The annealing effects of crystalline silicon (Si) implanted with argon (Ar) ions at a dose of 2×10 16 Ar + /cm 2 at room temperature and subsequently annealed at 400–1100°C for 30min were investigated. The samples were analyzed by transmission electron microscopy and Raman spectroscopy. Before and after annealing up to 600°C, an amorphous layer is formed but Ar bubbles are not observed in the damage layer. After annealing at 800°C, argon bubbles are observed together with extended defects. The damage layer evolves into a polycrystalline structure. After annealing at 1100°C; exfoliation occurs on the sample surface, and microtwin lamellas form in the damage layer. Raman scattering revealed that a strong recrystallization occurs from 600°C to 800°C. The results were compared with the case of helium implantation, with particular focus on bubble formation mechanisms.