of the current-voltage data using the diode equation. The measured PV efficiency under a 0.8 eV monochromatic illumination showed a power conversion efficiency of 0.2 %. However, the projected efficiency of these junctions is estimated to be > 5 %, especially when one considers the

  19. Gate-Free Electrical Breakdown of Metallic Pathways in Single-Walled Carbon Nanotube Crossbar Networks.

    PubMed

    Li, Jinghua; Franklin, Aaron D; Liu, Jie

    2015-09-01

    Aligned single-walled carbon nanotubes (SWNTs) synthesized by the chemical vapor deposition (CVD) method have exceptional potential for next-generation nanoelectronics. However, the coexistence of semiconducting (s-) and metallic (m-) SWNTs remains a considerable challenge since the latter causes significant degradation in device performance. Here we demonstrate a facile and effective approach to selectively break all m-SWNTs by stacking two layers of horizontally aligned SWNTs to form crossbars and applying a voltage to the crossed SWNT arrays. The introduction of SWNT junctions amplifies the disparity in resistance between s- and m-pathways, leading to a complete deactivation of m-SWNTs while minimizing the degradation of the semiconducting counterparts. Unlike previous approaches that required an electrostatic gate to achieve selectivity in electrical breakdown, this junction process is gate-free and opens the way for straightforward integration of thin-film s-SWNT devices. Comparison to electrical breakdown in junction-less SWNT devices without gating shows that this junction-based breakdown method yields more than twice the average on-state current retention in the resultant s-SWNT arrays. Systematic studies show that the on/off ratio can reach as high as 1.4 × 10(6) with a correspondingly high retention of on-state current compared to the initial current value before breakdown. Overall, this method provides important insight into transport at SWNT junctions and a simple route for obtaining pure s-SWNT thin film devices for broad applications. PMID:26263184

  20. Superconducting-semiconducting nanowire hybrid microwave circuits

    NASA Astrophysics Data System (ADS)

    de Lange, G.; van Heck, B.; Bruno, A.; van Woerkom, D.; Geresdi, A.; Plissard, S. R.; Bakkers, E. P. A. M.; Akhmerov, A. R.; Dicarlo, L.

    2015-03-01

    Hybrid superconducting-semiconducting circuits offer a versatile platform for studying quantum effects in mesoscopic solid-state systems. We report the realization of hybrid artificial atoms based on Indium-Arsenide nanowire Josephson elements in a circuit quantum electrodynamics architecture. Transmon-like single-junction devices have gate-tunable transition frequencies. Split-junction devices behave as transmons near zero applied flux and as flux qubits near half flux quantum, wherein states with oppositely flowing persistent current can be driven by microwaves. This flux-qubit like behaviour results from non-sinusoidal current-phase relations in the nanowire Josephson elements. These hybrid microwave circuits are made entirely of magnetic-field compatible materials, offering new opportunities for hybrid experiments combining microwave circuits with polarized spin ensembles and Majorana bound states. We acknowledge funding from Microsoft Research and the Dutch Organization for Fundamental Research on Matter (FOM).

  1. LDRD final report : chromophore-functionalized aligned carbon nanotube arrays.

    SciTech Connect

    Vance, Andrew L.; Yang, Chu-Yeu Peter; Krafcik, Karen Lee

    2011-09-01

    The goal of this project was to expand upon previously demonstrated single carbon nanotube devices by preparing a more practical, multi-single-walled carbon nanotube (SWNT) device. As a late-start, proof-of-concept project, the work focused on the fabrication and testing of chromophore-functionalized aligned SWNT field effect transistors (SWNT-FET). Such devices have not yet been demonstrated. The advantages of fabricating aligned SWNT devices include increased device cross-section to improve sensitivity to light, elimination of increased electrical resistance at nanotube junctions in random mat devices, and the ability to model device responses. The project did not achieve the goal of fabricating and testing chromophore-modified SWNT arrays, but a new SWNT growth capability was established that will benefit future projects. Although the ultimate goal of fabricating and testing chromophore-modified SWNT arrays was not achieved, the work did lead to a new carbon nanotube growth capability at Sandia/CA. The synthesis of dense arrays of horizontally aligned SWNTs is a developing area of research with significant potential for new discoveries. In particular, the ability to prepare arrays of carbon nanotubes of specific electronic types (metallic or semiconducting) could yield new classes of nanoscale devices.

  2. Carbon Nanotube Solar Cells

    PubMed Central

    Klinger, Colin; Patel, Yogeshwari; Postma, Henk W. Ch.

    2012-01-01

    We present proof-of-concept all-carbon solar cells. They are made of a photoactive side of predominantly semiconducting nanotubes for photoconversion and a counter electrode made of a natural mixture of carbon nanotubes or graphite, connected by a liquid electrolyte through a redox reaction. The cells do not require rare source materials such as In or Pt, nor high-grade semiconductor processing equipment, do not rely on dye for photoconversion and therefore do not bleach, and are easy to fabricate using a spray-paint technique. We observe that cells with a lower concentration of carbon nanotubes on the active semiconducting electrode perform better than cells with a higher concentration of nanotubes. This effect is contrary to the expectation that a larger number of nanotubes would lead to more photoconversion and therefore more power generation. We attribute this to the presence of metallic nanotubes that provide a short for photo-excited electrons, bypassing the load. We demonstrate optimization strategies that improve cell efficiency by orders of magnitude. Once it is possible to make semiconducting-only carbon nanotube films, that may provide the greatest efficiency improvement. PMID:22655070

  3. BiOI/TiO2 nanotube arrays, a unique flake-tube structured p-n junction with remarkable visible-light photoelectrocatalytic performance and stability.

    PubMed

    Liu, Jiaqin; Ruan, Lili; Adeloju, Samuel B; Wu, Yucheng

    2014-01-28

    A series of unique flake-tube structured p-n heterojunctions of BiOI/TiO2 nanotube arrays (TNTAs) were successfully prepared by loading large amounts of BiOI nanoflakes onto both the outer and inner walls of well-separated TiO2 nanotubes using anodization followed by the sequential chemical bath deposition (S-CBD) method. The as-prepared BiOI/TNTAs samples were characterized by X-ray diffraction, electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectroscopy and nitrogen sorption. The photoelectrocatalytic (PEC) activity and stability of the BiOI/TNTAs samples toward degradation of methyl orange (MO) solutions under visible-light irradiation (λ > 420 nm) were evaluated. The visible-light PEC performance of BiOI/TNTAs samples was further confirmed by the transient photocurrent response test. The results from the current study revealed that the 5-BiOI/TNTAs sample exhibited the best PEC activity, favourable stability, and the highest photocurrent density among all the BiOI/TNTAs heterostructured samples. The combined effects of several factors may contribute to the remarkable visible-light PEC performance for the 5-BiOI/TNTAs sample including a 3D connected intertube spacing system and an open tube-mouth structure, strong visible-light absorption by BiOI, the formation of a p-n junction, larger specific surface area, and the impact of the applied external electrostatic field. PMID:24225559

  4. Electrical characterization of single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Berliocchi, Marco; Brunetti, Francesca; Di Carlo, Aldo; Lugli, Paolo; Orlanducci, Silvia; Terranova, Maria Letizia

    2003-04-01

    Single Wall Carbon Nanotubes (SWCNTs) based nanotechnology appears to be promising for future nanoelectronics. The SWCNT may be either metallic or semiconducting and both metallic and semiconducting types of SWCNTs have been observed experimentally. This gives rise to intriguing possibilities to put together semiconductor-semiconductor and semiconductor-metal junctions for diodes and transistors. The potential for nanotubes in nanoelectronics devices, displays and nanosensors is enormous. However, in order to realize the potential of SWCNTs, it is critical to understand the properties of charge transport and to control phase purity, elicity and arrangement according to specific architectures. We have investigated the electrical properties of various SWCNTs samples whit different organization: bundles of SWCNTs, SWCNT fibres and different membranes and tablets obtained using SWCNTs purified and characterized. Electrical characterizations were carried out by a 4155B Agilent Semiconductor Parameter Analyser. In order to give a mechanical stability to SWCNTs fibres and bundles we have used a nafion matrix coating, so an electrical characterization has been performed on samples with and without this layer. I-V measurements were performed in vacuum and in air using aluminium interdigitated coplanar-electrodes (width=20mm or 40mm) on glass substrates. The behaviour observed is generally supralinear with currents of the order of mA in vacuum and lower values in air with the exception of the tablet samples where the behaviour is ohmic, the currents are higher and similar values of current are detected in air and vacuum.

  5. Fabrication of Carbon Nanotube Field Effect Transistors Using Plasma-Enhanced Chemical Vapor Deposition Grown Nanotubes

    NASA Astrophysics Data System (ADS)

    Ohnaka, Hirofumi; Kojima, Yoshihiro; Kishimoto, Shigeru; Ohno, Yutaka; Mizutani, Takashi

    2006-06-01

    Single-walled carbon nanotubes are grown using grid-inserted plasma-enhanced chemical vapor deposition (PECVD). The field effect transistor operation was confirmed using the PECVD grown carbon nanotubes (CNTs). The preferential growth of the semiconducting nanotubes was confirmed in the grid-inserted PECVD by measuring current-voltage (I-V) characteristics of the devices. Based on the measurement of the electrical breakdown of the metallic CNTs, the probability of growing the semiconducting nanotubes has been estimated to be more than 90%.

  6. The effects of 5-7 defects on the mechanical characteristics of carbon nanotubes intramolecular junctions and their influences on electronic properties

    NASA Astrophysics Data System (ADS)

    Lee, Wen-Jay; Chang, Jee-Gong; Wang, Yeng-Tseng; Su, Wan-Sheng

    2012-02-01

    This study utilizes molecular dynamics simulations and first-principles techniques to investigate mechanical and electronic properties of the single-walled carbon nanotube (SWCNT) intramolecular junctions (IMJs). Results show that the mechanical behaviors are mainly affected by the diameter of thinner segment of two composed tubes, whereas are barely able to be influenced by the number of 5-7 defects in the interface region. With applied compression, the yielding stress and Young's modulus of the SWCNT IMJs are found to be strongly associated with the orientation of two contacted heptagon rings where their ordering values are vertical > tilted > parallel to the axial direction. Under applied tensile, a lowest value in the yielding stress and Young's modulus is found on the parallel status, but the other two reveal alternating relations. Moreover, the magnitude of the stress amplitude is proportional to the Young's modulus and yielding stress and the buckling location is shown to be dependence on different orientations of two contacted heptagon rings. Finally, our first-principles calculations indicated that the considered SWCNT (5,0)/(8,0) IMJs at a certain length with different distributions of 5-7 defects on the tube wall exhibit diverse electronic properties, such as the changes of the density of states and modulation of energy gap. With increasing length, the numbers of states near the Fermi level region increase significantly and the energy gap tends to shrink as well.

  7. Carbon nanotube macroelectronics

    NASA Astrophysics Data System (ADS)

    Zhang, Jialu

    In this dissertation, I discuss the application of carbon nanotubes in macroelectronis. Due to the extraordinary electrical properties such as high intrinsic carrier mobility and current-carrying capacity, single wall carbon nanotubes are very desirable for thin-film transistor (TFT) applications such as flat panel display, transparent electronics, as well as flexible and stretchable electronics. Compared with other popular channel material for TFTs, namely amorphous silicon, polycrystalline silicon and organic materials, nanotube thin-films have the advantages of low-temperature processing compatibility, transparency, and flexibility, as well as high device performance. In order to demonstrate scalable, practical carbon nanotube macroelectroncis, I have developed a platform to fabricate high-density, uniform separated nanotube based thin-film transistors. In addition, many other essential analysis as well as technology components, such as nanotube film density control, purity and diameter dependent semiconducting nanotube electrical performance study, air-stable n-type transistor fabrication, and CMOS integration platform have also been demonstrated. On the basis of the above achievement, I have further demonstrated various kinds of applications including AMOLED display electronics, PMOS and CMOS logic circuits, flexible and transparent electronics. The dissertation is structured as follows. First, chapter 1 gives a brief introduction to the electronic properties of carbon nanotubes, which serves as the background knowledge for the following chapters. In chapter 2, I will present our approach of fabricating wafer-scale uniform semiconducting carbon nanotube thin-film transistors and demonstrate their application in display electronics and logic circuits. Following that, more detailed information about carbon nanotube thin-film transistor based active matrix organic light-emitting diode (AMOLED) displays is discussed in chapter 3. And in chapter 4, a technology to

  8. Networks of semiconducting SWNTs: contribution of midgap electronic states to the electrical transport.

    PubMed

    Itkis, Mikhail E; Pekker, Aron; Tian, Xiaojuan; Bekyarova, Elena; Haddon, Robert C

    2015-08-18

    presence of midgap electronic states in the semiconducting SWNTs, which provide a source of low-energy excitations, which can contribute to hopping conductance along the nanotubes following fluctuation induced tunneling across the internanotube junctions, which together dominate the low temperature transport and limit the resistivity of the films. At high temperatures, the intrinsic carriers thermally activated across the bandgap as in a traditional semiconductor became available for band transport. The midgap states pin the Fermi level to the middle of the bandgap, and their origin is ascribed to defects in the SWNT walls. The presence of such midgap states has been reported in connection with scanning tunneling spectroscopy experiments, Coulomb blockade observations in low temperature electrical measurements, selective electrochemical deposition imaging, tip-enhanced Raman spectroscopy, high resolution photocurrent spectroscopy, and the modeling of the electronic density of states associated with various defects. Midgap states are present in conventional semiconductors, but what is unusual in the present context is the extent of their contribution to the electrical transport in networks of semiconducting SWNTs. In this Account, we sharpen the focus on the midgap states in SC-SWNTs, their effect on the electronic properties of SC-SWNT networks, and the importance of these effects on efforts to develop electronic and photonic applications of SC-SWNTs. PMID:26244611

  9. Thermoelectrics: Carbon nanotubes get high

    NASA Astrophysics Data System (ADS)

    Crispin, Xavier

    2016-04-01

    Waste heat can be converted to electricity by thermoelectric generators, but their development is hindered by the lack of cheap materials with good thermoelectric properties. Now, carbon-nanotube-based materials are shown to have improved properties when purified to contain only semiconducting species and then doped.

  10. Chalcogenide Cobalt telluride nanotubes

    NASA Astrophysics Data System (ADS)

    Dahal, Bishnu; Dulal, Rajendra; Pegg, Ian L.; Philip, John

    Cobalt telluride nanotubes are grown using wet chemical and hydrothermal syntheses. Wet chemical synthesized nanotubes display nearly 1: 1 Co to Te ratio. On the other hand, CoTe nanotubes synthesized using hydrothermal method show excess Co content leading to the compound Co58Te42. Both CoTe and Co58Te42 display magnetic properties, but with totally different characteristics. The Curie temperature of CoTe is higher than 400 K. However, the Tc of Co58Te42 is below 50 K. Transport properties of cobalt telluride (CoTe) nanotube devices show that they exhibit p-type semiconducting behavior. The magnetoresistance measured at 10 K show a magnetoresistance of 54%. . National Science Foundation under ECCS-0845501 and NSF-MRI, DMR-0922997.

  11. Thermal conductivity of chirality-sorted carbon nanotube networks

    NASA Astrophysics Data System (ADS)

    Lian, Feifei; Llinas, Juan P.; Li, Zuanyi; Estrada, David; Pop, Eric

    2016-03-01

    The thermal properties of single-walled carbon nanotubes (SWNTs) are of significant interest, yet their dependence on SWNT chirality has been, until now, not explored experimentally. Here, we used electrical heating and infrared thermal imaging to simultaneously study thermal and electrical transport in chirality-sorted SWNT networks. We examined solution processed 90% semiconducting, 90% metallic, purified unsorted (66% semiconducting), and as-grown HiPco SWNT films. The thermal conductivities of these films range from 80 to 370 W m-1 K-1 but are not controlled by chirality, instead being dependent on the morphology (i.e., mass and junction density, quasi-alignment) of the networks. The upper range of the thermal conductivities measured is comparable to that of the best metals (Cu and Ag), but with over an order of magnitude lower mass density. This study reveals important factors controlling the thermal properties of light-weight chirality-sorted SWNT films, for potential thermal and thermoelectric applications.

  12. Carbon Nanotube Based Molecular Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1998-01-01

    Carbon nanotubes and the nanotube heterojunctions have recently emerged as excellent candidates for nanoscale molecular electronic device components. Experimental measurements on the conductivity, rectifying behavior and conductivity-chirality correlation have also been made. While quasi-one dimensional simple heterojunctions between nanotubes with different electronic behavior can be generated by introduction of a pair of heptagon-pentagon defects in an otherwise all hexagon graphene sheet. Other complex 3- and 4-point junctions may require other mechanisms. Structural stability as well as local electronic density of states of various nanotube junctions are investigated using a generalized tight-binding molecular dynamics (GDBMD) scheme that incorporates non-orthogonality of the orbitals. The junctions investigated include straight and small angle heterojunctions of various chiralities and diameters; as well as more complex 'T' and 'Y' junctions which do not always obey the usual pentagon-heptagon pair rule. The study of local density of states (LDOS) reveal many interesting features, most prominent among them being the defect-induced states in the gap. The proposed three and four pointjunctions are one of the smallest possible tunnel junctions made entirely of carbon atoms. Furthermore the electronic behavior of the nanotube based device components can be taylored by doping with group III-V elements such as B and N, and BN nanotubes as a wide band gap semiconductor has also been realized in experiments. Structural properties of heteroatomic nanotubes comprising C, B and N will be discussed.

  13. Doping of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Kutler, Paul (Technical Monitor)

    1997-01-01

    Due to the rapid progress in atom manipulation technology, atomic chain electronics would not be a dream, where foreign atoms are placed on a substrate to form a chain, and its electronic properties are designed by controlling the lattice constant d. It has been shown theoretically that a Si atomic chain is metallic regardless of d and that a Mg atomic chain is semiconducting or insulating with a band gap modified with d. For electronic applications, it is essential to establish a method to dope a semiconducting chain, which is to control the Fermi energy position without altering the original band structure. If we replace some of the chain atoms with dopant atoms randomly, the electrons will see random potential along the chain and will be localized strongly in space (Anderson localization). However, if we replace periodically, although the electrons can spread over the chain, there will generally appear new bands and band gaps reflecting the new periodicity of dopant atoms. This will change the original band structure significantly. In order to overcome this dilemma, we may place a dopant atom beside the chain at every N lattice periods (N > 1). Because of the periodic arrangement of dopant atoms, we can avoid the unwanted Anderson localization. Moreover, since the dopant atoms do not constitute the chain, the overlap interaction between them is minimized, and the band structure modification can be made smallest. Some tight-binding results will be discussed to demonstrate the present idea.

  14. Surface physics of semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Amato, Michele; Rurali, Riccardo

    2016-02-01

    Semiconducting nanowires (NWs) are firm candidates for novel nanoelectronic devices and a fruitful playground for fundamental physics. Ultra-thin nanowires, with diameters below 10 nm, present exotic quantum effects due to the confinement of the wave functions, e.g. widening of the electronic band-gap, deepening of the dopant states. However, although several reports of sub-10 nm wires exist to date, the most common NWs have diameters that range from 20 to 200 nm, where these quantum effects are absent or play a very minor role. Yet, the research activity on this field is very intense and these materials still promise to provide an important paradigm shift for the design of emerging electronic devices and different kinds of applications. A legitimate question is then: what makes a nanowire different from bulk systems? The answer is certainly the large surface-to-volume ratio. In this article we discuss the most salient features of surface physics and chemistry in group-IV semiconducting nanowires, focusing mostly on Si NWs. First we review the state-of-the-art of NW growth to achieve a smooth and controlled surface morphology. Next we discuss the importance of a proper surface passivation and its role on the NW electronic properties. Finally, stressing the importance of a large surface-to-volume ratio and emphasizing the fact that in a NW the surface is where most of the action takes place, we discuss molecular sensing and molecular doping.

  15. Redox sorting of carbon nanotubes.

    PubMed

    Gui, Hui; Streit, Jason K; Fagan, Jeffrey A; Hight Walker, Angela R; Zhou, Chongwu; Zheng, Ming

    2015-03-11

    This work expands the redox chemistry of single-wall carbon nanotubes (SWCNTs) by investigating its role in a number of SWCNT sorting processes. Using a polyethylene glycol (PEG)/dextran (DX) aqueous two-phase system, we show that electron-transfer between redox molecules and SWCNTs triggers reorganization of the surfactant coating layer, leading to strong modulation of nanotube partition in the two phases. While the DX phase is thermodynamically more favored by an oxidized SWCNT mixture, the mildly reducing PEG phase is able to recover SWCNTs from oxidation and extract them successively from the DX phase. Remarkably, the extraction order follows SWCNT bandgap: semiconducting nanotubes of larger bandgap first, followed by semiconducting nanotubes of smaller bandgap, then nonarmchair metallic tubes of small but nonvanishing bandgap, and finally armchair metallic nanotubes of zero bandgap. Furthermore, we show that redox-induced surfactant reorganization is a common phenomenon, affecting nanotube buoyancy in a density gradient field, affinity to polymer matrices, and solubility in organic solvents. These findings establish redox modulation of surfactant coating structures as a general mechanism for tuning a diverse range of SWCNT sorting processes and demonstrate for the first time that armchair and nonarmchair metallic SWCNTs can be separated by their differential response to redox. PMID:25719939

  16. Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O

    NASA Astrophysics Data System (ADS)

    Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V.; Pillai, Vijayamohanan K.

    2014-07-01

    Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers.Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, ``as grown'' CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ~470 μA cm-2) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar

  17. Facile fabrication of organic/inorganic nanotube heterojunction arrays for enhanced photoelectrochemical water splitting.

    PubMed

    Chen, Yingzhi; Li, Aoxiang; Yue, Xiaoqi; Wang, Lu-Ning; Huang, Zheng-Hong; Kang, Feiyu; Volinsky, Alex A

    2016-07-01

    Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi) layer were fabricated for photoelectrochemical water splitting. In this arrayed architecture, a PDi layer with a tunable thickness was coated on anodic TiO2 nanotube arrays by physical vapor deposition, which is advantageous for the formation of a uniform layer and an adequate interface contact between PDi and TiO2. The obtained PDi/TiO2 junction exhibited broadened visible light absorption, and an effective interface for enhanced photogenerated electron-hole separation, which is supported by the reduced charge transfer resistance and prolonged excitation lifetime via impedance spectroscopy analysis and fluorescence emission decay investigations. Consequently, such a heterojunction photoanode was photoresponsive to a wide visible light region of 400-600 nm, and thus demonstrated a highly enhanced photocurrent density at 1.23 V vs. a reversible hydrogen electrode. Additionally, the durability of such a photoanode can be guaranteed after long-time illumination because of the geometrical restraint imposed by the PDi aggregates. These results pave the way to discover new organic/inorganic assemblies for high-performance photoelectric applications and device integration. PMID:26926569

  18. Anomalous Josephson effect in semiconducting nanowires as a signature of the topologically nontrivial phase

    NASA Astrophysics Data System (ADS)

    Nesterov, Konstantin N.; Houzet, Manuel; Meyer, Julia S.

    2016-05-01

    We study Josephson junctions made of semiconducting nanowires with Rashba spin-orbit coupling, where superconducting correlations are induced by the proximity effect. In the presence of a suitably directed magnetic field, the system displays the anomalous Josephson effect: a nonzero supercurrent in the absence of a phase bias between two superconductors. We show that this anomalous current can be increased significantly by tuning the nanowire into the helical regime. In particular, in a short junction, a large anomalous current is a signature for topologically nontrivial superconductivity in the nanowire.

  19. Electrochemical preparation of vertically aligned, hollow CdSe nanotubes and their p-n junction hybrids with electrodeposited Cu2O.

    PubMed

    Debgupta, Joyashish; Devarapalli, Ramireddy; Rahman, Shakeelur; Shelke, Manjusha V; Pillai, Vijayamohanan K

    2014-08-01

    Vertically aligned, hollow nanotubes of CdSe are grown on fluorine doped tin oxide (FTO) coated glass substrates by ZnO nanowire template-assisted electrodeposition technique, followed by selective removal of the ZnO core using NH4OH. A detailed mechanism of nucleation and anisotropic growth kinetics of nanotubes have been studied by a combination of characterization tools such as chronoamperometry, SEM and TEM. Interestingly, "as grown" CdSe nanotubes (CdSe NTs) on FTO coated glass plates behave as n-type semiconductors exhibiting an excellent photo-response (with a generated photocurrent density value of ∼ 470 μA cm(-2)) while in contact with p-type Cu2O (p-type semiconductor, grown separately on FTO plates) because of the formation of a n-p heterojunction (type II). The observed photoresponse is 3 times higher than that of a similar device prepared with electrodeposited CdSe films (not nanotubes) and Cu2O on FTO. This has been attributed to the hollow 1-D nature of CdSe NTs, which provides enhanced inner and outer surface areas for better absorption of light and also assists faster transport of photogenerated charge carriers. PMID:24979744

  20. Scalable dielectrophoresis of single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Fitzhugh, William A.

    Single Walled Carbon Nanotubes (SWNTs) have attracted much attention as a candidate material for future nano-scale 'beyond silicon' devices. However industrial scale operations have been impeded by difficulties in separating the metallic and semiconducting species. This paper addresses the use of highly inhomogeneous alternating electric fields, dielectrophoresis, to isolate SWNT species in scaled systems. Both numerical and experimental methods will be discussed.

  1. Assembly of ordered carbon shells on semiconducting nanomaterials

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2012-10-02

    In some embodiments of the invention, encapsulated semiconducting nanomaterials are described. In certain embodiments the nanostructures described are semiconducting nanomaterials encapsulated with ordered carbon shells. In some aspects a method for producing encapsulated semiconducting nanomaterials is disclosed. In some embodiments applications of encapsulated semiconducting nanomaterials are described.

  2. Assembly of ordered carbon shells on semiconducting nanomaterials

    DOEpatents

    Sutter, Eli Anguelova; Sutter, Peter Werner

    2010-05-11

    In some embodiments of the invention, encapsulated semiconducting nanomaterials are described. In certain embodiments the nanostructures described are semiconducting nanomaterials encapsulated with ordered carbon shells. In some aspects a method for producing encapsulated semiconducting nanomaterials is disclosed. In some embodiments applications of encapsulated semiconducting nanomaterials are described.

  3. Carbon Nanotube-Nanocrystal Heterostructures

    SciTech Connect

    Peng, X.; Wong, S.

    2009-04-01

    The importance of generating carbon nanotube-nanoparticle heterostructures is that these composites ought to take advantage of and combine the unique physical and chemical properties of both carbon nanotubes and nanoparticles in one discrete structure. These materials have potential applicability in a range of diverse fields spanning heterogeneous catalysis to optoelectronic device development, of importance to chemists, physicists, materials scientists, and engineers. In this critical review, we present a host of diverse, complementary strategies for the reliable synthesis of carbon nanotube-nanoparticle heterostructures using both covalent as well as non-covalent protocols, incorporating not only single-walled and multi-walled carbon nanotubes but also diverse classes of metallic and semiconducting nanoparticles.

  4. Deterministic Modelling of Carbon Nanotube Near-Infrared Solar Cells

    NASA Astrophysics Data System (ADS)

    Bellisario, Darin

    2015-03-01

    With solution-process-ability, scale-able fabrication and purification, and cheap input materials, semiconducting single-walled carbon nanotube (SWNT) networks represent promising materials for near-IR solar cell (SC) applications. This promise has motivated a body of work not only developing solar cells but also exploring alignment/deposition methods and SWNT photovoltaic (PV) physics. Despite this interest, there is to date no quantitative model of SWNT solar cell operation analogous to bulk semiconductor p-n junction PVs, allowing a rigorous understanding of the physical tradeoffs driving experimental observations and informing what research will enable technological progress. In this work we have derived the steady state operation of planar heterojunction SWNT PVs from the fundamental light absorption, exciton transport, and free carrier transport behaviors of single nanotubes. Our method can treat arbitrary distributions of nanotube chiralities, lengths, orientations, defect types and concentration, bundle fraction and size, density, dielectric environment, electrode combinations, etc. We achieve this by treating individual SWNT properties as random variables, and describing the network by the dependent distributions of those properties, yielding coupled stochastic differential equations for light absorption, exciton transport, and free carrier transport. Applying the model to monochiral (6,5) films in aligned and isotropic configurations, we find that there is a strongly optimal film thickness at a given nanotube network density and orientation, reflecting an inherent tradeoff between light absorption (i.e. exciton generation) and diffusion to the electrodes. This optimal shifts lower with increasing density, and is ultra-thin (<10 nm) for horizontally-aligned films but 50-200 nm for vertically aligned films. We show that due to weak inter-SWNT exciton transport relative to exceptional intra-SWNT diffusion, vertically-aligned films are unambiguously favored

  5. All carbon nanotubes are not created equal

    SciTech Connect

    Geohegan, David B; Puretzky, Alexander A; Rouleau, Christopher M

    2010-01-01

    This chapter presents the various factors that enter into consideration when choosing the source of carbon nanotubes for a specific application. Carbon nanotubes are giant molecules made of pure carbon. They have captured the imagination of the scientific community by the unique structure that provides superior physical, chemical, and electrical properties. However, a surprisingly wide disparity exists between the intrinsic properties determined under ideal conditions and the properties that carbon nanotubes exhibit in real world situations. The lack of uniformity in carbon nanotube properties is likely to be the main obstacle holding back the development of carbon nanotube applications. This tutorial addresses the nonuniformity of carbon nanotube properties from the synthesis standpoint. This synthesis-related nonuniformity is on top of the intrinsic chirality distribution that gives the ~1:2 ratio of metallic to semiconducting nanotubes. From the standpoint of carbon bonding chemistry the variation in the quality and reproducibility of carbon nanotube materials is not unexpected. It is an intrinsic feature that is related to the metastability of carbon structures. The extent to which this effect is manifested in carbon nanotube formation is governed by the type and the kinetics of the carbon nanotube synthesis reaction. Addressing this variation is critical if nanotubes are to live up to the potential already demonstrated by their phenomenal physical properties.

  6. Electronic and Mechanical Properties of Hydrogen Functionalized Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Yang, Liu; Han, Jie; Jaffe, Richard L.; Arnold, Jim (Technical Monitor)

    2001-01-01

    We examined the electronic and mechanical properties of hydrogen functionalized carbon nanotubes. The functionalization pattern covers two extreme groups. One group has randomly selected functionalization sites including one to twenty percent of the carbon atoms. The other group has regularly patterned functional sites parallel to the tube axis. Metallic, small-gap semiconducting and large-gap semiconducting carbon nanotubes are studied. The results reveal that the electronic properties of the tubes are very sensitive to the degree of functionalization, with even one percent functionalization being enough to render metallic tubes semiconducting. On the other hand, the mechanical properties, like tensile modulus, are much less sensitive to functionalization. For carbon nanotubes functionalized with specific patterns, the electric properties depends strongly on the nature of the functionalization pattern.

  7. Structure and electronic properties of saturated and unsaturated gallium nitride nanotubes

    SciTech Connect

    Wang, Zhiguo; Wang, Shengjie; Li, Jingbo; Gao, Fei; Weber, William J.

    2009-11-05

    The atomic and electronic structures of saturated and unsaturated GaN nanotubes along the [001] direction with (100) lateral facets are studied using first-principles calculations. Atomic relaxation of nanotubes shows that appreciable distortion occurs in the unsaturated nanotubes. All the nanotubes considered, including saturated and unsaturated ones, exhibit semiconducting, with a direct band gap. Surface states arisen from the threefold-coordinated N and Ga atoms at the lateral facets exist inside the bulk-like band gap. When the nanotubes saturated with hydrogen, these dangling bond bands are removed from the band gap, but the band gap decreases with increasing the wall thickness of the nanotubes.

  8. Fundamental optical processes in armchair carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Hároz, Erik H.; Duque, Juan G.; Tu, Xiaomin; Zheng, Ming; Hight Walker, Angela R.; Hauge, Robert H.; Doorn, Stephen K.; Kono, Junichiro

    2013-01-01

    Single-wall carbon nanotubes provide ideal model one-dimensional (1-D) condensed matter systems in which to address fundamental questions in many-body physics, while, at the same time, they are leading candidates for building blocks in nanoscale optoelectronic circuits. Much attention has been recently paid to their optical properties, arising from 1-D excitons and phonons, which have been revealed via photoluminescence, Raman scattering, and ultrafast optical spectroscopy of semiconducting carbon nanotubes. On the other hand, dynamical properties of metallic nanotubes have been poorly explored, although they are expected to provide a novel setting for the study of electron-hole pairs in the presence of degenerate 1-D electrons. In particular, (n,n)-chirality, or armchair, metallic nanotubes are truly gapless with massless carriers, ideally suited for dynamical studies of Tomonaga-Luttinger liquids. Unfortunately, progress towards such studies has been slowed by the inherent problem of nanotube synthesis whereby both semiconducting and metallic nanotubes are produced. Here, we use post-synthesis separation methods based on density gradient ultracentrifugation and DNA-based ion-exchange chromatography to produce aqueous suspensions strongly enriched in armchair nanotubes. Through resonant Raman spectroscopy of the radial breathing mode phonons, we provide macroscopic and unambiguous evidence that density gradient ultracentrifugation can enrich ensemble samples in armchair nanotubes. Furthermore, using conventional, optical absorption spectroscopy in the near-infrared and visible range, we show that interband absorption in armchair nanotubes is strongly excitonic. Lastly, by examining the G-band mode in Raman spectra, we determine that observation of the broad, lower frequency (G-) feature is a result of resonance with non-armchair ``metallic'' nanotubes. These findings regarding the fundamental optical absorption and scattering processes in metallic carbon nanotubes

  9. Ubiquity of Exciton Localization in Cryogenic Carbon Nanotubes.

    PubMed

    Hofmann, Matthias S; Noé, Jonathan; Kneer, Alexander; Crochet, Jared J; Högele, Alexander

    2016-05-11

    We present photoluminescence studies of individual semiconducting single-wall carbon nanotubes at room and cryogenic temperatures. From the analysis of spatial and spectral features of nanotube photoluminescence, we identify characteristic signatures of unintentional exciton localization. Moreover, we quantify the energy scale of exciton localization potentials as ranging from a few to a few tens of millielectronvolts and stemming from both environmental disorder and shallow covalent side-wall defects. Our results establish disorder-induced crossover from the diffusive to the localized regime of nanotube excitons at cryogenic temperatures as a ubiquitous phenomenon in micelle-encapsulated and as-grown carbon nanotubes. PMID:27105355

  10. Single Wall Nanotube Type-Specific Functionalization and Separation

    NASA Technical Reports Server (NTRS)

    Boul, Peter; Nikolaev, Pavel; Sosa, Edward; Arepalli, Sivaram; Yowell, Leonard

    2008-01-01

    Metallic single-wall carbon nanotubes were selectively solubilized in THF and separated from semiconducting nanotubes. Once separated, the functionalized metallic tubes were de-functionalized to restore their metallic band structure. Absorption and Raman spectroscopy of the enriched samples support conclusions of the enrichment of nanotube samples by metallic type. A scalable method for enriching nanotube conductive type has been developed. Raman and UV-Vis data indicate SWCNT reaction with dodecylbenzenediazonium results in metallic enrichment. It is expected that further refinement of this techniques will lead to more dramatic separations of types and diameters.

