Electron-beam (E-beam) induced reduction has emerged as a technology for the rapid preparation of scalable metallic nanodots. Under a high energy electron bombardment in scanning electron microscopy or transmission electron microscopy, various metallic ions from an aqueous solution are reduced and self-aggregated into metallic nanodots on different host materials. The self-aggregated Ag nanodots prepared at an E-beam voltage of 80 kV exhibit variances in size deviation (sigma(D)/D) of 13.6% and in displacement deviation (sigma(X)/X) of 60%. By greatly increasing the E-beam voltage from 3 to 120 kV, the size deviation of the Ag nanodots increases from 1.7 to 7.3 nm, which is mainly attributed to the damage effect and to regrowth at the high accelerating voltage bombardment. The reduction of Cu and Fe nanodots is also demonstrated at an E-beam voltage of 80 kV, indicating a sigma(D)/D of 11.7% and a sigma(X)/X of 58.7%. The metallic nanodot diameter of 16 +/- 1.9 nm on the carbon nanowires is smaller than that on the carbon fiber (30 +/- 3.1 nm), as compared to other geometric host matrices. Furthermore, the results reveal that the nanodot size is precisely confined by decreasing the geometric scale of the host material to a submicrometer range.