Ion Implantation and Synthesis of Materials - Studium

7.5 Ion Damage Energy 83It should be noted that the damage energy of a PKA with energy E, ν (E), isclosely related to the PKA’s total nuclear stopping. This can be expressed as∫R Sn ( E )d xwhere R is the PKA range. In general, the PKA damage energy is alwaysapproximately 20–30% smaller than the total nuclear stopping. This differencearises because the PKA loses some of its kinetic energy to electronic excitationswhile traveling to the end of its range.7.5 Ion Damage EnergyIn radiation damage experiments, the damage density deposited in the target iscontrolled by the ion’s energy and mass. The calculated reduced damage energy,ν p (ε), resulting from energetic ions in silicon and germanium is presented inFig. 7.4, along with experimental data as a function of reduced energy. The dashedline corresponds to the situation in which all the incident energy is assumed to begoing into nonionizing (nuclear) processes. The data indicates that the calculatedν p (ε) relation derived for M 1 = M 2 holds approximately for M 1 ≠ M 2 . Note thatbelow ε ≈ 3 and for M 1 ≥ M 2 , more than half the incident energy is available fordisplacement processes. From Fig. 7.4, the damage energy in reduced notation canbe approximated asν ( ε) ≅ 0.8ε forε< 1 and Z > 5(7.6)p 1To convert to ν p (ε) values into laboratory damage energy ν p (E), we will makeuse of the relationshipν ( ε)/ ε = ν ( E)/Eppwhich allows us to rewrite (7.6) asν p ( E)≅ 0.8E(7.7)Table 7.1 gives calculated values for the total amount of energy, ν p (E 0 ), lost innuclear collisions by energetic Group IV ions incident on silicon and germanium.