  11. Ambipolar transistors based on random networks of WS2 nanotubes

    NASA Astrophysics Data System (ADS)

    Sugahara, Mitsunari; Kawai, Hideki; Yomogida, Yohei; Maniwa, Yutaka; Okada, Susumu; Yanagi, Kazuhiro

    2016-07-01

    WS2 nanotubes are rolled multiwalled nanotubes made of a layered material, tungsten disulfide. Their fibril structures enable the fabrication of random network films; however, these films are nonconducting, and thus have not been used for electronic applications. Here, we demonstrate that carrier injection into WS2 networks using an electrolyte gating approach could cause these networks to act as semiconducting channels. We clarify the Raman characteristics of WS2 nanotubes under electrolyte gating and confirm the feasibility of the injection of electrons and holes. We reveal ambipolar behaviors of the WS2 nanotube networks in field-effect transistor setups with electrolyte gating.

  12. New Insight into Carbon Nanotube Electronic Structure Selectivity

    SciTech Connect

    Sumpter, Bobby G; Meunier, Vincent; Jiang, Deen

    2009-01-01

    The fundamental role of aryl diazonium salts for post synthesis selectivity of carbon nanotubes is investigated using extensive electronic structure calculations. The resulting understanding for diazonium salt based selective separation of conducting and semiconducting carbon nanotubes shows how the primary contributions come from the interplay between the intrinsic electronic structure of the carbon nanotubes and that of the anion of the salt. We demonstrate how the electronic transport properties change upon the formation of charge transfer complexes and upon their conversion into covalently attached functional groups. Our results are found to correlate well with experiments and provide for the first time an atomistic description for diazonium salt based chemical separation of carbon nanotubes

  13. Ubiquity of Exciton Localization in Cryogenic Carbon Nanotubes

    PubMed Central

    2016-01-01

    We present photoluminescence studies of individual semiconducting single-wall carbon nanotubes at room and cryogenic temperatures. From the analysis of spatial and spectral features of nanotube photoluminescence, we identify characteristic signatures of unintentional exciton localization. Moreover, we quantify the energy scale of exciton localization potentials as ranging from a few to a few tens of millielectronvolts and stemming from both environmental disorder and shallow covalent side-wall defects. Our results establish disorder-induced crossover from the diffusive to the localized regime of nanotube excitons at cryogenic temperatures as a ubiquitous phenomenon in micelle-encapsulated and as-grown carbon nanotubes. PMID:27105355

  14. Plasmonic nature of the terahertz conductivity peak in single-wall carbon nanotubes.

    PubMed

    Zhang, Qi; Hároz, Erik H; Jin, Zehua; Ren, Lei; Wang, Xuan; Arvidson, Rolf S; Lüttge, Andreas; Kono, Junichiro

    2013-01-01

    Plasmon resonance is expected to occur in metallic and doped semiconducting carbon nanotubes in the terahertz frequency range, but its convincing identification has so far been elusive. The origin of the terahertz conductivity peak commonly observed for carbon nanotube ensembles remains controversial. Here we present results of optical, terahertz, and direct current (DC) transport measurements on highly enriched metallic and semiconducting nanotube films. A broad and strong terahertz conductivity peak appears in both types of films, whose behaviors are consistent with the plasmon resonance explanation, firmly ruling out other alternative explanations such as absorption due to curvature-induced gaps. PMID:24224898

  15. Carbon nanotube devices: Sorting, Assembling, Characterizing

    NASA Astrophysics Data System (ADS)

    Krupke, Ralph

    2009-03-01

    Carbon nanotubes have been studied extensively over the last decade. Various exceptional properties have been revealed which still drive the vision about using carbon nanotube in future electronics, for instance as molecular nanoscale transistors or electromigration resistant interconnects. For many years a major obstacle was the inability to grow nanotubes with defined dimensions (length, diameter) and electronic properties (metallic,semiconducting). Recently those problems have been solved to a large extent by advanced sorting techniques. Today the challenge is to assemble nanotubes devices with defined properties to form a complex circuitry. As progress is made in making highly-integrated nanotube device arrays new characterization techniques have to be developed which allow testing large number of devices within an acceptable time. Along this line I will report on the state-of-the-art of sorting of carbon nanotube, as a base for nanotube device fabrication [1]. I will then explain our strategy to assemble high-density arrays of nanotube devices [2] and discuss a new characterization technique for nanotube devices [3]. Finally I will introduce a novel device engineering tool [4]. [4pt] [1] R. Krupke et al., ``Separation techniques for carbon nanotubes'' in Chemistry of Carbon Nanotubes, p.129-139, American Scientific Publishers 2008[0pt] [2] A. Vijayaraghavan et al., ``Ultra-Large-Scale Directed Assembly of Single-Walled Carbon Nanotube Devices'', Nano Lett. 7 (2007) 1556-1560[0pt] [3] A. Vijayaraghavan et al., ``Imaging Electronic Structure of Carbon Nanotubes by Voltage-Contrast Scanning Electron Microscopy'', Nano Resarch 1 (2008) 321-332[0pt] [4] C. W. Marquardt et al., ``Reversible metal-insulator transitions in metallic single-walled carbon nanotubes'', Nano Lett. 9 (2008) 2767-2772

  16. Poly(3-hexylthiophene)/multiwalled carbon hybrid coaxial nanotubes: nanoscale rectification and photovoltaic characteristics.

    PubMed

    Kim, Kihyun; Shin, Ji Won; Lee, Yong Baek; Cho, Mi Yeon; Lee, Suk Ho; Park, Dong Hyuk; Jang, Dong Kyu; Lee, Cheol Jin; Joo, Jinsoo

    2010-07-27

    We fabricate hybrid coaxial nanotubes (NTs) of multiwalled carbon nanotubes (MWCNTs) coated with light-emitting poly(3-hexylthiophene) (P3HT). The p-type P3HT material with a thickness of approximately 20 nm is electrochemically deposited onto the surface of the MWCNT. The formation of hybrid coaxial NTs of the P3HT/MWCNT is confirmed by a transmission electron microscope, FT-IR, and Raman spectra. The optical and structural properties of the hybrid NTs are characterized using ultraviolet and visible absorption, Raman, and photoluminescence (PL) spectra where, it is shown that the PL intensity of the P3HT materials decreases after the hybridization with the MWCNTs. The current-voltage (I-V) characteristics of the outer P3HT single NT show the semiconducting behavior, while ohmic behavior is observed for the inner single MWCNT. The I-V characteristics of the hybrid junction between the outer P3HT NT and the inner MWCNT, for the hybrid single NT, exhibit the characteristics of a diode (i.e., rectification), whose efficiency is clearly enhanced with light irradiation. The rectification effect of the hybrid single NT has been analyzed in terms of charge tunneling models. The quasi-photovoltaic effect is also observed at low bias for the P3HT/MWCNT hybrid single NT. PMID:20533839

  17. Josephson junction

    DOEpatents

    Wendt, Joel R.; Plut, Thomas A.; Martens, Jon S.

    1995-01-01

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material.

  18. Josephson junction

    DOEpatents

    Wendt, J.R.; Plut, T.A.; Martens, J.S.

    1995-05-02

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material. 10 figs.

  19. Bimetallic junctions

    NASA Technical Reports Server (NTRS)

    Arcella, F. G.; Lessmann, G. G.; Lindberg, R. A. (Inventor)

    1977-01-01

    The formation of voids through interdiffusion in bimetallic welded structures exposed to high operating temperatures is inhibited by utilizing an alloy of the parent materials in the junction of the parent materials or by preannealing the junction at an ultrahigh temperature. These methods are also used to reduce the concentration gradient of a hardening agent.

  20. Spectroscopy of Optical Excitations in Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Ma, Yingzhong

    2006-03-01

    Understanding the optical spectra and electronic excited state dynamics of carbon naotubes is important both for fundamental research and a wide variety of potential applications. In this presentation, we will report the results of a systematic study on semiconducting single-walled carbon nanotubes (SWNTs) obtained by utilizing complementary femtosecond spectroscopic techniques, including fluorescence up-conversion, frequency-resolved transient absorption, and three-pulse photon echo peakshift (3PEPS) spectroscopy. Our efforts have focused on optically selective detection of the spectra and dynamics associated with structurally distinct semiconducting SWNT species. Using individual nanotube enriched micelle-dispersed SWNT preparations, in combination with resonant excitation and detection, has enabled us to independently access selected species, such as the (8,3), (6,5), (7,5), (11,0), (7,6) and (9,5) nanotubes. We will discuss the following topics: (1) the excitonic nature of the elementary excitation and its unambiguous identification from direct determination of the exciton binding energy for a selected semiconducting nanotube, the (8,3) tube; (2) the spectroscopic and dynamical signatures of exciton-exciton annihilation and its predominant role in governing ultrafast excited state relaxation; (3) the annihilation-concomitant exciton dissociation and the spectroscopic and dynamic features of the resulting electron-hole continuum; (4) timescales characterizing the ultrafast thermalization processes. In addition, we will demonstrate the power of 3PEPS spectroscopy to elucidate the spectral properties and dynamics of SWNTs. This work was supported by the NSF.

  1. Physical and Electronic Isolation of Carbon Nanotube Conductors

    NASA Technical Reports Server (NTRS)

    OKeeffe, James; Biegel, Bryan (Technical Monitor)

    2001-01-01

    Multi-walled nanotubes are proposed as a method to electrically and physically isolate nanoscale conductors from their surroundings. We use tight binding (TB) and density functional theory (DFT) to simulate the effects of an external electric field on multi-wall nanotubes. Two categories of multi-wall nanotube are investigated, those with metallic and semiconducting outer shells. In the metallic case, simulations show that the outer wall effectively screens the inner core from an applied electric field. This offers the ability to reduce crosstalk between nanotube conductors. A semiconducting outer shell is found not to perturb an electric field incident on the inner core, thereby providing physical isolation while allowing the tube to remain electrically coupled to its surroundings.

  2. Semiconducting compounds and devices incorporating same

    SciTech Connect

    Marks, Tobin J; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

    2014-06-17

    Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

  3. Semiconducting compounds and devices incorporating same

    DOEpatents

    Marks, Tobin J.; Facchetti, Antonio; Boudreault, Pierre-Luc; Miyauchi, Hiroyuki

    2016-01-19

    Disclosed are molecular and polymeric compounds having desirable properties as semiconducting materials. Such compounds can exhibit desirable electronic properties and possess processing advantages including solution-processability and/or good stability. Organic transistor and photovoltaic devices incorporating the present compounds as the active layer exhibit good device performance.

  4. Building Organized Structures using Nanotubes

    NASA Astrophysics Data System (ADS)

    Ajayan, Pulickel M.

    This talk will focus on the directed assembly of multiwalled carbon nanotubes on planar substrates into highly organized structures that include vertically and horizontally oriented arrays, ordered fibers and porous membranes. The concept of growing such architectures is based on growth selectivity on certain surfaces compared to others. Selective placement of ordered nanotube arrays is achieved on patterned templates prepared by lithography or oxide templates with well-defined pores. Growth of nanotubes is achieved by chemical vapor deposition (CVD) using hydrocarbon precursors and vapor phase catalyst delivery. The new technique developed in our laboratory allows enormous flexibility in building a large number of complex structures based on nanotube building units. We will also discuss some of our recent efforts in creating nanotube junctions selectively and controllably.

  5. Boron nitride nanotubes and nanosheets.

    PubMed

    Golberg, Dmitri; Bando, Yoshio; Huang, Yang; Terao, Takeshi; Mitome, Masanori; Tang, Chengchun; Zhi, Chunyi

    2010-06-22

    Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments. PMID:20462272

  6. Dispersionless propagation of electron wavepackets in single-walled carbon nanotubes

    SciTech Connect

    Rosati, Roberto; Rossi, Fausto; Dolcini, Fabrizio

    2015-06-15

    We investigate the propagation of electron wavepackets in single-walled carbon nanotubes via a Lindblad-based density-matrix approach that enables us to account for both dissipation and decoherence effects induced by various phonon modes. We show that, while in semiconducting nanotubes the wavepacket experiences the typical dispersion of conventional materials, in metallic nanotubes its shape remains essentially unaltered, even in the presence of the electron-phonon coupling, up to micron distances at room temperature.

  7. Medium scale carbon nanotube thin film integrated circuits on flexible plastic substrates

    DOEpatents

    Rogers, John A; Cao, Qing; Alam, Muhammad; Pimparkar, Ninad

    2015-02-03

    The present invention provides device components geometries and fabrication strategies for enhancing the electronic performance of electronic devices based on thin films of randomly oriented or partially aligned semiconducting nanotubes. In certain aspects, devices and methods of the present invention incorporate a patterned layer of randomly oriented or partially aligned carbon nanotubes, such as one or more interconnected SWNT networks, providing a semiconductor channel exhibiting improved electronic properties relative to conventional nanotubes-based electronic systems.

  8. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  9. Label-free immunodetection with CMOS-compatible semiconducting nanowires.

    PubMed

    Stern, Eric; Klemic, James F; Routenberg, David A; Wyrembak, Pauline N; Turner-Evans, Daniel B; Hamilton, Andrew D; LaVan, David A; Fahmy, Tarek M; Reed, Mark A

    2007-02-01

    Semiconducting nanowires have the potential to function as highly sensitive and selective sensors for the label-free detection of low concentrations of pathogenic microorganisms. Successful solution-phase nanowire sensing has been demonstrated for ions, small molecules, proteins, DNA and viruses; however, 'bottom-up' nanowires (or similarly configured carbon nanotubes) used for these demonstrations require hybrid fabrication schemes, which result in severe integration issues that have hindered widespread application. Alternative 'top-down' fabrication methods of nanowire-like devices produce disappointing performance because of process-induced material and device degradation. Here we report an approach that uses complementary metal oxide semiconductor (CMOS) field effect transistor compatible technology and hence demonstrate the specific label-free detection of below 100 femtomolar concentrations of antibodies as well as real-time monitoring of the cellular immune response. This approach eliminates the need for hybrid methods and enables system-scale integration of these sensors with signal processing and information systems. Additionally, the ability to monitor antibody binding and sense the cellular immune response in real time with readily available technology should facilitate widespread diagnostic applications. PMID:17268465

  10. Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice

    NASA Astrophysics Data System (ADS)

    Pu, Kanyi; Shuhendler, Adam J.; Jokerst, Jesse V.; Mei, Jianguo; Gambhir, Sanjiv S.; Bao, Zhenan; Rao, Jianghong

    2014-03-01

    Photoacoustic imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, photoacoustic molecular imaging probes have to be developed. Here, we introduce near-infrared light absorbing semiconducting polymer nanoparticles as a new class of contrast agents for photoacoustic molecular imaging. These nanoparticles can produce a stronger signal than the commonly used single-walled carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph-node photoacoustic mapping in living mice at a low systemic injection mass. Furthermore, the semiconducting polymer nanoparticles possess high structural flexibility, narrow photoacoustic spectral profiles and strong resistance to photodegradation and oxidation, enabling the development of the first near-infrared ratiometric photoacoustic probe for in vivo real-time imaging of reactive oxygen species--vital chemical mediators of many diseases. These results demonstrate semiconducting polymer nanoparticles to be an ideal nanoplatform for developing photoacoustic molecular probes.

  11. Semiconducting polymer nanoparticles as photoacoustic molecular imaging probes in living mice.

    PubMed

    Pu, Kanyi; Shuhendler, Adam J; Jokerst, Jesse V; Mei, Jianguo; Gambhir, Sanjiv S; Bao, Zhenan; Rao, Jianghong

    2014-03-01

    Photoacoustic imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, photoacoustic molecular imaging probes have to be developed. Here, we introduce near-infrared light absorbing semiconducting polymer nanoparticles as a new class of contrast agents for photoacoustic molecular imaging. These nanoparticles can produce a stronger signal than the commonly used single-walled carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph-node photoacoustic mapping in living mice at a low systemic injection mass. Furthermore, the semiconducting polymer nanoparticles possess high structural flexibility, narrow photoacoustic spectral profiles and strong resistance to photodegradation and oxidation, enabling the development of the first near-infrared ratiometric photoacoustic probe for in vivo real-time imaging of reactive oxygen species--vital chemical mediators of many diseases. These results demonstrate semiconducting polymer nanoparticles to be an ideal nanoplatform for developing photoacoustic molecular probes. PMID:24463363

  12. Superconducting Nanotube Dots

    NASA Astrophysics Data System (ADS)

    Schönenberger, Christian

    2007-03-01

    In this talk, I will focus on charge transport in carbon nanotube devices with superconducting source and drain contacts in the finite-bias non-equilibrium transport regime. As contact material, bi-layers of Au and Al were used and transport has been studied at temperatures in the 0.1 K range. Because carbon nanotubes are quantum dots (qdots), we in fact explore the physics of qdots with superconducting contacts, something which only recently became possible thanks to carbon nanotubes and most recently to semiconducting nanowires. In my talk, I will first summarize our pioneering work on multiwalled carbon nanotubes in which we could demonstrate proximity induced effects both in the weak and the strong coupling regime. In the latter an intriguing interplay between superconductivity and Kondo physics appears. Then, I will discuss the physics of multiple Andreev reflection in a situation when only one resonant state is present and compare this with experimental results. Finally, I will compare our early results with our recent measurements on single-wall carbon nanotubes. This work has been supported by the Swiss Institute on Nanoscience, the Swiss National Science Foundation, EU projects DIENOW and HYSWITCH. I gratefully acknowledge contribution of the following persons to this work (in alphabetic order): B. Babic, W. Belzig, C. Bruder, M. R. Buitelaar, J.-C. Cuevas, A. Eichler, L. Forro, J. Gobrecht, M. Gr"aber, M. Iqbal, T. Kontos, A. Levy Yeyati, A. Martin-Rodero, T. Nussbaumer, S. Oberholzer, C. Strunk, H. Scharf, J. Trbovic, E. Vecino, M. Weiss

  13. Single-Chain Semiconducting Polymer Dots

    PubMed Central

    2015-01-01

    This work describes the preparation and validation of single-chain semiconducting polymer dots (sPdots), which were generated using a method based on surface immobilization, washing, and cleavage. The sPdots have an ultrasmall size of ∼3.0 nm as determined by atomic force microscopy, a size that is consistent with the anticipated diameter calculated from the molecular weight of the single-chain semiconducting polymer. sPdots should find use in biology and medicine as a new class of fluorescent probes. The FRET assay this work presents is a simple and rapid test to ensure methods developed for preparing sPdot indeed produced single-chain Pdots as designed. PMID:25521606

  14. TEM-nanoindentation studies of semiconducting structures.

    PubMed

    Le Bourhis, E; Patriarche, G

    2007-01-01

    This paper reviews the application of nanoindentation coupled with transmission electron microscopy (TEM) to investigations of the plastic behaviour of semiconducting structures and its implication for device design. Instrumented nanoindentation has been developed to extract the mechanical behaviour of small volumes scaled to those encountered in semiconductor heterostructures. We illustrate that TEM is a powerful complementary tool for the study of local plasticity induced by nanoindentation. TEM-nanoindentation allows for detailed understanding of the plastic deformation in semiconducting structures and opens practical routes for improvement of devices. Performances of heterostructures are deteriously affected by dislocations that relax the lattice mismatched layers. Different ways to obtain compliant substructures are being developed in order to concentrate the plastic relaxation underneath the heterostructure. Such approaches allow for mechanical design of micro- and opto-electronic devices to be considered throughout the fabrication process. PMID:16901706

  15. Understanding electronic structure and transport properties in nanoscale junctions

    NASA Astrophysics Data System (ADS)

    Dhungana, Kamal B.

    Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder for theorist to interpret the experimental results. To identify the junction configuration that possibly exists during the experimental measurement of conductance in molecular junction, we created an ensemble of Ruthanium-bis(terpyridine) molecular devices, and studied the transport behavior in these molecular junctions. This helps us identifying the junction geometry that yields the experimentally measured current-voltage characteristics. Today's electronic devices mostly ignore the spin effect of an electron. The inclusion of spin effect of an electron on solid-state transistor allows us to build more efficient electronic devices; this also alleviates the problem of huge heat dissipation in the nanoscale electronic devices. Different materials have been utilized to build three terminals spin transistor since its inception in 1950. In search of suitable candidates for the molecular spin transistor, we have recently designed a spin-valve transistor based on an organometallic molecule; a large amplification (320 %) in tunnel magneto-resistance (TMR) is found to occur at an experimentally accessible gate field. This suggests that the organic molecules can be utilized for making the next generation three terminal spintronic devices. Similarly, we have designed a

  16. Low bandgap semiconducting polymers for polymeric photovoltaics.

    PubMed

    Liu, Chang; Wang, Kai; Gong, Xiong; Heeger, Alan J

    2016-08-22

    In order to develop high performance polymer solar cells (PSCs), full exploitation of the sun-irradiation from ultraviolet (UV) to near infrared (NIR) is one of the key factors to ensure high photocurrents and thus high efficiency. In this review, five of the effective design rules for approaching LBG semiconducting polymers with high molar absorptivity, suitable energy levels, high charge carrier mobility and high solubility in organic solvents are overviewed. These design stratagems include fused heterocycles for facilitating π-electron flowing along the polymer backbone, groups/atoms bridging adjacent rings for maintaining a high planarity, introduction of electron-withdrawing units for lowering the bandgap (Eg), donor-acceptor (D-A) copolymerization for narrowing Eg and 2-dimensional conjugation for broadened absorption and enhanced hole mobility. It has been demonstrated that LBG semiconducting polymers based on electron-donor units combined with strong electron-withdrawing units possess excellent electronic and optic properties, emerging as excellent candidates for efficient PSCs. While for ultrasensitive photodetectors (PDs), which have intensive applications in both scientific and industrial sectors, sensing from the UV to the NIR region is of critical importance. For polymer PDs, Eg as low as 0.8 eV has been obtained through a rational design stratagem, covering a broad wavelength range from the UV to the NIR region (1450 nm). However, the response time of the polymer PDs are severely limited by the hole mobility of LBG semiconducting polymers, which is significantly lower than those of the inorganic materials. Thus, further advancing the hole mobility of LBG semiconducting polymers is of equal importance as broadening the spectral response for approaching uncooled ultrasensitive broadband polymer PDs in the future study. PMID:26548402

  17. Magnetic nanotubes

    DOEpatents

    Matsui, Hiroshi; Matsunaga, Tadashi

    2010-11-16

    A magnetic nanotube includes bacterial magnetic nanocrystals contacted onto a nanotube which absorbs the nanocrystals. The nanocrystals are contacted on at least one surface of the nanotube. A method of fabricating a magnetic nanotube includes synthesizing the bacterial magnetic nanocrystals, which have an outer layer of proteins. A nanotube provided is capable of absorbing the nanocrystals and contacting the nanotube with the nanocrystals. The nanotube is preferably a peptide bolaamphiphile. A nanotube solution and a nanocrystal solution including a buffer and a concentration of nanocrystals are mixed. The concentration of nanocrystals is optimized, resulting in a nanocrystal to nanotube ratio for which bacterial magnetic nanocrystals are immobilized on at least one surface of the nanotubes. The ratio controls whether the nanocrystals bind only to the interior or to the exterior surfaces of the nanotubes. Uses include cell manipulation and separation, biological assay, enzyme recovery, and biosensors.

  18. Electrical device fabrication from nanotube formations

    DOEpatents

    Nicholas, Nolan Walker; Kittrell, W. Carter; Kim, Myung Jong; Schmidt, Howard K.

    2013-03-12

    A method for forming nanotube electrical devices, arrays of nanotube electrical devices, and device structures and arrays of device structures formed by the methods. Various methods of the present invention allow creation of semiconducting and/or conducting devices from readily grown SWNT carpets rather than requiring the preparation of a patterned growth channel and takes advantage of the self-controlling nature of these carpet heights to ensure a known and controlled channel length for reliable electronic properties as compared to the prior methods.

  19. Facile fabrication of organic/inorganic nanotube heterojunction arrays for enhanced photoelectrochemical water splitting

    NASA Astrophysics Data System (ADS)

    Chen, Yingzhi; Li, Aoxiang; Yue, Xiaoqi; Wang, Lu-Ning; Huang, Zheng-Hong; Kang, Feiyu; Volinsky, Alex A.

    2016-07-01

    Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi) layer were fabricated for photoelectrochemical water splitting. In this arrayed architecture, a PDi layer with a tunable thickness was coated on anodic TiO2 nanotube arrays by physical vapor deposition, which is advantageous for the formation of a uniform layer and an adequate interface contact between PDi and TiO2. The obtained PDi/TiO2 junction exhibited broadened visible light absorption, and an effective interface for enhanced photogenerated electron-hole separation, which is supported by the reduced charge transfer resistance and prolonged excitation lifetime via impedance spectroscopy analysis and fluorescence emission decay investigations. Consequently, such a heterojunction photoanode was photoresponsive to a wide visible light region of 400-600 nm, and thus demonstrated a highly enhanced photocurrent density at 1.23 V vs. a reversible hydrogen electrode. Additionally, the durability of such a photoanode can be guaranteed after long-time illumination because of the geometrical restraint imposed by the PDi aggregates. These results pave the way to discover new organic/inorganic assemblies for high-performance photoelectric applications and device integration.Organic/inorganic heterojunction photoanodes are appealing for making concurrent use of the highly photoactive organic semiconductors, and the efficient dielectric screening provided by their inorganic counterparts. In the present work, organic/inorganic nanotube heterojunction arrays composed of TiO2 nanotube arrays and a semiconducting N,N-(dicyclohexyl) perylene-3,4,9,10-tetracarboxylic diimide (PDi

  20. Carbon Nanotubes: Molecular Electronic Components

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Saini, Subhash; Menon, Madhu

    1997-01-01

    The carbon Nanotube junctions have recently emerged as excellent candidates for use as the building blocks in the formation of nanoscale molecular electronic networks. While the simple joint of two dissimilar tubes can be generated by the introduction of a pair of heptagon-pentagon defects in an otherwise perfect hexagonal graphene sheet, more complex joints require other mechanisms. In this work we explore structural characteristics of complex 3-point junctions of carbon nanotubes using a generalized tight-binding molecular-dynamics scheme. The study of pi-electron local densities of states (LDOS) of these junctions reveal many interesting features, most prominent among them being the defect-induced states in the gap.

  1. Carbon nanotube transistors, sensors, and beyond

    NASA Astrophysics Data System (ADS)

    Zhou, Xinjian

    Carbon nanotubes are tiny hollow cylinders, made from a single graphene sheet, that possess many amazing properties. Another reason why nanotubes have generated intense research activities from scientists of various disciplines is they represent a new class of materials for the study of one-dimensional physics. In this thesis we investigate the electrical transport of semiconducting single-walled carbon nanotubes and their potential applications as biological sensors. Electrons have been predicted, by theoretical physicists, to go through nanotubes without much resistance. But this has not been properly quantified experimentally, and the origin of the routinely observed large resistance in nanotubes is not clear. In this thesis we show that in moderate long high quality nanotubes the electrical transport is limited by electron-phonon scattering. Systematic studies are carried out using many devices of different diameters at various temperatures. The resistance and inverse of peak mobility are observed to decrease linearly with temperature, indicating the influence of phonons. The conductance and peak mobility scales with nanotube diameters also, in a linear fashion and quadratic fashion respectively. Based on electron-phonon scattering, a theory model is developed that can not only predict how the resistance changes with gate voltage but also explain the observed temperature and diameter dependence. This work clarifies the nature of electrical transport in nanotubes and sets a performance limit of nanotube devices in diffusive regime. The electrical transport in nanotubes is extremely sensitive to local electrostatic environment due to their small size, large surface to volume ratio and high mobility, making nanotubes ideal key elements in biological sensors. In the second part of this thesis, we integrate nanotubes with supported lipid bilayers, mimic structures of cell membranes, and use this platform as a way to introduce biomolecules into the vicinity of

  2. Analysis of long-channel nanotube field-effect-transistors (NT FETs)

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation provides an analysis of long-channel nanotube (NT) field effect transistors (FET) from NASA's Ames Research Center. The structure of such a transistor including the electrode contact, 1D junction, and the planar junction is outlined. Also mentioned are various characteristics of a nanotube tip-equipped scanning tunnel microscope (STM).

  3. Coupled study by TEM/EELS and STM/STS of electronic properties of C- and CN-nanotubes

    NASA Astrophysics Data System (ADS)

    Lin, Hong; Lagoute, Jérôme; Repain, Vincent; Chacon, Cyril; Girard, Yann; Lauret, Jean-Sébastien; Arenal, Raul; Ducastelle, François; Rousset, Sylvie; Loiseau, Annick

    2011-12-01

    Carbon nanotubes are the focus of considerable research efforts due to their fascinating physical properties. They provide an excellent model system for the study of one-dimensional materials and molecular electronics. The chirality of nanotubes can lead to very different electronic behaviour, either metallic or semiconducting. Their electronic spectrum consists of a series of Van Hove singularities defining a bandgap for semiconducting tubes and molecular orbitals at the corresponding energies. A promising way to tune the nanotubes electronic properties for future applications is to use doping by heteroatoms. Here we report on the experimental investigation of the role of many-body interactions in nanotube bandgaps, the visualization in direct space of the molecular orbitals of nanotubes and the properties of nitrogen doped nanotubes using scanning tunneling microscopy and transmission electron microscopy as well as electron energy loss spectroscopy.

  4. Electron transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide: first-principles analysis.

    PubMed

    Srivastava, Anurag; Sharma, Vikash; Kaur, Kamalpreet; Khan, Md Shahzad; Ahuja, Rajeev; Rao, V K

    2015-07-01

    First-principles analysis based on density functional theory was performed to compute the electronic and transport properties of a single-walled carbon nanotube in the presence of hydrogen cyanide. A chiral (4,1) carbon nanotube was found to become less metallic as the number of hydrogen cyanide molecules nearby increased. When there were a sufficient number of hydrogen cyanide molecules close to the nanotube, it became semiconducting. This metallic to semiconducting transformation of the nanotube was verified by analyzing its conductance and current as a function of the number of molecules of hydrogen cyanide present. The conductivity of the carbon nanotube was very high when no hydrogen cyanide molecules were present, but decreased considerably when even just a single hydrogen cyanide molecule approached the surface of the nanotube. PMID:26072123

  5. Radial pn Junction, Wire Array Solar Cells

    NASA Astrophysics Data System (ADS)

    Kayes, Brendan Melville

    Radial pn junctions are potentially of interest in photovoltaics as a way to decouple light absorption from minority carrier collection. In a traditional planar design these occur in the same dimension, and this sets a lower limit on absorber material quality, as cells must both be thick enough to effectively absorb the solar spectrum while also having minority-carrier diffusion lengths long enough to allow for efficient collection of the photo-generated carriers. Therefore, highly efficient photovoltaic devices currently require highly pure materials and expensive processing techniques, while low cost devices generally operate at relatively low efficiency. The radial pn junction design sets the direction of light absorption perpendicular to the direction of minority-carrier transport, allowing the cell to be thick enough for effective light absorption, while also providing a short pathway for carrier collection. This is achieved by increasing the junction area, in order to decrease the path length any photogenerated minority carrier must travel, to be less than its minority carrier diffusion length. Realizing this geometry in an array of semiconducting wires, by for example depositing a single-crystalline inorganic semiconducting absorber layer at high deposition rates from the gas phase by the vapor-liquid-solid (VLS) mechanism, allows for a "bottom up" approach to device fabrication, which can in principle dramatically reduce the materials costs associated with a cell.

  6. Effective-mass theory of collapsed carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Nakanishi, Takeshi; Ando, Tsuneya

    2015-04-01

    Band structure is theoretically studied in partially flattened carbon nanotubes within an effective-mass scheme. Effects of interwall interactions are shown to be important in nonchiral nanotubes such as zigzag and armchair and can essentially be neglected in chiral nanotubes except in the close vicinity of nonchiral tubes. In fact, interwall interactions significantly modify states depending on relative displacement in the flattened region in nonchiral tubes and can convert semiconducting tubes into metallic and vice versa. They diminish rapidly when the chiral angle deviates from that of the zigzag or armchair tube, although the decay is slower in the vicinity of armchair tubes.

  7. Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption.

    PubMed

    Ketolainen, T; Havu, V; Puska, M J

    2015-02-01

    The conductivity of carbon nanotube thin films is mainly determined by carbon nanotube junctions, the resistance of which can be reduced by several different methods. We investigate electronic transport through carbon nanotube junctions in a four-terminal configuration, where two metallic single-wall carbon nanotubes are linked by a group 6 transition metal atom. The transport calculations are based on the Green's function method combined with the density-functional theory. The transition metal atom is found to enhance the transport through the junction near the Fermi level. However, the size of the nanotube affects the improvement in the conductivity. The enhancement is related to the hybridization of chromium and carbon atom orbitals, which is clearly reflected in the character of eigenstates near the Fermi level. The effects of chromium atoms and precursor molecules remaining adsorbed on the nanotubes outside the junctions are also examined. PMID:25662658

  8. Enhancing conductivity of metallic carbon nanotube networks by transition metal adsorption

    SciTech Connect

    Ketolainen, T. Havu, V.; Puska, M. J.

    2015-02-07

    The conductivity of carbon nanotube thin films is mainly determined by carbon nanotube junctions, the resistance of which can be reduced by several different methods. We investigate electronic transport through carbon nanotube junctions in a four-terminal configuration, where two metallic single-wall carbon nanotubes are linked by a group 6 transition metal atom. The transport calculations are based on the Green’s function method combined with the density-functional theory. The transition metal atom is found to enhance the transport through the junction near the Fermi level. However, the size of the nanotube affects the improvement in the conductivity. The enhancement is related to the hybridization of chromium and carbon atom orbitals, which is clearly reflected in the character of eigenstates near the Fermi level. The effects of chromium atoms and precursor molecules remaining adsorbed on the nanotubes outside the junctions are also examined.

