3.2.3 Implantation

This chapter discusses direct implantation of α-particles or He³ ions, which is an effective means of introducing helium into solids and is increasingly employed mainly in basic investigations of helium effects. At very low injection energies E<E_d, the introduction of helium is "gentle", i.e. occurs without simultaneous production of displacement damage. Numerical values for threshold energy E_d and the pertinent projected ranges for a number of metals are tabulated. The threshold energy for creating displacement damage during the implantation of He³ and He⁴, respectively, into metals such as Al, V, Fe, Ni, Nb, Mo, Pd, Ag, Ta, W, Pt, Au are tabulated. Subthreshold or "gentle" helium implantation is necessary for studying the behaviour of helium atoms on interstitial positions in metal lattices. Such investigations are sometimes rendered difficult by the shallow depths where the helium is deposited.