Patterns have been observed on the surfaces of silicon epitaxial layers grown on annealed‐silicon substrates which had been implanted with arsenic at high doses and high dose rates. The patterns take the form of bands which lie parallel to the scanning direction of the ion beam and which contain a large density of pits. X‐ray topography reveals that the bands are present immediately after the slice had been annealed and the band contrast is sensitive to the diffraction conditions employed. Transmission electron microscopy shows that the bands contain a high density of dislocation loops, as well as the pits which always contain a small precipitate at their center. These results are discussed in terms of temperature variations in the slice during the implantation process which lead to inhomogeneities in the damage and impurity distribution.