  9. Single-walled carbon nanotube networks for flexible and printed electronics

    NASA Astrophysics Data System (ADS)

    Zaumseil, Jana

    2015-07-01

    Networks of single-walled carbon nanotubes (SWNTs) can be processed from solution and have excellent mechanical properties. They are highly flexible and stretchable. Depending on the type of nanotubes (semiconducting or metallic) they can be used as replacements for metal or transparent conductive oxide electrodes or as semiconducting layers for field-effect transistors (FETs) with high carrier mobilities. They are thus competitive alternatives to other solution-processable materials for flexible and printed electronics. This review introduces the basic properties of SWNTs, current methods for dispersion and separation of metallic and semiconducting SWNTs and techniques to deposit and pattern dense networks from dispersion. Recent examples of applications of carbon nanotubes as conductors and semiconductors in (opto-)electronic devices and integrated circuits will be discussed.

  10. Compressed carbon nanotubes: A family of new multifunctional carbon allotropes

    PubMed Central

    Hu, Meng; Zhao, Zhisheng; Tian, Fei; Oganov, Artem R.; Wang, Qianqian; Xiong, Mei; Fan, Changzeng; Wen, Bin; He, Julong; Yu, Dongli; Wang, Hui-Tian; Xu, Bo; Tian, Yongjun

    2013-01-01

    The exploration of novel functional carbon polymorphs is an enduring topic of scientific investigations. In this paper, we present simulations demonstrating metastable carbon phases as the result of pressure induced carbon nanotube polymerization. The configuration, bonding, electronic, and mechanical characteristics of carbon polymers strongly depend on the imposed hydrostatic/non-hydrostatic pressure, as well as on the geometry of the raw carbon nanotubes including diameter, chirality, stacking manner, and wall number. Especially, transition processes under hydrostatic/non-hydrostatic pressure are investigated, revealing unexpectedly low transition barriers and demonstrating sp2→sp3 bonding changes as well as peculiar oscillations of electronic property (e.g., semiconducting→metallic→semiconducting transitions). These polymerized nanotubes show versatile and superior physical properties, such as superhardness, high tensile strength and ductility, and tunable electronic properties (semiconducting or metallic). PMID:23435585

  11. Electrical properties and applications of carbon nanotube structures.

    PubMed

    Bandaru, Prabhakar R

    2007-01-01

    The experimentally verified electrical properties of carbon nanotube structures and manifestations in related phenomena such as thermoelectricity, superconductivity, electroluminescence, and photoconductivity are reviewed. The possibility of using naturally formed complex nanotube morphologies, such as Y-junctions, for new device architectures are then considered. Technological applications of the electrical properties of nanotube derived structures in transistor applications, high frequency nanoelectronics, field emission, and biological sensing are then outlined. The review concludes with an outlook on the technological potential of nanotubes and the need for new device architectures for nanotube systems integration. PMID:17450889

  12. Silicon Carbide Nanotube Synthesized

    NASA Technical Reports Server (NTRS)

    Lienhard, Michael A.; Larkin, David J.

    2003-01-01

    Carbon nanotubes (CNTs) have generated a great deal of scientific and commercial interest because of the countless envisioned applications that stem from their extraordinary materials properties. Included among these properties are high mechanical strength (tensile and modulus), high thermal conductivity, and electrical properties that make different forms of single-walled CNTs either conducting or semiconducting, and therefore, suitable for making ultraminiature, high-performance CNT-based electronics, sensors, and actuators. Among the limitations for CNTs is their inability to survive in high-temperature, harsh-environment applications. Silicon carbon nanotubes (SiCNTs) are being developed for their superior material properties under such conditions. For example, SiC is stable in regards to oxidation in air to temperatures exceeding 1000 C, whereas carbon-based materials are limited to 600 C. The high-temperature stability of SiCNTs is envisioned to enable high-temperature, harsh-environment nanofiber- and nanotube-reinforced ceramics. In addition, single-crystal SiC-based semiconductors are being developed for hightemperature, high-power electronics, and by analogy to CNTs with silicon semiconductors, SiCNTs with single-crystal SiC-based semiconductors may allow high-temperature harsh-environment nanoelectronics, nanosensors, and nanoactuators to be realized. Another challenge in CNT development is the difficulty of chemically modifying the tube walls, which are composed of chemically stable graphene sheets. The chemical substitution of the CNTs walls will be necessary for nanotube self-assembly and biological- and chemical-sensing applications. SiCNTs are expected to have a different multiple-bilayer wall structure, allowing the surface Si atoms to be functionalized readily with molecules that will allow SiCNTs to undergo self-assembly and be compatible with a variety of materials (for biotechnology applications and high-performance fiber-reinforced ceramics).

  13. Efficient photovoltaic cells from semiconducting polymer heterojunctions

    NASA Astrophysics Data System (ADS)

    Jenekhe, Samson A.; Yi, Shujian

    2000-10-01

    Solar cells made from spin-coated bilayer thin-film heterojunctions of poly(p-phenylene vinylene) and poly(benzimidazobenzophenanthroline ladder) were found to have photovoltaic charge collection efficiency as high as 49%. The power conversion efficiency varied from 1.4% under sunlight illumination to 2.0% at the peak wavelength. A space-charge region around the polymer/polymer interface, Ohmic contacts at the electrodes, and complementary absorption bands of the semiconducting polymers, play important roles in the efficient charge collection in the photocells.

  14. Bromophenyl functionalization of carbon nanotubes: an ab initio study.

    PubMed

    Janssen, Jonathan Laflamme; Beaudin, Jason; Hine, Nicholas D M; Haynes, Peter D; Côté, Michel

    2013-09-20

    We study the thermodynamics of bromophenyl functionalization of carbon nanotubes with respect to diameter and metallic/insulating character using density-functional theory (DFT). On the one hand, we show that the functionalization of metallic nanotubes is thermodynamically favoured over that of semiconducting ones, in agreement with what binding energy calculations previously suggested. On the other hand, we show that the activation energy for the grafting of a bromophenyl molecule onto a semiconducting zigzag nanotube ranges from 0.72 to 0.75 eV without any clear diameter dependence within numerical accuracy. This implies that this functionalization is not selective with respect to diameter at room temperature, which explains the contradictory experimental selectivities reported in the literature. This contrasts with what is suggested by the clear diameter dependence of the binding energy of a single bromophenyl molecule, which ranges from 1.52 eV for an (8, 0) zigzag nanotube to 0.83 eV for a (20, 0) zigzag nanotube. Also, attaching a single bromophenyl to a nanotube creates states in the gap close to the functionalization site. It therefore becomes energetically favourable for a second bromophenyl to attach close to the first one on semiconducting nanotubes. The para configuration is found to be favoured for resulting bromophenyl pairs and their binding energy is found to decrease with increasing diameter, ranging from 4.35 eV for a (7, 0) nanotube to 2.26 eV for a (29, 0) nanotube. An analytic form for this radius dependence is derived using a tight binding Hamiltonian and first order perturbation theory. The 1/R(2) dependence obtained (where R is the nanotube radius) is verified by our DFT results within numerical accuracy. Finally, bromophenyl pairs are shown to be favoured by only 50 meV with respect to separate moieties on (9, 0) metallic nanotubes, which suggests that pair formation is not significantly favoured on some metallic nanotubes. This

  15. Resonant ablation of single-wall carbon nanotubes by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Arutyunyan, N. R.; Komlenok, M. S.; Kononenko, V. V.; Pashinin, V. P.; Pozharov, A. S.; Konov, V. I.; Obraztsova, E. D.

    2015-01-01

    The thin 50 nm film of bundled arc-discharge single-wall carbon nanotubes was irradiated by femtosecond laser pulses with wavelengths 675, 1350 and 1745 nm corresponding to the absorption band of metallic nanotubes E11M, to the background absorption and to the absorption band of semiconducting nanotubes E11S, respectively. The aim was to induce a selective removal of nanotubes of specific type from the bundled material. Similar to conducted thermal heating experiments, the effect of laser irradiation results in suppression of all radial breathing modes in the Raman spectra, with preferential destruction of the metallic nanotubes with diameters less than 1.26 nm and of the semiconducting nanotubes with diameters 1.36 nm. However, the etching rate of different nanotubes depends on the wavelength of the laser irradiation. It is demonstrated that the relative content of nanotubes of different chiralities can be tuned by a resonant laser ablation of undesired nanotube fraction. The preferential etching of the resonant nanotubes has been shown for laser wavelengths 675 nm (E11M) and 1745 nm (E11S).

  16. Thermal emission spectra from individual suspended carbon nanotubes.

    PubMed

    Liu, Zuwei; Bushmaker, Adam; Aykol, Mehmet; Cronin, Stephen B

    2011-06-28

    We study the thermal emission spectra of individual suspended carbon nanotubes induced by electrical heating. Semiconducting and metallic devices exhibit different spectra, based on their distinctive band structures. These spectra are compared with the ideal blackbody emission spectrum. In the visible wavelength range, the thermal emission spectra of semiconducting devices agree well with Planck's law, while the spectra of metallic devices show an additional peak between 1.5 and 1.9 eV. In the near-infrared wavelength range, the semiconducting nanotubes exhibit a peak around 1 eV. These additional peaks are attributed to the E11M and E22SC transitions that are thermally driven under these high applied bias voltages. These peaks show a strong polarization dependence, while the blackbody tail is unpolarized, which provides further evidence for electron-hole recombination in thermal emission. For semiconducting devices, the temperature of the nanotube is fit to Planck's law and compared with the temperatures obtained from the G band and 2D band Raman downshifts, as well as the anti-Stokes/Stokes intensity ratio. For devices showing thermal non-equilibrium, the electron temperature agrees well with G+ downshift but deviates from G_ downshift. PMID:21545117

  17. Semiconducting conjugated polymer-inorganic tetrapod nanocomposites.

    PubMed

    Jung, Jaehan; Pang, Xinchang; Feng, Chaowei; Lin, Zhiqun

    2013-06-25

    Cadmium telluride (CdTe) tetrapods were synthesized via multiple injections of the Te precursor by utilizing bifunctional ligands. Subsequently, tetrapod-shaped semiconducting inorganic-organic nanocomposites (i.e., P3HT-CdTe tetrapod nanocomposites) were produced by directly grafting conjugated polymer ethynyl-terminated poly(3-hexylthiophene) (i.e., P3HT-≡) onto azide-functionalized CdTe tetrapods (i.e., CdTe-N3) via a catalyst-free click chemistry. The intimate contact between P3HT and CdTe tetrapod rendered the effective dispersion of CdTe tetrapods in nanocomposites and facilitated their efficient electronic interaction. The success of coupling reaction was confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy. The grafting density of P3HT chains on the CdTe tetrapods was estimated by thermogravimetric analysis. The photophysical properties of P3HT-CdTe tetrapod nanocomposites were studied using UV-vis and photoluminescence spectroscopies. These intimate semiconducting conjugated polymer-tetrapod nanocomposites may offer a maximized interface between conjugated polymers and tetrapods for efficient charge separation and enhanced charge transport regardless of their orientation for potential application in hybrid solar cells with improved power conversion efficiency. PMID:23600796

  18. Peltier cooling stage utilizing a superconductor-semiconductor junction

    SciTech Connect

    Skertic, M.M.

    1991-04-09

    This paper describes a Peltier cooling stack. It comprises: a first electrode; a superconducting layer electrically coupled to the first electrode; a semiconducting layer electrically coupled to the superconducting layer; and a second superconducting layer electrically coupled to the semiconductor layer; and a second electrode electrically coupled to the second superconducting layer, electrons flowing under an applied voltage from the first electrode through the first superconducting layer, semiconductor layer, second superconducting layer and second electrode, the electrical junction between the first superconducting layer and semiconductor providing Peltier cooling while the electrical junction between the semiconductor layer and the second superconducting layer providing Peltier heating, whereby a cryogenic Peltier cooling stack is provided.

  19. Suspended InAs nanowire Josephson junctions assembled via dielectrophoresis.

    PubMed

    Montemurro, D; Stornaiuolo, D; Massarotti, D; Ercolani, D; Sorba, L; Beltram, F; Tafuri, F; Roddaro, S

    2015-09-25

    We present a novel technique for the realization of suspended Josephson junctions based on InAs semiconductor nanowires. The devices are assembled using a technique of drop-casting guided by dielectrophoresis, which allows one to finely align the nanostructures on top of the electrodes. The proposed architecture removes the interaction between the nanowire and the substrate which is known to influence disorder and the orientation of the Rashba vector. The relevance of this approach in view of the implementation of hybrid Josephson junctions based on semiconducting nanowires coupled with high-temperature superconductors is discussed. PMID:26335273

  20. Suspended InAs nanowire Josephson junctions assembled via dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Montemurro, D.; Stornaiuolo, D.; Massarotti, D.; Ercolani, D.; Sorba, L.; Beltram, F.; Tafuri, F.; Roddaro, S.

    2015-09-01

    We present a novel technique for the realization of suspended Josephson junctions based on InAs semiconductor nanowires. The devices are assembled using a technique of drop-casting guided by dielectrophoresis, which allows one to finely align the nanostructures on top of the electrodes. The proposed architecture removes the interaction between the nanowire and the substrate which is known to influence disorder and the orientation of the Rashba vector. The relevance of this approach in view of the implementation of hybrid Josephson junctions based on semiconducting nanowires coupled with high-temperature superconductors is discussed.

  1. Pure carbon nanoscale devices: Nanotube heterojunctions

    SciTech Connect

    Chico, L.; Crespi, V.H.; Benedict, L.X.; Louie, S.G.; Cohen, M.L. |

    1996-02-01

    Introduction of pentagon-heptagon pair defects into the hexagonal network of a single carbon nanotube can change the helicity of the tube and alter its electronic structure. Using a tight-binding method to calculate the electronic structure of such systems we show that they behave as nanoscale metal/semiconductor or semiconductor/semiconductor junctions. These junctions could be the building blocks of nanoscale electronic devices made entirely of carbon. {copyright} {ital 1996 The American Physical Society.}

  2. Semiconducting monolayer materials as a tunable platform for excitonic solar cells.

    PubMed

    Bernardi, Marco; Palummo, Maurizia; Grossman, Jeffrey C

    2012-11-27

    The recent advent of two-dimensional monolayer materials with tunable optical properties and high carrier mobility offers renewed opportunities for efficient, ultrathin excitonic solar cells alternative to those based on conjugated polymer and small molecule donors. Using first-principles density functional theory and many-body calculations, we demonstrate that monolayers of hexagonal BN and graphene (CBN) combined with commonly used acceptors such as PCBM fullerene or semiconducting carbon nanotubes can provide excitonic solar cells with tunable absorber gap, donor-acceptor interface band alignment, and power conversion efficiency, as well as novel device architectures. For the case of CBN-PCBM devices, we predict power conversion efficiency limits in the 10-20% range depending on the CBN monolayer structure. Our results demonstrate the possibility of using monolayer materials in tunable, efficient, ultrathin solar cells in which unexplored exciton and carrier transport regimes are at play. PMID:23062107

  3. Semiconducting Polymer Nanoparticles as Photoacoustic Molecular Imaging Probes in Living Mice

    PubMed Central

    Pu, Kanyi; Shuhendler, Adam J.; Jokerst, Jesse V.; Mei, Jianguo; Gambhir, Sanjiv S.; Bao, Zhenan; Rao, Jianghong

    2014-01-01

    Photoacoustic (PA) imaging holds great promise for the visualization of physiology and pathology at the molecular level with deep tissue penetration and fine spatial resolution. To fully utilize this potential, PA molecular imaging probes have to be developed. Herein we introduce near infrared (NIR) light absorbing semiconducting polymer nanoparticles (SPNs) as a new class of contrast agents for PA molecular imaging. SPNs can produce stronger signal than commonly used single-wall carbon nanotubes and gold nanorods on a per mass basis, permitting whole-body lymph node PA mapping in living mice at a low systematic injection mass. Furthermore, SPNs possess high structural flexibility, narrow PA spectral profiles, and strong resistance to photodegradation and oxidation, which enables development of the first NIR ratiometric PA probe for in vivo real-time imaging of reactive oxygen species—vital chemical mediators of many diseases. These results demonstrate SPNs an ideal nanoplatform for developing PA molecular probes. PMID:24463363

  4. Doping Scheme of Semiconducting Atomic Chains

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Saini, Subhash (Technical Monitor)

    1998-01-01

    Atomic chains, precise structures of atomic scale created on an atomically regulated substrate surface, are candidates for future electronics. A doping scheme for intrinsic semiconducting Mg chains is considered. In order to suppress the unwanted Anderson localization and minimize the deformation of the original band shape, atomic modulation doping is considered, which is to place dopant atoms beside the chain periodically. Group I atoms are donors, and group VI or VII atoms are acceptors. As long as the lattice constant is long so that the s-p band crossing has not occurred, whether dopant atoms behave as donors or acceptors is closely related to the energy level alignment of isolated atomic levels. Band structures are calculated for Br-doped (p-type) and Cs-doped (n-type) Mg chains using the tight-binding theory with universal parameters, and it is shown that the band deformation is minimized and only the Fermi energy position is modified.

  5. Response functions of semiconducting lithium indium diselenide

    NASA Astrophysics Data System (ADS)

    Lukosi, Eric; Chvala, Ondrej; Stowe, Ashley

    2016-06-01

    This paper presents the results of a computational investigation that determined the gamma-ray and neutron response functions of a new semiconducting material, 6LiInSe2, which is very sensitive to thermal neutrons. Both MCNP6 simulations and custom post-processing/simulation techniques were used to determine various detection properties of LISe. The computational study included consideration of energetic electron escape, the contribution from the activation of 115In and subsequent decay of 116In, triton and alpha particle escape from the 6Li reaction pathway, and the effect of incomplete charge collection when detecting neutrons via the 6Li reaction pathway. The result of neutron detection with incomplete charge collection was compared to experimental results and showed general agreement, where holes exhibit a lower mobility-lifetime product than electrons, as expected for compound semiconductors.

  6. Bulk semiconducting scintillator device for radiation detection

    DOEpatents

    Stowe, Ashley C.; Burger, Arnold; Groza, Michael

    2016-08-30

    A bulk semiconducting scintillator device, including: a Li-containing semiconductor compound of general composition Li-III-VI.sub.2, wherein III is a Group III element and VI is a Group VI element; wherein the Li-containing semiconductor compound is used in one or more of a first mode and a second mode, wherein: in the first mode, the Li-containing semiconductor compound is coupled to an electrical circuit under bias operable for measuring electron-hole pairs in the Li-containing semiconductor compound in the presence of neutrons and the Li-containing semiconductor compound is also coupled to current detection electronics operable for detecting a corresponding current in the Li-containing semiconductor compound; and, in the second mode, the Li-containing semiconductor compound is coupled to a photodetector operable for detecting photons generated in the Li-containing semiconductor compound in the presence of the neutrons.

  7. semiconducting nanostructures: morphology and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Culebras, Mario; Torán, Raquel; Gómez, Clara M.; Cantarero, Andrés

    2014-08-01

    Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1- x Ca x MnO 3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content.

  8. Ordered Semiconducting Nitrogen-Graphene Alloys

    SciTech Connect

    Xiang, H. J.; Huang, B.; Li, Z. Y.; Wei, S. H.; Yang, J. L.; Gong, X. G.

    2012-01-01

    The interaction between substitutional nitrogen atoms in graphene is studied by performing first-principles calculations. The effective nearest-neighbor interaction between nitrogen dopants is found to be highly repulsive because of the strong electrostatic repulsion between nitrogen atoms. This interaction prevents the full nitrogen-carbon phase separation in nitrogen-doped graphene. Interestingly, there are two relatively stable nitrogen-nitrogen pair configurations, whose stability can be attributed to the anisotropy in the charge redistribution induced by nitrogen doping. We reveal two stable, ordered, semiconducting N-doped graphene structures, C{sub 3}N and C{sub 12}N, through the cluster-expansion technique and particle-swarm optimization method. In particular, we show that C{sub 12}N has a direct band gap of 0.98 eV. The heterojunctions between C{sub 12}N and graphene nanoribbons might be a promising basis for organic solar cells.

  9. Ni doping of semiconducting boron carbide

    SciTech Connect

    Hong, Nina; Liu Jing; Adenwalla, S.; Langell, M. A.; Kizilkaya, Orhan

    2010-01-15

    The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

  10. Ferromagnetism and semiconducting of boron nanowires

    PubMed Central

    2012-01-01

    More recently, motivated by extensively technical applications of carbon nanostructures, there is a growing interest in exploring novel non-carbon nanostructures. As the nearest neighbor of carbon in the periodic table, boron has exceptional properties of low volatility and high melting point and is stronger than steel, harder than corundum, and lighter than aluminum. Boron nanostructures thus are expected to have broad applications in various circumstances. In this contribution, we have performed a systematical study of the stability and electronic and magnetic properties of boron nanowires using the spin-polarized density functional calculations. Our calculations have revealed that there are six stable configurations of boron nanowires obtained by growing along different base vectors from the unit cell of the bulk α-rhombohedral boron (α-B) and β-rhombohedral boron (β-B). Well known, the boron bulk is usually metallic without magnetism. However, theoretical results about the magnetic and electronic properties showed that, whether for the α-B-based or the β-B-based nanowires, their magnetism is dependent on the growing direction. When the boron nanowires grow along the base vector [001], they exhibit ferromagnetism and have the magnetic moments of 1.98 and 2.62 μB, respectively, for the α-c [001] and β-c [001] directions. Electronically, when the boron nanowire grows along the α-c [001] direction, it shows semiconducting and has the direct bandgap of 0.19 eV. These results showed that boron nanowires possess the unique direction dependence of the magnetic and semiconducting behaviors, which are distinctly different from that of the bulk boron. Therefore, these theoretical findings would bring boron nanowires to have many promising applications that are novel for the boron bulk. PMID:23244063

  11. Gate-tunable carbon nanotube-MoS2 heterojunction p-n diode.

    PubMed

    Jariwala, Deep; Sangwan, Vinod K; Wu, Chung-Chiang; Prabhumirashi, Pradyumna L; Geier, Michael L; Marks, Tobin J; Lauhon, Lincoln J; Hersam, Mark C

    2013-11-01

    The p-n junction diode and field-effect transistor are the two most ubiquitous building blocks of modern electronics and optoelectronics. In recent years, the emergence of reduced dimensionality materials has suggested that these components can be scaled down to atomic thicknesses. Although high-performance field-effect devices have been achieved from monolayered materials and their heterostructures, a p-n heterojunction diode derived from ultrathin materials is notably absent and constrains the fabrication of complex electronic and optoelectronic circuits. Here we demonstrate a gate-tunable p-n heterojunction diode using semiconducting single-walled carbon nanotubes (SWCNTs) and single-layer molybdenum disulfide as p-type and n-type semiconductors, respectively. The vertical stacking of these two direct band gap semiconductors forms a heterojunction with electrical characteristics that can be tuned with an applied gate bias to achieve a wide range of charge transport behavior ranging from insulating to rectifying with forward-to-reverse bias current ratios exceeding 10(4). This heterojunction diode also responds strongly to optical irradiation with an external quantum efficiency of 25% and fast photoresponse <15 μs. Because SWCNTs have a diverse range of electrical properties as a function of chirality and an increasing number of atomically thin 2D nanomaterials are being isolated, the gate-tunable p-n heterojunction concept presented here should be widely generalizable to realize diverse ultrathin, high-performance electronics and optoelectronics. PMID:24145425

  12. Tunable resistance of a carbon nanotube-graphite interface.

    PubMed

    Paulson, S; Helser, A; Nardelli, M B; Taylor, R M; Falvo, M; Superfine, R; Washburn, S

    2000-12-01

    The transfer of electrons from one material to another is usually described in terms of energy conservation, with no attention being paid to momentum conservation. Here we present results on the junction resistance between a carbon nanotube and a graphite substrate and show that details of momentum conservation also can change the contact resistance. By changing the angular alignment of the atomic lattices, we found that contact resistance varied by more than an order of magnitude in a controlled and reproducible fashion, indicating that momentum conservation, in addition to energy conservation, can dictate the junction resistance in graphene systems such as carbon nanotube junctions and devices. PMID:11099407

  13. Growth and characterization of high-density mats of single-walled carbon nanotubes for interconnects

    SciTech Connect

    Robertson, J.; Zhong, G.; Telg, H.; Thomsen, C.; Warner, J. H.; Briggs, G. A. D.; Dettlaff-Weglikowska, U.; Roth, S.

    2008-10-20

    We grow high-density, aligned single wall carbon nanotube mats for use as interconnects in integrated circuits by remote plasma chemical vapor deposition from a Fe-Al{sub 2}O{sub 3} thin film catalyst. We carry out extensive Raman characterization of the resulting mats, and find that this catalyst system gives rise to a broad range of nanotube diameters, with no preferential selectivity of semiconducting tubes, but with at least 1/3 of metallic tubes.

  14. Optoelectronics with Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Kinoshita, Megumi

    2011-12-01

    The carbon nanotube is a promising material for future micro- and nano-scale electronics because of its unique electronic properties, high carrier mobility and extraordinary capacity for high current density. In particular, semiconducting carbon nanotubes are direct bandgap materials with a typical energy gap in the order of 1 eV, which means they emit light in the near-infrared range, making them an attractive option in telecommunications applications. However, there have been few systematic investigations of electrically-induced light emission (i.e. electroluminescence) from carbon nanotubes, and their emission properties are not well understood. In this dissertation, we explore the characteristics of electroluminescence in three different types of carbon-nanotube devices. The first is a single-tube field-effect transistor (CNTFET), whose emission has previously been found to have a very broad spectral shape and low emission efficiency. We analyze the spectral shape in detail, which reveals that a high electric field near metal contacts contributes most to the bias-dependent component of broadening, in addition to smaller contributions from tube nonuniformity, inelastic scattering of phonons, high temperature, etc. In the second part of the study, single-tube light-emitting diodes are constructed by employing a split top-gate scheme. The split gate creates p- and n-doped regions electrostatically, so that electrons and holes combine between the two sections and can decay radiatively. This configuration creates electron-hole pairs under much lower electric fields and gives us a greater control over carrier distribution in the device channel, resulting in much narrower spectral linewidths and an emission intensity several orders of magnitude larger than that of CNTFETs. The much better signal-to-noise also leads to the observation of emission from defect-induced states. Finally, we extend the idea of the single-tube p-n diode and fabricate CNT film diodes from many

  15. Nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    NASA Technical Reports Server (NTRS)

    Wang, Zhong L. (Inventor); Wang, Xudong (Inventor); Song, Jinhui (Inventor); Zhou, Jun (Inventor); He, Jr-Hau (Inventor)

    2011-01-01

    A semiconducting device includes a substrate, a piezoelectric wire, a structure, a first electrode and a second electrode. The piezoelectric wire has a first end and an opposite second end and is disposed on the substrate. The structure causes the piezoelectric wire to bend in a predetermined manner between the first end and the second end so that the piezoelectric wire enters a first semiconducting state. The first electrode is coupled to the first end and the second electrode is coupled to the second end so that when the piezoelectric wire is in the first semiconducting state, an electrical characteristic will be exhibited between the first electrode and the second electrode.

  16. Method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, J.

    1979-10-01

    The invention provides a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO/sub 3/ containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO/sub 3/ surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temmperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  17. Laser method for forming low-resistance ohmic contacts on semiconducting oxides

    DOEpatents

    Narayan, Jagdish

    1981-01-01

    This invention is a new method for the formation of high-quality ohmic contacts on wide-band-gap semiconducting oxides. As exemplified by the formation of an ohmic contact on n-type BaTiO.sub.3 containing a p-n junction, the invention entails depositing a film of a metallic electroding material on the BaTiO.sub.3 surface and irradiating the film with a Q-switched laser pulse effecting complete melting of the film and localized melting of the surface layer of oxide immediately underlying the film. The resulting solidified metallic contact is ohmic, has unusually low contact resistance, and is thermally stable, even at elevated temperatures. The contact does not require cleaning before attachment of any suitable electrical lead. This method is safe, rapid, reproducible, and relatively inexpensive.

  18. P-type Semiconducting Behavior of BaSn1-xRuxO3 system

    NASA Astrophysics Data System (ADS)

    Kwon, Hyukwoo; Shin, Juyeon; Char, Kookrin

    2015-03-01

    BaSnO3 is a promising transparent perovskite oxide semiconductor due to its high mobility and chemical stability. Exploiting such properties, we have applied BaSnO3 to the field effect, the 2-dimensional electron gas, and the pn-junction devices. In spite of the success of the K-doped BaSnO3 as a p-type doped, its carrier density at room temperature is rather small due to its high activation energy of about 0.5 eV. In continuation of our previous study on SrSn1-xRuxO3 system, we studied the p-type semiconducting behavior of BaSn1-xRuxO3 system. We have epitaxially grown the BaSn1-xRuxO3 (0 <=x <=0.12) thin films by pulsed laser deposition. X-ray diffraction measurements show that the films maintain a single phase over the entire doping range and the lattice constants of the system decrease monotonously as the doping increases. Transport measurements show that the films are semiconducting and their resistivities dramatically decrease as the Ru doping increases. Hall measurement data show that the charge carriers are p-type and its corresponding mobility values vary from 0.3 ~ 0.04 cm2/V .s, depending on the doping rate. The hole carrier densities, measured to be 1017 ~ 1019 /cm3, are larger than those of K-doped BaSnO3. Using BaSn1-xRuxO3 and Ba1-xLaxSnO3 as p-type and n-type semiconductors, we will fabricate pn-junctions and report its performance.

  19. Electronic interaction in composites of a conjugated polymer and carbon nanotubes: first-principles calculation and photophysical approaches

    PubMed Central

    Wéry, Jany; Duvail, Jean-Luc; Lefrant, Serge; Yaya, Abu; Ewels, Chris

    2015-01-01

    Summary The mechanisms that control the photophysics of composite films made of a semiconducting conjugated polymer (poly(paraphenylene vinylene), PPV) mixed with single-walled carbon nanotubes (SWNT) up to a concentration of 64 wt % are determined by using photoexcitation techniques and density functional theory. Charge separation is confirmed experimentally by rapid quenching of PPV photoluminescence and changes in photocurrent starting at relatively low concentrations of SWNT. Calculations predict strong electronic interaction between the polymer and the SWNT network when nanotubes are semiconducting. PMID:26171290

  20. Photoluminescence mechanisms of metallic Zn nanospheres, semiconducting ZnO nanoballoons, and metal-semiconductor Zn/ZnO nanospheres

    PubMed Central

    Lin, Jin-Han; Patil, Ranjit A.; Devan, Rupesh S.; Liu, Zhe-An; Wang, Yi-Ping; Ho, Ching-Hwa; Liou, Yung; Ma, Yuan-Ron

    2014-01-01

    We utilized a thermal radiation method to synthesize semiconducting hollow ZnO nanoballoons and metal-semiconductor concentric solid Zn/ZnO nanospheres from metallic solid Zn nanospheres. The chemical properties, crystalline structures, and photoluminescence mechanisms for the metallic solid Zn nanospheres, semiconducting hollow ZnO nanoballoons, and metal-semiconductor concentric solid Zn/ZnO nanospheres are presented. The PL emissions of the metallic Zn solid nanospheres are mainly dependent on the electron transitions between the Fermi level (EF) and the 3d band, while those of the semiconducting hollow ZnO nanoballoons are ascribed to the near band edge (NBE) and deep level electron transitions. The PL emissions of the metal-semiconductor concentric solid Zn/ZnO nanospheres are attributed to the electron transitions across the metal-semiconductor junction, from the EF to the valence and 3d bands, and from the interface states to the valence band. All three nanostructures are excellent room-temperature light emitters. PMID:25382186

  1. Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

    PubMed Central

    Kanan, Sofian M.; El-Kadri, Oussama M.; Abu-Yousef, Imad A.; Kanan, Marsha C.

    2009-01-01

    A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented. PMID:22408500

  2. Computational Nanotechnology of Materials, Devices, and Machines: Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak; Kwak, Dolhan (Technical Monitor)

    2000-01-01

    The mechanics and chemistry of carbon nanotubes have relevance for their numerous electronic applications. Mechanical deformations such as bending and twisting affect the nanotube's conductive properties, and at the same time they possess high strength and elasticity. Two principal techniques were utilized including the analysis of large scale classical molecular dynamics on a shared memory architecture machine and a quantum molecular dynamics methodology. In carbon based electronics, nanotubes are used as molecular wires with topological defects which are mediated through various means. Nanotubes can be connected to form junctions.

  3. Josephson radiation from InSb-nanowire junction

    NASA Astrophysics Data System (ADS)

    van Woerkom, David; Proutski, Alexander; Krivachy, Tamas; Bouman, Daniel; van Gulik, Ruben; Gul, Onder; Cassidy, Maja; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo; Geresdi, Attila

    Semiconducting nanowire Josephson junctions has recently gained interest as building blocks for Majorana circuits and gate-tuneable superconducting qubits . Here we investigate the rich physics of the Andreev bound state spectrum of InSb nanowire junctions utilizing the AC Josephson relation 2eV_bias =hf . We designed and characterized an on-chip microwave circuit coupling the nanowire junction to an Al/AlOx/Al tunnel junction. The DC response of the tunnel junction is affected by photon-assisted quasiparticle current, which gives us the possibility to measure the radiation spectrum of the nanowire junction up to several tens of GHz in frequency. Our circuit design allows for voltage or phase biasing of the Josephson junction enabling direct mapping of Andreev bound states. We discuss our fabrication methods and choice of materials to achieve radiation detection up to a magnetic field of few hundred milliTesla, compatible with Majorana states in spin-orbit coupled nanowires. This work has been supported by the Netherlands Foundations FOM, Abstract NWO and Microsoft Corporation Station Q.

