<i>Ab initio</i>study of the dielectric response of crystalline ropes of metallic single-walled carbon nanotubes: Tube-diameter and helicity effects

Marinopoulos, A. G.; Reining, Lucia; Rubio, Ángel

doi:10.1103/physrevb.78.235428

Cited by 16 publications

(14 citation statements)

References 63 publications

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“…50 Within the continuum-medium approximation which has been shown to work well even for nanostructures, 51 the ELF is defined as Im À1=eðx; kÞ f gwhere eðx; kÞ is the dielectric response function of the system with hx and hk being the energy-and momentum-transfer, respectively. It is well known that the dielectric response of CNT is anisotropic [52][53][54][55] and, in principle, a tensor description of its dielectric function is required, similar to the in-plane (e ? ) and outof-plane (e jj ) dielectric tensors of graphite.…”

Section: Dielectric Response Functionmentioning

confidence: 99%

Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

Kyriakou

Emfietzoglou

García-Molina

et al. 2011

Journal of Applied Physics

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The effect of bulk and surface excitations to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes (MWNTs) is studied using the dielectric formalism. Calculations are based on a semiempirical dielectric response function for MWCNTs determined by means of a many-pole plasmon model with parameters adjusted to available experimental spectroscopic data under theoretical sum-rule constrains. Finite-size effects are considered in the context of electron gas theory via a boundary correction term in the plasmon dispersion relations, thus, allowing a more realistic extrapolation of the electronic excitation spectrum over the whole energy-momentum plane. Energy-loss differential and total inelastic scattering cross sections as a function of electron energy and distance from the surface, valid over the energy range $50-30,000 eV, are calculated with the individual contribution of bulk and surface excitations separated and analyzed for the case of normally incident and escaping electrons. The sensitivity of the results to the various approximations for the spatial dispersion of the electronic excitations is quantified. Surface excitations are shown to have a strong influence upon the shape and intensity of the energy-loss differential cross section in the near surface region whereas the general notion of a spatially invariant inelastic mean free path inside the material is found to be of good approximation.

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Section: Dielectric Response Functionmentioning

confidence: 99%

Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

Kyriakou

Emfietzoglou

García-Molina

et al. 2011

Journal of Applied Physics

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“…Transitions associated with the σ/π electronic states emerge in the 12-to-20 eV range. [34][35][36][37][38] Since we are interested in a generic chiral mixture of specific electronic types, our approach is to model the Drude regime with type-specific dielectric spectroscopy data and the π regime with type-specific UV-Vis-NIR spectroscopy data. While the anisotropy and type dependence of the π plasmon is experimentally accessible, less is known about the σ + π plasmon.…”

Section: Methodsmentioning

confidence: 99%

Empirical evaluation of attractive van der Waals potentials for type-purified single-walled carbon nanotubes

et al. 2012

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Van der Waals forces play a critical role in the structure and stability of single-wall carbon nanotube (SWCNT) materials. Thin films assembled from SWCNTs purified by electronic type show particular promise for flexible electronics applications, but mechanical durability remains an unresolved issue. Using transition resonances determined from spectroscopic measurements of typepurified SWCNTs deposited on quartz, coupled with analogous spectroscopic characterization of polydimethylsiloxane (PDMS) substrates, we use the Lifshitz theory of van der Waals dispersion interactions developed by Rajter and co-workers [R. F. Rajter et. al., Phys. Rev. B 76, 045417 (2007)] to examine the influence of electronic type on van der Waals contact potentials in polymer supported nanotube networks. Our results suggest a significantly stronger nanotube-nanotube and nanotube-polymer attraction for the semiconducting SWCNT fractions, consistent with recent measurements of the electronic durability of flexible transparent SWCNT coatings.PACS numbers: 61.48. De, 78.67.Ch, 82.35.Np, 78.20.Bh 2 I. INTRODUCTIONVan der Waals (vdW) forces play a significant role in the structural stability of matter across a broad range of chemistry, physics, and biology. 1-6 They also play a particularly important role in nanotechnology, where they dominate the short-range attraction between nanoparticles and can hinder their dispersion and manipulation. [7][8][9][10][11] For particles lacking a permanent dipole moment, vdW dispersion forces arise solely from small fluctuations in the electromagnetic field -or more precisely, the dielectric permittivity -across the space between the particles, 12,13 which is dominated by the zero-point energy of quantum vacuum fluctuations. The quantum-field nature of such a mundane, ubiquitous and sometimes macroscopic force is quite remarkable, if on occasion not fully appreciated.Single-wall carbon nanotubes (SWCNTs) are nanometer thick tubes of graphene 100 nm to 100 µm in length. They can be either metallic or semiconducting, depending on the chiral vector (n, m) that characterizes the symmetry of rolling a 2D graphene sheet into a hollow tube. 14 They are one of the most studied materials within the realm of modern nanotechnology, with exceptional physical properties that herald the possibility of significant technological potential. 15 The importance of vdW forces in SWCNT materials cannot be overstated. The high aspect ratio and strong anisotropy create potential wells thousands of k B T in depth, but SWCNTs have yet to realize their full potential as mechanical reinforcing agents. This is primarily due to the mechanical failure of interfacial contacts, which are largely governed by vdW forces. Although chemical crosslinking can help mitigate such effects, this often occurs at the expense of the intrinsic SWCNT properties of interest, 16 which can limit the potential impact of applications.Raw nanotube materials typically contain a broad distribution of lengths and a mixture of the two distinct electronic species...

