Negative Differential Conductance and Hot Phonons in Suspended Nanotube Molecular Wires

Pop, Eric; Mann, David J.; Cao, Jiefeng; Wang, Qian; Goodson, Kenneth E.; Dai, Hongjie

doi:10.1103/physrevlett.95.155505

Cited by 408 publications

(523 citation statements)

References 20 publications

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“…50 Depending on the particular diameter and chirality of the SWNT, the nanotube is either metallic (~33% of structures) or semiconducting (~67% of structures). 58 SWNTs display fascinating electrical properties such as enormous current carrying capacity, ballistic charge transport, 59 negative differential conductance (NDC), 60 and field emission. 32,61 Metal SWNTs carry 1000 times more current density than copper wires 50 and transport charges down the nanotube without significant scattering.…”

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

“…59 Interestingly, when a voltage is applied to metallic nanotubes, they deviate from Ohm's law after a certain voltage threshold is reached; specifically, the current at the threshold voltage surprisingly decreases rather than increases, an effect known as NDC. 60,62,63 SWNTs are also exceptional field emitters due to their small diameters. In particular, when an electric field passes through a nanotube that is stood on its end, the sharp nanotube tip concentrates the electrons and rapidly projects them onto a target.…”

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

“…NDC is observed for metallic nanotubes at low electric fields, which is significant for electronic applications and holds general implications for high-current applications based on 1D materials. 60 In addition, semiconducting SWNTs have already been incorporated into field effect transistors (FETs) that transport electrons between two metal electrodes while a voltage is applied to a third gate electrode that switches the device on and off. 62,66 Processors that integrate SWNT FET switches could operate 1000 times faster than current silicon-based devices.…”

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

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Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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Single-walled carbon nanotubes (SWNTs) are cylindrical graphitic molecules that have remained at the forefront of nanomaterials research since 1991, largely due to their exceptional and unusual mechanical, electrical, and optical properties. The motivation for understanding how nanotubes interact with light (i.e., SWNT photophysics) is both fundamental and applied. Individual nanotubes may someday be used as superior near-infrared fluorophores, biological tags and sensors, and components for ultrahigh-speed optical communications systems. Establishing an understanding of basic nanotube photophysics is intrinsically significant and should enable the rapid development of such innovations. Unlike conventional molecules, carbon nanotubes are synthesized as heterogeneous samples, composed of molecules with different diameters, chiralities, and lengths. Because a nanotube can be either metallic or semiconducting depending on its particular molecular structure, SWNT samples are also mixtures of conductors and semiconductors. Early progress in understanding the optical characteristics of SWNTs was limited because nanotubes aggregate when synthesized, causing a mixing of the energy states of different nanotube structures. Recently, significant improvements in sample preparation have made it possible to isolate individual nanotubes, enabling many advances in characterizing their optical properties. In this Account, single-molecule confocal microscopy and spectroscopy were implemented to study the fluorescence from individual nanotubes. Single-molecule measurements naturally circumvent the difficulties associated with SWNT sample inhomogeneities. Intrinsic SWNT photoluminescence has a simple narrow Lorentzian line shape and a polarization dependence, as expected for a one-dimensional system. Although the local environment heavily influences the optical transition wavelength and intensity, single nanotubes are exceptionally photostable. In fact, they have the unique characteristic that their single molecule fluorescence intensity remains constant over time; SWNTs do not “blink” or photobleach under ambient conditions. In addition, transient absorption spectroscopy was used to examine the relaxation dynamics of photoexcited nanotubes and to elucidate the nature of the SWNT excited state. For metallic SWNTs, very fast initial recovery times (300–500 fs) corresponded to excited-state relaxation. For semiconducting SWNTs, an additional slower decay component was observed (50–100 ps) that corresponded to electron–hole recombination. As the excitation intensity was increased, multiple electron–hole pairs were generated in the SWNT; however, these e−h pairs annihilated each other completely in under 3 ps. Studying the dynamics of this annihilation process revealed the lifetimes for one, two, and three e−h pairs, which further confirmed that the photoexcitation of SWNTs produces not free electrons but rather one-dimensional bound electron–hole pairs (i.e., excitons). In summary, nanotube photophysics is a rapidly developing area o...

