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1.
Cumulative and continuous laser vaporization synthesis of single wall carbon nanotubes and nanohorns
A. A. Puretzky D. J. Styers-Barnett C. M. Rouleau H. Hu B. Zhao I. N. Ivanov D. B. Geohegan 《Applied Physics A: Materials Science & Processing》2008,93(4):849-855
The conditions for the scaled synthesis of single wall carbon nanotubes (SWNTs) and single wall carbon nanohorns (SWNHs) by
laser vaporization at high temperatures are investigated and compared using in situ diagnostics. An industrial Nd:YAG laser
(600 W, 1–500 Hz repetition rate) with tunable pulse widths (0.5–50 ms) is utilized to explore conditions for high-yield production.
High-speed videography (50000 frames/s) of the laser plume and pyrometry of the target surface are correlated with ex situ
high resolution transmission electron microscopy analysis of the products for pure carbon targets and carbon/catalyst targets
to understand the effects of the processing conditions on the resulting nanostructures. Carbon is shown to self-assemble into
single-wall nanohorn structures at rates of ∼1 nm/ms, which is comparable to the catalyst-assisted SWNT growth rates. Two
regimes of laser ablation, cumulative ablation by multiple pulses and continuous ablation by individual pulses, were explored. Cumulative ablation with spatially overlapping 0.5-ms pulses is favorable for
the high yield and production rate of SWNTs at ∼6 g/h while continuous ablation by individual long laser pulses (∼20 ms) at
high temperatures results in the highest yield of SWNHs at ∼10 g/h. Adjustment of the laser pulse width is shown to control
SWNH morphology. 相似文献
2.
Fumio Kokai Naoki Tachi Keita Kobayashi Akira Koshio 《Applied Surface Science》2009,255(24):9622-9625
Three types of single-wall carbon nanohorn (SWNH) aggregates hybridized with carbon nanocapsules (CNCs) containing Fe3C, Co, or Ag were produced by laser vaporization of graphite mixed with Fe, Co, or Ag in Ar gas. Characterization by transmission electron microscopy revealed that although the three hybrid structures had different diameter distributions with average diameters of 96, 90, and 85 nm, respectively, their SWNH layers had similar thicknesses (17-18 nm on average). The diameter difference is explained by the sizes (16-24 nm on average) of the encapsulated CNCs, the formation of which depended on the carbon solubility of the three metals and the precipitation of the graphitic layers. In addition, there was a stronger correlation between the diameters of the hybrids and the thicknesses of the SWNH layers for the three types. We suggest that the formation mechanism of the three structures is based on the assembly of SWNHs around a molten metal-carbon particle with certain ranges of lengths and diameters, respectively. 相似文献
3.
M. Pudlak R. Pincak 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(4):565-576
The electronic spectra for double-wall zigzag and armchair
nanotubes are found. The influence of nanotube curvatures on the
electronic spectra is also calculated. Our finding that the outer
shell is hole doped by the inner shell is in the difference
between Fermi levels of individual shells which originate from the
different hybridization of π orbital. The shift and rotation
of the inner nanotube with respect to the outer nanotube are
investigated. We found stable semimetal characteristics of the
armchair DWNTs in regard of the shift and rotation of the inner
nanotube. We predict the shift of kF towards the bigger wave
vectors with decreasing of the radius of the armchair nanotube. 相似文献
4.
A. S. Fedorov A. F. Sadreev 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(3):363-368
By use both of the plane wave DFT and the empirical
exp-6 Lennard-Jones potential methods we calculate the inner
potential in narrow single-wall carbon nanotubes (SWCNT) (6, 0),
(7, 0) and (3, 3) which affects the hydrogen molecules. The inner
potential forms a goffered potential surface and can be
approximated as V(z,r,φ)≈V0sin (2πz/a)+V(r). We
show that in these SWCNTs transport of molecules is given mainly
by thermoactivated hoppings between minima of the periodic
potential along the tube axis. The rate hoppings is substantially
depends on temperature because of thermal fluctuations of tube
wall. 相似文献
5.
