Nanotubes for Electronics

Collins, Philip G.; Avouris, Phaedon

doi:10.1038/scientificamerican1200-62

Cited by 798 publications

(528 citation statements)

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“…51 SWNTs are predicted to exceed the heat transmission of pure diamond by nearly a factor of 2 (6000 W/mK) and can withstand temperatures up to 2800 ºC in vacuum or 750 ºC in air. 50 As expected, each of these remarkable traits has led to unique innovations ( Figure 1 -5 …”

Section: Mechanical Properties and Applicationssupporting

confidence: 53%

“…50 The diameter of a carbon nanotube is ~1 nm and its density is 1.4 g/cm 3 , about half that of aluminum. 50 The cylindrical arrangement of carbon atoms, coupled with the immense energy of the carbon-carbon bond, is responsible for the superlative strength and flexibility of carbon nanotubes. SWNTs have an incredible tensile strength of 45 billion Pa, at least 20 times greater than that of steel.…”

Section: Mechanical Properties and Applicationsmentioning

confidence: 99%

“…SWNTs have an incredible tensile strength of 45 billion Pa, at least 20 times greater than that of steel. 50 These flexible particles can be deformed, flattened, or bent at large angles and restraightened without damage owing to their extremely high Young's modulus (970 billion Pa). 51 SWNTs are predicted to exceed the heat transmission of pure diamond by nearly a factor of 2 (6000 W/mK) and can withstand temperatures up to 2800 ºC in vacuum or 750 ºC in air.…”

Section: Mechanical Properties and Applicationsmentioning

confidence: 99%

“…Consider that an electron can behave as both a particle and a wave; electron waves can add either constructively or destructively around the SWNT circumference, and only electrons with the right wavelength, or quantum state, are not cancelled out by destructive interference. 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.…”

Section: Electronic Properties and Applicationsmentioning

confidence: 99%

“…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. 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.…”

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: Mechanical Properties and Applicationssupporting

confidence: 53%

Section: Mechanical Properties and Applicationsmentioning

confidence: 99%