Nanostructuring via ion beam irradiation on Ge substrates can be activated by ion beam sputtering and self-organization of point defects (SPDs). For evaluating the mechanism by which these formation factors compete, we studied nanostructuring on Ge substrates subjected to sputtering-dominant conditions, viz., the low-energy ion incidence. A focused ion beam was used for nanostructuring and adjusting an angle of ion incidence to the surface normal range of 0°–60°. The ions accelerated for irradiation were Ga+ with an incident energy of 5–30 keV, and the fluence and beam current were 1 × 1020–1 × 1022 ions/m2 and 0.5–16.7 nA, respectively. Based on the results of serial experiments, the incident energy of 5 keV can be the threshold for the activation of nanostructuring by SPD.

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