K. Kobayashi T. Shimazu Y. Yamada A. Koshio Y. Takahashi F. Kokai 《Applied Physics A: Materials Science & Processing》2007,89(1):121-126
Single-wall carbon nanohorn (SWNH) aggregates hybridized with carbon nanocapsules (CNCs) were fabricated at a high yield (∼70%).
The carbon was laser-vaporized for 2 s into an Ar gas atmosphere with one of the following: Fe, Al, Si, Co, Ni, Cu, Ag, La2O3, Y2O3, and G2O3. By optimizing the Ar gas pressure and metal content, we were able to produce hybridized SWNH structures for Fe, Co, Ni,
Cu, and Ag. Possible mechanisms for governing hybrid production, which occurs with smaller CNCs (<100 nm) with only certain
metals and carbide, are discussed on the basis of thermal and catalytic graphitization.
PACS 61.46.Df; 68.37.Lp; 81.16.Mk 相似文献
6.
Using the Lennard-Jones interaction potential between the impurity atom and carbon atom, we have studied the dependence of in-tube impurity doping on the radius of a single-wall carbon nanotube (SWNT), as well as its helicity. The obtained results show that the radius of the most stably doped SWNT is different for different kinds of impurity atoms. This is useful for producing the required doped SWNT. In addition, it is found that the helicity of tube has a strong effect on the potential energy of the atoms doped in the SWNT. 相似文献
7.
J. González E. Perfetto 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(4):571-581
We investigate the electronic instabilities of the small-diameter
(3, 3) carbon nanotubes by studying the low-energy perturbations of the
normal Luttinger liquid regime. The bosonization approach is adopted
to deal exactly with the interactions in the forward-scattering
channels, while renormalization group methods are used to analyze
the low-energy instabilities. In this respect, we take into account
the competition between the effective e–e interaction mediated by
phonons and the Coulomb interaction in backscattering and Umklapp
channels. Moreover, we apply our analysis to relevant experimental
conditions where the nanotubes are assembled into large
three-dimensional arrays, which leads to an efficient screening of
the Coulomb potential at small momentum-transfer. We find that the
destabilization of the normal metallic behavior takes place through
the onset of critical behavior in some of the two charge stiffnesses
that characterize the Luttinger liquid state. From a physical point
of view, this results in either a divergent compressibility or a
vanishing renormalized velocity for current excitations at the point
of the transition. We observe anyhow that this kind of critical
behavior occurs without the development of any appreciable sign
of superconducting correlations. 相似文献
8.
S. Bandow F. Kokai K. Takahashi M. Yudasaka S. Iijima 《Applied Physics A: Materials Science & Processing》2001,73(3):281-285
The magnetic properties of single-wall carbon nanohorns (SWNH) were studied by electron spin resonance (ESR) and static magnetic
susceptibility measurements. The SWNHs were ESR active with linewidth (ΔH) of ∼6 G in vacuo at room temperature. ΔH was susceptible
to the partial pressure of O2 and became 53 G at 1 atmospheric pressure of O2, while the integrated ESR intensity was independent on O2 pressure and behaved as Curie-like, suggesting an intrinsic ESR origin with localized electron spin character. The diamagnetic
susceptibility for SWNHs indicated a value smaller than that of randomly oriented graphite by an order of magnitude, but showing
a magnitude comparable to those of C60 and C70. It is suggested that the large diamagnetism expecting for sp2 networked carbon materials will be canceled by the Van Vleck constant paramagnetism.
Received: 20 November 2000 / Accepted: 21 November 2000 / Published online: 25 July 2001 相似文献
9.
