A study of radiation damage resulting from the implantation of molecular ions, using electron microscopy techniques

The nature and the form of the radiation damage resulting from the implantation of molecular ions has been studied using electron microscopy techniques. Di- and tri-atomic molecular ions have been implanted and comparisons made with the result for atomic ions. The experiment has been devised to determine if separate cascades are visible in the electron microscope images and, if so, what information can be obtained about their nature and relative separation. The electron microscope images of the radiation-damage cascades, which result from the implantation of atoms into single-crystal metal specimens, have been extensively studied by many workers and this information is applicable to the examination of the radiation damage of molecular ions. The conditions used for this experiment entail the creation of approximately one defect image for each incident atomic ion. The defects seen are predominantly vacancy loops. The ion beam must satisfy stringent purity requirements and the techniques used to ensure the purity of the molecular ion beam are described in detail. Preliminary results have been obtained for the implantation of antimony into silver and copper crystals. Multiple defect images have been observed in the case of implanted molecular ions, supporting the contention that the atoms of the molecule become dissociated and form individual collision cascades. This technique can, consequently, be used to give information relating to the lateral displacement of implanted ions. (author)