The Experts below are selected from a list of 94923 Experts worldwide ranked by ideXlab platform
Y K Kato - One of the best experts on this subject based on the ideXlab platform.
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spectral tuning of optical coupling between air mode nanobeam cavities and Individual Carbon nanotubes
Applied Physics Letters, 2018Co-Authors: Hidenori Machiya, Akihiro Ishii, T Uda, Y K KatoAbstract:We demonstrate control over optical coupling between air-suspended Carbon nanotubes and air-mode nanobeam cavities by spectral tuning. Taking advantage of the large dielectric screening effects caused by adsorbed molecules, laser heating is used to blueshift the nanotube photoluminescence. A significant increase in the cavity peak is observed when the nanotube emission is brought into resonance, and the spontaneous emission enhancement is estimated from the photoluminescence spectra. We find that the enhancement shows good correlation with the spectral overlap of the nanotube emission and the cavity peak. Our technique offers a convenient method for controlling the optical coupling of air-suspended nanotubes to photonic structures.
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gate controlled generation of optical pulse trains using Individual Carbon nanotubes
Nature Communications, 2015Co-Authors: M Jiang, Y Kumamoto, Akihiro Ishii, Minoru Yoshida, T Shimada, Y K KatoAbstract:The photocurrent and luminescence of Carbon nanotubes is governed by excitonic processes with diverse uses in nano-photonics. Here, Jiang et al. generate optical pulses from Individual air-suspended Carbon nanotubes under an application of square-wave gate voltages with control over pulse timing and duration.
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ultralow mode volume photonic crystal nanobeam cavities for high efficiency coupling to Individual Carbon nanotube emitters
Nature Communications, 2014Co-Authors: R Miura, Sousuke Imamura, Akihiro Ishii, T Shimada, R Ohta, Xin Liu, Satoshi Iwamoto, Yasuhiko Arakawa, Y K KatoAbstract:The unique emission properties of single-walled Carbon nanotubes are attractive for achieving increased functionality in integrated photonics. In addition to being room-temperature telecom-band emitters that can be directly grown on silicon, they are ideal for coupling to nanoscale photonic structures. Here we report on high-efficiency coupling of Individual air-suspended Carbon nanotubes to silicon photonic crystal nanobeam cavities. Photoluminescence images of dielectric- and air-mode cavities reflect their distinctly different mode profiles and show that fields in the air are important for coupling. We find that the air-mode cavities couple more efficiently, and estimated spontaneous emission coupling factors reach a value as high as 0.85. Our results demonstrate advantages of ultralow mode-volumes in air-mode cavities for coupling to low-dimensional nanoscale emitters.
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optical control of Individual Carbon nanotube light emitters by spectral double resonance in silicon microdisk resonators
Applied Physics Letters, 2013Co-Authors: Sousuke Imamura, R Watahiki, R Miura, Takashi Shimada, Y K KatoAbstract:We demonstrate integration of Individual light-emitting Carbon nanotubes with silicon microdisk resonators. Photons emitted from nanotubes are efficiently coupled to whispering gallery modes, circulating within the disks and lighting up their perimeters. Furthermore, we control such emission by tuning the excitation wavelength in and out of resonance with higher order modes in the same disk. Our results open up the possibilities of using nanotube emitters embedded in photonic circuits that are Individually addressable through spectral double resonance.
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optical control of Individual Carbon nanotube light emitters by spectral double resonance in silicon microdisk resonators
arXiv: Mesoscale and Nanoscale Physics, 2013Co-Authors: Sousuke Imamura, R Watahiki, R Miura, Takashi Shimada, Y K KatoAbstract:Single-walled Carbon nanotubes have advantages as a nanoscale light source compatible with silicon photonics because they show room-temperature luminescence at telecom-wavelengths and can be directly synthesized on silicon substrates. Here we demonstrate integration of Individual light-emitting Carbon nanotubes with silicon microdisk resonators. Photons emitted from nanotubes are efficiently coupled to whispering gallery modes, circulating within the disks and lighting up their perimeters. Furthermore, we control such emission by tuning the excitation wavelength in and out of resonance with higher order modes in the same disk. Our results open up the possibilities of using nanotube emitters embedded in photonic circuits that are Individually addressable through spectral double resonance.
Phaedon Avouris - One of the best experts on this subject based on the ideXlab platform.
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efficient narrow band light emission from a single Carbon nanotube p n diode
Nature Nanotechnology, 2010Co-Authors: Thomas Mueller, Megumi Kinoshita, Mathias Steiner, Vasili Perebeinos, Damon B Farmer, Phaedon AvourisAbstract:Electrically induced light emission from an Individual Carbon nanotube p–n diode is both more efficient and has a narrower spectrum than previously demonstrated, allowing emission from free and localized excitons to be identified.