Laila Jaber-Ansari Myung Gwan Hahm Tae Hoon Kim Sivasubramanian Somu Ahmed Busnaina Yung Joon Jung 《Applied Physics A: Materials Science & Processing》2009,96(2):373-377
Large-scale room-temperature liquid-phase directed assembly of highly organized single-walled carbon nanotubes (SWNT) over
large areas is demonstrated. The presented process utilizes lithographically patterned template to guide the fluidic self-assembly
of SWNTs on a silicon-dioxide substrate. The width of these highly organized SWNT structures are in the micron range while
their heights are in orders of nanometers. Room temperature electrical I–V characterization of these fabricated high coverage SWNT wires show linear ohmic behavior. The resistivity of these assembled
SWNT network is in the order of 10−6 Ω m demonstrating their metallic characteristics during conductance. Scaling of the assembly processes on a wafer level with
high yield is demonstrated. Our developed assembly process is compatible with complimentary metal oxide semiconductor (CMOS)
processes and provides a simple and flexible way of building SWNT nanotube-based electronics in a large scale. 相似文献
10.
C. Tang K. Deng W. Tan Y. Yuan Y. Liu J. Yang X. Wang 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):125-128
The formation mechanism, geometric structures, and
electronic properties of a metal-substituted fullerene
C58Fe2 have been studied using frontier orbital theory
(FOT) and density functional theory (DFT). FOT predicts that two
Fe atoms prefer to substitute the two carbons of a [6,6] double
bond of C60 yielding a structure denoted as C58Fe2-3, which
is different from the two equivalent substitution sites, i.e., the
sites on the opposite of C60 cage or in the nearest
neighboring sites of a pentagonal ring for C58X2 (X=N and
B), and also different from the cross sites of a hexagonal ring
for C58Si2. Five possible structures of C58Fe2 are
optimized using DFT to see whether FOT works. The DFT calculations
support the prediction of FOT. The Mulliken charge of Fe atom in
C58Fe2-3 shows that the two Fe atoms of C58Fe2-3
lose 0.70 electron to the carbons of the cage, and the net spin
populations of Fe atom indicate that each Fe atom has 1.11 μB
magnetic moments, while each of the four nearest neighboring
carbons has
magnetic moments. Thus, the two Fe
atoms have ferromagnetic interaction with each other, and have
weak antiferromagnetic interaction with their four nearest
neighboring carbons, leaving 2.0 μB magnetic moments for the
molecule. 相似文献
11.
I. Vilfan 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,51(2):277-284
The properties of
nanowires were investigated with
ab initio calculations based on the density-functional theory.
The molecules build weakly coupled one-dimensional chains, like
and Mo6S9-xIx, and the crystals are
strongly uniaxial in their mechanical and electronic properties.
The calculated moduli of elasticity and resilience along the chain axis are
c11 = 320 GPa and ER = 0.53 GPa, respectively.
The electronic band structure and optical conductivity indicate
that the
crystals are good quasi-one-dimensional conductors.
The frequency-dependent complex dielectric tensor ε, calculated
in the random-phase approximation, shows a strong Drude peak in
ε∥, i.e., for the electric field polarised parallel to
the chain axis, and several peaks related to interband transitions.
The electron energy loss spectrum is weakly anisotropic and has a strong peak
at the plasma frequency ħωp ≈20 eV.
The stability analysis shows that
is metastable against the
formation of the layered
. 相似文献
12.
We present a real-time investigation of ultra-fast carrier dynamics in single-wall carbon nanotube bundles using femtosecond
time-resolved photoelectron spectroscopy. The experiments allow us to study the processes governing the sub-picosecond and
the picosecond dynamics of non-equilibrium charge carriers. On the sub-picosecond time scale the dynamics are dominated by
ultra-fast electron–electron scattering processes, which lead to internal thermalization of the laser-excited electron gas.
We find that quasiparticle lifetimes decrease strongly as a function of their energy up to 2.38 eV above the Fermi level –
the highest energy studied experimentally. The subsequent cooling of the laser-heated electron gas to the lattice temperature
by electron–phonon interaction occurs on the picosecond time scale and allows us to determine the electron–phonon mass-enhancement
parameter λ. The latter is found to be over an order of magnitude smaller if compared, for example, with that of a good conductor
such as copper.
Received: 4 March 2002 / Accepted: 7 March 2002 / Published online: 3 June 2002 相似文献
13.
