The size, density and distribution of the clusters produced by Copper ions in Copper

Abstract

The precise mechanism by which the damage is produced in copper by energetic particles has not yet been elucidated. In order to throw some light on this problem, the quantity of damage produced by copper ion irradiation of copper has been studied in detail by means of transmission electron microscopy. Two irradiation directions were used : one was chosen such that the incident ions were not channelled; the other was <110>, a good channelling direction. In the former case, a 30 kev Cu⁺ ion produces about one defect cluster larger than 20 Å in diameter, and a 90 kev Cu⁺ produces three; the cluster size distributions are identical for the two energies, indicating similar formation mechanisms. In the case of the <110> irradiation direction, channelling reduces the number of 30 Å diameter clusters produced by a Cu⁺ ion by a factor of two, and the number of 60 Å diameter clusters by a factor of four. Such behaviour is in agreement with theoretical predictions. As would be expected, 30 kev Cu⁺ ions incident along a <110> direction produce a damaged layer which extends deeper into the crystal than that produced by Cu⁺ ions of the same energy but incident along a non-channelling direction.