CARBON nanotubes1 are expected to have a wide variety of interesting properties. Capillarity in open tubes has already been demonstrated2–5, while predictions regarding their electronic structure6–8 and mechanical strength9 remain to be tested. To examine the properties of these structures, one needs tubes with well defined morphologies, length, thickness and a number of concentric shells; but the normal carbon-arc synthesis10,11 yields a range of tube types. In particular, most calculations have been concerned with single-shell tubes, whereas the carbon-arc synthesis produces almost entirely multi-shell tubes. Here we report the synthesis of abundant single-shell tubes with diameters of about one nanometre. Whereas the multi-shell nanotubes are formed on the carbon cathode, these single-shell tubes grow in the gas phase. Electron diffraction from a single tube allows us to confirm the helical arrangement of carbon hexagons deduced previously for multi-shell tubes1.

Single-shell carbon nanotubes of 1-nm diameter

The use of individual molecules as functional electronic devices was first proposed in the 1970s (ref 1) Since then, molecular electronics2,3 has attracted much interest, particularly because it could lead to conceptually new miniaturization strategies in the electronics and computer industry The realization of single-molecule devices has remained challenging, largely owing to difficulties in achieving electrical contact to individual molecules Recent advances in nanotechnology, however, have resulted in electrical measurements on single molecules4,5,6,7 Here we report the fabrication of a field-effect transistor—a three-terminal switching device—that consists of one semiconducting8,9,10 single-wall carbon nanotube11,12 connected to two metal electrodes By applying a voltage to a gate electrode, the nanotube can be switched from a conducting to an insulating state We have previously reported5 similar behaviour for a metallic single-wall carbon nanotube operated at extremely low temperatures The present device, in contrast, operates at room temperature, thereby meeting an important requirement for potential practical applications Electrical measurements on the nanotube transistor indicate that its operation characteristics can be qualitatively described by the semiclassical band-bending models currently used for traditional semiconductor devices The fabrication of the three-terminal switching device at the level of a single molecule represents an important step towards molecular electronics

Room-temperature transistor based on a single carbon nanotube

The major part of this chapter has already appeared in [1], but because of the length restrictions (in Science), the discussion on why we think this form is given in only brief detail. This chapter goes into more depth to try to answer the questions of why the fullerenes form themselves. This is another example of the very special behavior of carbon. From a chemist’s standpoint, it is carbon’s ability to form multiple bonds that allows it to make these low dimensional forms rather than to produce tetrahedral forms. Carbon can readily accomplish this and it is in the mathematics and physics of the way this universe was put together, that carbon is given this property. One of the consequences of this property is that, if left to its own devices as carbon condenses from the vapor and if the temperature range is just right, above 1000°C, but lower than 1400°C, there is an efficient self-assembly process whose endpoint is C60.

https://science.sciencemag.org/content/sci/273/5274/483.full.pdf

Crystalline Ropes of Metallic Carbon Nanotubes

CARBON nanotubes are predicted to have interesting mechanical properties—in particular, high stiffness and axial strength—as a result of their seamless cylindrical graphitic structure1–5. Their mechanical properties have so far eluded direct measurement, however, because of the very small dimensions of nanotubes. Here we estimate the Young's modulus of isolated nanotubes by measuring, in the transmission electron microscope, the amplitude of their intrinsic thermal vibrations. We find that carbon nanotubes have exceptionally high Young's moduli, in the terapascal (TPa) range. Their high stiffness, coupled with their low density, implies that nanotubes might be useful as nanoscale fibres in strong, lightweight composite materials.