K. P. McKenna G. J. Morgan 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,59(4):451-456
A quantum equation of motion method is applied to simulate conduction electron spin-relaxation and transport in the presence
of the spin-orbit interaction and disorder. A spin-relaxation time of 25ps is calculated for Cu with a realistic low temperature
resistivity of 3.2 μΩ cm – corresponding to a spin-diffusion length of about 0.4 μm. Spin-relaxation in a finite nanocrystallite
of Cu is also simulated and a short spin-relaxation time (0.47 ps) is calculated for a crystallite with 7% surface atoms.
The spin-relaxation calculated for bulk Cu is in good agreement with experimental evidence, and the dramatic nanocrystallite
effect observed has important implications for nano-spintronic devices. 相似文献
14.
M. Yamazaki N. Kishimoto K. Ohno 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2006,38(1):47-57
Collisional ionization of styrene (phenylethylene), 2-vinylpyridine, and
4-vinylpyridine with metastable He*(23S) atoms were studied by means of
collision-energy/electron-energy resolved two-dimensional Penning
ionization electron spectroscopy. Collision energy dependence of partial
ionization cross-sections, which reflects the anisotropic interactions
between a He*(23S) atom and the target molecules, indicates that
attractive interaction for the out-of-plane access of a He*(23S) atom
to phenyl group is stronger than that for the out-of-plane access to vinyl
group. Moreover, it was found for vinylpyridines that the attractive
interaction around π electrons became weaker than that for styrene, and
that the attractive interaction for the in-plane access to the nitrogen atom
is stronger than that for out-of-plane π-directions. However, in
2-vinylpyridine, the hydrogen atom of vinyl group prevents a He*(23S)
atom from approaching to the nitrogen atom along in-plane directions, and
thus the attractive interactions around the nitrogen atom were shielded by
the vinyl group. The experimentally observed anisotropic interactions were
qualitatively supported with ab initio model interaction potential calculations
between a Li (He*(23S)) atom and the target molecule. Concerning with
electronic structures of investigated molecules, the assignment of Penning
ionization electron spectrum for 4-vinylpyridine was discussed on the basis
of different behavior of collision-energy dependence of partial ionization
cross-sections, and the satellite ionization band in Penning ionization
electron spectra was also reported for styrene. 相似文献
15.
Odair P. Ferreira Larissa Otubo Acrisio L. Aguiar Jose J. A. Silva Josue Mendes Filho Antonio G. Souza Filho Solange B. Fagan Oswaldo L. Alves 《Journal of nanoparticle research》2009,11(8):2163-2170
We have studied the interaction of benzonitrile with as-prepared and purified single-walled carbon nanotubes (SWCNTs). As-prepared
SWCNTs, when suspended in benzonitrile, lead to a red colored dispersion which contains fragments composed mostly of amorphous
carbon and carbon-coated catalyst, thus suggesting that benzonitrile is a solvent that can be used as one step of the purification
process. Optical spectroscopic data (infrared, Raman, absorption) showed that purified carbon nanotubes interact weakly with
benzonitrile. These experimental results are confirmed by first principles calculations that predict a very weak adsorption
process through π–π interaction instead of through the free electron pair of the nitrile. 相似文献
16.
I. Popov T. Kunze S. Gemming G. Seifert 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):439-446
The preferred adsorption sites and the propensity for a self-organised growth of the molybdenum sulfide cluster Mo6S8 on the Au(111) surface are investigated by density-functional band-structure calculations with pseudopotentials and a plane
wave basis set. The quasi-cubic cluster preferentially adsorbs via a face and remains structurally intact.
