Near-threshold ion-induced defect production in graphite

Abstract

Subplantation of the noble-gas ions ${\mathrm{He}}^{+}$, ${\mathrm{Ne}}^{+}$, ${\mathrm{Ar}}^{+}$, and ${\mathrm{Kr}}^{+}$ into graphite in the energy range of 10--150 eV with doses in the range of 1--15\ifmmode\times\else\texttimes\fi{}${10}^{14}$ ions/${\mathrm{cm}}^{2}$ has been studied by Auger electron spectroscopy (AES) and computer simulations. A technique based on AES line-shape analysis has been employed to describe quantitatively the ion-induced damage to the lattice. The carbon KLL AES line shapes and the AES spectra from subplanted Ne, Ar, and Kr were used to determine the ion penetration thresholds ${\mathit{E}}_{\mathit{p}}$, ion displacement thresholds ${\mathit{E}}_{\mathrm{th}}$, and the lattice displacement energies ${\mathit{E}}_{\mathit{d}}$. The ${\mathit{E}}_{\mathit{p}}$'s scale linearly with the atomic radius of the projectiles. Defect production begins at ${\mathit{E}}_{\mathit{p}}$, although these energies are below ${\mathit{E}}_{\mathrm{th}}$. A mechanism for defect production at energies below ${\mathit{E}}_{\mathrm{th}}$ based on noble-gas interstitials and lattice strain and distortion is developed. This process is modeled through the charmm molecular modeling program and the trim classical trajectory simulation.