  4. Light-emitting polymer/carbon nanotube hybrid transistors: below and above the percolation limit

    NASA Astrophysics Data System (ADS)

    Wang, Ming; Jakubka, Florian; Gannott, Florentina; Zaumseil, Jana

    2013-09-01

    Hybrids of semiconducting polymers and single-walled carbon nanotubes (SWNT) are interesting for organic electronic devices such as solar cells, light-emitting diodes and field-effect transistors (FETs). They are easily produced by selective dispersion of SWNTs in polymer solutions by ultrasonication followed by centrifugation. We demonstrate that nanotubes at concentration levels well below the percolation limit significantly improve charge injection of both holes and electrons into semiconducting polymers in top-gate FETs. This leads to lower contact resistances and reduced threshold voltages, thus the maximum ambipolar currents and visible light emission due to electron-hole recombination are considerably enhanced. The improved injection of holes and electrons allows for a much wider range of accessible polymers for ambipolar and light-emitting transistors. The same conjugated polymers can also be used to enrich specific semiconducting SWNT and to produce high-performance ambipolar nanotube network FETs. These show efficient nearinfrared electroluminescence. Mapping the emission from these networks during a gate voltage sweep allows us to visualize preferential current paths and investigate percolation models for purely semiconducting nanotube networks.

  5. Nanotubes, Nanowires, and Nanocantilevers in Biosensor Development

    SciTech Connect

    Wang, Jun; Liu, Guodong; Lin, Yuehe

    2007-03-08

    In this chapter, the reviews on biosensor development based on 1-D nanomaterials, CNTs, semiconducting nanowires, and some cantilevers will be introduced. The emphasis of this review will be placed on CNTs and electrochemical/electronic biosensor developments. Section 2 of this chapter gives a detailed description of carbon nanotubes-based biosensor development, from fabrication of carbon nanotubes, the strategies for construction of carbon nanotube based biosensors to their bioapplications. In the section of the applications of CNTs based biosensors, various detection principles, e. g. electrochemical, electronic, and optical method, and their applications are reviewed in detail. Section 3 introduces the method for synthesis of semiconducting nanowires, e.g. silicon nanowires, conducting polymer nanowires and metal oxide nanowires and their applications in DNA and proteins sensing. Section 4 simply describes the development for nanocantilevers based biosensors and their application in DNA and protein diagnosis. Each section starts from a brief introduction and then goes into details. Finally in the Conclusion section, the development of 1-D nanomaterials based biosensor development is summarized.

  6. Improving the electrical conductivity of carbon nanotube networks: a first-principles study.

    PubMed

    Li, Elise Y; Marzari, Nicola

    2011-12-27

    We address the issue of the low electrical conductivity observed in carbon nanotube networks using first-principles calculations of the structure, stability, and ballistic transport of different nanotube junctions. We first study covalent linkers, using the nitrene-pyrazine case as a model for conductance-preserving [2 + 1] cycloadditions, and discuss the reasons for their poor performance. We then characterize the role of transition-metal adsorbates in improving mechanical coupling and electrical tunneling between the tubes. We show that the strong hybridization between the transition-metal d orbitals with the π orbitals of the nanotube can provide an excellent electrical bridge for nanotube-nanotube junctions. This effect is maximized in the case of nitrogen-doped nanotubes, thanks to the strong mechanical coupling between the tubes mediated by a single transition metal adatom. Our results suggest effective strategies to optimize the performance of carbon nanotube networks. PMID:22059779

  7. Carbon nanotubes: Electrons in one dimension

    NASA Astrophysics Data System (ADS)

    Bockrath, Marc William

    The work presented in this thesis will discuss transport measurements on individual single-walled nanotubes (SWNTs) and SWNT bundles. SWNTs, which are essentially rolled-up sheets of graphite, are either one-dimensional (1D) metals or 1D semiconductors depending on how they are rolled-up. Measurements on both metallic and semiconducting SWNTs will be presented. Chapter 1 will present an introductory overview to the thesis, discussing prior related experimental work and introducing basic concepts that are used in subsequent chapters. Chapter 2 discusses the experimental methods we have used to study transport in SWNTs. Chapters 3 and 4 discuss low temperature measurements of metallic SWNTs. Chapter 3 will discuss the low temperature behavior of the conductance of a SWNT bundle, or rope, that shows quantum mechanical effects resulting from the finite size of the sample. Chapter 4 will discuss how these finite size effects can be used to experimentally study the quantum level structure in metallic nanotubes and the effects of an applied magnetic field. In chapters 5 and 6, we discuss transport measurements of semiconducting SWNTs. In chapter 5, we show that semiconducting SWNT's can be doped with potassium. Chapter 6 presents experiment and theory that indicate that the elastic mean free path in metallic tubes is far longer than in semiconducting tubes. Chapters 7 and 8 address the effects of electron-electron (e-e) interactions on the transport properties of metallic SWNTs. Chapter 7 discusses some theoretical aspects of 1D wires when e-e interactions are taken account, giving a simplified picture of the Luttinger-liquid state expected for a 1D system of interacting electrons. Finally, chapter 8 will discuss measurements on metallic samples with extremely long mean free paths. These experiments show evidence of this Luttinger-liquid behavior, in which the electron-electron interactions lead to a qualitatively different ground state than what would be expected with

  8. Innate cation sensitivity in a semiconducting polymer.

    PubMed

    Althagafi, Talal M; Algarni, Saud A; Grell, Martin

    2016-09-01

    Water-gated organic thin film transistors (OTFTs) using the hole transporting semiconducting polymer, poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), show an innate response of their threshold voltage to the addition of divalent metal cations to the gating water, without deliberately introducing an ion-sensitive component. A similar threshold response is shown for several divalent cations, but is absent for monovalent cations. Response is absent for transistors using the inorganic semiconductor ZnO, or the similar organic semiconductor poly(3-hexylthiophene) (rrP3HT), instead of PBTTT. We assign innate cation sensitivity to residues of the organometallic Pd(0) complex used as catalyst in PBTTT synthesis which bears strong resemblance to typical metal chelating agents. Organometallic Pd(0) residues are absent from ZnO, and also from rrP3HT which is polymerised with a different type of catalyst. However, when Pd(0) complex is deliberately added to rrP3HT casting solutions, resulting OTFTs also display threshold response to a divalent cation. PMID:27343580

  9. Optical near-field investigations of individual single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Hartschuh, Achim

    2009-03-01

    Optical excitation of semiconducting nanotubes creates excitons that determine nearly all light-based applications. Near-field photoluminescence (PL) and Raman imaging with a spatial resolution better than 15 nm was used to probe the spectroscopic properties of excitonic states along single nanotubes on substrates [1,2]. The PL intensity was found to decrease towards the nanotube ends on a length scale of few 10 nm probably caused by exciton transport to localized end states followed by efficient non-radiative recombination. DNA-wrapping of nanotubes results in pronounced emission energy variations on a length scale of few 10 nm indicating the potential of the material for nanoscale sensing applications [3]. Inter-nanotube energy transfer was studied for different pairs of semiconducting nanotubes forming bundles and crossings [4]. Efficient transfer is found to be limited to a few nanometres because of competing fast non-radiative relaxation and can be explained in terms of electromagnetic near-field coupling. We also report on our recent experimental results on time-resolved near-field PL measurements, electrically gated nanotubes and the PL of nanotubes on metal surfaces. [4pt] References: [0pt] [1] A. Hartschuh, Angew. Chem. Int. Ed. 47, 8178 (2008). [0pt] [2] I. O. Maciel et. al, Nature Mat. 7, 878 (2008). [0pt] [3] H. Qian et. al, Nano Lett. 8, 2706 (2008). [0pt] [4] H. Qian et. al, Nano Lett. 8, 1363 (2008).

  10. Prediction of the electronic structure of single-walled black phosphorus nanotubes.

    PubMed

    Guan, Lixiu; Chen, Guifeng; Tao, Junguang

    2016-06-01

    Due to its high carrier mobility and tunable bandgap, phosphorene has been the subject of immense interest recently. Herein, we show using density functional theory based calculations that black phosphorus (BP) nanotubes are achievable. Moreover, the electronic properties of BP nanotubes are explored. In contrast to their monolayer and bulk counterparts, most BP nanotubes possess indirect band gaps. In addition, strong anisotropic electronic behaviors are observed between zigzag and armchair nanotubes. Semiconducting to semi-metallic transition occurs only for zigzag tubes when its diameter shrinks to ∼1.5 nm. This difference is strongly related to the bond bending after the formation of the nanotubes which governs the s-p hybridization, as well as electron distribution in different p orbitals and this eventually determines the electronic structure of BP nanotubes. PMID:27198550

  11. Comparative study on different carbon nanotube materials in terms of transparent conductive coatings.

    PubMed

    Li, Zhongrui; Kandel, Hom R; Dervishi, Enkeleda; Saini, Viney; Xu, Yang; Biris, Alexandru R; Lupu, Dan; Salamo, Gregory J; Biris, Alexandru S

    2008-03-18

    We compared conductive transparent carbon nanotube coatings on glass substrates made of differently produced single-wall (SWNT), double-wall, and multiwall carbon nanotubes. The airbrushing approach and the vacuum filtration method were utilized for the fabrication of carbon nanotube films. The optoelectronic performance of the carbon nanotube film was found to strongly depend on many effects including the ratio of metallic-to-semiconducting tubes, dispersion, length, diameter, chirality, wall number, structural defects, and the properties of substrates. The electronic transportability and optical properties of the SWNT network can be significantly altered by chemical doping with thionyl chloride. Hall effect measurements revealed that all of these thin carbon nanotube films are of p-type probably due to the acid reflux-based purification and atmospheric impurities. The competition between variable-range hoping and fluctuation-assisted tunneling in the functionized carbon nanotube system could lead to a crossover behavior in the temperature dependence of the network resistance. PMID:18251555

  12. Fabrication of hetero-junction diode using NiO thin film on ITO/glass substrate

    NASA Astrophysics Data System (ADS)

    Soni, Sonali; Sharma, Vinay; Kuanr, Bijoy K.

    2016-05-01

    Fabrication, characterization and testing of hetero-junctions of NiO thin films were done. Nickel films were evaporated on polished ITO coated glass substrates using thermal deposition. The films were annealed at high temperatures in the presence of oxygen to obtain NiO films. The rectifying current-voltage (I-V) properties confirmed that a hetero-junction diode was successfully formed. The AC and DC behavior of hetero-junction using DC silver-probes were determined. The threshold voltage, ideality factor and reverse saturation current of hetero junction were determined. We have compared these I-V characteristics with semiconducting PN junction diode. To test the device characteristics, we used the structure as a diode clipper at various frequencies. It is showed that our device is a better high-frequency junction-device than a normal PN junction diode.

  13. Carbon nanotube based pressure sensor for flexible electronics

    SciTech Connect

    So, Hye-Mi; Sim, Jin Woo; Kwon, Jinhyeong; Yun, Jongju; Baik, Seunghyun; Chang, Won Seok

    2013-12-15

    Highlights: • The electromechanical change of vertically aligned carbon nanotubes. • Fabrication of CNT field-effect transistor on flexible substrate. • CNT based FET integrated active pressure sensor. • The integrated device yields an increase in the source-drain current under pressure. - Abstract: A pressure sensor was developed based on an arrangement of vertically aligned carbon nanotubes (VACNTs) supported by a polydimethylsiloxane (PDMS) matrix. The VACNTs embedded in the PDMS matrix were structurally flexible and provided repeated sensing operation due to the high elasticities of both the polymer and the carbon nanotubes (CNTs). The conductance increased in the presence of a loading pressure, which compressed the material and induced contact between neighboring CNTs, thereby producing a dense current path and better CNT/metal contacts. To achieve flexible functional electronics, VACNTs based pressure sensor was integrated with field-effect transistor, which is fabricated using sprayed semiconducting carbon nanotubes on plastic substrate.

  14. Joint measurement of current-phase relations and transport properties of hybrid junctions using a three junctions superconducting quantum interference device

    SciTech Connect

    Basset, J.; Delagrange, R.; Weil, R.; Kasumov, A.; Bouchiat, H.; Deblock, R.

    2014-07-14

    We propose a scheme to measure both the current-phase relation and differential conductance dI/dV of a superconducting junction, in the normal and the superconducting states. This is done using a dc Superconducting Quantum Interference Device with two Josephson junctions in parallel with the device under investigation and three contacts. As a demonstration, we measure the current-phase relation and dI/dV of a small Josephson junction and a carbon nanotube junction. In this latter case, in a regime where the nanotube is well conducting, we show that the non-sinusoidal current phase relation we find is consistent with the theory for a weak link, using the transmission extracted from the differential conductance in the normal state. This method holds great promise for future investigations of the current-phase relation of more exotic junctions.

  15. Multi-Scale Simulations of Carbon Nanotubes: Mechanics and Electronics

    NASA Technical Reports Server (NTRS)

    Srivastava, Deepak

    2003-01-01

    Carbon Nanotube (CNT) is a tubular form of carbon with diameter as small as 1 nm. Length: few mn to microns. CNT is configurationally equivalent to a two dimensional graphene sheet rolled into a tube. CNT exhibits extraordinary mechanical properties; Young's modulus over 1 Tera Pascal, as stiff as diamond, and tensile strength approx. 200 GPa. CNT can be metallic or semiconducting, depending on chirality.

  16. Guided Photoluminescence from Integrated Carbon-Nanotube-Based Optical Waveguides.

    PubMed

    Bodiou, Loïc; Gu, Qingyuan; Guézo, Maud; Delcourt, Enguerran; Batté, Thomas; Lemaitre, Jonathan; Lorrain, Nathalie; Guendouz, Mohammed; Folliot, Hervé; Charrier, Joël; Mistry, Kevin S; Blackburn, Jeffrey L; Doualan, Jean-Louis; Braud, Alain; Camy, Patrice

    2015-10-28

    Thin films and ridge waveguides based on large-diameter semiconducting single-wall carbon nanotubes (s-SWCNTs) dispersed in a polyfluorene derivative are fabricated and optically characterized. Ridge waveguides are designed with appropriate dimensions for single-mode propagation at 1550 nm. Using multimode ridge waveguides, guided s-SWCNT photoluminescence is demonstrated for the first time in the near-infrared telecommunications window. PMID:26350035

  17. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  18. Junction-based field emission structure for field emission display

    DOEpatents

    Dinh, Long N.; Balooch, Mehdi; McLean, II, William; Schildbach, Marcus A.

    2002-01-01

    A junction-based field emission display, wherein the junctions are formed by depositing a semiconducting or dielectric, low work function, negative electron affinity (NEA) silicon-based compound film (SBCF) onto a metal or n-type semiconductor substrate. The SBCF can be doped to become a p-type semiconductor. A small forward bias voltage is applied across the junction so that electron transport is from the substrate into the SBCF region. Upon entering into this NEA region, many electrons are released into the vacuum level above the SBCF surface and accelerated toward a positively biased phosphor screen anode, hence lighting up the phosphor screen for display. To turn off, simply switch off the applied potential across the SBCF/substrate. May be used for field emission flat panel displays.

  19. Boron Nitride Nanotubes for Engineering Applications

    NASA Technical Reports Server (NTRS)

    Hurst, Janet; Hull, David; Gorican, Daniel

    2005-01-01

    Boron nitride nanotubes (BNNT) are of significant interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted wide attention. Both materials have potentially unique and important properties for structural and electronic applications. However of even more consequence than their similarities may be the complementary differences between carbon and boron nitride nanotubes While BNNT possess a very high modulus similar to CNT, they also possess superior chemical and thermal stability. Additionally, BNNT have more uniform electronic properties, with a uniform band gap of 5.5 eV while CNT vary from semi-conductive to highly conductive behavior. Boron nitride nanotubes have been synthesized both in the literature and at NASA Glenn Research Center, by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistent large scale production of a reliable product has proven difficult. Progress in the reproducible synthesis of 1-2 gram sized batches of boron nitride nanotubes will be discussed as well as potential uses for this unique material.

  20. A facile and low-cost length sorting of single-wall carbon nanotubes by precipitation and applications for thin-film transistors

    NASA Astrophysics Data System (ADS)

    Gui, Hui; Chen, Haitian; Khripin, Constantine Y.; Liu, Bilu; Fagan, Jeffrey A.; Zhou, Chongwu; Zheng, Ming

    2016-02-01

    Semiconducting single-wall carbon nanotubes (SWCNTs) with long lengths are highly desirable for many applications such as thin-film transistors and circuits. Previously reported length sorting techniques usually require sophisticated instrumentation and are hard to scale up. In this paper, we report for the first time a general phenomenon of a length-dependent precipitation of surfactant-dispersed carbon nanotubes by polymers, salts, and their combinations. Polyelectrolytes such as polymethacrylate (PMAA) and polystyrene sulfonate (PSS) are found to be especially effective on cholate and deoxycholate dispersed SWCNTs. By adding PMAA to these nanotube dispersions in a stepwise fashion, we have achieved nanotube precipitation in a length-dependent order: first nanotubes with an average length of 650 nm, and then successively of 450 nm, 350 nm, and 250 nm. A similar effect of nanotube length sorting has also been observed for PSS. To demonstrate the utility of the length fractionation, the 650 nm-long nanotube fraction was subjected to an aqueous two-phase separation to obtain semiconducting enriched nanotubes. Thin-film transistors fabricated with the resulting semiconducting SWCNTs showed a carrier mobility up to 18 cm2 (V s)-1 and an on/off ratio up to 107. Our result sheds new light on the phase behavior of aqueous nanotube dispersions under high concentrations of polymers and salts, and offers a facile, low-cost, and scalable method to produce length sorted semiconducting nanotubes for macroelectronics applications.Semiconducting single-wall carbon nanotubes (SWCNTs) with long lengths are highly desirable for many applications such as thin-film transistors and circuits. Previously reported length sorting techniques usually require sophisticated instrumentation and are hard to scale up. In this paper, we report for the first time a general phenomenon of a length-dependent precipitation of surfactant-dispersed carbon nanotubes by polymers, salts, and their

  1. Physical Properties of Thin Film Semiconducting Materials

    NASA Astrophysics Data System (ADS)

    Bouras, N.; Djebbouri, M.; Outemzabet, R.; Sali, S.; Zerrouki, H.; Zouaoui, A.; Kesri, N.

    2005-10-01

    The physics and chemistry of semiconducting materials is a continuous question of debate. We can find a large stock of well-known properties but at the same time, many things are not understood. In recent years, porous silicon (PS-Si), diselenide of copper and indium (CuInSe2 or CIS) and metal oxide semiconductors like tin oxide (SnO2) and zinc oxide (ZnO) have been subjected to extensive studies because of the rising interest their potential applications in fields such as electronic components, solar panels, catalysis, gas sensors, in biocompatible materials, in Li-based batteries, in new generation of MOSFETS. Bulk structure and surface and interface properties play important roles in all of these applications. A deeper understanding of these fundamental properties would impact largely on technological application performances. In our laboratory, thin films of undoped and antimony-doped films of tin oxide have been deposited by chemical vapor deposition. Spray pyrolysis was used for ZnO. CIS was prepared by flash evaporation or close-space vapor transport. Some of the deposition parameters have been varied, such as substrate temperature, time of deposition (or anodization), and molar concentration of bath preparation. For some samples, thermal annealing was carried out under oxygen (or air), under nitrogen gas and under vacuum. Deposition and post-deposition parameters are known to strongly influence film structure and electrical resistivity. We investigated the influence of film thickness and thermal annealing on structural optical and electrical properties of the films. Examination of SnO2 by x-ray diffraction showed that the main films are polycrystalline with rutile structure. The x-ray spectra of ZnO indicated a hexagonal wurtzite structure. Characterizations of CIS films with compositional analysis, x-ray diffraction, scanning microscopy, spectrophotometry, and photoluminescence were carried out.

  2. Electronic modulations in a single wall carbon nanotube induced by the Au(111) surface reconstruction

    SciTech Connect

    Clair, Sylvain; Shin, Hyung-Joon; Kim, Yousoo E-mail: maki@riken.jp; Kawai, Maki E-mail: maki@riken.jp

    2015-02-02

    The structural and electronic structure of single wall carbon nanotubes adsorbed on Au(111) has been investigated by low-temperature scanning tunneling microscopy and spectroscopy. The nanotubes were dry deposited in situ in ultrahigh vacuum onto a perfectly clean substrate. In some cases, the native herringbone reconstruction of the Au(111) surface interacted directly with adsorbed nanotubes and produced long-range periodic oscillations in their local density of states, corresponding to charge transfer modulations along the tube axis. This effect, however, was observed not systematically for all tubes and only for semiconducting tubes.

  3. Binding energies and electronic structures of adsorbed titanium chains on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Yang, Chih-Kai; Zhao, Jijun; Lu, Jianping

    2002-03-01

    Our calculations based on first principles have shown that titanium is much favored energetically over gold and aluminum to form a continuous chain on a variety of single-wall carbon nanotubes (SWNT). Results from two zigzag nanotubes, (10,0) and (14,0), and two armchairs, (6,6) and (8,8), indicate that binding energy for a Ti-adsorbed SWNT is generally six to seven eV per unit cell larger than a Au or Al-adsorbed SWNT. Furthermore, the adsorbed Ti chain generates additional states in the band gaps of the two semi-conducting zigzag nanotubes, transforming them into metals.

  4. Reversibility, Dopant Desorption, and Tunneling in the Temperature-Dependent Conductivity of Type-Separated, Conductive Carbon Nanotube Networks

    SciTech Connect

    Barnes, T. M.; Blackburn, J. L.; van de Lagemaat, J.; Coutts, T. J.; Heben, M. J.

    2008-09-01

    We present a comprehensive study of the effects of doping and temperature on the conductivity of single-walled carbon nanotube (SWNT) networks. We investigated nearly type-pure networks as well as networks comprising precisely tuned mixtures of metallic and semiconducting tubes. Networks were studied in their as-produced state and after treatments with nitric acid, thionyl chloride, and hydrazine to explore the effects of both intentional and adventitious doping. For intentionally and adventitiously doped networks, the sheet resistance (R{sub s}) exhibits an irreversible increase with temperature above {approx}350 K. Dopant desorption is shown to be the main cause of this increase and the observed hysteresis in the temperature-dependent resistivity. Both thermal and chemical dedoping produced networks free of hysteresis. Temperature-programmed desorption data showed that dopants are most strongly bound to the metallic tubes and that networks consisting of metallic tubes exhibit the best thermal stability. At temperatures below the dopant desorption threshold, conductivity in the networks is primarily controlled by thermally assisted tunneling through barriers at the intertube or interbundle junctions.

  5. Growth of Horizontal Semiconducting SWNT Arrays with Density Higher than 100 tubes/μm using Ethanol/Methane Chemical Vapor Deposition.

    PubMed

    Kang, Lixing; Zhang, Shuchen; Li, Qingwen; Zhang, Jin

    2016-06-01

    Horizontally aligned semiconducting single-walled carbon nanotube (s-SWNT) arrays with a certain density are highly desirable for future electronic devices. However, obtaining s-SWNT arrays with simultaneously high purity and high density is extremely challenging. We report herein a rational approach, using ethanol/methane chemical vapor deposition, to grow SWNT arrays with a s-SWNT ratio over 91% and a density higher than 100 tubes/μm. In this approach, at a certain temperature, ethanol was fully thermally decomposed to feed carbon atoms for Trojan-Mo catalysts growing high density SWNT arrays, while the incomplete pyrolysis of methane provided appropriate active H radicals with the help of catalytic sapphire surface to inhibit metallic SWNT (m-SWNT) growth. The synergistic effect of ethanol/methane mixtures resulted in enriched semiconducting SWNTs and no obvious decrease in nanotube density due to their milder reactivity and higher controllability at suitable growth conditions. This work represents a step forward in large-area synthesis of high density s-SWNT arrays on substrates and demonstrates potential applications in scalable carbon nanotube electronics. PMID:27177360

  6. Carbon Nanotube Based Light Sensor

    NASA Technical Reports Server (NTRS)

    Wincheski, russell A. (Inventor); Smits, Jan M. (Inventor); Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor); Ingram, JoAnne L. (Inventor)

    2006-01-01

    A light sensor substrate comprises a base made from a semi-conductive material and topped with a layer of an electrically non-conductive material. A first electrode and a plurality of carbon nanotube (CNT)-based conductors are positioned on the layer of electrically non-conductive material with the CNT-based conductors being distributed in a spaced apart fashion about a periphery of the first electrode. Each CNT-based conductor is coupled on one end thereof to the first electrode and extends away from the first electrode to terminate at a second free end. A second or gate electrode is positioned on the non-conductive material layer and is spaced apart from the second free end of each CNT-based conductor. Coupled to the first and second electrode is a device for detecting electron transfer along the CNT-based conductors resulting from light impinging on the CNT-based conductors.

  7. Photonics based on carbon nanotubes

    PubMed Central

    2013-01-01

    Among direct-bandgap semiconducting nanomaterials, single-walled carbon nanotubes (SWCNT) exhibit strong quasi-one-dimensional excitonic optical properties, which confer them a great potential for their integration in future photonics devices as an alternative solution to conventional inorganic semiconductors. In this paper, we will highlight SWCNT optical properties for passive as well as active applications in future optical networking. For passive applications, we directly compare the efficiency and power consumption of saturable absorbers (SAs) based on SWCNT with SA based on conventional multiple quantum wells. For active applications, exceptional photoluminescence properties of SWCNT, such as excellent light-emission stabilities with temperature and excitation power, hold these nanometer-scale materials as prime candidates for future active photonics devices with superior performances. PMID:23803293

  8. Photonics based on carbon nanotubes.

    PubMed

    Gu, Qingyuan; Gicquel-Guézo, Maud; Loualiche, Slimane; Pouliquen, Julie Le; Batte, Thomas; Folliot, Hervé; Dehaese, Olivier; Grillot, Frederic; Battie, Yann; Loiseau, Annick; Liang, Baolai; Huffaker, Diana

    2013-01-01

    Among direct-bandgap semiconducting nanomaterials, single-walled carbon nanotubes (SWCNT) exhibit strong quasi-one-dimensional excitonic optical properties, which confer them a great potential for their integration in future photonics devices as an alternative solution to conventional inorganic semiconductors. In this paper, we will highlight SWCNT optical properties for passive as well as active applications in future optical networking. For passive applications, we directly compare the efficiency and power consumption of saturable absorbers (SAs) based on SWCNT with SA based on conventional multiple quantum wells. For active applications, exceptional photoluminescence properties of SWCNT, such as excellent light-emission stabilities with temperature and excitation power, hold these nanometer-scale materials as prime candidates for future active photonics devices with superior performances. PMID:23803293

  9. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2007-05-29

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  10. Heteroporphyrin nanotubes and composites

    DOEpatents

    Shelnutt, John A.; Medforth, Craig J.; Wang, Zhongchun

    2006-11-07

    Heteroporphyrin nanotubes, metal nanostructures, and metal/porphyrin-nanotube composite nanostructures formed using the nanotubes as photocatalysts and structural templates, and the methods for forming the nanotubes and composites.

  11. Imaging dissipation and hot spots in carbon nanotube network transistors

    NASA Astrophysics Data System (ADS)

    Estrada, David; Pop, Eric

    2011-02-01

    We use infrared thermometry of carbon nanotube network (CNN) transistors and find the formation of distinct hot spots during operation. However, the average CNN temperature at breakdown is significantly lower than expected from the breakdown of individual nanotubes, suggesting extremely high regions of power dissipation at the CNN junctions. Statistical analysis and comparison with a thermal model allow the estimate of an upper limit for the average tube-tube junction thermal resistance, ˜4.4×1011 K/W (thermal conductance of ˜2.27 pW/K). These results indicate that nanotube junctions have a much greater impact on CNN transport, dissipation, and reliability than extrinsic factors such as low substrate thermal conductivity.

  12. Semiconducting III-V nanowires with nanogaps for molecular junctions: DFT transport simulations.

    PubMed

    Kallesøe, Christian; Fürst, Joachim A; Mølhave, Kristian; Bøggild, Peter; Brandbyge, Mads

    2009-11-18

    We consider here the possibility of using III-V heterostructure nanowires as electrodes for molecular electronics instead of metal point contacts. Using ab initio electronic structure and transport calculations, we study the effect on electronic properties of placing a small molecule with thiol linking groups, benzene-di-thiol (BDT), within a nanosize gap in a III-V nanowire. Furthermore, it is investigated how surface states affect the transport through pristine III-V nanowires and through the BDT molecule situated within the nanogap. Using GaAs and GaP as III-V materials we find that the BDT molecule provides transport through the entire system comparable to the case of gold electrodes. PMID:19843997

  13. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage.

    PubMed

    Cai, Ronggang; Kassa, Hailu G; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H; Ruzié, Christian; van Breemen, Albert J J M; Gelinck, Gerwin H; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M

    2016-03-21

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices. PMID:26927694

  14. Hybrid semiconducting polymer nanoparticles as polarization-sensitive fluorescent probes

    PubMed Central

    Zeigler, Maxwell B.; Sun, Wei; Rong, Yu; Chiu, Daniel T.

    2013-01-01

    Much work has been done on collapsed chains of conjugated semiconducting polymers and their applications as fluorescent probes or sensors. On surfaces spin-coated with semiconducting polymers, excitation energy transfer along the polymer backbone can be used to quickly and efficiently funnel energy to chromophores with localized energy minima. If each chromophore is immobilized within its matrix, this can result in large fluorescence anisotropy. Through nanoprecipitation of a matrix polymer blended at low mass ratios with short-chain, hydrophobic, fluorescent semiconducting polymers, we take advantage of this large fluorescence anisotropy to make polarization-sensitive nanoparticles. These nanoparticles are small at approximately 7 nm in diameter; exhibit a high quantum yield of 0.75; and are easily functionalized to bind to protein targets. By exciting the nanoparticles with polarized light on a wide-field fluorescence microscope, we are able to monitor not only protein location, but also changes in their orientation. PMID:23895535

  15. Electron transport through molecular junctions

    NASA Astrophysics Data System (ADS)

    Zimbovskaya, Natalya A.; Pederson, Mark R.

    2011-12-01

    At present, metal-molecular tunnel junctions are recognized as important active elements in molecular electronics. This gives a strong motivation to explore physical mechanisms controlling electron transport through molecules. In the last two decades, an unceasing progress in both experimental and theoretical studies of molecular conductance has been demonstrated. In the present work we give an overview of theoretical methods used to analyze the transport properties of metal-molecular junctions as well as some relevant experiments and applications. After a brief general description of the electron transport through molecules we introduce a Hamiltonian which can be used to analyze electron-electron, electron-phonon and spin-orbit interactions. Then we turn to description of the commonly used transport theory formalisms including the nonequilibrium Green’s functions based approach and the approach based on the “master” equations. We discuss the most important effects which could be manifested through molecules in electron transport phenomena such as Coulomb, spin and Frank-Condon blockades, Kondo peak in the molecular conductance, negative differential resistance and some others. Bearing in mind that first principles electronic structure calculations are recognized as the indispensable basis of the theory of electron transport through molecules, we briefly discuss the main equations and some relevant applications of the density functional theory which presently is often used to analyze important characteristics of molecules and molecular clusters. Finally, we discuss some kinds of nanoelectronic devices built using molecules and similar systems such as carbon nanotubes, various nanowires and quantum dots.

  16. Semiconducting glasses: A new class of thermoelectric materials?

    SciTech Connect

    Goncalves, A.P.; Vaney, J.B.; Lenoir, B.; Piarristeguy, A.; Pradel, A.; Monnier, J.; Ochin, P.; Godart, C.

    2012-09-15

    The deeper understanding of the factors that affect the dimensionless figure of merit, ZT, and the use of new synthetic methods has recently led to the development of novel systems with improved thermoelectric performances. Albeit up to now with ZT values lower than the conventional bulk materials, semiconducting glasses have also emerged as a new family of potential thermoelectric materials. This paper reviews the latest advances on semiconducting glasses for thermoelectric applications. Key examples of tellurium-based glasses, with high Seebeck coefficients, very low thermal conductivities and tunable electrical conductivities, are presented. ZT values as high as 0.2 were obtained at room temperature for several tellurium-based glasses with high copper concentrations, confirming chalcogenide semiconducting glasses as good candidates for high-performance thermoelectric materials. However, the temperature stability and electrical conductivity of the reported glasses are still not good enough for practical applications and further studies are still needed to enhance them. - Graphical abstract: Power factor as a function of the temperature for the Cu{sub 27.5}Ge{sub 2.5}Te{sub 70} and Cu{sub 30}As{sub 15}Te{sub 55} seniconducting glasses. Highlights: Black-Right-Pointing-Pointer A review of semiconducting glasses for thermoelectrics applications is presented. Black-Right-Pointing-Pointer The studied semiconducting glasses present very low thermal conductivities. Black-Right-Pointing-Pointer Composition can tune electrical conductivity and Seebeck coefficient. Black-Right-Pointing-Pointer ZT=0.2 is obtained at 300 K for different semiconducting glasses.

  17. Organic ferroelectric/semiconducting nanowire hybrid layer for memory storage

    NASA Astrophysics Data System (ADS)

    Cai, Ronggang; Kassa, Hailu G.; Haouari, Rachid; Marrani, Alessio; Geerts, Yves H.; Ruzié, Christian; van Breemen, Albert J. J. M.; Gelinck, Gerwin H.; Nysten, Bernard; Hu, Zhijun; Jonas, Alain M.

    2016-03-01

    Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction intrinsic to the nanostructured hybrid layer offers opportunities for the development of strongly miniaturized ferroelectric and piezoelectric devices.Ferroelectric materials are important components of sensors, actuators and non-volatile memories. However, possible device configurations are limited due to the need to provide screening charges to ferroelectric interfaces to avoid depolarization. Here we show that, by alternating ferroelectric and semiconducting nanowires over an insulating substrate, the ferroelectric dipole moment can be stabilized by injected free charge carriers accumulating laterally in the neighboring semiconducting nanowires. This lateral electrostatic coupling between ferroelectric and semiconducting nanowires offers new opportunities to design new device architectures. As an example, we demonstrate the fabrication of an elementary non-volatile memory device in a transistor-like configuration, of which the source-drain current exhibits a typical hysteretic behavior with respect to the poling voltage. The potential for size reduction

  18. Electronic transport properties of inner and outer shells in near ohmic-contacted double-walled carbon nanotube transistors

    SciTech Connect

    Zhang, Yuchun; Zhou, Liyan; Zhao, Shangqian; Wang, Wenlong; Liang, Wenjie; Wang, Enge

    2014-06-14

    We investigate electronic transport properties of field-effect transistors based on double-walled carbon nanotubes, of which inner shells are metallic and outer shells are semiconducting. When both shells are turned on, electron-phonon scattering is found to be the dominant phenomenon. On the other hand, when outer semiconducting shells are turned off, a zero-bias anomaly emerges in the dependence of differential conductance on the bias voltage, which is characterized according to the Tomonaga-Luttinger liquid model describing tunneling into one-dimensional materials. We attribute these behaviors to different contact conditions for outer and inner shells of the double-walled carbon nanotubes. A simple model combining Luttinger liquid model for inner metallic shells and electron-phonon scattering in outer semiconducting shells is given here to explain our transport data at different temperatures.

