198 research outputs found
Buckling of Carbon Nanotubes: A State of the Art Review
The nonlinear mechanical response of carbon nanotubes, referred to as their
"buckling" behavior, is a major topic in the nanotube research community.
Buckling means a deformation process in which a large strain beyond a threshold
causes an abrupt change in the strain energy vs. deformation profile. Thus far,
much effort has been devoted to analysis of the buckling of nanotubes under
various loading conditions: compression, bending, torsion, and their certain
combinations. Such extensive studies have been motivated by (i) the structural
resilience of nanotubes against buckling and (ii) the substantial influence of
buckling on their physical properties. In this contribution, I review the
dramatic progress in nanotube buckling research during the past few years.Comment: 38 pages, 21 figure
Electronic and Transport Properties of Radially Deformed Double-walled Carbon Nanotube Intramolecular Junction
The electronic and transport property of a radially deformed double-walled
carbon nanotube (DWNT) intramolecular junction (IMJ) has been studied by the
tight-binding (TB) model combined with the first-principle calculations. The
geometrical structures of the DWNT IMJ have been first optimized in energy by
the universal force field (UFF) method. It is found that when heavily squashed,
the DWNT will become an insulator-coated metallic wire, and the conductance
near the Fermi level has been significantly changed by the radial squash.
Specially, several resonance conductance peaks appear at some energies in the
conduction band of the squashed DWNT IMJ. Finally, we have also investigated
the conductance variation due to change of the length of the central
semiconductor in the squashed DWNT IMJ. Furthermore, a promising pure carbon
nanoscale electronic device is proposed based on the DWNT IMJ.Comment: 11 pages, 4 figure
Electron-Phonon Scattering in Metallic Single-Walled Carbon Nanotubes
Electron scattering rates in metallic single-walled carbon nanotubes are
studied using an atomic force microscope as an electrical probe. From the
scaling of the resistance of the same nanotube with length in the low and high
bias regimes, the mean free paths for both regimes are inferred. The observed
scattering rates are consistent with calculations for acoustic phonon
scattering at low biases and zone boundary/optical phonon scattering at high
biases.Comment: 4 pages, 5 figure
Carbon Nanotubes as Nanoelectromechanical Systems
We theoretically study the interplay between electrical and mechanical
properties of suspended, doubly clamped carbon nanotubes in which charging
effects dominate. In this geometry, the capacitance between the nanotube and
the gate(s) depends on the distance between them. This dependence modifies the
usual Coulomb models and we show that it needs to be incorporated to capture
the physics of the problem correctly. We find that the tube position changes in
discrete steps every time an electron tunnels onto it. Edges of Coulomb
diamonds acquire a (small) curvature. We also show that bistability in the tube
position occurs and that tunneling of an electron onto the tube drastically
modifies the quantized eigenmodes of the tube. Experimental verification of
these predictions is possible in suspended tubes of sub-micron length.Comment: 8 pages, 5 eps figures included. Major changes; new material adde
Stochastic Heterostructures in B/N-Doped Carbon Nanotubes
Carbon nanotubes are one-dimensional and very narrow. These obvious facts
imply that under doping with boron and nitrogen, microscopic doping
inhomogeneity is much more important than for bulk semiconductors. We consider
the possibility of exploiting such fluctuations to create interesting devices.
Using self-consistent tight-binding (SCTB), we study heavily doped highly
compensated nanotubes, revealing the spontaneous formation of structures
resembling chains of random quantum dots, or nano-scale diode-like elements in
series. We also consider truly isolated impurities, revealing simple scaling
properties of bound state sizes and energies.Comment: 4 pages RevTeX, 4 PostScript figure
Reversible Band Gap Engineering in Carbon Nanotubes by Radial Deformation
We present a systematic analysis of the effect of radial deformation on the
atomic and electronic structure of zigzag and armchair single wall carbon
nanotubes using the first principle plane wave method. The nanotubes were
deformed by applying a radial strain, which distorts the circular cross section
to an elliptical one. The atomic structure of the nanotubes under this strain
are fully optimized, and the electronic structure is calculated
self-consistently to determine the response of individual bands to the radial
deformation. The band gap of the insulating tube is closed and eventually an
insulator-metal transition sets in by the radial strain which is in the elastic
range. Using this property a multiple quantum well structure with tunable and
reversible electronic structure is formed on an individual nanotube and its
band-lineup is determined from first-principles. The elastic energy due to the
radial deformation and elastic constants are calculated and compared with
classical theories.Comment: To be appear in Phys. Rev. B, Apr 15, 200
Quantum Interference Effects in Electronic Transport through Nanotube Contacts
Quantum interference has dramatic effects on electronic transport through
nanotube contacts. In optimal configuration the intertube conductance can
approach that of a perfect nanotube (). The maximum conductance
increases rapidly with the contact length up to 10 nm, beyond which it exhibits
long wavelength oscillations. This is attributed to the resonant cavity-like
interference phenomena in the contact region. For two concentric nanotubes
symmetry breaking reduces the maximum intertube conductance from to
. The phenomena discussed here can serve as a foundation for building
nanotube electronic circuits and high speed nanoscale electromechanical
devices
Design and Fabrication of Single-Walled Carbon Nanonet Flexible Strain Sensors
This study presents a novel flexible strain sensor for real-time strain sensing. The material for strain sensing is single-walled carbon nanonets, grown using the alcohol catalytic chemical vapor deposition method, that were encapsulated between two layers of Parylene-C, with a polyimide layer as the sensing surface. All of the micro-fabrication was compatible with the standard IC process. Experimental results indicated that the gauge factor of the proposed strain sensor was larger than 4.5, approximately 2.0 times greater than those of commercial gauges. The results also demonstrated that the gauge factor is small when the growth time of SWCNNs is lengthier, and the gauge factor is large when the line width of the serpentine pattern of SWCNNs is small
Structural and Electronic Properties of a Carbon Nanotorus: Effects of Delocalized Vs Localized Deformations
The bending of a carbon nanotube is studied by considering the structural
evolution of a carbon nanotorus from elastic deformation to the onset of the
kinks and eventually to the collapse of the walls of the nanotorus. The changes
in the electronic properties due to {\it non-local} deformation are contrasted
with those due to {\it local} deformation to bring out the subtle issue
underlying the reason why there is only a relatively small reduction in the
electrical conductance in the former case even at large bending angles while
there is a dramatic reduction in the conductance in the latter case at
relatively small bending angles.Comment: 10 pages, 6 figure
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