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Section: Electronic Properties and Applicationsmentioning

confidence: 99%

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

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Photophysics of Individual Single-Walled Carbon Nanotubes

2008

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“…On the basis of this information, a 1 V bias voltage applied to the MWCNT in an argon environment is estimated to increase the average MWCNT temperatures by 40 and 140 K over the ambient temperature under the pressures of 10 5 Pa and 6.5 × 10 3 Pa, respectively. Although a previous report shows that a suspended metallic single-walled CNT (SWCNT) has a negative differential conductance due to electron scattering by hot nonequilibrium optical phonons under a much higher power density, 17 this phenomenon has not been explored here as our sensor works under low power density for moderate operating temperatures.…”

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confidence: 99%

An Electrothermal Carbon Nanotube Gas Sensor

et al. 2007

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We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor deposition that is accomplished within seconds via real-time electrical feedback control. Vacuum pressure sensitivity and gas species differentiability are observed and analyzed. Such MWCNT electrothermal sensors are compact, fast and reversible in responses, and fully integratable with microelectronics.Carbon nanotube (CNT) gas sensors based on fundamentally different mechanisms have been demonstrated, 1 including electrical conductance or capacitance changes 2-4 or using the sharp tips of the CNT as gas ionization sensors. 5 Limiting factors for sorption-based CNT sensors include low adsorption energies, diffusion kinetics, response speed, selectivity, and reversibility. We report on the electrothermal effect of a single multiwalled carbon nanotube (MWCNT) suspended between two silicon microbridges. When a Joule-heated MWCNT is exposed to different pressures, the electrical resistance change follows the conductive heat-transfer variances of gas molecules. The MWCNT is grown on silicon using the local synthesis method and is accomplished within tens of seconds via real-time electrical feedback control. Our findings suggest that the MWCNT electrothermal mechanism has applications to both gas sensing and species differentiation, with advantages of compactness, fast and reversible responses, low power consumption, and being fully integratable with microelectronics.The electrothermal gas sensing mechanism is schematically illustrated in Figure 1a. A single MWCNT is suspended between two silicon microstructures and heated by electrical current in the system. Energy conservation calls for total heat generation equal to the summation of heat conduction to the two microstructures (W C ), heat transfer via gases (W G , shown in the figure as W gas1 and W gas2 representing the case of two types of gases of different thermal conductivity values), and heat radiation (W R ). Both gas pressure and species can affect the heat-transfer process and result in MWCNT temperature changes and therefore resistance changes.To realize this architecture, we use a complementary metal oxide semiconductor (CMOS)-compatible, in situ controlled synthesis, assembly, and integration process previously reported in the literature. 6-9 Synthesis and assembly of carbon nanotubes has been heavily investigated with various device demonstrations using high-temperature synthesis processes 10,11 and labor-intensive assembly steps, 12,13 but assembly and heterogeneous integration of CNTs with microelectronics such as standard CMOS circuitry are still problematic. Many issues still need to be resolved, such as the synthesis and accurate placement...

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“…14,15) The high κ of individual SWCNTs, however, is not directly reflected in the observed κ in bulk SWCNT films, which depends significantly on the morphology of the bulk SWCNTs, such as the degree of SWCNT alignment and SWCNT length. The reported values ranges from 0.1 to 250 W/mK in bulk SWCNTs.…”

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confidence: 99%

Giant Seebeck coefficient in semiconducting single-wall carbon nanotube film

Nakai

Honda

Yanagi

et al. 2014

Appl. Phys. Express

215

220

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We found a giant Seebeck effect in semiconducting single-wall carbon nanotube (SWCNT) films, which exhibited a performance comparable to that of commercial Bi 2 Te 3 alloys. Carrier doping of semiconducting SWCNT films further improved the thermoelectric performance. These results were reproduced well by first-principles transport simulations based on a simple SWCNT junction model. These findings suggest strategies that pave the way for emerging printed, allcarbon, flexible thermoelectric devices.

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Negative Differential Conductance and Hot Phonons in Suspended Nanotube Molecular Wires

Cited by 408 publications

References 20 publications

Photophysics of Individual Single-Walled Carbon Nanotubes

Photophysics of Individual Single-Walled Carbon Nanotubes

An Electrothermal Carbon Nanotube Gas Sensor

Giant Seebeck coefficient in semiconducting single-wall carbon nanotube film

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