Defect formation in silicon implanted with ∼1 MeV/nucleon ions

Defect formation processes in silicon implanted with ∼1 MeV/nucleon boron, oxygen, and argon ions have been studied using microhardness and Hall effect measurements. The results indicate that ion implantation increases the surface strength of silicon single crystals owing to the formation of electrically inactive interstitials through the diffusion of self-interstitials from the implantation-damaged layer to the silicon surface. The radiation-induced surface hardening depends significantly on the nature of the ion, its energy, and the implant dose. In the case of low-Z (boron) ion implantation, the effect had a maximum at an implant dose of ∼5 × 1014 cm−2, whereas that for O+ and Ar+ ions showed no saturation even at the highest dose reached, 1 × 1016 cm−2. When the ion energy was increased to ∼3 MeV/nucleon (210-MeV Kr+ ion implantation), we observed an opposite effect, surface strength loss, due to the predominant generation of vacancy-type defects.