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efficient narrow band light emission from a single Carbon nanotube p n diode
Nature Nanotechnology, 2010Co-Authors: Thomas Mueller, Megumi Kinoshita, Mathias Steiner, Vasili Perebeinos, Damon B Farmer, Ageeth A Bol, Phaedon AvourisAbstract:Electrically induced light emission from an Individual Carbon nanotube p–n diode is both more efficient and has a narrower spectrum than previously demonstrated, allowing emission from free and localized excitons to be identified.
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An integrated logic circuit assembled on a single Carbon nanotube
Science, 2006Co-Authors: Zhihong Chen, Jennifer Sippel-oakley, Paul M Solomon, Shalom J. Wind, Joerg Appenzeller, Jinyao Tang, Andrew G Rinzler, Phaedon AvourisAbstract:Single-walled Carbon nanotubes (SWCNTs) have been shown to exhibit excellent electrical properties, such as ballistic transport over several hundred nanometers at room temperature. Field-effect transistors (FETs) made from Individual tubes show dc performance specifications rivaling those of state-of-the-art silicon devices. An important next step is the fabrication of integrated circuits on SWCNTs to study the high-frequency ac capabilities of SWCNTs. We built a five-stage ring oscillator that comprises, in total, 12 FETs side by side along the length of an Individual Carbon nanotube. A complementary metal-oxide semiconductor-type architecture was achieved by adjusting the gate work functions of the Individual p-type and n-type FETs used.
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Manipulation of Individual Carbon Nanotubes and Their Interaction with Surfaces
The Journal of Physical Chemistry B, 1998Co-Authors: Tobias Hertel, Richard Martel, Phaedon AvourisAbstract:We demonstrate that the tip of an atomic force microscope (AFM) can be used to control the shape and position of Individual multiwalled Carbon nanotubes dispersed on a surface. Specifically we can bend, straighten, translate. rotate, and-under certain conditions-cut nanotubes. Such manipulations are feasible due to the interaction between nanotubes and the substrate, which can stabilize highly strained nanotube configurations. Direct evidence for this interaction is provided by the study of elastic distortions of tubes interacting with other tubes and the substrate, From the observed deformations of nanotubes with 100 Angstrom diameter. For example, we obtain a binding energy of 0.8 +/- 0.3 eV/Angstrom. This interaction forces nanotubes to conform to the structure of the substrate, and the resulting distortions should induce corresponding changes in their electronic structure and electrical transport properties.
Tony F Heinz - One of the best experts on this subject based on the ideXlab platform.
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excitons and high order optical transitions in Individual Carbon nanotubes a rayleigh scattering spectroscopy study
Physical Review B, 2010Co-Authors: Stephane Berciaud, James Hone, Louis E Brus, Christophe Voisin, Hugen Yan, Bhupesh Chandra, Robert Caldwell, Yuyao Shan, Tony F HeinzAbstract:We examine the excitonic nature of high-lying optical transitions in single-walled Carbon nanotubes by means of Rayleigh scattering spectroscopy. A careful analysis of the principal transitions of Individual semiconducting and metallic nanotubes reveals that in both cases the line shape is consistent with an excitonic model, but not one of free carriers. For semiconducting species, sidebands are observed at $\ensuremath{\sim}200\text{ }\text{meV}$ above the third and fourth optical transitions. These features are ascribed to exciton-phonon bound states. Such sidebands are not apparent for metallic nanotubes, as expected from the reduced strength of excitonic interactions in these systems.
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interactions between Individual Carbon nanotubes studied by rayleigh scattering spectroscopy
Physical Review Letters, 2006Co-Authors: Feng Wang, James Hone, Matthew Y Sfeir, Limin Huang, Stephen Obrien, Louis E Brus, X Henry M Huang, Jaehee Kim, Tony F HeinzAbstract:The electronic properties of single-walled Carbon nanotubes (SWNTs) are altered by intertube coupling whenever bundles are formed. These effects are examined experimentally by applying Rayleigh scattering spectroscopy to probe the optical transitions of given Individual SWNTs in their isolated and bundled forms. The transition energies of SWNTs are observed to undergo redshifts of tens of meVs upon bundling with other SWNTs. These intertube coupling effects can be understood as arising from the mutual dielectric screening of SWNTs in a bundle.
