A silicon crystal slice of 0.2 mm thickness is implanted with 28 ke V phosphorus ions at a dose of 2 × 1015 cm−2. Both thermal neutron and X‐ray double crystal diffractometry and X‐ray topography demonstrate the existence of a distorted crystal region near the amorphous layer. The mean atomic distance is increased by 3.1 × 10−5 and 1.5 × 10−5 perpendicular and parallel to the implanted layer, respectively. By isochronal annealing in the temperature range of 400 to 1000 °C radiation defects recover, the implanted layer is recrystallized, and at higher temperatures crystal lattice defects are generated.