Exceptionally high Young's modulus observed for individual carbon nanotubes

The Young's modulus, strength, and toughness of nanostructures are important to proposed applications ranging from nanocomposites to probe microscopy, yet there is little direct knowledge of these key mechanical properties. Atomic force microscopy was used to determine the mechanical properties of individual, structurally isolated silicon carbide (SiC) nanorods (NRs) and multiwall carbon nanotubes (MWNTs) that were pinned at one end to molybdenum disulfide surfaces. The bending force was measured versus displacement along the unpinned lengths. The MWNTs were about two times as stiff as the SiC NRs. Continued bending of the SiC NRs ultimately led to fracture, whereas the MWNTs exhibited an interesting elastic buckling process. The strengths of the SiC NRs were substantially greater than those found previously for larger SiC structures, and they approach theoretical values. Because of buckling, the ultimate strengths of the stiffer MWNTs were less than those of the SiC NRs, although the MWNTs represent a uniquely tough, energy-absorbing material.

http://science.sciencemag.org/content/sci/277/5334/1971.full.pdf

Nanobeam mechanics: Elasticity, strength, and toughness of nanorods and nanotubes

Two different local density approximation (X{alpha} and Kohn-Sham exchange and Perdew-Zunger correlation) of the density funcitonal method have been used to calculate structural and electronic properties of six kinds of polyfluoroethylene, including polytetrafluoroethylene (PTFE), poly(1,2-difluorethylene) (PDFE), and others, for several different dihedral angles. For PTFE and PDFE, all the geometric parameters are optimized simultaneously in the stable helical conformation. The position of the minimum and the depth of the potential well are in good agreement with the experimental results. The stable helical conformation are found for PTFE and PDFE. For PDFE a shoulder close to the stable gauche conformation is found in the energy curve. The potential curves of another four kinds of polyfluorethylene are studied in detail close to the planar conformation. The side fluorine atoms strongly affect the conformation and the electronic structure. The band structure of PTFE and PDFE in optimized geometry and the other PFEs in planar zigzag conformation are calculated in good agreement with experimental results.

An LDA calculation of the conformation and electronic structure of polytetrafluoroethylene

Hartree--Fock methods are used to calculate the interaction energy of Ar and H/sub 2/ in the region of the attractive (van der Waals) minimum. As expected this leads to poor agreement with experiment. When a semiempirical correction term representing the induced dipole--induced dipole dispersion energy is added to the Hartree--Fock potential, the resulting potential agrees quite well with experimental results. This scheme is then used for investigation of two similar systems: Ne--H/sub 2/ and Na/sup +/--H/sub 2/. The procedure is found to describe qualitatively quite well the potentials of the two systems.

Intermolecular potential studies of hydrogen‐molecule interactions with rare‐gas atoms

A semiempirical model based on density functional results is used to study the effects of chemical edge disorder on the transport properties of armchair-edge graphene nanoribbons. Despite a strong scattering potential induced by substituting randomly F for H atoms along their edges, carriers injected close to the band gap in ribbons as narrow as 4.8 nm exhibit ballistic transport over hundreds of nanometers. The results indicate that robust ballistic transport can be maintained in the presence of chemical edge disorder so long as the terminating atoms and/or functional groups remain one-fold-coordinated to the edges and do not contribute states to the π-network within several eV of the gap.

Robust Ballistic Transport in Narrow Armchair-Edge Graphene Nanoribbons with Chemical Edge Disorder

Photoelectron spectra from local-density-functional calculations: Application to chain polymers

Molecular dynamics simulations are used to study hypervelocity impacts of an ultrathin flyer plate with a semi-infinite two-dimensional model diatomic molecular solid. We show that these hypervelocity impacts can produce a dissociative phase transition from a molecular to a close-packed solid in the target material. We also show that hypervelocity impacts of ultrathin plates can produce extensive chemical reactions leading to a detonation accompanied by a phase transition in an energetic version of the model. © 1994 John Wiley & Sons, Inc.

John W. Mintmire

Papers

An LDA calculation of the conformation and electronic structure of polytetrafluoroethylene

Intermolecular potential studies of hydrogen‐molecule interactions with rare‐gas atoms

Robust Ballistic Transport in Narrow Armchair-Edge Graphene Nanoribbons with Chemical Edge Disorder

Photoelectron spectra from local-density-functional calculations: Application to chain polymers

Chemistry and phase transitions from hypervelocity impacts