The interaction of polyatomic ions with surfaces occurs in a variety of industrially important processes, including low energy plasma deposition and ion beam deposition. These processes are used to deposit thin films, develop novel nanostructures, and dope semiconductors. In this presentation, the use of polyatomic ion beam deposition to develop and modify nanometer-scale composites will be discussed.
Both simulations and experiments have found that at incident energies of 10-80 eV/ion, ion deposition on carbon nanotube bundles leads to covalent bond formation between nanotubes or adjacent tube walls [1,2]. In this presentation, classical molecular dynamics simulations are used to study the polyatomic-ion beam deposition on carbon nanotube-polystyrene composites and nanopeapods that are composed of carbon nanotubes filled with fullerenes. The forces in the simulations are calculated using a short-ranged many-body, reactive empirical bond-order potential for hydrocarbons and fluorocarbons that is coupled to long-range Lennard Jones potentials .
In the case of the nanotubes-polystyrene composite, the ion beam consists of 50 C3F5+ ions. The incident energies considered are 50 eV/ion and 80 eV/ion, respectively. The composite consists of (10,10) single-walled carbon nanotubes embedded at different depths in crystalline polystyrene. Two composite geometries are considered: one with the axis of the nanotube parallel to the polymer chain and the other with the axis of the nanotube perpendicular to the polymer chain. The simulations confirm the effectiveness of chemical functionalization of carbon nanotubes by using polyatomic-ion beam deposition, and predict the dependence of such modifications on the incident energy, embedding depth of the carbon nanotube, and the composite geometry from an atomic-scale point of view. The findings could have important implications for the production of carbon nanotube-based nanocomposite materials with improved adhesion between the nanotube and the polymer matrix.
In the case of the nanopeapods, the ion beam consists of 20 CF3+ ions and the incident energies considered are 50 eV/ion and 80 eV/ion. The system consists of a bundle of (10,10) single-walled carbon nanotubes filled with fullerene molecules. The simulations confirm the effectiveness of ion beam deposition in producing covalent cross-links between the carbon nanotubes and the C60 molecules. They also predict the dependence of such modifications on the incident energy and location of the nanotube within the bundle relative to the ion beam from an atomic-scale point of view. The findings could have important implications for the production of carbon nanotube-based nanocomposite materials and electronic devices.
This work is supported by the National Science Foundation (grant CHE 0200838).
1. B. Ni and S.B. Sinnott, Phys. Rev. B 61, R16343-R16346 (2000).
2. B. Ni, R. Andrews, D. Jacques, D. Qian, M. B. J. Wijesundara, Y. Choi, L. Hanley, and S.B. Sinnott, J. Phys. Chem. B 105, 12719-12725 (2001).
3. D.W. Brenner, O.A. Shenderova, J.A. Harrison, S.J. Stewart, B. Ni, S.B. Sinnott, J. Phys.: Condensed Matter 14, 783-802 (2002).
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