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The transport properties of B-doped single-walled carbon nanotubes (SWNTs) are studied from both experimental and theoretical standpoints. Experimentally, it is found that the semiconducting behavior of SWNTs is drastically changed after B-doping, and the unusual abrupt current drops are observed at low temperatures, which may imply the possibility of superconducting transition in B-doped SWNTs. Using the density-functional tight-binding calculation, it is observed that B-doping induces the presence of density of state peaks near the Fermi level which shifts toward the valence band region, showing a clear charge-transfer characteristic, which agrees well with the experimental observations. [ABSTRACT FROM AUTHOR]

Crystal growth of liquid silicon on the heterogeneous surfaces of carbon nanotubes (CNTs) is simulated. Silicon atoms are concentrated to form perfect coaxial cylindrical configurations around CNT cores. The heredity effect makes silicon imprint cylindrical shapes of CNTs during the solidification. The CNTs have a great influence on the stacking sequence of silicon atoms. Growth competition between CNT cores is clearly observed, which results in defects at the shared interface. The internal potential field around CNTs is responsible for growth competition and the heredity effect. [ABSTRACT FROM AUTHOR]

The authors report negative differential resistance (NDR) characteristics observed in nanodevices constructed using three types of fullerenes (C60, C70, and C84) encapsulated metallic double-walled carbon nanotubes. The NDR behavior persists from room temperature (300 K) to lower temperatures, and a significantly high on-off peak-to-valley current ratio is observed for many of the devices examined. The fullerene species exerts a strong influence on the peak voltage of the NDR, which exhibits a linear decrease with increasing fullerene size. The observed current-voltage curves are highly reproducible during measurements, and fully reversible upon change in the bias sweep direction. In addition, the peak current of the NDR is found to increase significantly under light illumination and is recoverable in the absence of light, which indicates potential for applications such as logic optoelectronic devices. [ABSTRACT FROM AUTHOR]

Using density functional theory (DFT) computations, we investigated pyridinelike structures in a series of single-walled CNx nanotubes and found that tube chirality and diameter play important roles in the formation of pyridinelike structures. Not pyridinelike structures but more NC defects (N atoms substituting for C atoms) should be responsible for the experimentally observed donor states of CNx nanotubes. The adsorption energies of Li at the pyridinelike defect are so large and the energy barrier for lithium penetrating the defect is so low that CNx nanotubes with pyridinelike structures have enhanced capability for lithium storage. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation is used to observe the traveling behavior of a water cluster released from the interior of single-walled carbon nanotube (SWCNT) to a graphite sheet. The simulation results reveal that there is a need for the water cluster overcoming the energy barrier of the binding energy between the water cluster and the SWCNT to escape from the tube. The water cluster undergoes a three-dimensional motion when released from the SWCNT, due to the effect of the thermal velocity. When encountering the graphite sheet in the forward direction, the x axis impact velocity has much effect on the delivery of the water cluster. The fact that the water cluster is bounced back reduces the possibility of being captured by the graphite sheet, resulting in a decrease in the delivery efficiency of the water cluster. The presence of the electric charges can help the graphite sheet to effectively trap the water cluster. These results have implications for the design and fabrication of novel drug delivery devices. [ABSTRACT FROM AUTHOR]

We have investigated the possibility of using single-walled carbon nanotubes (SWNTs) as the infrared energy conversion material based on the configuration of SWNT/Si heterojunction. The performance of solar cells based on SWNTs has been examined under illumination by the light with different wavelengths. Our experimental results confirm that SWNTs play a critical role in transforming the infrared light (1550 nm) into the electrical energy. The encapsulation of C60 fullerene inside SWNTs is found to significantly enhance the performance of solar cells through adjusting the Fermi level of SWNTs. [ABSTRACT FROM AUTHOR]

The growth of silicon atoms at the heterogeneous surface of carbon nanotubes (CNTs) is studied by means of molecular dynamics simulations. The results indicate that silicon atoms are concentrated to form an “annual ring” structure around CNTs. The structures of CNTs have strong correlation with the stacking sequence of silicon atoms. Heredity effect can be clearly observed during the heterogeneous nucleation. The uniform internal potential field around CNTs results in the formation of annual ring structures. [ABSTRACT FROM AUTHOR]

The authors report electrical transport properties of p-n junction based on semiconducting single-walled carbon nanotubes (SWCNTs). The formation of p-n junction is realized in SWCNTs, which are encapsulated with Fe nanoparticles at low filling fractions. The devices exhibit an excellent rectifying behavior, and no current down to 10-14 A level flows when the device is biased in reverse. During measurements performed in the temperature range from 10 to 300 K, the devices maintain high reproducibility. More importantly, even after exposure to air, the rectifying characteristic keeps stable, which strongly suggests that ideal p-n junction diodes can be fabricated by SWCNTs. [ABSTRACT FROM AUTHOR]

The authors report electric transport properties of resonance tunneling field-effect transistors fabricated using C60-filled metallic double-walled carbon nanotubes. The devices exhibit strong resonance tunneling characteristics and the distinct negative differential resistance with high peak-to-valley current ratio about 1300 is observed at room temperature. In particular, at high bias voltages, the tunneling current is completely dominated by the Coulomb oscillation peaks with uniform conductance at room temperature, reflecting a strong single-electron tunneling effect. [ABSTRACT FROM AUTHOR]