In situ measurements of non-equilibrium positron state defects during He irradiation in Si

Radiation-induced property changes in materials originate with the energy transfer from an incoming particle to a lattice and the displacement of the atoms from their original location. The displaced atoms can, depending on conditions, lead to the formation of extended defects such as dislocation loops, voids, or precipitates. The non-equilibrium defects created during damage events and that determine the extent of these larger defects are a function of dose rate, material, and temperature. However, these defects are transient and can only be probed indirectly. This work presents direct experimental measurements and evidence of non-equilibrium vacancy formation during irradiation, where in-situ positron annihilation spectroscopy was used to prove the generation of non-equilibrium defects in silicon.