  19. Selective Surface Charge Sign Reversal on Metallic Carbon Nanotubes for Facile Ultrahigh Purity Nanotube Sorting.

    PubMed

    Wang, Jing; Nguyen, Tuan Dat; Cao, Qing; Wang, Yilei; Tan, Marcus Y C; Chan-Park, Mary B

    2016-03-22

    Semiconducting (semi-) single-walled carbon nanotubes (SWNTs) must be purified of their metallic (met-) counterparts for most applications including nanoelectronics, solar cells, chemical sensors, and artificial skins. Previous bulk sorting techniques are based on subtle contrasts between properties of different nanotube/dispersing agent complexes. We report here a method which directly exploits the nanotube band structure differences. For the heterogeneous redox reaction of SWNTs with oxygen/water couple, the aqueous pH can be tuned so that the redox kinetics is determined by the availability of nanotube electrons only at/near the Fermi level, as predicted quantitatively by the Marcus-Gerischer (MG) theory. Consequently, met-SWNTs oxidize much faster than semi-SWNTs and only met-SWNTs selectively reverse the sign of their measured surface zeta potential from negative to positive at the optimized acidic pH when suspended with nonionic surfactants. By passing the redox-reacted nanotubes through anionic hydrogel beads, we isolate semi-SWNTs to record high electrically verified purity above 99.94% ± 0.04%. This facile charge sign reversal (CSR)-based sorting technique is robust and can sort SWNTs with a broad diameter range. PMID:26901408

  20. Solitons in Josephson junctions

    NASA Astrophysics Data System (ADS)

    Ustinov, A. V.

    1998-11-01

    Magnetic flux quanta in Josephson junctions, often called fluxons, in many cases behave as solitons. A review of recent experiments and modelling of fluxon dynamics in Josephson circuits is presented. Classic quasi-one-dimensional junctions, stacked junctions (Josephson superlattices), and discrete Josephson transmission lines (JTLs) are discussed. Applications of fluxon devices as high-frequency oscillators and digital circuits are also addressed.

  1. One-dimensional transport in hybrid metal-semiconductor nanotube systems

    NASA Astrophysics Data System (ADS)

    Gelin, M. F.; Bondarev, I. V.

    2016-03-01

    We develop an electron transport theory for the hybrid system of a semiconducting carbon nanotube that encapsulates a one-atom-thick metallic wire. The theory predicts Fano resonances in electron transport through the system, whereby the interaction of electrons on the wire with nanotube plasmon generated near fields blocks some of the wire transmission channels to open up the new coherent plasmon-mediated channel in the nanotube forbidden gap outside the wire transmission band. Such a channel makes the entire hybrid system transparent in the energy domain where neither wire nor nanotube is individually transparent. This effect can be used to control and optimize charge transfer in hybrid nanodevices built on metal-semiconductor nanotube systems.

  2. Electrostatic Simulation of Charge Trapping in Carbon Nanotube Vertical Organic Field Effect Transistors

    NASA Astrophysics Data System (ADS)

    Crawford, Jennifer; Rinzler, Andrew; Hershfield, Selman

    The carbon nanotube vertical organic field effect transistor is a vertical sequence consisting of a gate electrode, gate dielectric, thin nanotube network source electrode, organic semiconducting channel and finally the drain electrode. The drain current is modulated by the gate voltage which varies a Schottky barrier between source and channel layers. Hysteresis in the current-voltage characteristic has been observed when a electret charge trapping layer is placed between the nanotube source and the gate dielectric. We provide a model for charge injection into a trapping layer placed in contact with the carbon nanotube film and solve self-consistently for the electrostatics and the occupancy of the traps. For a range of applied gate voltages the simulations demonstrate hysteresis of the carbon nanotubes' charge as a result of the electric field produced by the trapped charge. This affects the current by modulating the Schottky barrier. This work was supported by the NSF Grant DMR-1461019.

  3. Resonant phase matching of Josephson junction traveling wave parametric amplifiers.

    PubMed

    O'Brien, Kevin; Macklin, Chris; Siddiqi, Irfan; Zhang, Xiang

    2014-10-10

    We propose a technique to overcome phase mismatch in Josephson-junction traveling wave parametric amplifiers in order to achieve high gain over a broad bandwidth. Using "resonant phase matching," we design a compact superconducting device consisting of a transmission line with subwavelength resonant inclusions that simultaneously achieves a gain of 20 dB, an instantaneous bandwidth of 3 GHz, and a saturation power of -98 dBm. Such an amplifier is well suited to cryogenic broadband microwave measurements such as the multiplexed readout of quantum coherent circuits based on superconducting, semiconducting, or nanomechanical elements, as well as traditional astronomical detectors. PMID:25375734

  4. Resonant Phase Matching of Josephson Junction Traveling Wave Parametric Amplifiers

    NASA Astrophysics Data System (ADS)

    O'Brien, Kevin; Macklin, Chris; Siddiqi, Irfan; Zhang, Xiang

    2014-10-01

    We propose a technique to overcome phase mismatch in Josephson-junction traveling wave parametric amplifiers in order to achieve high gain over a broad bandwidth. Using "resonant phase matching," we design a compact superconducting device consisting of a transmission line with subwavelength resonant inclusions that simultaneously achieves a gain of 20 dB, an instantaneous bandwidth of 3 GHz, and a saturation power of -98 dBm. Such an amplifier is well suited to cryogenic broadband microwave measurements such as the multiplexed readout of quantum coherent circuits based on superconducting, semiconducting, or nanomechanical elements, as well as traditional astronomical detectors.

  5. Spin and charge transport in double-junction Fe/MgO/GaAs/MgO/Fe heterostructures

    SciTech Connect

    Wolski, S. Szczepański, T.; Dugaev, V. K.; Barnaś, J.; Landgraf, B.; Slobodskyy, T.; Hansen, W.

    2015-01-28

    We present theoretical and experimental results on tunneling current in single Fe/MgO/GaAs and double Fe/MgO/GaAs/MgO/Fe tunnel junctions. The charge and spin currents are calculated as a function of external voltage for different sets of parameters characterizing the semiconducting GaAs layer. Transport characteristics of a single Fe/MgO/GaAs junction reveal typical diode as well as spin diode features. The results of numerical calculations are compared with current-voltage characteristics measured experimentally for double tunnel junction structures, and a satisfactory agreement of the theoretical and experimental results has been achieved.

  6. Tunneling Nanotubes

    PubMed Central

    Lou, Emil; Fujisawa, Sho; Barlas, Afsar; Romin, Yevgeniy; Manova-Todorova, Katia; Moore, Malcolm A.S.; Subramanian, Subbaya

    2012-01-01

    Tunneling nanotubes are actin-based cytoplasmic extensions that function as intercellular channels in a wide variety of cell types.There is a renewed and keen interest in the examination of modes of intercellular communication in cells of all types, especially in the field of cancer biology. Tunneling nanotubes –which in the literature have also been referred to as “membrane nanotubes,” “’intercellular’ or ‘epithelial’ bridges,” or “cytoplasmic extensions” – are under active investigation for their role in facilitating direct intercellular communication. These structures have not, until recently, been scrutinized as a unique and previously unrecognized form of direct cell-to-cell transmission of cellular cargo in the context of human cancer. Our recent study of tunneling nanotubes in human malignant pleural mesothelioma and lung adenocarcinomas demonstrated efficient transfer of cellular contents, including proteins, Golgi vesicles, and mitochondria, between cells derived from several well-established cancer cell lines. Further, we provided effective demonstration that such nanotubes can form between primary malignant cells from human patients. For the first time, we also demonstrated the in vivo relevance of these structures in humans, having effectively imaged nanotubes in intact solid tumors from patients. Here we provide further analysis and discussion on our findings, and offer a prospective ‘road map’ for studying tunneling nanotubes in the context of human cancer. We hope that further understanding of the mechanisms, methods of transfer, and particularly the role of nanotubes in tumor-stromal cross-talk will lead to identification of new selective targets for cancer therapeutics. PMID:23060969

  7. Universal nonresonant absorption in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Vialla, Fabien; Malic, Ermin; Langlois, Benjamin; Chassagneux, Yannick; Diederichs, Carole; Deleporte, Emmanuelle; Roussignol, Philippe; Lauret, Jean-Sébastien; Voisin, Christophe

    2014-10-01

    Photoluminescence excitation measurements in semiconducting carbon nanotubes show a systematic nonresonant contribution between the well-known excitonic resonances. Using a global analysis method, we were able to delineate the contribution of each chiral species, including its tiny nonresonant component. By comparison with the recently reported excitonic absorption cross section on the S22 resonance, we found a universal nonresonant absorbance which turns out to be of the order of one-half of that of an equivalent graphene sheet. This value, as well as the absorption line shape in the nonresonant window, is in excellent agreement with microscopic calculations based on the density-matrix formalism. This nonresonant absorption of semiconducting nanotubes is essentially frequency independent over 0.5-eV-wide windows and reaches approximately the same value between the S11 and S22 resonances and between the S22 and S33 resonances. In addition, the nonresonant absorption cross section turns out to be the same for all the chiral species we measured in this study. From a practical point of view, this study provides a solid framework for sample content analysis based on photoluminescence studies by targeting specific excitation wavelengths that lead to almost uniform excitation of all the chiral species of a sample within a given diameter range.

  8. Selective interaction of a soluble pentacene derivative with metallic single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Liu, Cai-Hong; Liu, Yi-Yang; Zhang, Yong-Hui; Wei, Rui-Rui; Li, Bing-Rui; Zhang, Hao-Li; Chen, Yong

    2009-03-01

    We report a soluble pentacene derivative, 6,13-bis(2-(trimethylsilyl)ethynyl)pentacene, can be used for efficient extraction of metallic single-walled carbon nanotubes (SWCNTs), which is proven by resonance Raman spectroscopy (RRS), Vis-NIR absorption spectroscopy and conductivity measurements. RRS studies reveal that the separation is solvent-dependent and is more efficient for small diameter tubes. Theoretical simulation suggests that the adsorption of pentacene on (7, 7) metallic SWCNT is about 34% more favorable than that on (13, 0) semiconducting SWCNT. This work provides a new direction in seeking reagents to facilitate high efficiency and nondestructive separation of metallic and semiconducting SWCNTs.

  9. Shot noise in a toroidal carbon nanotube coupled with Majorana fermion states

    NASA Astrophysics Data System (ADS)

    Zhang, Jian; Zhao, Hong-Kang; Wang, Qing

    2016-03-01

    The shot noise of a toroidal carbon nanotube (TCN) interferometer coupled with Majorana fermions is deduced from evaluating the current correlation. Many novel channels are opened for electrons to transport, and the energy gap of the semiconducting TCN becomes narrower. The Majorana fermions cause additional current correlations among the normal tunneling currents and Andreev reflection currents, and hence the shot noise and Fano factor are enhanced. The conductance, current, and shot noise are modified by Majorana fermions to exhibit different oscillation and resonance structures. The detailed behaviors of these quantities are quite different from the metal and semiconducting TCNs.

  10. Anomalous aharonov-bohm gap oscillations in carbon nanotubes.

    PubMed

    Sangalli, Davide; Marini, Andrea

    2011-10-12

    The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the Aharonov-Bohm effect at the nanoscale. Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. Using an ab initio approach based on density functional theory, we show that this assumption fails at the nanoscale inducing important corrections to the physics of the Aharonov-Bohm effect. Curvature effects and electronic density that is spilled out of the nanotube surface are shown to break the periodicity of the gap oscillations. We predict the key phenomenological features of this anomalous Aharonov-Bohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results. PMID:21805987

  11. Electrical properties of carbon nanotube FETs

    NASA Astrophysics Data System (ADS)

    Mizutani, T.; Ohno, Y.; Kishimoto, S.

    2008-08-01

    The electrical properties of carbon nanotube FETs (CNTFETs) have been studied in detail. The conduction type of the CNTFETs was dependent on the work function of the contact metal, which suggests that Fermi level pinning at the metal/nanotube interface is not strong. Based on the two-probe and four-probe resistance measurements, it has been shown that the carrier transport at the contact is explained by the edge contact model even in the diffusive regime. The chemical doping using F4TCNQ was effective in reducing not only the channel resistance but also the contact resistance. In the CNTFETs fabricated using plasma-enhanced (PE) CVD-grown nanotubes, the drain current of the most of the devices could be modulated by the gate voltage with small OFF current suggesting the preferential growth of the nanotubes with semiconducting behavior. Multichannel top-gate CNTFETs with horizontally-aligned nanotubes as channels have been successfully fabricated using CNT growth on the ST-cut quartz substrate, arc-discharge plasma deposition of the catalyst metal, and ALD gate insulator deposition. The devices show normally-on and n-type conduction property with a relatively-high ON current of 13 mA/mm. CNTFETs with nanotube network have also been fabricated by direct growth on the SiO2/Si substrate using grid-inserted PECVD and using catalyst formed on the channel area of the FETs. The uniformity of the electrical properties of the network channel CNTFETs were very good. Finally, it has been shown that the surface potential profile measurement based on the electrostatic force detection in the scanning probe microscopy was effective in studying the behavior of the CNTFETs such as the transient behavior and the effect of the defects.

  12. A Single-Material Logical Junction Based on 2D Crystal PdS2.

    PubMed

    Ghorbani-Asl, Mahdi; Kuc, Agnieszka; Miró, Pere; Heine, Thomas

    2016-02-01

    A single-material logical junction with negligible contact resistance is designed by exploiting quantum-confinement effects in 1T PdS2 . The metallic bilayer serves as electrodes for the semiconducting channel monolayer, avoiding contact resistance. Heat dissipation is then governed by tunnel loss, which becomes negligible at channel lengths larger than 2.45 nm. This value marks the integration limit for a conventional 2D transistor. PMID:26632273

  13. Electromechanical effects in carbon nanotubes: Ab initio and analytical tight-binding calculations

    NASA Astrophysics Data System (ADS)

    Verissimo-Alves, M.; Koiller, Belita; Chacham, H.; Capaz, R. B.

    2003-04-01

    We perform ab initio calculations of charged graphene and single-wall carbon nanotubes (CNTs). A wealth of electromechanical behaviors is obtained. (1) Both nanotubes and graphene expand upon electron injection. (2) Upon hole injection, metallic nanotubes and graphene display a nonmonotonic behavior. Upon increasing hole densities, the lattice constant initially contracts, reaches a minimum, and then starts to expand. The hole densities at minimum lattice constants are 0.3 |e|/atom for graphene and between 0.1 and 0.3|e|/atom for the metallic nanotubes studied. (3) Semiconducting CNT’s with small diameters (d≲20 Å) always expand upon hole injection. (4) Semiconducting CNT’s with large diameters (d≳20 Å) display a behavior intermediate between those of metallic and large-gap CNT’s. (5) The strain versus extra charge displays a linear plus power-law behavior, with characteristic exponents for graphene, metallic, and semiconducting CNT’s. All these features are physically understood within a simple tight-binding total-energy model.

  14. Plasmonic sensing structure of carbon nanotubes and gold nanoparticles for hydrogen detection (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Angiola, Marco; Rutherglen, Chris; Galatsis, Kosmas; Martucci, Alessandro

    2015-09-01

    Large attention has been directed toward carbon nanotubes as material for chemical sensors. However, little attention was paid toward the different behavior of the metallic and semiconductive carbon nanotubes as optical sensing materials. Semiconductive or metallic Single Wall Carbon Nanotubes (SWCNTs) have been deposited on gold nanoparticles (NPs) monolayer and used as plasmonic based gas sensor. The coupling between SWCNTs and Au NPs has the aim of combining the reactivity of the nanotubes towards hazardous gases, such as H2, CO, NO2, with the Localized Surface Plasmon Resonance (LSPR) of gold NPs. The LSPR is known to be extremely sensitive to the changes in the dielectric properties of the surrounding medium, a characteristic that has been widely exploited for the preparation of sensing devices. While the use of SWCNTs for gas sensing has been covered in multiple reports, to the best of our knowledge this is the first time that SWCNTs are used as sensing material in an optical sensor for the detection of reducing and oxidizing gases. Two different techniques, ink-jet printer and dropcasting, were used for depositing the transparent CNTs film on the plasmonic layer. Both the deposition techniques proved to be effective for the development of transparent optical sensing films. Metallic SWCNTs showed high sensitivity toward H2 at low temperature and an enhancement of performance at 300°C with the detection of low concentration of H2 and NO2. On the contrary, the semiconductive SWCNTs displayed very poor gas sensing properties, especially for the thinner film.

  15. Separated Carbon Nanotube Macroelectronics for Active Matrix Organic Light-Emitting Diode Displays

    NASA Astrophysics Data System (ADS)

    Fu, Yue; Zhang, Jialu; Wang, Chuan; Chen, Pochiang; Zhou, Chongwu

    2012-02-01

    Active matrix organic light-emitting diode (AMOLED) display holds great potential for the next generation visual technologies due to its high light efficiency, flexibility, lightweight, and low-temperature processing. However, suitable thin-film transistors (TFTs) are required to realize the advantages of AMOLED. Pre-separated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose because of their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report, for the first time, the demonstration of AMOLED displays driven by separated nanotube thin-film transistors (SN-TFTs) including key technology components such as large-scale high-yield fabrication of devices with superior performance, carbon nanotube film density optimization, bilayer gate dielectric for improved substrate adhesion to the deposited nanotube film, and the demonstration of monolithically integrated AMOLED display elements with 500 pixels driven by 1000 SN-TFTs. Our approach can serve as the critical foundation for future nanotube-based thin-film display electronics.

  16. Separated carbon nanotube macroelectronics for active matrix organic light-emitting diode displays.

    PubMed

    Zhang, Jialu; Fu, Yue; Wang, Chuan; Chen, Po-Chiang; Liu, Zhiwei; Wei, Wei; Wu, Chao; Thompson, Mark E; Zhou, Chongwu

    2011-11-01

    Active matrix organic light-emitting diode (AMOLED) display holds great potential for the next generation visual technologies due to its high light efficiency, flexibility, lightweight, and low-temperature processing. However, suitable thin-film transistors (TFTs) are required to realize the advantages of AMOLED. Preseparated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose because of their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report, for the first time, the demonstration of AMOLED displays driven by separated nanotube thin-film transistors (SN-TFTs) including key technology components, such as large-scale high-yield fabrication of devices with superior performance, carbon nanotube film density optimization, bilayer gate dielectric for improved substrate adhesion to the deposited nanotube film, and the demonstration of monolithically integrated AMOLED display elements with 500 pixels driven by 1000 SN-TFTs. Our approach can serve as the critical foundation for future nanotube-based thin-film display electronics. PMID:21942351

  17. Dielectric response of carbon and boron nitride nanotubes from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Kozinsky, Boris; Marzari, Nicola

    2007-03-01

    We present a complete characterization of the dielectric response of isolated single- and multi-wall carbon (CNT) and boron-nitride nanotubes (BNNT) using first-principles calculations and density-functional theory. The longitudinal polarizability of a nanotube is sensitive to the band gap and its radius, and in multi-wall nanotubes and bundles it is trivially given by the sum of the polarizabilities of the constituent tubes. The transverse polarizability of both types of nanotubes is insensitive to band gap and chirality and depends only on the radius. However, the transverse response and screening properties of BNNTs are qualitatively different from those of metallic and semiconducting CNTs. The fundamental differences in electronic properties of the two materials are inherited from the corresponding two-dimensional sheets - graphene and boron-nitride. The screening of the external field in CNTs is stronger than in BNNTs and has a different radius dependence. The transverse response in BNNTs is found to be that of an insulator, while in CNTs it is intermediate between metallic and semiconducting. Our results have practical implications for selective growth of different types of nanotubes using aligning electric fields and for Raman characterization of nanotubes.

  18. Nanotube cathodes.

    SciTech Connect

    Overmyer, Donald L.; Lockner, Thomas Ramsbeck; Siegal, Michael P.; Miller, Paul Albert

    2006-11-01

    Carbon nanotubes have shown promise for applications in many diverse areas of technology. In this report we describe our efforts to develop high-current cathodes from a variety of nanotubes deposited under a variety of conditions. Our goal was to develop a one-inch-diameter cathode capable of emitting 10 amperes of electron current for one second with an applied potential of 50 kV. This combination of current and pulse duration significantly exceeds previously reported nanotube-cathode performance. This project was planned for two years duration. In the first year, we tested the electron-emission characteristics of nanotube arrays fabricated under a variety of conditions. In the second year, we planned to select the best processing conditions, to fabricate larger cathode samples, and to test them on a high-power relativistic electron beam generator. In the first year, much effort was made to control nanotube arrays in terms of nanotube diameter and average spacing apart. When the project began, we believed that nanotubes approximately 10 nm in diameter would yield sufficient electron emission properties, based on the work of others in the field. Therefore, much of our focus was placed on measured field emission from such nanotubes grown on a variety of metallized surfaces and with varying average spacing between individual nanotubes. We easily reproduced the field emission properties typically measured by others from multi-wall carbon nanotube arrays. Interestingly, we did this without having the helpful vertical alignment to enhance emission; our nanotubes were randomly oriented. The good emission was most likely possible due to the improved crystallinity, and therefore, electrical conductivity, of our nanotubes compared to those in the literature. However, toward the end of the project, we learned that while these 10-nm-diameter CNTs had superior crystalline structure to the work of others studying field emission from multi-wall CNT arrays, these nanotubes still

  19. Strongly Anisotropic Ballistic Magnetoresistance in Compact Three-Dimensional Semiconducting Nanoarchitectures

    NASA Astrophysics Data System (ADS)

    Ortix, Carmine; Chang, Ching-Hao; van den Brink, Jeroen

    2015-03-01

    In this talk, I will show that in non-magnetic semiconducting bilayer or multilayer thin film systems rolled-up into compact quasi-one-dimensional nanoarchitectures, the ballistic magnetoresistance is very anisotropic: conductances depend strongly on the direction of an externally applied magnetic field. This phenomenon originates from the curved open geometry of rolled-up nanotubes, which leads to a tunability of the number of one-dimensional magnetic subbands crossing the Fermi energy. The experimental significance of this phenomenon is illustrated by a sizable anisotropy that scales with the inverse of the number of windings, and persists up to a critical temperature that can be strongly enhanced by increasing the strength of the external magnetic field or the characteristic radius of curvature, and can reach room temperature. The financial support of the Future and Emerging Technologies (FET) programme within the Seventh Framework Programme for Research of the European Commission, under FET-Open Grant Number: 618083 (CNTQC), is gratefully acknowledged.

  20. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

    PubMed Central

    Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

    2016-01-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor. PMID:26860367

  1. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls.

    PubMed

    Filippin, A Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A; Borras, Ana

    2016-01-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor. PMID:26860367

  2. Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

    NASA Astrophysics Data System (ADS)

    Filippin, A. Nicolas; Macias-Montero, Manuel; Saghi, Zineb; Idígoras, Jesús; Burdet, Pierre; Barranco, Angel; Midgley, Paul; Anta, Juan A.; Borras, Ana

    2016-02-01

    A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a post-annealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensor.

  3. Formation of in-situ CNT junction by direct lateral growth

    NASA Astrophysics Data System (ADS)

    Lee, Yun-Hi; Jang, Yoon-Taek; Choi, Chang-Hoon; Ju, Byeong-Kwon

    2003-03-01

    We present an approach to form a reliable integration of carbon nanotubes via direct parallel growth method. The method involves in-situ growth of carbon naotubes to bridge predefined junction electrodes of Nb/Co(or Ni), and furthermore, a high degree of ordering parallel suspended nanotubes can be obtained by applying DC bias during the growth. The arrays with robust contacts are unique system for explorations of collective behavior in coupled systems, and are useful for applications in nanoelectronics and NEMS.

  4. Structure and stability of SnS2-based single- and multi-wall nanotubes

    NASA Astrophysics Data System (ADS)

    Bandura, Andrei V.; Evarestov, Robert A.

    2015-11-01

    Hybrid density functional method PBE0 which mixes the 75% Perdew-Burke-Ernzerhof and 25% Hartree-Fock exchange functional has been applied for investigation of the electronic and atomic structures of nanotubes obtained by rolling up of hexagonal layers of tin disulfide. Calculations have been performed on the basis of the localized atomic functions by means of the CRYSTAL09 computer code. The calculated strain energy of SnS2 single-wall nanotubes approximately obeys the R- 2 law (R is nanotube radius) of the classical elasticity theory. The SnS2 nanotube electronic band structures yield a semiconducting behavior. Band gap of single-wall nanotubes decreases linearly with R- 1. The dispersion force correction is found to be important for prediction of the multi-wall nanotube stability. The distance and interaction energy between the single-wall components of the double-wall nanotubes are proved to be close to the distance and interaction energy between layers in the bulk crystal. Analysis of the relaxed nanotube shape using the offered method demonstrates a small but noticeable deviation from completely cylindrical cross-section of the external walls in the armchair-like double- and triple-walled nanotubes.

  5. Quantum conductance of carbon nanotubes with defects

    SciTech Connect

    Chico, L.; Benedict, L.X.; Louie, S.G.; Cohen, M.L. |

    1996-07-01

    We study the conductance of metallic carbon nanotubes with vacancies and pentagon-heptagon pair defects within the Landauer formalism. Using a tight-binding model and a Green{close_quote}s function technique to calculate the scattering matrix, we examine the one-dimensional to two-dimensional crossover in these systems and show the existence of metallic tube junctions in which the conductance is suppressed for symmetry reasons. {copyright} {ital 1996 The American Physical Society.}

  6. EDITORIAL: Focus on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    2003-09-01

    The study of carbon nanotubes, since their discovery by Iijima in 1991, has become a full research field with significant contributions from all areas of research in solid-state and molecular physics and also from chemistry. This Focus Issue in New Journal of Physics reflects this active research, and presents articles detailing significant advances in the production of carbon nanotubes, the study of their mechanical and vibrational properties, electronic properties and optical transitions, and electrical and transport properties. Fundamental research, both theoretical and experimental, represents part of this progress. The potential applications of nanotubes will rely on the progress made in understanding their fundamental physics and chemistry, as presented here. We believe this Focus Issue will be an excellent guide for both beginners and experts in the research field of carbon nanotubes. It has been a great pleasure to edit the many excellent contributions from Europe, Japan, and the US, as well from a number of other countries, and to witness the remarkable effort put into the manuscripts by the contributors. We thank all the authors and referees involved in the process. In particular, we would like to express our gratitude to Alexander Bradshaw, who invited us put together this Focus Issue, and to Tim Smith and the New Journal of Physics staff for their extremely efficient handling of the manuscripts. Focus on Carbon Nanotubes Contents Transport theory of carbon nanotube Y junctions R Egger, B Trauzettel, S Chen and F Siano The tubular conical helix of graphitic boron nitride F F Xu, Y Bando and D Golberg Formation pathways for single-wall carbon nanotube multiterminal junctions Inna Ponomareva, Leonid A Chernozatonskii, Antonis N Andriotis and Madhu Menon Synthesis and manipulation of carbon nanotubes J W Seo, E Couteau, P Umek, K Hernadi, P Marcoux, B Lukic, Cs Mikó, M Milas, R Gaál and L Forró Transitional behaviour in the transformation from active end

  7. Modeling of Branched (L, T and Y) Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Han, Jie; Jaffe, Richard; Saini, Subhash (Technical Monitor)

    1998-01-01

    Models for connecting two or three carbon nanotubes (CNT) using topological defects (i.e., pentagons and heptagons) are presented for the characterization of experimentally observed L, T and Y CNT junctions. The effects of the separation and orientation of the topological defects on the structures and energetics of these junctions are investigated using the nonlocal density function theory (DFT) and semi-empirical molecular orbital (AM1) calculations, and the Brenner empirical potential molecular mechanics simulations. The potential applications of L, Y and T CNT junctions in nanoelectronic devices are also discussed.

  8. Nanotube phonon waveguide

    DOEpatents

    Chang, Chih-Wei; Zettl, Alexander K.

    2013-10-29

    Disclosed are methods and devices in which certain types of nanotubes (e.g., carbon nanotubes and boron nitride nanotubes conduct heat with high efficiency and are therefore useful in electronic-type devices.

  9. Periodically striped films produced from super-aligned carbon nanotube arrays.

    PubMed

    Liu, Kai; Sun, Yinghui; Liu, Peng; Wang, Jiaping; Li, Qunqing; Fan, Shoushan; Jiang, Kaili

    2009-08-19

    We report a novel way to draw films from super-aligned carbon nanotube arrays at large drawing angles. The obtained super-aligned carbon nanotube films have a periodically striped configuration with alternating thinner and thicker film sections, and the width of the stripes is equal to the height of the original arrays. Compared with ordinary uniform films, the striped films provide a better platform for understanding the mechanism of spinning films from arrays because carbon nanotube junctions are easily observed and identified at the boundary of the stripes. Further studies show that the carbon nanotube junctions are bottleneck positions for thermal conduction and mechanical strength of the film, but do not limit its electrical conduction. These films can be utilized as striped and high-degree polarized light emission sources. Our results will be valuable for new applications and future large-scale production of tunable super-aligned carbon nanotube films. PMID:19636102

  10. Characteristic features of an ionization system with semiconducting cathode

    NASA Astrophysics Data System (ADS)

    Salamov, B. G.; Altındal, Ş.; Özer, M.; Çolakoğlu, K.; Bulur, E.

    1998-06-01

    The characteristic features of a dc discharge generated between parallel plate electrodes and especially the discharge stabilization by the GaAs semiconducting cathode in such a system are studied. The cathode was irradiated on the back-side with IR light in a particular wavelength range that was used to control the photoconductivity of the material. The semiconductor material was found to stabilize the discharge. The current-voltage and radiation-voltage characteristics of the gas discharge cell with a semiconducting cathode were obtained experimentally. An investigation of the effect of the voltage amplitude on the dynamics of transient processes in the plane semiconductor-discharge gap structure was made for explanation of the light intensity and current decay. Expressions are obtained for the photoelectric gain.

  11. Morphology control in biphasic hybrid systems of semiconducting materials.

    PubMed

    Mathias, Florian; Fokina, Ana; Landfester, Katharina; Tremel, Wolfgang; Schmid, Friederike; Char, Kookheon; Zentel, Rudolf

    2015-06-01

    Simple blends of inorganic nanocrystals and organic (semiconducting) polymers usually lead to macroscopic segregation. Thus, such blends typically exhibit inferior properties than expected. To overcome the problem of segregation, polymer coated nanocrystals (nanocomposites) have been developed. Such nanocomposites are highly miscible within the polymer matrix. In this Review, a summary of synthetic approaches to achieve stable nanocomposites in a semiconducting polymer matrix is presented. Furthermore, a theoretical background as well as an overview concerning morphology control of inorganic NCs in polymer matrices are provided. In addition, the morphologic behavior of highly anisotropic nanoparticles (i.e. liquid crystalline phase formation of nanorod-composites) and branched nanoparticles (spatial orientation of tetrapods) is described. Finally, the morphology requirements for the application of inorganic/organic hybrid systems in light emitting diodes and solar cells are discussed, and potential solutions to achieve the required morphologies are provided. PMID:25737161

  12. An alternative approach to charge transport in semiconducting electrodes

    NASA Technical Reports Server (NTRS)

    Thomchick, J.; Buoncristiani, A. M.

    1980-01-01

    The excess-carrier charge transport through the space-charge region of a semiconducting electrode is analyzed by a technique known as the flux method. In this approach reflection and transmission coefficients appropriate for a sheet of uniform semiconducting material describe its transport properties. A review is presented of the flux method showing that the results for a semiconductor electrode reduce in a limiting case to those previously found by Gaertner if the depletion layer is treated as a perfectly transmitting medium in which scattering and recombination are ignored. Then, in the framework of the flux method the depletion layer is considered more realistically by explicitly taking into account scattering and recombination processes which occur in this region.

  13. Transport properties in semiconducting NbS{sub 2} nanoflakes

    SciTech Connect

    Huang, Y. H.; Chen, R. S. Ho, C. H.; Peng, C. C.; Huang, Y. S.

    2014-09-01

    The electronic transport properties in individual niobium disulphide (NbS{sub 2}) nanoflakes mechanically exfoliated from the bulk crystal with three rhombohedral (3R) structure grown by chemical vapor transport were investigated. It is found that the conductivity values of the single-crystalline nanoflakes are approximately two orders of magnitude lower than that of their bulk counterparts. Temperature-dependent conductivity measurements show that the 3R-NbS{sub 2} nanoflakes exhibit semiconducting transport behavior, which is also different from the metallic character in the bulk crystals. In addition, the noncontinuous conductivity variations were observed at the temperature below 180 K for both the nanoflakes and the bulks, which is attributed to the probable charge density wave transition. The photoconductivities in the semiconducting nanoflakes were also observed under the excitation at 532 nm wavelength. The probable mechanisms resulting in the different transport behaviors between the NbS{sub 2} nanostructure and bulk were discussed.

  14. The high-pressure semiconducting phase of LiBC

    NASA Astrophysics Data System (ADS)

    Zhang, Meiguang

    2016-04-01

    A high-pressure hexagonal semiconducting phase (space group P63mc , 2f.u./cell) of LiBC stable above 108 GPa was predicted through first-principles calculations combined with unbiased swarm structure searching techniques. This new phase consisted of three-dimensional B-C networks which originate from the dramatic out-of-plane distortions of the graphene-like B-C sublattice in the low-pressure P63/mmc phase under compression. Contrary to the metallizations of LiBC under high pressure previously proposed, the resulting three-dimensional B-C framework lacks the system of π bonds with mobile electrons and has more localized electrons, as a result of the semiconducting nature of this high-pressure LiBC phase.

  15. Current-voltage characteristics and parameter retrieval of semiconducting nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Z. Y.; Jin, C. H.; Liang, X. L.; Chen, Q.; Peng, L.-M.

    2006-02-01

    Electrical transport measurements were conducted on semiconducting nanowires and three distinct current-voltage (I-V) characteristics were observed, i.e., almost symmetric, almost rectifying, and almost linear. These I-V characteristics were modeled by treating the transport in the nanowire as in a metal-semiconductor-metal structure involving two Schottky barriers and a resistor in between these barriers, and the transport is shown to be dominated by the reverse-biased Schottky barrier under low bias and by the semiconducting nanowire at large bias. In contrast to the conventional Schottky diode, the reverse current in the nano-Schottky barrier structure is not negligible and the current is largely tunneling rather than thermionic. Experimental I-V curves are reproduced very well using our model, and a method for extracting nanowire resistance, electron density, and mobility is proposed and applied to ZnO, CdS, and Bi2S3 nanowires.