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probing electronic transitions in Individual Carbon nanotubes by rayleigh scattering
Science, 2004Co-Authors: Matthew Y Sfeir, James Hone, Tony F Heinz, Feng Wang, Limin Huang, Chiachin Chuang, Stephen Obrien, Louis E BrusAbstract:Rayleigh scattering spectra were obtained from Individual single-walled Carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic and semiconducting nanotubes. We analyzed spectral lineshapes in relation to the role of excitonic effects and correlated the results with Raman scattering data on Individual tubes. The nanotube structure remained the same over distances of tens of micrometers. Small nanotube bundles retained distinct Rayleigh spectroscopic signatures of their component nanotubes, thus allowing the probing of nanotube-nanotube interactions.
Tsuwei Chou - One of the best experts on this subject based on the ideXlab platform.
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state of the art of Carbon nanotube fibers opportunities and challenges
Advanced Materials, 2012Co-Authors: Joonhyung Byun, Byungsun Kim, Tsuwei ChouAbstract:The superb mechanical and physical properties of Individual Carbon nanotubes (CNTs) have provided the impetus for researchers in developing high-performance continuous fibers based upon CNTs. The reported high specific strength, specific stiffness and electrical conductivity of CNT fibers demonstrate the potential of their wide application in many fields. In this review paper, we assess the state of the art advances in CNT-based continuous fibers in terms of their fabrication methods, characterization and modeling of mechanical and physical properties, and applications. The opportunities and challenges in CNT fiber research are also discussed.
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Carbon nanotube Carbon fiber hybrid multiscale composites
Journal of Applied Physics, 2002Co-Authors: Erik T Thostenso, D Z Wang, Tsuwei ChouAbstract:Carbon nanotubes were grown directly on Carbon fibers using chemical vapor deposition. When embedded in a polymer matrix, the change in length scale of Carbon nanotubes relative to Carbon fibers results in a multiscale composite, where Individual Carbon fibers are surrounded by a sheath of nanocomposite reinforcement. Single-fiber composites were fabricated to examine the influence of local nanotube reinforcement on load transfer at the fiber/matrix interface. Results of the single-fiber composite tests indicate that the nanocomposite reinforcement improves interfacial load transfer. Selective reinforcement by nanotubes at the fiber/matrix interface likely results in local stiffening of the polymer matrix near the fiber/matrix interface, thus, improving load transfer.
Limin Huang - One of the best experts on this subject based on the ideXlab platform.
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interactions between Individual Carbon nanotubes studied by rayleigh scattering spectroscopy
Physical Review Letters, 2006Co-Authors: Feng Wang, James Hone, Matthew Y Sfeir, Limin Huang, Stephen Obrien, Louis E Brus, X Henry M Huang, Jaehee Kim, Tony F HeinzAbstract:The electronic properties of single-walled Carbon nanotubes (SWNTs) are altered by intertube coupling whenever bundles are formed. These effects are examined experimentally by applying Rayleigh scattering spectroscopy to probe the optical transitions of given Individual SWNTs in their isolated and bundled forms. The transition energies of SWNTs are observed to undergo redshifts of tens of meVs upon bundling with other SWNTs. These intertube coupling effects can be understood as arising from the mutual dielectric screening of SWNTs in a bundle.
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directing and sensing changes in molecular conformation on Individual Carbon nanotube field effect transistors
Journal of the American Chemical Society, 2005Co-Authors: Xuefeng Guo, P. Kim, Limin Huang, Stephen Obrien, Colin NuckollsAbstract:This study explores how to populate the surface of the Carbon nanotubes with functional molecules that can be toggled back-and-forth between different molecular conformations. The molecules synthesized for this study are tagged with a photoswitchable headgroup and a functional group which directs the assembly on the surface of the Carbon nanotubes. Single-walled Carbon nanotube field effect transistors switch between high and low conductance as the molecules are switched with light between open and closed conformations. These devices detect the photoswitching of ∼104 molecules.
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probing electronic transitions in Individual Carbon nanotubes by rayleigh scattering
Science, 2004Co-Authors: Matthew Y Sfeir, James Hone, Tony F Heinz, Feng Wang, Limin Huang, Chiachin Chuang, Stephen Obrien, Louis E BrusAbstract:Rayleigh scattering spectra were obtained from Individual single-walled Carbon nanotubes with the use of a laser-generated visible and near-infrared supercontinuum. This diagnostic method is noninvasive and general for nanoscale objects. The approach permits clear identification of excited states in arbitrary metallic and semiconducting nanotubes. We analyzed spectral lineshapes in relation to the role of excitonic effects and correlated the results with Raman scattering data on Individual tubes. The nanotube structure remained the same over distances of tens of micrometers. Small nanotube bundles retained distinct Rayleigh spectroscopic signatures of their component nanotubes, thus allowing the probing of nanotube-nanotube interactions.