NEAR-THRESHOLD ION-INDUCED DEFECT PRODUCTION IN GRAPHITE

Subplantation of the noble-gas ions He+, Ne+, Ar+, and Kr+ into graphite in the energy range of 10-150 eV with doses in the range of 1-15 X 10(14) ions/cm2 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 E(p), ion displacement thresholds E(th), and the lattice displacement energies E(d). The E(p)'s scale linearly with the atomic radius of the projectiles. Defect production begins at E(p), although these energies are below E(th). A mechanism for defect production at energies below E(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.