Formation of the anomalous cellular structure in (100) GaSb with Sn ion-implantation at a low temperature is investigated by cross-sectional scanning electron microscopy, atomic force microscopy, and transmission electron microscopy. A fine structure consisting of many cells was formed on GaSb surface implanted by 60 keV Sn. The cell diameter and the thickness of the walls partitioning the cells were about 50 and 10 nm, respectively, which are almost constant in the range of the ion dose 4.0×1014–8.9×1014 ions/cm2. The depth of the cells increased linearly with increasing ion dose, from 100 nm in the sample implanted with a dose of 4.0×1014 ions/cm2 to 220 nm in that implanted with a dose of 8.9×1014 ions/cm2. From the experimental results, it is concluded that the development of the cellular structure originates in formation of the voids. An improved defect formation mechanism based on movement of the implantation-induced point defects is discussed.

The formation of Cu precipitates was investigated in two Fe-Cu binary model alloys irradiated at 573 K with fission neutrons at doses from 4 ϫ 10 −4 to 6 ϫ 10 −3 displacement per atom ͑dpa͒. Experimental positron annihilation results indicated that Cu precipitates were formed even after irradiation to 4 ϫ 10 −4 dpa. Microvoids formed and grew at the Cu precipitates upon irradiation from 4 ϫ 10 −4 to 3 ϫ 10 −3 dpa. These microvoids shrank and a prominent aggregation of Cu atoms occurred upon irradiation from 3 ϫ 10 −3 to 6 ϫ 10 −3 dpa. The formation processes of Cu precipitates and microvoids were simulated on the basis of a rate theory. The results indicate that Cu precipitates are formed first, follow by the generation of microvoids at the Cu precipitates as Cu cluster-vacancies complexes, which agree qualitatively with the experimental results.

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