TABLE OF CONTENTS As we have shown in the preceding chapters, collisions between ions and target atoms result in the slowing down of the ion, and the energy loss resulting from nuclear stopping contributes significantly to determining the ion's range. In our discussion of range theory we have to consider how the nuclear energy losses contribute to the energy dissipation of the ion. From our discussion of elastic collisions we know that the energy loss by the ion is transferred to lattice atoms. In these collisions, sufficient energy may be transferred from the ion to displace an atom from its lattice site. Lattice atoms that are displaced by incident ions are called primary knock-on atoms or PKAs. The PKAs can in turn displace other atoms, i.e., secondary knock-on atoms, tertiary knock-ons, etc., thus creating a cascade of atomic collisions. This leads to a distribution of vacancies, interstitial atoms and other types of lattice disorder in the region around the ion track. As the number of ions incident on the crystal increases, the individual disordered regions begin to overlap. At some point, a heavily damaged layer is formed. The total amount of disorder and the distribution in depth depend on ion species, temperature, energy, total dose and channeling effects.
Radiation damage theories are based on the assumption that a lattice atom struck by an energetic ion or recoiling target atom must receive a minimum amount of energy in the collision to be displaced from its...
