Many potential applications have been proposed for carbon nanotubes, including conductive and high-strength composites; energy storage and energy conversion devices; sensors; field emission displays and radiation sources; hydrogen storage media; and nanometer-sized semiconductor devices, probes, and interconnects. Some of these applications are now realized in products. Others are demonstrated in early to advanced devices, and one, hydrogen storage, is clouded by controversy. Nanotube cost, polydispersity in nanotube type, and limitations in processing and assembly methods are important barriers for some applications of single-walled nanotubes.

http://science.sciencemag.org/content/sci/297/5582/787.full.pdf

Carbon Nanotubes--the Route Toward Applications

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

https://www.bc.edu/content/dam/files/schools/cas_sites/physics/pdf/Ren/p85.pdf

Advances in the science and technology of carbon nanotubes and their composites: a review

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

A method combining laser ablation cluster formation and vapor-liquid-solid (VLS) growth was developed for the synthesis of semiconductor nanowires. In this process, laser ablation was used to prepare nanometer-diameter catalyst clusters that define the size of wires produced by VLS growth. This approach was used to prepare bulk quantities of uniform single-crystal silicon and germanium nanowires with diameters of 6 to 20 and 3 to 9 nanometers, respectively, and lengths ranging from 1 to 30 micrometers. Studies carried out with different conditions and catalyst materials confirmed the central details of the growth mechanism and suggest that well-established phase diagrams can be used to predict rationally catalyst materials and growth conditions for the preparation of nanowires.

/pdf/a-laser-ablation-method-for-the-synthesis-of-crystalline-102tprgisp.pdf

A laser ablation method for the synthesis of crystalline semiconductor nanowires

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

The effect of carrier concentration on fulleride superconductivity is studied by x ray, Raman, magnetization, and ESR of two new cubic families: ${\mathrm{Na}}_{2}{\mathrm{Cs}}_{x}{\mathrm{C}}_{60}$ $(0lxl1)$ and ${M}_{3\ensuremath{-}y}{\mathrm{Ba}}_{y}{\mathrm{C}}_{60}$ ( $0.2lyl2$, $M\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}\mathrm{K}$, Rb, or Cs). These are isostructural with known $\mathrm{Pa}\overline{3}$ and $\mathrm{Fm}\overline{3}m$ trivalent superconductors, respectively, but with variable valence $2lnl5$. ${T}_{c}$ is peaked at or very near $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}3$, decreasing rapidly in either direction to $l0.5\mathrm{K}$ for $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}2.5$ and 5. These results underscore the failure of both one-electron and strong correlation models to explain the dependence of ${T}_{c}$ on band filling.

Tc vs Carrier Concentration in Cubic Fulleride Superconductors

T c vs. Carrier Concentration in Cubic Fulleride Superconductors

Recent x-ray results show that quenching the high-temperature fcc (rocksalt) phase of ${\mathrm{KC}}_{60}$ below 280 K produces a metastable orthorhombic structure in which the molecules exist as dimer pairs. Using electron-spin resonance, we find that this state is nonmagnetic and describe evidence for \ensuremath{\sigma} bonding. Upon heating, the dimer structure transforms first to the fcc phase at 280 K. The fcc phase is unstable at 300 K and transforms to the polymeric state at 340 K rather than undergoing equilibrium phase separation. We suggest that the transformation from dimer to fcc is driven by the onset of molecular orientational disorder.

Electron-spin-resonance study of the dimer state of KC60 and its transformations.

Using electron-spin resonance, we measured conduction-electron-spin susceptibility versus temperature for three alkali-fulleride compounds in the normal state. Converting the observed Pauli-spin susceptibility into density of states at the Fermi level $N(0)$ and using the temperature dependence of the lattice parameter we fit the experimental variation of $N(0)$ as a function of the inter-${\mathrm{C}}_{60}$ distance $d$ with an exponential functional form. Assuming a universal ${T}_{c}$ dependence on the lattice constant for every alkali fulleride, we used the value $N(0)=f(d)$ in the McMillan formula to fit the ${(T}_{c},d)$ data points taken from the literature.

J. Robert

Papers

Crystalline Ropes of Metallic Carbon Nanotubes

Tc vs Carrier Concentration in Cubic Fulleride Superconductors

T c vs. Carrier Concentration in Cubic Fulleride Superconductors

Electron-spin-resonance study of the dimer state of KC60 and its transformations.

Experimental lattice dependence of the density of states in alkali fullerides