During implantation the incident ions interact with stable atoms of the target crystal lattice and energy is transfered to the target atom. If the transfered energy exceeds the binding energy of the solid atom, it is removed from its lattice position and a mobile recoil is generated. The produced recoil penetrates deeper into the target and generates further recoils.
Each recoil event creates one vacancy at the point from where the atom is displaced and an interstitial at the point where it comes to rest. Thus an equal number of interstitals and vacancies (known as Frankel pairs) is created during this process.
For each dopant ion entering the silicon crystal the point defect concentration consists of the number of residual Frankel pairs plus one interstitial. Essentially, all the interstitials and vacancies produced, annihilate in the early stages of the anneal, leaving only a dose of interstitials due to extra dopant ions introduced into the lattice. This distribution is known as plus-one distribution.
Point-defect diffusion models based on the plus-one distribution were succesuffuly applied for the microscopic explanation of the energy dependence of transient enhanced diffusion (TED) .