It experiences a strong, mostly non-ionic attraction to the surface
at several quasi-isoenergetic adsorption positions. A scan of the potential energy surface exhibits only small barriers between
adjacent strong adsorption sites. Hence, the cluster may move in a potential well with degenerate local energy minima at room
temperature. The analysis of the electronic structure reveals a negligible
electron transfer and S-Au hybridised states, which indicate that the cluster-surface
interaction is dominated by S-Au bonds, with minor contributions from
the Mo atom in the surface vicinity. All results indicate that Mo6S8 clusters
on the Au(111) surface can undergo a template-mediated self-assembly to an ordered inorganic monolayer, which is still redox
active and may be employed as surface-active agent in the integration of noble metal and ionic or biological components within
nano-devices.
Therefore, a classical potential model was developed on the basis of the DFT data,
which allows to study larger cluster assemblies on the Au(111). 相似文献
17.
H. Hövel M. De Menech M. Bödecker C. Rettig U. Saalmann M. E. Garcia 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(3):459-463
By means of STM measurements and fully self-consistent
transport calculations we analyze how STM trajectories for the
mapping of nanostructures on surfaces are affected by the
atomic structure of the tip.
For the particular case of carbon nanotubes we show that
considerable distortions of the STM trajectory with respect to
the actual structure, position and diameter of the nanotube
can occur for certain tip geometries. Comparison between
theory and experiment can allow to characterize and correct
these distortions. 相似文献
18.
In this work, the electronic properties of the system composed by the CO molecules adsorbed on Ti-coated single-wall carbon nanotubes (SWNTs) are studied through first principles calculations. The changes in the electronic properties of the interaction of the CO molecules with a linear Ti wire covering an (8, 0) semiconductor SWNT are analyzed for different CO concentrations. A strong interaction between CO molecules and the SWCT/Ti system is observed, which decreases when the concentration of CO molecules increases. The resulting system are shown to be very sensitive to the CO concentration adsorbed on the tube/Ti system, making that the SWNT, which is originally semiconductor and becomes metallic after Ti covering, to recover the semiconductor behavior again when enough high concentrations of CO molecules is adsorbed on the SWNT/Ti system. These three distinct steps (semiconductor/metallic/semiconductor) constitute the basis for a feasible, flexible and efficient sensor device for CO molecule recognition. 相似文献
19.
C. Schönenberger A. Bachtold C. Strunk J.-P. Salvetat L. Forró 《Applied Physics A: Materials Science & Processing》1999,69(3):283-295
We report equilibrium electric resistance R and tunneling spectroscopy (dI/dV)measurements obtained on single multi-wall nanotubes
contacted by four metallic Au fingers from above. At low temperature quantum interference phenomena dominate the magnetoresistance.
The phase-coherence (lφ)and elastic-scattering lengths (le)are deduced. Because le is of order of the circumference of the nanotubes, transport is quasi-ballistic. This result is supported by a dI/dV spectrum
which is in good agreement with the density of states (DOS) due to the one-dimensional subbands expected for a perfect single-wall
tube. As a function of temperature T the resistance increases on decreasing T and saturates at ≈1–10 Kfor all measured nanotubes.
R(T) cannot be related to the energy-dependent DOS of graphene but is mainly caused by interaction and interference effects.
On a relatively small voltage scale of the order ≈10 meV, a pseudogap is observed in dI/dV which agrees with Luttinger-liquid
theories for nanotubes. Because we have used quantum diffusion based on Fermi-liquid as well as Luttinger-liquid theory in
trying to understand our results, a large fraction of this paper is devoted to a careful discussion of all our results.
Received: 17 May 1999 / Accepted: 18 May 1999 / Published online: 4 August 1999 相似文献
20.
H. Shiroishi T. Oda H. Sakashita N. Fujima 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,43(1-3):129-132
We have studied the electronic structure of the carbon nanotubes which
include Fe atomic wire with using the density functional theory.
As the stable geometries, we obtained the straight and zigzag wires,
which have ferromagnetic and antiferromagnetic alignments, respectively.
The antiferromagnets consists of the two ferromagnetic dimers which
couple in antiparallel alignment.
We presents the band dispersions and the density of states for the
magnetic nanotubes.
The electronic structure at the Fermi level consists of the
Fe 3d and C 2pπ states, which shows a strong hybridization
between them. 相似文献