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

Abstract

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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“…For radiation interactions with GNPs, Geant4-Penelope is unable to precisely reproduce very low-energy electron interactions in the GNP since it is limited to electrons of energies above 100 eV and neglects the reduced dimensionality of the GNPs, this has been shown in work on nanotubes. 31, 43, 44 Furthermore, the interaction probability per Gray with 6 MV photons in this study was found to be higher than that reported in previous studies 9, 18 . We found that this difference was due to the different physics setting used in the two simulations.…”

Nanostructures, concentrations and energies: an ideal equation to extend therapeutic efficiency on radioresistant 9L tumor cells using ${{\rm{Ta}}}_{2}{{\rm{O}}}_{5}$ ceramic nanostructured particles

“…the nanostructure material), which strongly influences mean free paths, energy loss, penetration ranges, etc [40]. Plasmon decay from the NP should also be considered [41] and be included in theoretical studies and Monte Carlo simulations [42].…”

Monte Carlo study of electron-beam penetration and backscattering in multi-walled carbon nanotube materials: The effect of different scattering models

“…An approximate scheme has been described elsewhere. 28 However, the details of this procedure are important only for verylow-energy electrons (below $50 eV), and therefore, they are of little practical significance in the present study.…”

“…Recently, the inelastic scattering of low-energy electrons (<30 keV) in CNTs was studied using a dielectric response function determined from experimental optical data and appropriate dispersion relations 25,26 and, along with the original Browning model, 27 was implemented in a homemade MC code to simulate electron transport and energy dissipation in MWCNT materials. 28 The use of a discrete-energy-loss model based on a semi-empirical dielectric response function is presently considered the state-of-the-art for low-energy electron transport in bulk solids and solid surfaces, because it offers a realistic description of the electronic excitations of the material with single-particle and plasmon losses computed self-consistently (under the constraint of sum-rules) within a single model. [29][30][31][32] Furthermore, in place of an undamped plasmon (used in both the UBC 22 and MONSEL 24 codes), more realistic models that account for plasmon dispersion and lifetime broadening can be included.…”