Field ion microscope examination of heavy ion radiation damage in iridium

Abstract Results of experiments in which iridium field ion specimens were bombarded with 20-100 kev heavy ions are presented. Specimens were bombarded in situ in the microscope at 78°k and room temperature to doses in the range 1011-1016 ions/cm2. After room temperature irradiations field evaporation revealed radiation damage predominantly in the form of compact vacancy clusters and perfect dislocation loops. After irradiation at 78°k single vacancies, dispersed and compact clusters and dislocation loops were observed. The size of the loops and compact clusters was independent of ion dose and independent of incident ion energy above about 60 kev. Above this energy the mean cluster diameter was 25 Å whilst at lower ion energies many smaller vacancy aggregates were formed. The dispersed clusters contained about 100 vacancies in a concentration of 1-20%. Most of these clusters remained dispersed after annealing at room temperature. Results of observing heavy ion damage iridium foils by transmission electron microscopy are briefly described together with preliminary annealing results.