  16. Electronic transport through nanotube contacts and devices

    NASA Astrophysics Data System (ADS)

    Buia, Calin Ioan

    2003-10-01

    Carbon nanotubes are materials with amazing mechanical and electronic properties, which makes them suitable for building nanoscale electronic devices and circuits. However, their electronic transport properties are not yet fully understood. In this study we aim to investigate the electronic transport through nanotube/nanotube contacts. Our calculations are based on Land auer-Buttiker formalism. The transmission function is computed using a Green's functions technique and a tight-binding hamiltonian. Two types of geometries are considered: parallel contact and concentric contact. Additionally we analyze the behavior of a nanotube Y-junction. We find that out of all the properties of individual nanotubes, chirality and symmetry have the most important effect on the electronic transport. As a rule, armchair/armchair and metallic zigzag/zigzag contacts show the best conduction. This is explained by the perfect in-registry atomic arrangement they can provide. The contact length and the local arrangement of the atoms in the contact area are factors that further influence the conductance. We found that in optimal conditions (i.e. in-registry atomic arrangement), a contact length of ˜10 nm is enough to achieve the same conductance as a perfect nanotube. Beyond that the conductance is modulated by quantum interference effects, due to the formation of a resonant cavity in the contact area. For concentric contacts, the states between which the electron hops when passing from one tube to the other must have compatible rotational symmetries, otherwise, the corresponding conduction channel will be suppressed. This results can be used to predict the electronic transport through various setups, including nanotube bundles and multiwall nanotubes.

  17. Thiofluorographene-hydrophilic graphene derivative with semiconducting and genosensing properties.

    PubMed

    Urbanová, Veronika; Holá, Kateřina; Bourlinos, Athanasios B; Čépe, Klára; Ambrosi, Adriano; Loo, Adeline Huiling; Pumera, Martin; Karlický, František; Otyepka, Michal; Zbořil, Radek

    2015-04-01

    We present the first example of covalent chemistry on fluorographene, enabling the attachment of -SH groups through nucleophilic substitution of fluorine in a polar solvent. The resulting thiographene-like, 2D derivative is hydrophilic with semiconducting properties and bandgap between 1 and 2 eV depending on F/SH ratio. Thiofluorographene is applied in DNA biosensing by electrochemical impedance spectroscopy. PMID:25692678

  18. Dynamic manipulation and separation of individual semiconducting and metallic nanowires

    PubMed Central

    Jamshidi, Arash; Pauzauskie, Peter J.; Schuck, P. James; Ohta, Aaron T.; Chiou, Pei-Yu; Chou, Jeffrey; Yang, Peidong; Wu, Ming C.

    2009-01-01

    The synthesis of nanowires has advanced in the last decade to a point where a vast range of insulating, semiconducting, and metallic materials1 are available for use in integrated, heterogeneous optoelectronic devices at nanometer scales 2. However, a persistent challenge has been the development of a general strategy for the manipulation of individual nanowires with arbitrary composition. Here we report that individual semiconducting and metallic nanowires with diameters below 20 nm, are addressable with forces generated by optoelectronic tweezers (OET) 3. Using 100,000× less optical power density than optical tweezers, OET is capable of transporting individual nanowires with speeds 4× larger than maximum speeds achieved by optical tweezers. A real-time array of silver nanowires is formed using photopatterned virtual-electrodes, demonstrating the potential for massively parallel assemblies. Furthermore, OET enables the separation of semiconducting and metallic nanowires, suggesting a broad range of applications for the separation and heterogenous integration of one-dimensional nanoscale materials. PMID:19789729

  19. Nanotube News

    ERIC Educational Resources Information Center

    Journal of College Science Teaching, 2005

    2005-01-01

    Smaller, faster computers, bullet-proof t-shirts, and itty-bitty robots--such are the promises of nanotechnology and the cylinder-shaped collection of carbon molecules known as nanotubes. But for these exciting ideas to become realities, scientists must understand how these miracle molecules perform under all sorts of conditions. This brief…

  20. Chemical modification of multi-walled carbon nanotubes using a tetrazine derivative

    NASA Astrophysics Data System (ADS)

    Hayden, Hugh; Gun'ko, Yurii K.; Perova, Tatiana S.

    2007-02-01

    Multi-walled carbon nanotubes (MWNTs) have been reacted with 3,6-diaminotetrazine under heating. This process involves series of interactions between tetrazines and carbon nanotubes including π-π interactions, cycloaddition (Diels-Alder) and cross-linking reactions. These interactions resulted in coating of the MWNTs and in the formation of Y-junctions between nanotubes. Long heating (48 h) of MWNTs with the terazine resulted in a partial destruction of nanotubes due to their excessive functionalisation. The new nanocomposites have been studied by TEM, FTIR and Raman spectroscopy.

  1. Chirality Characterization of Dispersed Single Wall Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Namkung, Min; Williams, Phillip A.; Mayweather, Candis D.; Wincheski, Buzz; Park, Cheol; Namkung, Juock S.

    2005-01-01

    Raman scattering and optical absorption spectroscopy are used for the chirality characterization of HiPco single wall carbon nanotubes (SWNTs) dispersed in aqueous solution with the surfactant sodium dodecylbenzene sulfonate. Radial breathing mode (RBM) Raman peaks for semiconducting and metallic SWNTs are identified by directly comparing the Raman spectra with the Kataura plot. The SWNT diameters are calculated from these resonant peak positions. Next, a list of (n, m) pairs, yielding the SWNT diameters within a few percent of that obtained from each resonant peak position, is established. The interband transition energies for the list of SWNT (n, m) pairs are calculated based on the tight binding energy expression for each list of the (n, m) pairs, and the pairs yielding the closest values to the corresponding experimental optical absorption peaks are selected. The results reveal that (1, 11), (4, 11), and (0, 11) as the most probable chiralities of the semiconducting nanotubes. The results also reveal that (4, 16), (6, 12) and (8, 8) are the most probable chiralities for the metallic nanotubes. Directly relating the Raman scattering data to the optical absorption spectra, the present method is considered the simplest technique currently available. Another advantage of this technique is the use of the E(sup 8)(sub 11) peaks in the optical absorption spectrum in the analysis to enhance the accuracy in the results.

  2. Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation.

    PubMed

    Xu, Shuo; Wang, Fengqiu; Zhu, Chunhui; Meng, Yafei; Liu, Yujie; Liu, Wenqing; Tang, Jingyi; Liu, Kaihui; Hu, Guohua; Howe, Richard C T; Hasan, Tawfique; Zhang, Rong; Shi, Yi; Xu, Yongbing

    2016-04-28

    Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband 'degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ∼2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of SWNTs' nonlinear absorption characteristics, and help provide updated design guidelines for SWNT based nonlinear optical devices. PMID:27088630

  3. High performance organic transistors: Percolating arrays of nanotubes functionalized with an electron deficient olefin

    NASA Astrophysics Data System (ADS)

    Kanungo, Mandakini; Malliaras, George G.; Blanchet, Graciela B.

    2010-08-01

    Precise control over the electronic properties of carbon nanotubes is key to their application in plastic electronics. In the present work, we have functionalized carbon nanotubes with an electron withdrawing nonfluorinated olefins via a 2-2 cycloaddition reaction. Our results suggest that the formation of cyclobutanelike four-member ring at the functionalization site is a fairly general approach, independent of specifics of the addend, to converting the grown mixture of metal and semiconductor tubes into high mobility semiconducting tubes without tedious separation requirements. Thin film transistors fabricated from such functionalized tubes exhibit mobilities of ˜30 cm2/V s and on/off ratios in excess of 106. This simple functionalization represents a low cost path to high performance semiconducting inks for printable electronics.

  4. Electron backscattering on single-wall carbon nanotubes observed by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Clauss, W.; Bergeron, D. J.; Freitag, M.; Kane, C. L.; Mele, E. J.; Johnson, A. T.

    1999-09-01

    Single-wall carbon nanotubes, seamless cylindrical molecules formed from a graphene sheet, are either conducting or semiconducting, depending on the particular "wrapping vector" that defines the waist of the tube. Scanning tunneling microscopy experiments have tested this idea by simultaneously measuring a tube's lattice structure and electronic properties. Here we present a series of STM images of single-wall carbon nanotubes with a strikingly rich set of superstructures. The observed patterns can be understood as due to interference between propagating electron waves that are reflected from defects on the tube walls and ends, or as intrinsic to states propagating on semiconducting tubes. The measured broken symmetries can be used to directly probe electronic backscattering on the tube and provide a key element in the understanding of low-energy electron transport on these structures.

  5. Spin Dependent Transport Properties of Metallic and Semiconducting Nanostructures

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.

    Present computing and communication devices rely on two different classes of technologies; information processing devices are based on electrical charge transport in semiconducting materials while information storage devices are based on orientation of electron spins in magnetic materials. A realization of a hybrid-type device that is based on charge as well as spin properties of electrons would perform both of these actions thereby enhancing computation power to many folds and reducing power consumptions. This dissertation focuses on the fabrication of such spin-devices based on metallic and semiconducting nanostructures which can utilize spin as well as charge properties of electrons. A simplified design of the spin-device consists of a spin injector, a semiconducting or metallic channel, and a spin detector. The channel is the carrier of the spin signal from the injector to the detector and therefore plays a crucial role in the manipulation of spin properties in the device. In this work, nanostructures like nanowires and nanostripes are used to function the channel in the spin-device. Methods like electrospinning, hydrothermal, and wet chemical were used to synthesize nanowires while physical vapor deposition followed by heat treatment in controlled environment was used to synthesis nanostripes. Spin-devices fabrication of the synthesized nanostructures were carried out by electron beam lithography process. The details of synthesis of nanostructures, device fabrication procedures and measurement techniques will be discussed in the thesis. We have successfully fabricated the spin-devices of tellurium nanowire, indium nanostripe, and indium oxide nanostripe and studied their spin transport properties for the first time. These spin-devices show large spin relaxation length compared to normal metals like copper and offer potentials for the future technologies. Further, Heusler alloys nanowires like nanowires of Co 2FeAl were synthesized and studied for electrical

  6. Effect of UV irradiation on adsorption/desorption of oxygen and water on carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Muckley, Eric S.; Nelson, Anthony J.; Jacobs, Christopher B.; Ivanov, Ilia N.

    2016-02-01

    Carbon nanotube (CNT) films composed of semiconducting single wall nanotubes (s-SWNTs), metallic single wall nanotubes (m-SWNTs), and multiwall nanotubes (MWNTs) were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in the film conductivity and mass were measured in situ. We find that UV irradiation increases the resistive response of CNT films to O2 and H2O by more than an order of magnitude. In m-SWNT and MWNT films, UV irradiation changes the sign of the resistive response to O2 and H2O by generating free charge carriers. S-SWNTs show the largest UV-induced resistive response and exhibit weakening of van der Waals interactions with the QCM crystal when exposed to gas/vapor.

  7. Effect of UV irradiation on the dynamics of oxygen and water interaction with carbon nanotubes

    SciTech Connect

    Nelson, Anthony J; Ivanov, Ilia N

    2016-01-01

    Carbon nanotube (CNT) films composed of semiconducting single wall nanotubes (s-SWNTs), metallic single wall nanotubes (m-SWNTs), and multiwall nanotubes (MWNTs) were exposed to O2 and H2O vapor in the dark and under UV irradiation. Changes in the film conductivity and mass were measured in situ. We find that UV irradiation increases the resistive response of CNT films to O2 and H2O by more than an order of magnitude. In m-SWNT and MWNT films, UV irradiation changes the sign of the resistive response to O2 and H2O by generating free charge carriers. S-SWNTs show the largest UV-induced resistive response and exhibit weakening of van der Waals interactions with the QCM crystal when exposed to gas/vapor.

  8. Graphene nanoribbons production from flat carbon nanotubes

    SciTech Connect

    Melo, W. S.; Guerini, S.; Diniz, E. M.

    2015-11-14

    Graphene nanoribbons are of great interest for pure and applied sciences due to their unique properties which depend on the nanoribbon edges, as, for example, energy gap and antiferromagnetic coupling. Nevertheless, the synthesis of nanoribbons with well-defined edges remains a challenge. To collaborate with this subject, here we propose a new route for the production of graphene nanoribbons from flat carbon nanotubes filled with a one-dimensional chain of Fe atoms by first principles calculations based on density functional theory. Our results show that Fe-filled flat carbon nanotubes are energetically more stable than non flattened geometries. Also we find that by hydrogenation or oxygenation of the most curved region of the Fe-filled flat armchair carbon nanotube, it occurred a spontaneous production of zigzag graphene nanoribbons which have metallic or semiconducting behavior depending on the edge and size of the graphene nanoribbon. Such findings can be used to create a new method of synthesis of regular-edge carbon nanoribbons.

  9. Three-junction solar cell

    DOEpatents

    Ludowise, Michael J.

    1986-01-01

    A photovoltaic solar cell is formed in a monolithic semiconductor. The cell contains three junctions. In sequence from the light-entering face, the junctions have a high, a medium, and a low energy gap. The lower junctions are connected in series by one or more metallic members connecting the top of the lower junction through apertures to the bottom of the middle junction. The upper junction is connected in voltage opposition to the lower and middle junctions by second metallic electrodes deposited in holes 60 through the upper junction. The second electrodes are connected to an external terminal.

  10. Thermoelectric properties of single-wall carbon nanotube films: Effects of diameter and wet environment

    NASA Astrophysics Data System (ADS)

    Hayashi, Daisuke; Ueda, Tomohiro; Nakai, Yusuke; Kyakuno, Haruka; Miyata, Yasumitsu; Yamamoto, Takahiro; Saito, Takeshi; Hata, Kenji; Maniwa, Yutaka

    2016-02-01

    The Seebeck coefficient S and the electrical resistivity ρ of single-wall carbon nanotube (SWCNT) films were investigated as a function of the SWCNT diameter and carrier concentration. The S and ρ significantly changed in humid environments through p-type carrier doping. Experiments, combined with theoretical simulations based on the non-equilibrium Green’s function theory, indicated that the power factor P can be increased threefold by the enrichment of semiconducting SWCNTs, but the nanotube diameter has little effect. The improvement of the film resistivity strongly enhances the film thermoelectric performance, manifested as increasing the value of P above 1200 µW/(m·K2).

  11. Ab-initio study of structural, mechanical and electronic properties of functionalized carbon nanotubes

    SciTech Connect

    Milowska, Karolina Z.; Birowska, Magdalena; Majewski, Jacek A.

    2013-12-04

    We present exemplary results of extensive studies of structural, mechanical and electronic properties of covalent functionalization of carbon nanotubes (CNTs). We report new results for metallic (9,0), and semiconducting (10,0) single-wall carbon nanotubes (CNT) functionalized with -COOH, -OH, and both groups with concentration up to 12.5%. Our studies are performed in the framework of the density functional theory (DFT). We discuss here the stability, local and global changes in structure, elastic moduli (Young's, Shear, and Bulk), electronic structure and resulting band gaps, as a function of the density of the adsorbed molecules.

  12. Ultrafast nonlinear photoresponse of single-wall carbon nanotubes: a broadband degenerate investigation

    NASA Astrophysics Data System (ADS)

    Xu, Shuo; Wang, Fengqiu; Zhu, Chunhui; Meng, Yafei; Liu, Yujie; Liu, Wenqing; Tang, Jingyi; Liu, Kaihui; Hu, Guohua; Howe, Richard C. T.; Hasan, Tawfique; Zhang, Rong; Shi, Yi; Xu, Yongbing

    2016-04-01

    Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband `degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ~2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of SWNTs' nonlinear absorption characteristics, and help provide updated design guidelines for SWNT based nonlinear optical devices.Understanding of the fundamental photoresponse of carbon nanotubes has broad implications for various photonic and optoelectronic devices. Here, Z-scan and pump-probe spectroscopy performed across 600-2400 nm were combined to give a broadband `degenerate' mapping of the nonlinear absorption properties of single-wall carbon nanotubes (SWNTs). In contrast to the views obtained from non-degenerate techniques, sizable saturable absorption is observed from the visible to the near-infrared range, including the spectral regions between semiconducting excitonic peaks and metallic tube transitions. In addition, the broadband mapping unambiguously reveals a photobleaching to photoinduced absorption transition feature within the first semiconducting excitonic band ~2100 nm, quantitatively marking the long-wavelength cut-off for saturable absorption of the SWNTs investigated. Our findings present a much clearer physical picture of

  13. Intense photoluminescence from dried double-stranded DNA and single-walled carbon nanotube hybrid

    SciTech Connect

    Ito, M.; Kobayashi, T.; Ito, Y.; Hayashida, T.; Nii, D.; Umemura, K.; Homma, Y.

    2014-01-27

    Semiconducting single-walled carbon nanotubes (SWNTs) show near-infrared photoluminescence (PL) when they are individually isolated. This was an obstacle to use photonic properties of SWNTs on a solid surface. We show that SWNTs wrapped with DNA maintain intense PL under the dry conditions. SWNTs are well isolated individually by DNA even when the DNA-SWNT hybrids are agglomerated. This finding opens up application of SWNTs to photonic devices.

  14. Single Particle Transport Through Carbon Nanotube Wires: Effect of Defects and Polyhedral Cap

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Govidan, T. R.

    1999-01-01

    The ability to manipulate carbon nanotubes with increasing precision has enabled a large number of successful electron transport experiments. These studies have primarily focussed on characterizing transport through both metallic and semiconducting wires. Tans et al. demonstrated ballistic transport in single-wall nanotubes for the first time, although the experimental configuration incurred large contact resistance. Subsequently, methods of producing low contact resistances have been developed and two terminal conductances smaller than 50 k-ohms have been repeatably demonstrated in single-wall and multi-wall nanotubes. In multi-wall nanotubes, Frank et al. demonstrated a resistance of approximately h/2e(exp 2) in a configuration where the outermost layer made contact to a liquid metal. This was followed by the work of de Pablo et al. where a resistance of h(bar)/27e(exp 2) (approximately 478 ohms) was measured in a configuration where electrical contact was made to many layers of a multi-wall nanotube. Frank et al. and Pablo et al. note that each conducting layer contributes a conductance of only 2e(exp 2)/h, instead of the 4e(exp 2)/h that a single particle mode counting picture yields. These small resistances have been obtained in microns long nanotubes, making them the best conducting molecular wires to date. The large conductance of nanotube wires stems from the fact that the crossing bands of nanotubes are robust to defect scattering.

  15. Electronic structure and optical property of boron doped semiconducting graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Chen, Aqing; Shao, Qingyi; Wang, Li; Deng, Feng

    2011-08-01

    We present a system study on the electronic structure and optical property of boron doped semiconducting graphene nanoribbons using the density functional theory. Energy band structure, density of states, deformation density, Mulliken popular and optical spectra are considered to show the special electronic structure of boron doped semiconducting graphene nanoribbons. The C-B bond form is discussed in detail. From our analysis it is concluded that the Fermi energy of boron doped semiconducting graphene nanoribbons gets lower than that of intrinsic semiconducting graphene nanoribbons. Our results also show that the boron doped semiconducting graphene nanoribbons behave as p-type semiconducting and that the absorption coefficient of boron doped armchair graphene nanoribbons is generally enhanced between 2.0 eV and 3.3 eV. Therefore, our results have a great significance in developing nano-material for fabricating the nano-photovoltaic devices.

  16. Mechanism of amperometric biosensor with electronic-type-controlled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Hidaka, Hiroki; Nowaki, Kohei; Muguruma, Hitoshi

    2016-03-01

    An amperometric enzyme biosensor with electronic-type-controlled (metallic and semiconducting) single-walled carbon nanotubes (CNTs) is presented. In this research, we investigate how the electronic types of CNTs influence the amperometric response of enzyme biosensors and what their working mechanisms are. The biosensor of interest is for glucose detection using enzyme glucose oxidase (GOD). In the presence of oxygen, the response of a metallic CNT-GOD electrode was 2.5 times more sensitive than that of a semiconducting CNT-GOD electrode. In contrast, in the absence of oxygen, the response of the semiconducting CNT-GOD electrode was retained, whereas that of the metallic CNT-GOD electrode was significantly reduced. This indicates that direct electron transfer occurred with the semiconducting CNT-GOD electrode, whereas the metallic CNT-GOD electrode was dominated by a hydrogen peroxide pathway caused by an enzymatic reaction. Electrochemical impedance spectroscopy was used to show that the semiconducting CNT network has less resistance for electron transfer than the metallic CNT network. The optimized glucose biosensor revealed a sensitivity of 5.6 µA mM-1 cm-2 at +0.6 V vs Ag/AgCl, a linear dynamic range of 0.025-1.4 mM, and a response time of 8 s.

  17. Carbon nanotubes for biomedical imaging: the recent advances.

    PubMed

    Gong, Hua; Peng, Rui; Liu, Zhuang

    2013-12-01

    This article reviews the latest progresses regarding the applications of carbon nanotubes (CNTs), including single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs), as multifunctional nano-probes for biomedical imaging. Utilizing the intrinsic band-gap fluorescence of semi-conducting single-walled carbon nanotubes (SWNTs), fluorescence imaging in the near infrared II (NIR-II) region with enhanced tissue penetration and spatial resolution has shown great promise in recent years. Raman imaging based on the resonance Raman scattering of SWNTs has also been explored by a number of groups for in vitro and in vivo imaging of biological samples. The strong absorbance of CNTs in the NIR region can be used for photoacoustic imaging, and their photoacoustic signals can be dramatically enhanced by adding organic dyes, or coating with gold shells. Taking advantages of metal nanoparticle impurities attached to nanotubes, CNTs can also serve as a T2-contrast agent in magnetic resonance (MR) imaging. In addition, when labeled with radioactive isotopes, many groups have developed nuclear imaging with functionalized CNTs. Therefore CNTs are unique imaging probes with great potential in biomedical multimodal imaging. PMID:24184130

  18. Physically unclonable cryptographic primitives using self-assembled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Hu, Zhaoying; Comeras, Jose Miguel M. Lobez; Park, Hongsik; Tang, Jianshi; Afzali, Ali; Tulevski, George S.; Hannon, James B.; Liehr, Michael; Han, Shu-Jen

    2016-06-01

    Information security underpins many aspects of modern society. However, silicon chips are vulnerable to hazards such as counterfeiting, tampering and information leakage through side-channel attacks (for example, by measuring power consumption, timing or electromagnetic radiation). Single-walled carbon nanotubes are a potential replacement for silicon as the channel material of transistors due to their superb electrical properties and intrinsic ultrathin body, but problems such as limited semiconducting purity and non-ideal assembly still need to be addressed before they can deliver high-performance electronics. Here, we show that by using these inherent imperfections, an unclonable electronic random structure can be constructed at low cost from carbon nanotubes. The nanotubes are self-assembled into patterned HfO2 trenches using ion-exchange chemistry, and the width of the trench is optimized to maximize the randomness of the nanotube placement. With this approach, two-dimensional (2D) random bit arrays are created that can offer ternary-bit architecture by determining the connection yield and switching type of the nanotube devices. As a result, our cryptographic keys provide a significantly higher level of security than conventional binary-bit architecture with the same key size.

  19. Physically unclonable cryptographic primitives using self-assembled carbon nanotubes.

    PubMed

    Hu, Zhaoying; Comeras, Jose Miguel M Lobez; Park, Hongsik; Tang, Jianshi; Afzali, Ali; Tulevski, George S; Hannon, James B; Liehr, Michael; Han, Shu-Jen

    2016-06-01

    Information security underpins many aspects of modern society. However, silicon chips are vulnerable to hazards such as counterfeiting, tampering and information leakage through side-channel attacks (for example, by measuring power consumption, timing or electromagnetic radiation). Single-walled carbon nanotubes are a potential replacement for silicon as the channel material of transistors due to their superb electrical properties and intrinsic ultrathin body, but problems such as limited semiconducting purity and non-ideal assembly still need to be addressed before they can deliver high-performance electronics. Here, we show that by using these inherent imperfections, an unclonable electronic random structure can be constructed at low cost from carbon nanotubes. The nanotubes are self-assembled into patterned HfO2 trenches using ion-exchange chemistry, and the width of the trench is optimized to maximize the randomness of the nanotube placement. With this approach, two-dimensional (2D) random bit arrays are created that can offer ternary-bit architecture by determining the connection yield and switching type of the nanotube devices. As a result, our cryptographic keys provide a significantly higher level of security than conventional binary-bit architecture with the same key size. PMID:26900757

  20. Electronic structure of carbon-boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Sanginés-Mendoza, Raúl; Martinez, Edgar

    2013-03-01

    Structures of carbon and boron nitride nanotubes (CNTs, BNNTs) are quite similar, conversely, electronic properties are radically different from each other. Carbon nanotubes, whose electronic properties can be either metallic or semiconducting depending on their chiral structure, boron nitride nanotubes are always semiconductors with bandgaps over 4 eV. We have looked to hybrid systems, to predict a new kind of nanostructures with novel electronic properties. In this way, we explore the electronic properties of C-BN nanotubes. In particular, we studied the electronic structure of armchair C-BN nanotubes. The calculations were performed using the pseudopotential LCAO method with a Generalized Gradient Approximation for the exchange-correlation energy functional. The band structure of most of these systems have semiconductor character with an indirect gap smaller than its analogous BNNTs. In addition, the most prominent feature of these systems is the existence of flat bands both at the valence band top and at the conduction band minimum. Such flat bands results in sharp and narrow peaks on the total density of states. The behavior of these flat bands mainly indicates that electrons are largely localized. Thus, a detailed analysis on the electronic band structure shows that hybridization between those orbitals on the interfaces is responsible to exhibit localization effects on the hybrid systems.This research was supported by Conacyt under Grant No. 133022.

  1. Electronically type-sorted carbon nanotube-based electrochemical biosensors with glucose oxidase and dehydrogenase.

    PubMed

    Muguruma, Hitoshi; Hoshino, Tatsuya; Nowaki, Kohei

    2015-01-14

    An electrochemical enzyme biosensor with electronically type-sorted (metallic and semiconducting) single-walled carbon nanotubes (SWNTs) for use in aqueous media is presented. This research investigates how the electronic types of SWNTs influence the amperometric response of enzyme biosensors. To conduct a clear evaluation, a simple layer-by-layer process based on a plasma-polymerized nano thin film (PPF) was adopted because a PPF is an inactive matrix that can form a well-defined nanostructure composed of SWNTs and enzyme. For a biosensor with the glucose oxidase (GOx) enzyme in the presence of oxygen, the response of a metallic SWNT-GOx electrode was 2 times larger than that of a semiconducting SWNT-GOx electrode. In contrast, in the absence of oxygen, the response of the semiconducting SWNT-GOx electrode was retained, whereas that of the metallic SWNT-GOx electrode was significantly reduced. This indicates that direct electron transfer occurred with the semiconducting SWNT-GOx electrode, whereas the metallic SWNT-GOx electrode was dominated by a hydrogen peroxide pathway caused by an enzymatic reaction. For a biosensor with the glucose dehydrogenase (GDH; oxygen-independent catalysis) enzyme, the response of the semiconducting SWNT-GDH electrode was 4 times larger than that of the metallic SWNT-GDH electrode. Electrochemical impedance spectroscopy was used to show that the semiconducting SWNT network has less resistance for electron transfer than the metallic SWNT network. Therefore, it was concluded that semiconducting SWNTs are more suitable than metallic SWNTs for electrochemical enzyme biosensors in terms of direct electron transfer as a detection mechanism. This study makes a valuable contribution toward the development of electrochemical biosensors that employ sorted SWNTs and various enzymes. PMID:25522366

  2. Carbon nanotube composite materials

    DOEpatents

    O'Bryan, Gregory; Skinner, Jack L; Vance, Andrew; Yang, Elaine Lai; Zifer, Thomas

    2015-03-24

    A material consisting essentially of a vinyl thermoplastic polymer, un-functionalized carbon nanotubes and hydroxylated carbon nanotubes dissolved in a solvent. Un-functionalized carbon nanotube concentrations up to 30 wt % and hydroxylated carbon nanotube concentrations up to 40 wt % can be used with even small concentrations of each (less than 2 wt %) useful in producing enhanced conductivity properties of formed thin films.

  3. Spin glass in semiconducting KFe1.05Ag0.88Te2 single crystals

    DOE PAGESBeta

    Ryu, H.; Lei, H.; Klobes, B.; Warren, J. B.; Hermann, R. P.; Petrovic, C.

    2015-05-26

    We report discovery of KFe1.05Ag0.88Te2 single crystals with semiconducting spin glass ground state. Composition and structure analysis suggest nearly stoichiometric I4/mmm space group but allow for the existence of vacancies, absent in long range semiconducting antiferromagnet KFe1.05Ag0.88Te2. The subtle change in stoichometry in Fe/Ag sublattice changes magnetic ground state but not conductivity, giving further insight into the semiconducting gap mechanism.

  4. Nanochannel-Directed Growth of One-Dimensional Multi-Segment Heterojunctions of Metallic Au1-xGex and Semiconducting Ge

    SciTech Connect

    Li, Xiangdong; Meng, Guowen; Qin, Shengyong; Xu, Qiaoling; Chu, Zhaoqin; Zhu, Xiaoguang; Kong, Mingguang; Li, An-Ping

    2012-01-01

    We report on the synthesis of multi-segment nanowire (NW) junctions of Au{sub 1-x}Ge{sub x} and Ge inside the nanochannels of porous anodic aluminum oxide template. The one-dimensional heterostructures are grown with a low-temperature chemical vapor deposition process, assisted by electrodeposited Au nanowires (AuNWs). The Au-catalyzed vapor-liquid-solid growth process occurs simultaneously in multiple locations along the nanochannel, which leads to multi-segment Au{sub 1-x}Ge{sub x}/Ge heterojunctions. The structures of the as-grown hybrid NWs, analyzed by using transmission electron microscopy and energy-dispersive X-ray spectroscopy elemental mapping, show clear compositional modulation with variable modulation period and controllable junction numbers. Remarkably, both GeNW and Au{sub 1-x}Ge{sub x}NW segments are single crystalline with abrupt interfaces and good crystallographic coherences. The electronic and transport properties of individual NW junctions are measured by using a multi-probe scanning tunneling microscope, which confirms the semiconducting nature of Ge segments and the metallic behavior of Au{sub 1-x}Ge{sub x} segments, respectively. The high yield of multiple segment NW junctions of a metal-semiconductor can facilitate the applications in nanoelectronics and optoelectronics that harness multiple functionalities of heterointerfaces.

  5. Distinct electrical effects of multi-walled carbon nanotubes in two composites

    NASA Astrophysics Data System (ADS)

    Wang, Leizhi; Wang, Hua; Datta, Timir; Yin, Ming; Tian, Xingyou

    2014-11-01

    The temperature dependent conductivity of multi-walled carbon nanotube film (MWNT) is reported and the different electrical properties of nanotubes in two composites are compared. Due to the disordered structures, our carbon nanotube film displays variable range hopping behavior. While the geometric distributions of carbon nanotubes in the conducting polyaniline (PANI) and insulating polyamide (PA66) are similar, charge carriers transport distinctly. The conductive PANI, following one-dimensional variable range hopping, dominates the electrical properties of MWNT/PANI composites. The effect of MWNTs becomes prominent only at low temperature range. However, the contact junctions composed by adjacent carbon nanotubes, instead of nanotubes themselves or the polymer matrix, determine the electrical properties of MWNT/PA66 composites, showing the fluctuation induced tunneling characteristic.

  6. Encapsulation of Semiconducting Polymers in Vault Protein Cages

    SciTech Connect

    Ng, B.C.; Yu, M.; Gopal, A.; Rome, L.H.; Monbouquette, H.G.; Tolbert, S.H.

    2009-05-22

    We demonstrate that a semiconducting polymer [poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene), MPS-PPV] can be encapsulated inside recombinant, self-assembling protein nanocapsules called 'vaults'. Polymer incorporation into these nanosized protein cages, found naturally at {approx}10,000 copies per human cell, was confirmed by fluorescence spectroscopy and small-angle X-ray scattering. Although vault cellular functions and gating mechanisms remain unknown, their large internal volume and natural prevalence within the human body suggests they could be used as carriers for therapeutics and medical imaging reagents. This study provides the groundwork for the use of vaults in encapsulation and delivery applications.

  7. Annealing effects on the optical properties of semiconducting boron carbide

    SciTech Connect

    Billa, R. B.; Robertson, B. W.; Hofmann, T.; Schubert, M.

    2009-08-01

    Infrared vibrations of as-deposited and annealed semiconducting boron carbide thin films were investigated by midinfrared spectroscopic ellipsometry. The strong boron-hydrogen resonance at approx2560 cm{sup -1} in as-deposited films reveals considerable hydrogen incorporation during plasma-enhanced chemical vapor deposition. Extended annealing at 600 deg. C caused significant reduction in film thickness, substantial reduction of boron-hydrogen bond resonance absorption, and development of distinct blue-shifted boron-carbon and icosahedral vibration mode resonances. Our findings suggest that annealing results in substantial loss of hydrogen and in development of icosahedral structure, accompanied by strain relaxation and densification.

