Cryotransfer transmission electron microscopy experiment of low-temperature 14 MeV-neutron-irradiated aluminium

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Abstract
Cryotransfer transmission electron microscopy (TEM) was applied to examine the defect structure created by displacement collision cascades in a thin foil A1 specimen which was irradiated at 20 K with 14MeV neutrons to a dose of 1.8 × 1021 neutrons m−2. No visible defect clusters were found in the as-irradiated specimen or after isochronal anneals to 323K. The results presented here are consistent with a nascent defect structure consisting of submicroscopic interstitialtype clusters, single vacancies and submicroscopic vacancy-type clusters. Subthreshold (100kV) electron illumination, however, induced the formation of TEM visible defect clusters at 150K. 91% of these TEM-created visible defect clusters in the as-irradiated specimen were interstitial type, and all the TEM-created visible clusters in the specimen isochronally annealed at 273 K were vacancy type. The growth of interstitial-type defect clusters is the result of the production of migrating interstitial atoms by the decomposition of submicroscopic interstitialtype clusters, and that of vacancy-type defect clusters is attributed to the electron-radiation-induced diffusion of single vacancies. Comparisons with other cryotransfer TEM experiments are also presented.