Abstract: Si wafer (N-type, P-doped, 1kΩ.cm) is implanted with ~(111)In by nuclearreaction recoils. Thermal annealing behavior of In in Si is studied by the timedifferential perturbed angular correlation technique. It is found that after 798℃annealing 55% of the In atoms occupy substitutional lattice sites in Si with theremainder in perturbed sites.