  8. An Exploration of Neutron Detection in Semiconducting Boron Carbide

    NASA Astrophysics Data System (ADS)

    Hong, Nina

    The 3He supply problem in the U.S. has necessitated the search for alternatives for neutron detection. The neutron detection efficiency is a function of density, atomic composition, neutron absorption cross section, and thickness of the neutron capture material. The isotope 10B is one of only a handful of isotopes with a high neutron absorption cross section---3840 barns for thermal neutrons. So a boron carbide semiconductor represents a viable alternative to 3He. This dissertation provides an evaluation of the performance of semiconducting boron carbide neutron detectors grown by plasma enhance chemical vapor deposition (PECVD) in order to determine the advantages and drawbacks of these devices for neutron detection. Improved handling of the PECVD system has resulted in an extremely stable plasma, enabling deposition of thick films of semiconducting boron carbide. A variety of material and semiconducting characterization tools have been used to investigate the structure and electronic properties of boron carbide thin films, including X-ray diffraction, X-ray photoelectron spectroscopy, atomic force microscopy, infrared/Raman spectroscopy, current-voltage measurements and capacitance-voltage measurements. Elemental concentrations in the boron carbide films have been obtained from Rutherford backscattering and elastic recoil detection analysis. Solid state neutron detection devices have been fabricated in the form of heterostructured p-n diodes, p-type boron carbide/n-type Si. Operating conditions, including applied bias voltage, and time constants, have been optimized for maximum detection efficiency and correlated to the semiconducting properties investigated in separate electronic measurements. Accurate measurements of the neutron detection efficiency and the response of the detector to a wide range of neutron wavelengths have been performed at a well calibrated, tightly collimated, "white" cold neutron beam source using time-of-flight neutron detection technique

  9. Silicon germanium semiconductive alloy and method of fabricating same

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor)

    2008-01-01

    A silicon germanium (SiGe) semiconductive alloy is grown on a substrate of single crystalline Al.sub.2O.sub.3. A {111} crystal plane of a cubic diamond structure SiGe is grown on the substrate's {0001} C-plane such that a <110> orientation of the cubic diamond structure SiGe is aligned with a <1,0,-1,0> orientation of the {0001} C-plane. A lattice match between the substrate and the SiGe is achieved by using a SiGe composition that is 0.7223 atomic percent silicon and 0.2777 atomic percent germanium.

  10. Ultraviolet optical absorptions of semiconducting copper phosphate glasses

    NASA Technical Reports Server (NTRS)

    Bae, Byeong-Soo; Weinberg, Michael C.

    1993-01-01

    Results are presented of a quantitative investigation of the change in UV optical absorption in semiconducting copper phosphate glasses with batch compositions of 40, 50, and 55 percent CuO, as a function of the Cu(2+)/Cu(total) ratio in the glasses for each glass composition. It was found that optical energy gap, E(opt), of copper phosphate glass is a function of both glass composition and Cu(2+)/Cu(total) ratio in the glass. E(opt) increases as the CuO content for fixed Cu(2+)/Cu(total) ratio and the Cu(2+)/Cu(total) ratio for fixed glass composition are reduced.

  11. Covalent Metal-Nanotube Heterojunctions as Ultimate Nano-Contacts

    SciTech Connect

    Rodriguez-Manzo, Jose; Banhart, Florian; Terrones Maldonado, Mauricio; Terrones Maldonado, Humberto; Grobert, Nicole; Ajayan, Pullikel M; Sumpter, Bobby G; Meunier, Vincent

    2009-01-01

    We report the controlled formation and characterization of heterojunctions between carbon nanotubes and different metal nanocrystals (Fe, Co, Ni, and FeCo). The heterojunctions are formed from metal-filled multiwall carbon nanotubes (MWNTs) via intense electron beam irradiation at temperatures in the range of 450-700 C and observed in situ in a transmission electron microscope. Under irradiation, the segregation of metal and carbon atoms occurs, leading to the formation of heterojunctions between metal and graphite. Metallic conductivity of the metal-nanotube junctions was found by using in situ transport measurements in an electron microscope. Density functional calculations show that these structures are mechanically strong, the bonding at the interface is covalent, and the electronic states at and around the Fermi level are delocalized across the entire system. These properties are essential for the application of such heterojunctions as contacts in electronic devices and vital for the fabrication of robust nanotube-metal composite materials.

  12. Noise characteristics of single-walled carbon nanotube network transistors

    NASA Astrophysics Data System (ADS)

    Kim, Un Jeong; Kim, Kang Hyun; Kim, Kyu Tae; Min, Yo-Sep; Park, Wanjun

    2008-07-01

    The noise characteristics of randomly networked single-walled carbon nanotubes grown directly by plasma enhanced chemical vapor deposition (PECVD) are studied with field effect transistors (FETs). Due to the geometrical complexity of nanotube networks in the channel area and the large number of tube-tube/tube-metal junctions, the inverse frequency, 1/f, dependence of the noise shows a similar level to that of a single single-walled carbon nanotube transistor. Detailed analysis is performed with the parameters of number of mobile carriers and mobility in the different environment. This shows that the change in the number of mobile carriers resulting in the mobility change due to adsorption and desorption of gas molecules (mostly oxygen molecules) to the tube surface is a key factor in the 1/f noise level for carbon nanotube network transistors.

  13. Noise characteristics of single-walled carbon nanotube network transistors.

    PubMed

    Kim, Un Jeong; Kim, Kang Hyun; Kim, Kyu Tae; Min, Yo-Sep; Park, Wanjun

    2008-07-16

    The noise characteristics of randomly networked single-walled carbon nanotubes grown directly by plasma enhanced chemical vapor deposition (PECVD) are studied with field effect transistors (FETs). Due to the geometrical complexity of nanotube networks in the channel area and the large number of tube-tube/tube-metal junctions, the inverse frequency, 1/f, dependence of the noise shows a similar level to that of a single single-walled carbon nanotube transistor. Detailed analysis is performed with the parameters of number of mobile carriers and mobility in the different environment. This shows that the change in the number of mobile carriers resulting in the mobility change due to adsorption and desorption of gas molecules (mostly oxygen molecules) to the tube surface is a key factor in the 1/f noise level for carbon nanotube network transistors. PMID:21828739

  14. Electro-mechanical Properties of Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    Anantram, M. P.; Yang, Liu; Han, Jie; Liu, J. P.; Saubum Subhash (Technical Monitor)

    1998-01-01

    We present a simple picture to understand the bandgap variation of carbon nanotubes with small tensile and torsional strains, independent of chirality. Using this picture, we are able to predict a simple dependence of d(Bandoap)$/$d(strain) on the value of $(N_x-N_y)*mod 3$, for semiconducting tubes. We also predict a novel change in sign of d(Bandgap)$/$d(strain) as a function of tensile strain arising from a change in the value of $q$ corresponding to the minimum bandgap. These calculations are complemented by calculations of the change in bandgap using energy minimized structures, and some important differences are discussed. The calculations are based on the $i$ electron approximation.

  15. Doped semiconductor nanocrystal junctions

    NASA Astrophysics Data System (ADS)

    Borowik, Ł.; Nguyen-Tran, T.; Roca i Cabarrocas, P.; Mélin, T.

    2013-11-01

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (ND≈1020-1021cm-3) silicon nanocrystals (NCs) in the 2-50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as ND-1/3, and depleted charge linearly increasing with the NC diameter and varying as ND1/3. We thus establish a "nanocrystal counterpart" of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  16. Mechanical properties of DNA origami nanoassemblies are determined by Holliday junction mechanophores.

    PubMed

    Shrestha, Prakash; Emura, Tomoko; Koirala, Deepak; Cui, Yunxi; Hidaka, Kumi; Maximuck, William J; Endo, Masayuki; Sugiyama, Hiroshi; Mao, Hanbin

    2016-08-19

    DNA nanoassemblies have demonstrated wide applications in various fields including nanomaterials, drug delivery and biosensing. In DNA origami, single-stranded DNA template is shaped into desired nanostructure by DNA staples that form Holliday junctions with the template. Limited by current methodologies, however, mechanical properties of DNA origami structures have not been adequately characterized, which hinders further applications of these materials. Using laser tweezers, here, we have described two mechanical properties of DNA nanoassemblies represented by DNA nanotubes, DNA nanopyramids and DNA nanotiles. First, mechanical stability of DNA origami structures is determined by the effective density of Holliday junctions along a particular stress direction. Second, mechanical isomerization observed between two conformations of DNA nanotubes at 10-35 pN has been ascribed to the collective actions of individual Holliday junctions, which are only possible in DNA origami with rotational symmetric arrangements of Holliday junctions, such as those in DNA nanotubes. Our results indicate that Holliday junctions control mechanical behaviors of DNA nanoassemblies. Therefore, they can be considered as 'mechanophores' that sustain mechanical properties of origami nanoassemblies. The mechanical properties observed here provide insights for designing better DNA nanostructures. In addition, the unprecedented mechanical isomerization process brings new strategies for the development of nano-sensors and actuators. PMID:27387283

  17. Quantum junction solar cells.

    PubMed

    Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics. PMID:22881834

  18. Carbon nanotubes and microwaves: interactions, responses, and applications.

    PubMed

    Vázquez, Ester; Prato, Maurizio

    2009-12-22

    The interaction of microwaves with carbon nanotubes (CNTs) is an interesting topic for a variety of potential applications. Microwaves have been used for the purification of CNTs and for their chemical functionalization, providing a technique for simple, green, and large-scale protocols. In addition, the selective destruction of metallic CNTs under microwave irradiation could potentially result in a batch of semiconducting-only nanotubes. As an innovative application, the combination of microwaves with well-aligned CNTs could produce a new illumination technology. Moreover, the microwave absorbing properties of CNTs and their different behavior from typical organic compounds may open the door to the preparation of a wide range of new materials useful in many fields. A few examples of practical applications include electromagnetic interference for protecting the environment from radiation and microwave hyperthermia for cancer treatment as well as other medical therapies requiring precise heating of biological tissues. PMID:20025299

  19. Nanotube Tunneling as a Consequence of Probable Discrete Trajectories

    NASA Technical Reports Server (NTRS)

    Robinson, Daryl C.

    2001-01-01

    It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but is divided into charge "islands." A clear understanding of tunneling phenomena can be useful to elucidate the mechanism for electrical conduction in nanotubes. This paper represents the first attempt to shed light on the aforementioned phenomenon through viewing tunneling as a natural consequence of "discrete trajectories." The relevance of this analysis is that it may provide further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. In a situation involving particles impinging on a classically impenetrable barrier, the result of quantum mechanics that the probability of detecting transmitted particles falls off exponentially is derived without wave theory. This paper should provide a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

  20. 2D Carbon Nanotube Network: A New material for Electronics

    NASA Astrophysics Data System (ADS)

    Gruner, George

    2006-03-01

    This talk will focus on the electronic properties of two dimensional carbon nanotube networks, and on their application potential. Percolation issues, together with the frequency, and temperature dependent activity will be discussed. The network can be tuned from having semiconducting to metallic like behavior, and doping with electron withdrawing and donating species leads to networks with tailor-made electronic properties. The network is also highly transparent in the visible spectral range, this attribute -- together with simple room temperature fab processes -- opens up application opportunities in the area of electronics, opto-electronics, photovoltaics and sensors. Recent results on solar cells, OLEDs and smart windows will be reviewed. Field effect transistors that incorporate nanotube network conducting channels, together with complex functional devices that incorporate networks and functional molecules will also be discussed. Finally a comparison will be made with conventional and emerging materials that compete area of disposable, flexible and printable electronics.

  1. Single Wall Carbon Nanotube-Based Structural Health Sensing Materials

    NASA Technical Reports Server (NTRS)

    Watkins, A. Neal; Ingram, JoAnne L.; Jordan, Jeffrey D.; Wincheski, Russell A.; Smits, Jan M.; Williams, Phillip A.

    2004-01-01

    Single wall carbon nanotube (SWCNT)-based materials represent the future aerospace vehicle construction material of choice based primarily on predicted strength-to-weight advantages and inherent multifunctionality. The multifunctionality of SWCNTs arises from the ability of the nanotubes to be either metallic or semi-conducting based on their chirality. Furthermore, simply changing the environment around a SWCNT can change its conducting behavior. This phenomenon is being exploited to create sensors capable of measuring several parameters related to vehicle structural health (i.e. strain, pressure, temperature, etc.) The structural health monitor is constructed using conventional electron-beam lithographic and photolithographic techniques to place specific electrode patterns on a surface. SWCNTs are then deposited between the electrodes using a dielectrophoretic alignment technique. Prototypes have been constructed on both silicon and polyimide substrates, demonstrating that surface-mountable and multifunctional devices based on SWCNTs can be realized.

  2. Selective bundling of zigzag single-walled carbon nanotubes.

    PubMed

    Blum, Carolin; Stürzl, Ninette; Hennrich, Frank; Lebedkin, Sergei; Heeg, Sebastian; Dumlich, Heiko; Reich, Stephanie; Kappes, Manfred M

    2011-04-26

    A simple, high throughput fractionation procedure for aqueous/SDS (sodium dodecyl sulfate) suspensions of single-walled carbon nanotubes (SWNTs) is presented, which yields thin bundles of semiconducting-SWNTs with small chiral angles. To demonstrate this we show the photoluminescence signatures of nanotube suspensions that contain almost exclusively zigzag and near-zigzag tubes. Starting suspensions and resulting fractions were characterized using optical absorption, resonance Raman and photoluminescence spectroscopies as well as scanning force microscopy. Taken together with literature observations, our findings suggest that near zigzag edge tubes of similar diameters in a bundle are harder to separate from each other than for other chiral index combinations. We discuss the implications of these observations for SWNT growth and dispersion. PMID:21410134

  3. Stable and responsive fluorescent carbon nanotube silica gels

    SciTech Connect

    Dattelbaum, Andrew M; Gupta, Gautam; Doorn, Stephen K; Duque, Juan G

    2010-05-03

    Here we report a general route to prepare silica nanocomposite gels doped with fluorescent single walled carbon nanotubes (SWNT). We show that tetramethylorthosilicate (TMOS) vapors can be used to gel an aqueous suspension of surfactant-wrapped SWNT while maintaining fluorescence from the semiconducting nanotubes. The vapor phase silica process is performed at room temperature and is simple, reproducible, relatively quick, and requires no dilution of SWNT dispersions. However, exposure of aqueous SWNT suspensions to TMOS vapors resulted in an acidification of the suspension prior to gelation that caused a decrease in the emission signal from sodium dodecylsulfate (SDS) wrapped SWNT. We also show that although the SWNT are encapsulated in silica the emission signal from the encapsulated SWNT may be attenuated by exposing the nanocomposites to small aromatic molecules known to mitigate SWNT emission. These results demonstrate a new route for the preparation of highly luminescent SWNT/silica composite materials that are potentially useful for future sensing applications.

  4. Synthesis and Electronic Transport in Single-Walled Carbon Nanotubes of Known Chirality

    NASA Astrophysics Data System (ADS)

    Caldwell, Robert Victor

    Since their discovery in 1991, carbon nanotubes have proven to be a very interesting material for its physical strength, originating from the pure carbon lattice and strong covalent sp2 orbital bonds, and electronic properties which are derived from the lattice structure lending itself to either a metallic or semiconducting nature among its other properties. Carbon nanotubes have been researched with an eye towards industry applications ranging from use as an alloy in metals and plastics to improve physical strength of the resulting materials to uses in the semiconductor industry as either an interconnect or device layer for computer chips to chemical or biological sensors. This thesis focuses on both the synthesis of individual single-walled carbon nanotubes as well as the electrical properties of those tubes. What makes the work herein different from that of other thesis is that the research has been performed on carbon nanotubes of known chirality. Having first grown carbon nanotubes with a chemical vapor deposition growth in a quartz tube using ethanol vapor as a feedstock to grow long individual single-walled carbon nanotubes on a silicon chip that is also compatible with Rayleigh scattering spectroscopy to identify the chiral indices of the carbon nanotubes in question, those tubes were then transferred with a mechanical transfer process specially designed in our research lab onto a substrate of our choosing before an electrical device was made out of those tubes using standard electron beam lithography. The focus in this thesis is on the work that went into designing and testing this process as well as the initial results of the electronic properties of those carbon nanotubes of known chirality, such as the first known electrical measurements on single individual armchair carbon nanotubes as well as the first known electrical measurements of a single semiconducting carbon nanotube on thin hexagonal boron nitride to study the effects of the surface optical

  5. Spatial confinement effects on ultrathin semiconducting polymer heterojunction thin films

    SciTech Connect

    Xuejun Zhang; Jenekhe, S.A.

    1996-12-31

    Thin and ultrathin films of electroactive and photoactive polymers are of growing interest for applications in electronic and optoelectronic devices such as thin film transistors, light emitting diodes, solar cells, and xerographic photoreceptors. Although spatial confinement effects on the electronic, optical, optoelectronic, magnetic, and mechanical properties of inorganic semiconductors, metals, oxides, and ceramics are well known and understood, very little is currently known about nanoscale size effects in electroactive and photoactive polymers. Therefore, we recently initiated studies aimed at the understanding of spatial confinement effects on electroactive and photoactive nanostructured polymers and related thin film devices. We have extensively investigated layered nanoscale semiconducting polymer heterojunctions by applying several experimental techniques including photoluminescence, optical absorption, transient absorption, electroluminescence, cyclic voltammetry, and current-voltage measurements. Our findings reveal clear evidence of spatial confinement effects, including: dramatic enhancement of photoconductivity in ultrathin films; enhancement of electroluminescence efficiency and performance characteristics in nanoscale heterojunction devices; observation of novel phenomena in nanoscale devices. These spatial confinement effects in nanostructured semiconducting polymers can be understood in terms of classical charge transport and interfacial processes without invoking quantum size effects.

  6. Large-Area Semiconducting Graphene Nanomesh Tailored by Interferometric Lithography

    PubMed Central

    Kazemi, Alireza; He, Xiang; Alaie, Seyedhamidreza; Ghasemi, Javad; Dawson, Noel Mayur; Cavallo, Francesca; Habteyes, Terefe G.; Brueck, Steven R. J.; Krishna, Sanjay

    2015-01-01

    Graphene nanostructures are attracting a great deal of interest because of newly emerging properties originating from quantum confinement effects. We report on using interferometric lithography to fabricate uniform, chip-scale, semiconducting graphene nanomesh (GNM) with sub-10 nm neck widths (smallest edge-to-edge distance between two nanoholes). This approach is based on fast, low-cost, and high-yield lithographic technologies and demonstrates the feasibility of cost-effective development of large-scale semiconducting graphene sheets and devices. The GNM is estimated to have a room temperature energy bandgap of ~30 meV. Raman studies showed that the G band of the GNM experiences a blue shift and broadening compared to pristine graphene, a change which was attributed to quantum confinement and localization effects. A single-layer GNM field effect transistor exhibited promising drive current of ~3.9 μA/μm and ON/OFF current ratios of ~35 at room temperature. The ON/OFF current ratio of the GNM-device displayed distinct temperature dependence with about 24-fold enhancement at 77 K. PMID:26126936

  7. High-mobility ultrathin semiconducting films prepared by spin coating

    NASA Astrophysics Data System (ADS)

    Mitzi, David B.; Kosbar, Laura L.; Murray, Conal E.; Copel, Matthew; Afzali, Ali

    2004-03-01

    The ability to deposit and tailor reliable semiconducting films (with a particular recent emphasis on ultrathin systems) is indispensable for contemporary solid-state electronics. The search for thin-film semiconductors that provide simultaneously high carrier mobility and convenient solution-based deposition is also an important research direction, with the resulting expectations of new technologies (such as flexible or wearable computers, large-area high-resolution displays and electronic paper) and lower-cost device fabrication. Here we demonstrate a technique for spin coating ultrathin (~50Å), crystalline and continuous metal chalcogenide films, based on the low-temperature decomposition of highly soluble hydrazinium precursors. We fabricate thin-film field-effect transistors (TFTs) based on semiconducting SnS2-xSex films, which exhibit n-type transport, large current densities (>105Acm-2) and mobilities greater than 10cm2V-1s-1-an order of magnitude higher than previously reported values for spin-coated semiconductors. The spin-coating technique is expected to be applicable to a range of metal chalcogenides, particularly those based on main group metals, as well as for the fabrication of a variety of thin-film-based devices (for example, solar cells, thermoelectrics and memory devices).

  8. Large-Area Semiconducting Graphene Nanomesh Tailored by Interferometric Lithography

    NASA Astrophysics Data System (ADS)

    Kazemi, Alireza; He, Xiang; Alaie, Seyedhamidreza; Ghasemi, Javad; Dawson, Noel Mayur; Cavallo, Francesca; Habteyes, Terefe G.; Brueck, Steven R. J.; Krishna, Sanjay

    2015-07-01

    Graphene nanostructures are attracting a great deal of interest because of newly emerging properties originating from quantum confinement effects. We report on using interferometric lithography to fabricate uniform, chip-scale, semiconducting graphene nanomesh (GNM) with sub-10 nm neck widths (smallest edge-to-edge distance between two nanoholes). This approach is based on fast, low-cost, and high-yield lithographic technologies and demonstrates the feasibility of cost-effective development of large-scale semiconducting graphene sheets and devices. The GNM is estimated to have a room temperature energy bandgap of ~30 meV. Raman studies showed that the G band of the GNM experiences a blue shift and broadening compared to pristine graphene, a change which was attributed to quantum confinement and localization effects. A single-layer GNM field effect transistor exhibited promising drive current of ~3.9 μA/μm and ON/OFF current ratios of ~35 at room temperature. The ON/OFF current ratio of the GNM-device displayed distinct temperature dependence with about 24-fold enhancement at 77 K.

  9. Surface passivation of semiconducting oxides by self-assembled nanoparticles

    PubMed Central

    Park, Dae-Sung; Wang, Haiyuan; Vasheghani Farahani, Sepehr K.; Walker, Marc; Bhatnagar, Akash; Seghier, Djelloul; Choi, Chel-Jong; Kang, Jie-Hun; McConville, Chris F.

    2016-01-01

    Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials. PMID:26757827

  10. Surface passivation of semiconducting oxides by self-assembled nanoparticles

    NASA Astrophysics Data System (ADS)

    Park, Dae-Sung; Wang, Haiyuan; Vasheghani Farahani, Sepehr K.; Walker, Marc; Bhatnagar, Akash; Seghier, Djelloul; Choi, Chel-Jong; Kang, Jie-Hun; McConville, Chris F.

    2016-01-01

    Physiochemical interactions which occur at the surfaces of oxide materials can significantly impair their performance in many device applications. As a result, surface passivation of oxide materials has been attempted via several deposition methods and with a number of different inert materials. Here, we demonstrate a novel approach to passivate the surface of a versatile semiconducting oxide, zinc oxide (ZnO), evoking a self-assembly methodology. This is achieved via thermodynamic phase transformation, to passivate the surface of ZnO thin films with BeO nanoparticles. Our unique approach involves the use of BexZn1-xO (BZO) alloy as a starting material that ultimately yields the required coverage of secondary phase BeO nanoparticles, and prevents thermally-induced lattice dissociation and defect-mediated chemisorption, which are undesirable features observed at the surface of undoped ZnO. This approach to surface passivation will allow the use of semiconducting oxides in a variety of different electronic applications, while maintaining the inherent properties of the materials.

  11. Superconducting qubits with semiconductor nanowire Josephson junctions

    NASA Astrophysics Data System (ADS)

    Petersson, K. D.; Larsen, T. W.; Kuemmeth, F.; Jespersen, T. S.; Krogstrup, P.; Nygård, J.; Marcus, C. M.

    2015-03-01

    Superconducting transmon qubits are a promising basis for a scalable quantum information processor. The recent development of semiconducting InAs nanowires with in situ molecular beam epitaxy-grown Al contacts presents new possibilities for building hybrid superconductor/semiconductor devices using precise bottom up fabrication techniques. Here, we take advantage of these high quality materials to develop superconducting qubits with superconductor-normal-superconductor Josephson junctions (JJs) where the normal element is an InAs semiconductor nanowire. We have fabricated transmon qubits in which the conventional Al-Al2O3-Al JJs are replaced by a single gate-tunable nanowire JJ. Using spectroscopy to probe the qubit we observe fluctuations in its level splitting with gate voltage that are consistent with universal conductance fluctuations in the nanowire's normal state conductance. Our gate-tunable nanowire transmons may enable new means of control for large scale qubit architectures and hybrid topological quantum computing schemes. Research supported by Microsoft Station Q, Danish National Research Foundation, Villum Foundation, Lundbeck Foundation and the European Commission.

  12. Stacked mechanical nanogenerator comprising piezoelectric semiconducting nanostructures and Schottky conductive contacts

    DOEpatents

    Wang, Zhong L.; Xu, Sheng

    2011-08-23

    An electric power generator includes a first conductive layer, a plurality of semiconducting piezoelectric nanostructures, a second conductive layer and a plurality of conductive nanostructures. The first conductive layer has a first surface from which the semiconducting piezoelectric nanostructures extend. The second conductive layer has a second surface and is parallel to the first conductive layer so that the second surface faces the first surface of the first conductive layer. The conductive nanostructures depend downwardly therefrom. The second conductive layer is spaced apart from the first conductive layer at a distance so that when a force is applied, the semiconducting piezoelectric nanostructures engage the conductive nanostructures so that the piezoelectric nanostructures bend, thereby generating a potential difference across the at semiconducting piezoelectric nanostructures and also thereby forming a Schottky barrier between the semiconducting piezoelectric nanostructures and the conductive nanostructures.

  13. Asymmetric resonance Raman excitation profiles and violation of the Condon approximation in single-wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Doorn, Stephen; Duque, Juan; Telg, Hagen; Chen, Hang; Swan, Anna; Haroz, Erik; Kono, Junichiro; Tu, Xiaomin; Zheng, Ming

    2012-02-01

    DNA wrapping-based ion exchange chromatography and density gradient ultracentrifugation provide nanotube samples highly enriched in single chiralities. We present resonance Raman excitation profiles for the G-band of several single chirality semiconducting and metallic species. The expected incoming and outgoing resonance peaks are observed in the profiles, but contrary to long-held assumptions, the outgoing resonance is always significantly weaker than the ingoing resonance peak. This strong asymmetry in the profiles arises from a violation of the Condon approximation [1]. Results will be discussed in the context of theoretical models that suggest significant coordinate dependence in the transition dipole (non-Condon effects). The generality of the behavior across semiconducting and metallic types, nanotube family, phonon mode, and Eii will be demonstrated. [4pt] [1] J. Duque et. al., ACS Nano, 5, 5233 (2011).

  14. Functionalization of silicon carbide nanotube by dichlorocarbene: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Xiao, Bo; Hu, Hong; Zhao, Jing-xiang; Ding, Yi-hong

    2014-02-01

    The existence of numerous unsaturated π bonds on surface of nanotubes is hopeful for effective chemical functionalization. Recently, the dichlorocarbene (CCl2)-functionalization has been widely applied to modify the electronic properties of carbon nanotubes (CNTs) and boron nitride nanotubes (BNNTs), through a simple one-step formation of the open three-membered-ring (3MR) structure. Here using density functional theory methods, we study the CCl2-functionalization of silicon carbide nanotubes (SiCNTs). Three distinct sequential steps are identified as: (1) 3MR formation, (2) Cl shift from C to Si atom, and (3) C bridging between a Si-C bond. Since the initial 3MR-formation is notably exothermic (2.47 eV), the subsequent steps take place easily, leading to the eventual adjacent C2 formation in the alternative C-Si network. Clearly, the adsorption behavior of CCl2 on SiCNTs contrasts sharply to that on CNTs and BNNTs, where the open 3MR structure is the eventually stabilized state with the two C-Cl bonds intactness. Such effective C-Cl splitting significantly decreases the band gap of SiCNT by about 50%. The adsorption of more CCl2 molecules leads to a transition from semiconducting SiCNT to degenerated p-type semiconducting SiCNT. The present results not only testify the high surface chemical reactivity of SiCNT, but also show a new way of tuning the electronic properties of SiCNT.

  15. An algorithm for constructing various kinds of nanojunctions using zig-zag and armchair nanotubes.

    PubMed

    Taşci, Emre; Erkoç, Sakir

    2007-01-01

    A method for generating various forms of junctions involving armchair and zig-zag nanotubes, firstly introduced by Zsoldos et al., is developed to cover all types of armchair and zig-zag nanotubes in a systematical way. This method can also be used to produce nanogears and toothed canals. The method is explained and flowcharts are included to aid in programming into a code. PMID:17450939

  16. First-Principles Simulations of Chemical Reactions in an HCl Molecule Embedded inside a C or BN Nanotube Induced by Ultrafast Laser Pulses

    SciTech Connect

    Miyamoto, Yoshiyuki; Zhang Hong; Rubio, Angel

    2010-12-10

    We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

  17. EDITORIAL: Focus on Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    2003-09-01

    The study of carbon nanotubes, since their discovery by Iijima in 1991, has become a full research field with significant contributions from all areas of research in solid-state and molecular physics and also from chemistry. This Focus Issue in New Journal of Physics reflects this active research, and presents articles detailing significant advances in the production of carbon nanotubes, the study of their mechanical and vibrational properties, electronic properties and optical transitions, and electrical and transport properties. Fundamental research, both theoretical and experimental, represents part of this progress. The potential applications of nanotubes will rely on the progress made in understanding their fundamental physics and chemistry, as presented here. We believe this Focus Issue will be an excellent guide for both beginners and experts in the research field of carbon nanotubes. It has been a great pleasure to edit the many excellent contributions from Europe, Japan, and the US, as well from a number of other countries, and to witness the remarkable effort put into the manuscripts by the contributors. We thank all the authors and referees involved in the process. In particular, we would like to express our gratitude to Alexander Bradshaw, who invited us put together this Focus Issue, and to Tim Smith and the New Journal of Physics staff for their extremely efficient handling of the manuscripts. Focus on Carbon Nanotubes Contents <;A article="1367-2630/5/1/117">Transport theory of carbon nanotube Y junctions R Egger, B Trauzettel, S Chen and F Siano The tubular conical helix of graphitic boron nitride F F Xu, Y Bando and D Golberg Formation pathways for single-wall carbon nanotube multiterminal junctions Inna Ponomareva, Leonid A Chernozatonskii, Antonis N Andriotis and Madhu Menon Synthesis and manipulation of carbon nanotubes J W Seo, E Couteau

  18. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  19. Four-junction superconducting circuit

    NASA Astrophysics Data System (ADS)

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-06-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.

  20. Four-junction superconducting circuit

    PubMed Central

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  1. Electronic property modification of single-walled carbon nanotubes by encapsulation of sulfur-terminated graphene nanoribbons.

    PubMed

    Pollack, Andrew; Alnemrat, Sufian; Chamberlain, Thomas W; Khlobystov, Andrei N; Hooper, Joseph P; Osswald, Sebastian

    2014-12-29

    The use of carbon nanotubes (CNTs) as cylindrical reactor vessels has become a viable means for synthesizing graphene nanoribbons (GNRs). While previous studies demonstrated that the size and edge structure of the as-produced GNRs are strongly dependent on the diameter of the tubes and the nature of the precursor, the atomic interactions between GNRs and surrounding CNTs and their effect on the electronic properties of the overall system are not well understood. Here, it is shown that the functional terminations of the GNR edges can have a strong influence on the electronic structure of the system. Analysis of SWCNTs before and after the insertion of sulfur-terminated GNRs suggests a metallization of the majority of semiconducting SWCNTs. This is indicated by changes in the radial breathing modes and the D and G band Raman features, as well as UV-vis-NIR absorption spectra. The variation in resonance conditions of the nanotubes following GNR insertion make direct (n,m) assignment by Raman spectroscopy difficult. Thus, density functional theory calculations of representative GNR/SWCNT systems are performed. The results confirm significant changes in the band structure, including the development of a metallic state in the semiconducting SWCNTs due to sulfur/tube interactions. The GNR-induced metallization of semiconducting SWCNTs may offer a means of controlling the electronic properties of bulk CNT samples and eliminate the need for a physical separation of semiconducting and metallic tubes. PMID:25123503

  2. On the Electronic and Geometric Structures of Armchair GeC Nanotubes: A Hybrid Density Functional Study

    NASA Astrophysics Data System (ADS)

    Rathi, Somilkumar; Ray, Asok

    2008-03-01

    Ab initio calculations within the framework of hybrid density functional theory and finite cluster approximation have been performed for the electronic and geometric structures of three different types of armchair germanium carbide nanotubes from (3, 3) to (11, 11). Full geometry and spin optimizations with unrestricted symmetry have been performed. A detailed comparison of the structures and stabilities of the three types of nanotubes will be presented. The dependence of the electronic band gaps on the respective tube diameters, energy density of states, dipole moments as well as Mulliken charge distributions have been investigated. Radial buckling of tube along with bond length variations is also studied. All armchair GeC nanotubes investigated so far are semiconducting in nature. Applications in the field of nano-optoelectronic devices, molecular electronics and band gap engineering are envisioned for GeC nanotubes.

  3. Rare-earth metal halogenide encapsulation-induced modifications in Raman spectra of single-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Kharlamova, M. V.

    2015-01-01

    In the present work, a detailed Raman spectroscopy investigation on the single-walled carbon nanotubes (SWCNTs) filled with praseodymium chloride, terbium chloride and thulium chloride was performed. The salts were incorporated inside the SWCNTs by a capillary filling method using melts, and the high-resolution transmission electron microscopy data proved the high filling degree of the nanotube channels. A thorough analysis of the radial breathing mode and G-band of the Raman spectra of the pristine and filled SWCNTs showed that the encapsulated salts cause acceptor doping of the host nanotubes, and the doping efficiency depends on the compound. The incorporated thulium chloride has the strongest doping effect on the SWCNTs, whereas praseodymium chloride has the weakest effect. It was found that the encapsulated salts modify more significantly the electronic structure of metallic nanotubes than semiconducting SWCNTs.

  4. T-Junction Benchmark

    SciTech Connect

    2010-01-01

    Part 1: Two different volume renderings of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000. Part 2: Volume rendering of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 at three different resolutions. Part 3: Temperature distribution for a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 with 89056 spectral elements of order N=9 (65 million grid points). Credits: Science: Aleks Obabko and Paul Fisher, Argonne National Laboratory
 Visualization: Hank Childs, Lawrence Berkeley National Laboratory

 This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357

  5. Ultrafast exciton energy transfer between nanoscale coaxial cylinders: intertube transfer and luminescence quenching in double-walled carbon nanotubes.

    PubMed

    Koyama, Takeshi; Asada, Yuki; Hikosaka, Naoki; Miyata, Yasumitsu; Shinohara, Hisanori; Nakamura, Arao

    2011-07-26

    We study exciton energy transfer in double-walled carbon nanotubes using femtosecond time-resolved luminescence measurements. From direct correspondence between decay of the innertube luminescence and the rise behavior in outertube luminescence, it is found that the time constant of exciton energy transfer from the inner to the outer semiconducting tubes is ∼150 fs. This ultrafast transfer indicates that the relative intensity of steady-state luminescence from the innertubes is ∼700 times weaker than that from single-walled carbon nanotubes. PMID:21682277

  6. Detection of single ion channel activity with carbon nanotubes

    PubMed Central

    Zhou, Weiwei; Wang, Yung Yu; Lim, Tae-Sun; Pham, Ted; Jain, Dheeraj; Burke, Peter J.

