Atomic resolution study of displacement cascades in ion-irradiated platinum

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Abstract
The field‐ion microscope technique has been employed to study, on an atomic scale, the vacancy structure of individual depleted zones (DZs) in platinum specimens which had been created by 20‐keV Kr+ ions. DZs are the final quiescent state of collision cascades. The irradiations were performed in situ at 60 K and the specimens were examined at this temperature by the pulse field‐evaporation technique. The following experimental quantities were determined for each DZ: (a) the absolute number of vacancies (ν); (b) the average diameter; (c) the average vacancy concentration based on ν and the actual volume filled by the vacancies; (d) the radial distribution function of the vacancies out to the ninth nearest‐neighbor; (e) the fraction of first‐nearest‐neighbor vacancies in clusters of size n; (f) the average depth (L) from the irradiated surface, measured along a direction parallel to the incident ion beam, at which each DZ was detected and its direction of elongation; and (g) the sputtering yield based on the number of vacancies detected in the near‐surface region (<5 Å thick). All of the measured quantities are compared with corresponding quantities extracted from either an analytical model or a Monte Carlo computer code (Transport of Ions in Matter—trim) of radiation damage. We demonstrate that it is possible to transform a microscopic spatial distribution of vacancies to a continuous radiation damage profile with atomic resolution.