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“…Among several approaches [21][22][23][24] for modeling charged particle induced electronic excitations in CNTs, the opticaldata method 25 is perhaps most convenient for MC simulation 26 since it allows important energy-loss magnitudes to be expressed in useful analytic forms 27,28 with direct use of available experimental data for CNTs. 29 Therefore, we here employ a many-pole plasmon model of electronic excitations in MWCNTs that permits, within the plane-wave Born approximation (PWBA), the calculation of differential and total inelastic electron-electron scattering cross sections from first-principles.…”

mentioning

confidence: 99%

Quasi first-principles Monte Carlo modeling of energy dissipation by low-energy electron beams in multi-walled carbon nanotube materials

Emfietzoglou

Kyriakou

García-Molina

et al. 2012

Applied Physics Letters

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The energy dissipation pattern of low-energy electron beams (0.3-30 keV) in multi-walled carbon nanotube (MWCNT) materials is studied by Monte Carlo simulation taking into account secondary-electron cascade generation. A quasi first-principles discrete-energy-loss model deduced from a dielectric response function description of electronic excitations in MWCNTs is employed whereby both single-particle and plasmon excitations are included in a unified and self-consistent manner. Our simulations provide practical analytical functions for computing depth-dose curves and charged-carrier generation volumes in MWCNT materials under low-energy electron beam irradiation. Recent work on the irradiation of carbon nanotubes (CNTs) by energetic charged particles has unambiguously revealed various beneficial effects towards beam-assisted engineering of CNT-based nanodevices with the desired properties. 1,2 Scanning electron microscopy (SEM) and electron-beam lithography (EBL) are increasingly being used for the characterization and fabrication of CNT-based field-effect-transistors 3-5 and stimulated field-emitters. [6][7][8][9] Since electron transport plays a fundamental role in the ultimate performance of these techniques, knowledge of the energy dissipation pattern of low-energy electron beams (0.3-30 keV) in CNT materials becomes of prime importance. Monte Carlo (MC) simulations offer a valuable tool for investigating energy-transfer phenomena in irradiated solids. 10,11 In the present energy range, energy dissipation in matter by electron beams is almost exclusively due to inelastic electron-electron scattering. Elastic electron scattering by target nuclei, well-known to be responsible for irradiation damage via knock-on atomic displacement at high beam energies (above about 80 keV for CNTs), 12,13 results in significant momentum transfer (or equivalent, angular deflection) but practically zero energy loss. 14 Contrary to the continuous energy-loss models (e.g., from stopping power theory) widely used for studying irradiation effects in bulk solids, MC models of materials with restricted dimensions (e.g., CNTs and nanodevices in general) must account for secondary-electron cascade generation through the use of discrete (or single-scattering) energy-loss models. [15][16][17] Such models will also complement current computational studies of high-energy electron-beam (e.g., from a transmission electron microscope, TEM) irradiation effects in CNTs lying on substrates from backscattered electrons. 18,19 Binary collision theory has been widely used in this context due to its computational convenience, despite its wellknown simplistic description of the materials excitation properties. 20 In the present work, we advance a MC model of electron-beam energy dissipation in multi-walled carbon nanotube (MWCNT) materials based on a quasi firstprinciples discrete-energy-loss model deduced from a realistic description of the target electronic excitations. This approach has the advantage that secondary-electron cascade generation can be...

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Ab initiostudy of the dielectric response of crystalline ropes of metallic single-walled carbon nanotubes: Tube-diameter and helicity effects

Cited by 16 publications

References 63 publications

Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

Simple model of bulk and surface excitation effects to inelastic scattering in low-energy electron beam irradiation of multi-walled carbon nanotubes

Empirical evaluation of attractive van der Waals potentials for type-purified single-walled carbon nanotubes

Quasi first-principles Monte Carlo modeling of energy dissipation by low-energy electron beams in multi-walled carbon nanotube materials

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