    2015-01-01

    Many processes in life are based on ion currents and membrane voltages controlled by a sophisticated and diverse family of membrane proteins (ion channels), which are comparable in size to the most advanced nanoelectronic components currently under development. Here we demonstrate an electrical assay of individual ion channel activity by measuring the dynamic opening and closing of the ion channel nanopores using single-walled carbon nanotubes (SWNTs). Two canonical dynamic ion channels (gramicidin A (gA) and alamethicin) and one static biological nanopore (α-hemolysin (α-HL)) were successfully incorporated into supported lipid bilayers (SLBs, an artificial cell membrane), which in turn were interfaced to the carbon nanotubes through a variety of polymer-cushion surface functionalization schemes. The ion channel current directly charges the quantum capacitance of a single nanotube in a network of purified semiconducting nanotubes. This work forms the foundation for a scalable, massively parallel architecture of 1d nanoelectronic devices interrogating electrophysiology at the single ion channel level. PMID:25778101

  7. Detection of single ion channel activity with carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Zhou, Weiwei; Wang, Yung Yu; Lim, Tae-Sun; Pham, Ted; Jain, Dheeraj; Burke, Peter J.

    2015-03-01

    Many processes in life are based on ion currents and membrane voltages controlled by a sophisticated and diverse family of membrane proteins (ion channels), which are comparable in size to the most advanced nanoelectronic components currently under development. Here we demonstrate an electrical assay of individual ion channel activity by measuring the dynamic opening and closing of the ion channel nanopores using single-walled carbon nanotubes (SWNTs). Two canonical dynamic ion channels (gramicidin A (gA) and alamethicin) and one static biological nanopore (α-hemolysin (α-HL)) were successfully incorporated into supported lipid bilayers (SLBs, an artificial cell membrane), which in turn were interfaced to the carbon nanotubes through a variety of polymer-cushion surface functionalization schemes. The ion channel current directly charges the quantum capacitance of a single nanotube in a network of purified semiconducting nanotubes. This work forms the foundation for a scalable, massively parallel architecture of 1d nanoelectronic devices interrogating electrophysiology at the single ion channel level.

  8. Detection of single ion channel activity with carbon nanotubes.

    PubMed

    Zhou, Weiwei; Wang, Yung Yu; Lim, Tae-Sun; Pham, Ted; Jain, Dheeraj; Burke, Peter J

    2015-01-01

    Many processes in life are based on ion currents and membrane voltages controlled by a sophisticated and diverse family of membrane proteins (ion channels), which are comparable in size to the most advanced nanoelectronic components currently under development. Here we demonstrate an electrical assay of individual ion channel activity by measuring the dynamic opening and closing of the ion channel nanopores using single-walled carbon nanotubes (SWNTs). Two canonical dynamic ion channels (gramicidin A (gA) and alamethicin) and one static biological nanopore (α-hemolysin (α-HL)) were successfully incorporated into supported lipid bilayers (SLBs, an artificial cell membrane), which in turn were interfaced to the carbon nanotubes through a variety of polymer-cushion surface functionalization schemes. The ion channel current directly charges the quantum capacitance of a single nanotube in a network of purified semiconducting nanotubes. This work forms the foundation for a scalable, massively parallel architecture of 1d nanoelectronic devices interrogating electrophysiology at the single ion channel level. PMID:25778101

  9. Semiconducting nanowire field effect transistor for nanoelectronics and nanomechanics

    NASA Astrophysics Data System (ADS)

    Deshmukh, Mandar

    2013-02-01

    Semiconducting nanowire transistors offer an interesting avenue to make fundamentally new device architecture for future switching devices. I will our work to develop a simple fabrication technique for lateral nanowire wrap-gate devices with high capacitive coupling and field-effect mobility using InAs nanowires and also discuss electrical characterization of these devices. Our process uses e-beam lithography with a single resist-spinning step and does not require chemical etching. We measure significantly larger mobility and good sub-threshold characteristics [1]. I will also discuss the applications of using suspended nanowire transistors in studying mechanics and thermal properties of nanostructures as they can be useful in studying a wide variety of physics at the nanoscale. This work is supported by Government of India and partially supported by IBM India.

  10. Investigation of charge injection characteristics in diketopyrrolopyrrole ambipolar semiconducting polymers

    NASA Astrophysics Data System (ADS)

    Lee, Seon Jeng; Jung, Seok Heon; Lee, Jin-Kyun; Kim, Cheawon; Lee, Mi Jung

    2014-10-01

    A semiconducting polymers with conjugated diketopyrrolopyrrole (DPP) unit was developed for high performance ambipolar organic field-effect transistors (OFETs). We report electrical characteristics of DPP OFETs in various ways which measured transistor and inverter performance with various bias conditions and self-assembled monolayers (SAMs) treatment. Ambipolar DPP conjugated polymer OFETs showed high hole and electron mobility of μh=0.57 cm2V-1s-1 and μe=0.51 cm2V-1s-1 with O2 plasma treatment and 1-decanethiol SAMs treatment, respectively with annealing at 100°C. Contact resistance effect on mobilities was investigated by measuring contact resistance during device operation through gated four-point probe (gFPP) and simultaneous contact resistance extraction model directly from current voltage characteristics.

  11. Semiconducting Ge clathrates: Promising candidates for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Nolas, G. S.; Cohn, J. L.; Slack, G. A.; Schujman, S. B.

    1998-07-01

    Transport properties of polycrystalline Ge clathrates with general composition Sr8Ga16Ge30 are reported in the temperature range 5 K⩽T⩽300 K. These compounds exhibit N-type semiconducting behavior with relatively high Seebeck coefficients and electrical conductivity, and room temperature carrier concentrations in the range of 1017-1018cm-3. The thermal conductivity is more than an order of magnitude smaller than that of crystalline germanium and has a glasslike temperature dependence. The resulting thermoelectric figure of merit, ZT, at room temperature for the present samples is 1/4 that of Bi2Te3 alloys currently used in devices for thermoelectric cooling. Extrapolating our measurements to above room temperature, we estimate that ZT>1 at T>700 K, thus exceeding that of most known materials.

  12. BaMn2Sb2: A New Semiconducting Ferromagnet

    NASA Astrophysics Data System (ADS)

    Li, Jianneng; Stadler, S.; Karki, A.; Xiong, Y.; Jin, R.

    2012-02-01

    We have grown high-quality single crystals of BaMn2Sb2, which possesses the ThCr2Si2 structure as determined by X-ray powder diffraction technique. Magnetization measurements indicate that BaMn2Fe2 is ferromagnetic below TC = 580K. On the other hand, the temperature dependence of electrical resistivity shows semiconducting behavior, which can be described by thermally-activated resistivity formula with thermal activation energy about 0.25 eV . While the Hall coefficient has positive sign between 2 and 300 K, the Seebeck Coefficient undergoes sign change from positive at high temperatures to negative at low temperatures, reaching -260 μV/K at 70 K. The implication will be discussed.

  13. Nanoscale semiconducting silicon as a nutritional food additive

    NASA Astrophysics Data System (ADS)

    Canham, L. T.

    2007-05-01

    Very high surface area silicon powders can be realized by high energy milling or electrochemical etching techniques. Such nanoscale silicon structures, whilst biodegradable in the human gastrointestinal tract, are shown to be remarkably stable in most foodstuffs and beverages. The potential for using silicon to improve the shelf life and bioavailability of specific nutrients in functional foods is highlighted. Published drug delivery data implies that the nanoentrapment of hydrophobic nutrients will significantly improve their dissolution kinetics, through a combined effect of nanostructuring and solid state modification. Nutrients loaded to date include vitamins, fish oils, lycopene and coenzyme Q10. In addition, there is growing published evidence that optimized release of orthosilicic acid, the biodegradation product of semiconducting silicon in the gut, offers beneficial effects with regard bone health. The utility of nanoscale silicon in the nutritional field shows early promise and is worthy of much further study.

  14. Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

    NASA Astrophysics Data System (ADS)

    Zhuang, Shendong; Chen, Yan; Xia, Yidong; Tang, Nujiang; Xu, Xiaoyong; Hu, Jingguo; Chen, Zhuo

    2016-04-01

    Solution-processed graphene quantum dots (GQDs) possess a moderate bandgap, which make them a promising candidate for optoelectronics devices. However, negative photoconductivity (NPC) and hysteresis that happen in the photoelectric conversion process could be harmful to performance of the GQDs-based devices. So far, their origins and relations have remained elusive. Here, we investigate experimentally the origins of the NPC and hysteresis in GQDs. By comparing the hysteresis and photoconductance of GQDs under different relative humidity conditions, we are able to demonstrate that NPC and hysteresis coexist in GQDs and both are attributed to the carrier trapping effect of surface adsorbed moisture. We also demonstrate that GQDs could exhibit positive photoconductivity with three-order-of-magnitude reduction of hysteresis after a drying process and a subsequent encapsulation. Considering the pervasive moisture adsorption, our results may pave the way for a commercialization of semiconducting graphene-based and diverse solution-based optoelectronic devices.

  15. Metal Contacts on Semiconducting Two-Dimension Crystals

    NASA Astrophysics Data System (ADS)

    Liu, Han; Neal, Adam; Du, Yuchen; Ye, Peide

    2013-03-01

    Semiconducting 2-D crystals, such as MoS2, WSe2, are viewed as promising candidates for electronic applications for their high carrier mobility, thermal stability, compatibility to CMOS process, and superior immunity to short channel effects. However, with the difficulty in ion implantation, the metal contacts on 2-D crystals are yet with large contact resistance, thus eliminates further device performance. We study different metal contacts from low work function to high work function metals on MoS2 and WSe2 crystals with various thicknesses and discuss the Fermi level pinning at the metal/semiconductor interface. Effective Schottky Barrier Heights (SBHs) are also measured. Molecular doping and dual-side contacts metals are performed as two tentative solutions to reduce the effective SBHs, and high-performance of field effect transistors are achieved by reduced contact resistance.

  16. Amplified Spontaneous Emission Properties of Semiconducting Organic Materials

    PubMed Central

    Calzado, Eva M.; Boj, Pedro G.; Díaz-García, María A.

    2010-01-01

    This paper aims to review the recent advances achieved in the field of organic solid-state lasers with respect to the usage of semiconducting organic molecules and oligomers in the form of thin films as active laser media. We mainly focus on the work performed in the last few years by our research group. The amplified spontaneous emission (ASE) properties, by optical pump, of various types of molecules doped into polystyrene films in waveguide configuration, are described. The various systems investigated include N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), several perilenediimide derivatives (PDIs), as well as two oligo-phenylenevinylene derivatives. The ASE characteristics, i.e., threshold, emission wavelength, linewidth, and photostability are compared with that of other molecular materials investigated in the literature. PMID:20640167

  17. Janus Composite Nanotubes.

    PubMed

    Chen, Ying; Liu, Zhen; Qu, Xiaozhong; Liang, Fuxin; Yang, Zhenzhong

    2016-06-21

    We propose a facile method to achieve paramagnetic Janus nanotubes with two compositions compartmentalized onto the interior and exterior surfaces, respectively. A sulfonated polydivinylbenzene (PDVB) nanotube is prepared by simple sulfonation of the exterior surface of a PDVB nanotube. Silica@FeOOH dual layers are sequentially grown onto the sulfonated PDVB nanotube surface. The composite nanotubes become paramagnetic after calcination and can be broken into shorter pieces under vigorous ultrasonication. After selective modification of the interior and exterior surfaces of the paramagnetic nanotubes, the nanotube shell becomes Janus in wettability. Desired hydrophobic species can be selectively captured inside the cavity. The paramagnetic Janus composite nanotubes can align into parallel chains under a magnetic field, which is self-disassembled upon removal of the magnetic field. PMID:27124877

  18. Plumbing carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jin, Chuanhong; Suenaga, Kazu; Iijima, Sumio

    2008-01-01

    Since their discovery, the possibility of connecting carbon nanotubes together like water pipes has been an intriguing prospect for these hollow nanostructures. The serial joining of carbon nanotubes in a controlled manner offers a promising approach for the bottom-up engineering of nanotube structures-from simply increasing their aspect ratio to making integrated carbon nanotube devices. To date, however, there have been few reports of the joining of two different carbon nanotubes. Here we demonstrate that a Joule heating process, and associated electro-migration effects, can be used to connect two carbon nanotubes that have the same (or similar) diameters. More generally, with the assistance of a tungsten metal particle, this technique can be used to seamlessly join any two carbon nanotubes-regardless of their diameters-to form new nanotube structures.

  19. Carbon nanotube nanoelectrode arrays

    DOEpatents

    Ren, Zhifeng; Lin, Yuehe; Yantasee, Wassana; Liu, Guodong; Lu, Fang; Tu, Yi

    2008-11-18

    The present invention relates to microelectode arrays (MEAs), and more particularly to carbon nanotube nanoelectrode arrays (CNT-NEAs) for chemical and biological sensing, and methods of use. A nanoelectrode array includes a carbon nanotube material comprising an array of substantially linear carbon nanotubes each having a proximal end and a distal end, the proximal end of the carbon nanotubes are attached to a catalyst substrate material so as to form the array with a pre-determined site density, wherein the carbon nanotubes are aligned with respect to one another within the array; an electrically insulating layer on the surface of the carbon nanotube material, whereby the distal end of the carbon nanotubes extend beyond the electrically insulating layer; a second adhesive electrically insulating layer on the surface of the electrically insulating layer, whereby the distal end of the carbon nanotubes extend beyond the second adhesive electrically insulating layer; and a metal wire attached to the catalyst substrate material.

  20. Fiber and fabric solar cells by directly weaving carbon nanotube yarns with CdSe nanowire-based electrodes

    NASA Astrophysics Data System (ADS)

    Zhang, Luhui; Shi, Enzheng; Ji, Chunyan; Li, Zhen; Li, Peixu; Shang, Yuanyuan; Li, Yibin; Wei, Jinquan; Wang, Kunlin; Zhu, Hongwei; Wu, Dehai; Cao, Anyuan

    2012-07-01

    Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications of semiconducting nanowires and carbon nanotubes in woven photovoltaics.Electrode materials are key components for fiber solar cells, and when combined with active layers (for light absorption and charge generation) in appropriate ways, they enable design and fabrication of efficient and innovative device structures. Here, we apply carbon nanotube yarns as counter electrodes in combination with CdSe nanowire-grafted primary electrodes (Ti wire) for making fiber and fabric-shaped photoelectrochemical cells with power conversion efficiencies in the range 1% to 2.9%. The spun-twist long nanotube yarns possess both good electrical conductivity and mechanical flexibility compared to conventional metal wires or carbon fibers, which facilitate fabrication of solar cells with versatile configurations. A unique feature of our process is that instead of making individual fiber cells, we directly weave single or multiple nanotube yarns with primary electrodes into a functional fabric. Our results demonstrate promising applications

  1. Cross-polarized excitons in carbon nanotubes.

    PubMed

    Kilina, Svetlana; Tretiak, Sergei; Doorn, Stephen K; Luo, Zhengtang; Papadimitrakopoulos, Fotios; Piryatinski, Andrei; Saxena, Avadh; Bishop, Alan R

    2008-05-13

    Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties of cross-polarized excitons, which lead to the transverse optical absorption of nanotubes and presumably couple to intermediate-frequency modes recently observed in resonance Raman excitation spectroscopy. We identify up to 12 distinct excitonic transitions below the second fundamental band associated with the E(22) van Hove singularity. Calculations for several chiral SWNTs distinguish the optically active "bright" excitonic band polarized parallel to the tube axis and several optically "weak" cross-polarized excitons. The rest are optically (near) forbidden "dark" transitions. An analysis of the transition density matrices related to excitonic bands provides detailed information about delocalization of excitonic wavefunction along the tube. Utilization of the natural helical coordinate system accounting for the tube chirality allows one to disentangle longitudinal and circumferential components. The distribution of the transition density matrix along a tube axis is similar for all excitons. However, four parallel-polarized excitons associated with the E(11) transition are more localized along the circumference of a tube, compared with others related to the E(12) and E(21) cross-polarized transitions. Calculated splitting between optically active parallel- and cross-polarized transitions increases with tube diameter, which compares well with experimental spectroscopic data. PMID:18463293

  2. Cross-polarized excitons in carbon nanotubes

    PubMed Central

    Kilina, Svetlana; Tretiak, Sergei; Doorn, Stephen K.; Luo, Zhengtang; Papadimitrakopoulos, Fotios; Piryatinski, Andrei; Saxena, Avadh; Bishop, Alan R.

    2008-01-01

    Polarization of low-lying excitonic bands in finite-size semiconducting single-walled carbon nanotubes (SWNTs) is studied by using quantum-chemical methodologies. Our calculations elucidate properties of cross-polarized excitons, which lead to the transverse optical absorption of nanotubes and presumably couple to intermediate-frequency modes recently observed in resonance Raman excitation spectroscopy. We identify up to 12 distinct excitonic transitions below the second fundamental band associated with the E22 van Hove singularity. Calculations for several chiral SWNTs distinguish the optically active “bright” excitonic band polarized parallel to the tube axis and several optically “weak” cross-polarized excitons. The rest are optically (near) forbidden “dark” transitions. An analysis of the transition density matrices related to excitonic bands provides detailed information about delocalization of excitonic wavefunction along the tube. Utilization of the natural helical coordinate system accounting for the tube chirality allows one to disentangle longitudinal and circumferential components. The distribution of the transition density matrix along a tube axis is similar for all excitons. However, four parallel-polarized excitons associated with the E11 transition are more localized along the circumference of a tube, compared with others related to the E12 and E21 cross-polarized transitions. Calculated splitting between optically active parallel- and cross-polarized transitions increases with tube diameter, which compares well with experimental spectroscopic data. PMID:18463293

  3. Electronic and magnetic properties of yttrium-doped silicon carbide nanotubes: Density functional theory investigations

    SciTech Connect

    Khaira, Jobanpreet S.; Jain, Richa N.; Chakraborty, Brahmananda; Ramaniah, Lavanya M.

    2015-06-24

    The electronic structure of yttrium-doped Silicon Carbide Nanotubes has been theoretically investigated using first principles density functional theory (DFT). Yttrium atom is bonded strongly on the surface of the nanotube with a binding energy of 2.37 eV and prefers to stay on the hollow site at a distance of around 2.25 Å from the tube. The semi-conducting nanotube with chirality (4, 4) becomes half mettalic with a magnetic moment of 1.0 µ{sub B} due to influence of Y atom on the surface. There is strong hybridization between d orbital of Y with p orbital of Si and C causing a charge transfer from d orbital of the Y atom to the tube. The Fermi level is shifted towards higher energy with finite Density of States for only upspin channel making the system half metallic and magnetic which may have application in spintronic devices.

  4. Three-particle correlation from a Many-Body Perspective: Trions in a Carbon Nanotube.

    PubMed

    Deilmann, Thorsten; Drüppel, Matthias; Rohlfing, Michael

    2016-05-13

    Trion states of three correlated particles (e.g., two electrons and one hole) are essential to understand the optical spectra of doped or gated nanostructures, like carbon nanotubes or transition-metal dichalcogenides. We develop a theoretical many-body description for such correlated states using an ab initio approach. It can be regarded as an extension of the widely used GW method and Bethe-Salpeter equation, thus allowing for a direct comparison with excitons. We apply this method to a semiconducting (8,0) carbon nanotube, and find that the lowest optically active trions are redshifted by ∼130  meV compared to the excitons, confirming experimental findings for similar tubes. Moreover, our method provides detailed insights in the physical nature of trion states. In the prototypical carbon nanotube we find a variety of different excitations, discuss the spectra, energy compositions, and correlated wave functions. PMID:27232034

  5. Three-particle correlation from a Many-Body Perspective: Trions in a Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Deilmann, Thorsten; Drüppel, Matthias; Rohlfing, Michael

    2016-05-01

    Trion states of three correlated particles (e.g., two electrons and one hole) are essential to understand the optical spectra of doped or gated nanostructures, like carbon nanotubes or transition-metal dichalcogenides. We develop a theoretical many-body description for such correlated states using an ab initio approach. It can be regarded as an extension of the widely used G W method and Bethe-Salpeter equation, thus allowing for a direct comparison with excitons. We apply this method to a semiconducting (8,0) carbon nanotube, and find that the lowest optically active trions are redshifted by ˜130 meV compared to the excitons, confirming experimental findings for similar tubes. Moreover, our method provides detailed insights in the physical nature of trion states. In the prototypical carbon nanotube we find a variety of different excitations, discuss the spectra, energy compositions, and correlated wave functions.

  6. Scattering strength of potassium on a carbon nanotube with known chirality

    NASA Astrophysics Data System (ADS)

    Tsuchikawa, Ryuichi; Heligman, D.; Blue, B. T.; Zhang, Z. Y.; Ahmadi, A.; Mucciolo, E. R.; Hone, J.; Ishigami, M.

    2016-07-01

    We have measured the scattering strength of charged impurities on a semiconducting single-walled carbon nanotube with known chirality. The resistivity of the nanotube is measured as a function of the density of adsorbed potassium atoms, enabling the determination of the resistance added by an individual potassium atom. Holes are scattered 37 times more efficiently than electrons by an adsorbed potassium atom. The determined scattering strength is used to reveal the spatial extent and depth of the scattering potential for potassium, a model Coulomb adsorbate. Our result represents an essential experimental input to understand adsorbate-induced scattering and provides a crucial step for paving the way to rational design of nanotube-based sensors.

  7. Three-dimensional polymeric structures of single-wall carbon nanotubes.

    PubMed

    Lian, Chao-Sheng; Wang, Jian-Tao

    2014-05-28

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp(3) intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure. PMID:24880313

  8. Three-dimensional polymeric structures of single-wall carbon nanotubes

    SciTech Connect

    Lian, Chao-Sheng; Wang, Jian-Tao

    2014-05-28

    We explore by ab initio calculations the possible crystalline phases of polymerized single-wall carbon nanotubes (P-SWNTs) and determine their structural, elastic, and electronic properties. Based on direct cross-linking and intertube sliding-assisted cross-linking mechanisms, we have identified a series of stable three-dimensional polymeric structures for the zigzag nanotubes up to (10,0). Among proposed P-SWNT phases, the structures with favorable diamond-like sp{sup 3} intertube bonding configuration and small tube cross-section distortion are found to be the most energetically stable ones. These polymeric crystalline phases exhibit high bulk and shear moduli superior to SWNT bundles, and show metallic or semiconducting properties depending on the diameter of constituent tubes. We also propose by hydrostatic pressure simulations that the intertube sliding between van der Waals bonded nanotubes may be an effective route to promote the polymerization of SWNTs under pressure.

  9. A first principles study of NO 2 chemisorption on silicon carbide nanotubes

    NASA Astrophysics Data System (ADS)

    Gao, Guohua; Park, Sung Ho; Kang, Hong Seok

    2009-01-01

    Using methods based on first principles, we find that an NO 2 molecules can be chemisorbed on silicon carbide nanotubes (SiCNTs) with an appreciable binding energy (˜-1.0 eV), and that this is not the case for either carbon nanotubes (CNTs) or boron nitride nanotubes (BNNTs). A detailed analysis of the energetics, geometry, and electronic structure of various isomers of the complexes was performed. The SiCNT-NO 2 complex can be metallic or nonmetallic depending on the type of adsorption site and the chirality of the tube. However, our analysis of the electronic structure predicts that a strong p-type effect of the adsorption turns semiconducting systems into metallic ones at room temperature, irrespective of the chirality of the tube.

  10. Electronic and magnetic properties of yttrium-doped silicon carbide nanotubes: Density functional theory investigations

    NASA Astrophysics Data System (ADS)

    Khaira, Jobanpreet S.; Jain, Richa N.; Chakraborty, Brahmananda; Ramaniah, Lavanya M.

    2015-06-01

    The electronic structure of yttrium-doped Silicon Carbide Nanotubes has been theoretically investigated using first principles density functional theory (DFT). Yttrium atom is bonded strongly on the surface of the nanotube with a binding energy of 2.37 eV and prefers to stay on the hollow site at a distance of around 2.25 Å from the tube. The semi-conducting nanotube with chirality (4, 4) becomes half mettalic with a magnetic moment of 1.0 µB due to influence of Y atom on the surface. There is strong hybridization between d orbital of Y with p orbital of Si and C causing a charge transfer from d orbital of the Y atom to the tube. The Fermi level is shifted towards higher energy with finite Density of States for only upspin channel making the system half metallic and magnetic which may have application in spintronic devices.

  11. Design and characterization of metal and semiconducting nanostructures and nanodevices

    NASA Astrophysics Data System (ADS)

    Theiss, Jesse Robert

    This dissertation presents several studies that look at the unique properties and applications of metals and semiconductors when the dimensions of these materials are confined to the nanoscale. Chapter 1 provides background material that will aid in understanding the research presented in this dissertation. It begins with an introduction to plasmonics and an analytical derivation of the electromagnetic resonance conditions that have made this field so popular in the last 10--15 years. Particular interest is given to localized surface plasmon resonances that occur when light is incident on metallic nanoparticles, and how these plasmon resonances interact with one another. The second half of the introductory chapter turns to a slightly older but still exciting material, the carbon nanotube, whose electronic and optical properties vary significantly due to a slight change in crystal orientation. We discuss both of these topics in the context of Raman spectroscopy, where plasmons can be used to enhance the scattering process and Raman can be used to give detailed information about the structure of nanotubes. Chapter 2 presents the first plasmonics research project, where we demonstrate an angle evaporation method for fabricating arrays of metal nanoparticle pairs with separations on the order of a single nanometer. We image the small separations between particles, which we often refer to as "nanogaps," using high resolution transmission electron microscopy (TEM). Then, we use Raman spectroscopy to characterize the high electric field enhancements produced when the particles are illuminated with a visible wavelength laser. We find a very strong polarization dependence of the Raman intensity. We use numerical simulations to confirm both the high electric field enhancements and the observed polarization dependence for a particular nanoparticle geometry imaged by TEM, suggesting these particles might provide exceptionally high field enhancements and Raman scattering

  12. Fabrication and characterization of all oxidep-n junction diodes

    NASA Astrophysics Data System (ADS)

    Zhuang, Lin

    We have grown ZnO and MgO mixed oxide thin films by pulsed laser deposition. Most other similar work reported in the open literature so far involved preparing wurtzite structured MgxZn1-xO (w-MZO) films on sapphire substrates with x<0.4. We argue that the cubic form of ZnO, including cubic MgxZn1-xO (c-MZO) could be useful as transparent conducting oxide (TCO), n-type or p-type doped semiconducting oxide, wide bandgap UV detector and dilute magnetic semiconductor (DMS) that can be matched with and grown on many other cubic oxides and perovskites to form interesting devices. By the use of single crystal substrate of matched cubic structures, such as MgO and LaAlO3 (LAO), we have demonstrated that cubic Mgx Zn1-xO thin films even with x=0.57, representing maximum reported solubility of Zn in MgO, can be stabilized under normal ambient. High quality homoepitaxially and heteroepitaxially grown c-MZO films on MgO and LAO respectively have also been obtained. MZO is a wide bandgap material. Its absorption band edge shifts deep into UV with increased MgO content. Indium doped c-MZO (In-MZO) thin films show typical n-type semiconducting properties. Electrical conductivity at room temperature as high as 102 S cm-1 has been achieved for samples with In 8 at.% doping. Yet they remain optically transparent over the whole visible spectrum. Thus they become desirable n-type TCO. Li-doped NiO (Li0.15Ni0.85O, LNO), on the other hand, is a p-type conductor with good optical transmittance. We have fabricated a number of optical transparent all-oxide p-n junctions based on p-LNO/n-Nb doped SrTiO3 single crystal substrate, p-LNO/n-ZnO(wurtzite) and p-LNO/n-In-MZO. Their structural qualities have been studied and excellent heteroepitaxial relationships have been demonstrated. The results of our present investigation provide affirmative evidence for using all-oxide to develop p-n diode junction devices. In particular the advantages of utilizing the diversified properties of oxide such

  13. Semiconducting boron carbides with better charge extraction through the addition of pyridine moieties

    NASA Astrophysics Data System (ADS)

    Echeverria, Elena; Dong, Bin; Peterson, George; Silva, Joseph P.; Wilson, Ethiyal R.; Sky Driver, M.; Jun, Young-Si; Stucky, Galen D.; Knight, Sean; Hofmann, Tino; Han, Zhong-Kang; Shao, Nan; Gao, Yi; Mei, Wai-Ning; Nastasi, Michael; Dowben, Peter A.; Kelber, Jeffry A.

    2016-09-01

    The plasma-enhanced chemical vapor (PECVD) co-deposition of pyridine and 1,2 dicarbadodecaborane, 1,2-B10C2H12 (orthocarborane) results in semiconducting boron carbide composite films with a significantly better charge extraction than plasma-enhanced chemical vapor deposited semiconducting boron carbide synthesized from orthocarborane alone. The PECVD pyridine/orthocarborane based semiconducting boron carbide composites, with pyridine/orthocarborane ratios ~3:1 or 9:1 exhibit indirect band gaps of 1.8 eV or 1.6 eV, respectively. These energies are less than the corresponding exciton energies of 2.0 eV–2.1 eV. The capacitance/voltage and current/voltage measurements indicate the hole carrier lifetimes for PECVD pyridine/orthocarborane based semiconducting boron carbide composites (3:1) films of ~350 µs compared to values of  ⩽35 µs for the PECVD semiconducting boron carbide films fabricated without pyridine. The hole carrier lifetime values are significantly longer than the initial exciton decay times in the region of ~0.05 ns and 0.27 ns for PECVD semiconducting boron carbide films with and without pyridine, respectively, as suggested by the time-resolved photoluminescence. These data indicate enhanced electron–hole separation and charge carrier lifetimes in PECVD pyridine/orthocarborane based semiconducting boron carbide and are consistent with the results of zero bias neutron voltaic measurements indicating significantly enhanced charge collection efficiency.

  14. Nanoscale thermocapillarity enabled purification for horizontally aligned arrays of single walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Jin, Sung Hun; Dunham, Simon; Xie, Xu; Rogers, John A.

    2015-09-01

    Among the remarkable variety of semiconducting nanomaterials that have been discovered over the past two decades, single-walled carbon nanotubes remain uniquely well suited for applications in high-performance electronics, sensors and other technologies. The most advanced opportunities demand the ability to form perfectly aligned, horizontal arrays of purely semiconducting, chemically pristine carbon nanotubes. Here, we present strategies that offer this capability. Nanoscale thermos-capillary flows in thin-film organic coatings followed by reactive ion etching serve as highly efficient means for selectively removing metallic carbon nanotubes from electronically heterogeneous aligned arrays grown on quartz substrates. The low temperatures and unusual physics associated with this process enable robust, scalable operation, with clear potential for practical use. Especially for the purpose of selective joule heating over only metallic nanotubes, two representative platforms are proposed and confirmed. One is achieved by selective joule heating associated with thin film transistors with partial gate structure. The other is based on a simple, scalable, large-area scheme through microwave irradiation by using micro-strip dipole antennas of low work-function metals. In this study, based on purified semiconducting SWNTs, we demonstrated field effect transistors with mobility (> 1,000 cm2/Vsec) and on/off switching ratio (~10,000) with current outputs in the milliamp range. Furthermore, as one demonstration of the effectiveness over large area-scalability and simplicity, implementing the micro-wave based purification, on large arrays consisting of ~20,000 SWNTs completely removes all of the m-SWNTs (~7,000) to yield a purity of s-SWNTs that corresponds, quantitatively, to at least to 99.9925% and likely significantly higher.

  15. Victory Junction Gang Camp

    ERIC Educational Resources Information Center

    Shell, Ryan

    2007-01-01

    This article describes the Victory Junction Gang Camp, a not-for-profit, NASCAR-themed camp for children with chronic medical conditions that serves 24 different disease groups. The mission of the camp is to give children life-changing camping experiences that are exciting, fun, and empowering in a safe and medically sound environment. While doing…

  16. Josephson junction mixing.

    NASA Technical Reports Server (NTRS)

    Thompson, E. D.

    1973-01-01

    A theory is presented which, though too simple to explain quantitative details in the Josephson junction mixing response, is sufficient for explaining qualitatively the results observed. Crucial to the theory presented, and that which differentiates it from earlier ones, is the inclusion of harmonic voltages across the ideal Josephson element.

  17. Squeezable electron tunneling junctions

    NASA Astrophysics Data System (ADS)

    Moreland, J.; Alexander, S.; Cox, M.; Sonnenfeld, R.; Hansma, P. K.

    1983-09-01

    We report a versatile new technique for constructing electron tunneling junctions with mechanically-adjusted artificial barriers. I-V curves are presented for tunneling between Ag electrodes with vacuum, gas, liquid or solid in the barrier. An energy gap is apparent in the measured I-V curve when tunneling occurs between superconducting Pb electrodes.

  18. Doped semiconductor nanocrystal junctions

    SciTech Connect

    Borowik, Ł.; Mélin, T.; Nguyen-Tran, T.; Roca i Cabarrocas, P.

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  19. Recent advances in large-scale assembly of semiconducting inorganic nanowires and nanofibers for electronics, sensors and photovoltaics.

    PubMed

    Long, Yun-Ze; Yu, Miao; Sun, Bin; Gu, Chang-Zhi; Fan, Zhiyong

    2012-06-21

    Semiconducting inorganic nanowires (NWs), nanotubes and nanofibers have been extensively explored in recent years as potential building blocks for nanoscale electronics, optoelectronics, chemical/biological/optical sensing, and energy harvesting, storage and conversion, etc. Besides the top-down approaches such as conventional lithography technologies, nanowires are commonly grown by the bottom-up approaches such as solution growth, template-guided synthesis, and vapor-liquid-solid process at a relatively low cost. Superior performance has been demonstrated using nanowires devices. However, most of the nanowire devices are limited to the demonstration of single devices, an initial step toward nanoelectronic circuits, not adequate for production on a large scale at low cost. Controlled and uniform assembly of nanowires with high scalability is still one of the major bottleneck challenges towards the materials and device integration for electronics. In this review, we aim to present recent progress toward nanowire device assembly technologies, including flow-assisted alignment, Langmuir-Blodgett assembly, bubble-blown technique, electric/magnetic- field-directed assembly, contact/roll printing, planar growth, bridging method, and electrospinning, etc. And their applications in high-performance, flexible electronics, sensors, photovoltaics, bioelectronic interfaces and nano-resonators are also presented. PMID:22573265

  20. Brain barriers: Crosstalk between complex tight junctions and adherens junctions

    PubMed Central

    Tietz, Silvia

    2015-01-01

    Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood–brain barrier (BBB) and the epithelial blood–cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function. PMID:26008742