*Review* **Control and Modification of Nanostructured Materials by Electron Beam Irradiation**

**Shun-Ichiro Tanaka**

Micro System Integration Center (µSIC), Tohoku University, Aramaki, Sendai 980-0845, Japan; shunichiro.tanaka.d2@tohoku.ac.jp

**Abstract:** I have proposed a bottom-up technology utilising irradiation with active beams, such as electrons and ions, to achieve nanostructures with a size of 3–40 nm. This can be used as a nanotechnology that provides the desired structures, materials, and phases at desired positions. Electron beam irradiation of metastable θ-Al2O<sup>3</sup> , more than 10<sup>19</sup> e/cm<sup>2</sup> s in a transmission electron microscope (TEM), enables the production of oxide-free Al nanoparticles, which can be manipulated to undergo migration, bonding, rotation, revolution, and embedding. The manipulations are facilitated by momentum transfer from electrons to nanoparticles, which takes advantage of the spiral trajectory of the electron beam in the magnetic field of the TEM pole piece. Furthermore, onion-like fullerenes and intercalated structures on amorphous carbon films are induced through catalytic reactions. δ-, θ-Al2O<sup>3</sup> ball/wire hybrid nanostructures were obtained in a short time using an electron irradiation flashing mode that switches between 10<sup>19</sup> and 10<sup>22</sup> e/cm<sup>2</sup> s. Various α-Al2O<sup>3</sup> nanostructures, such as encapsulated nanoballs or nanorods, are also produced. In addition, the preparation or control of Pt, W, and Cu nanoparticles can be achieved by electron beam irradiation with a higher intensity.

**Keywords:** electron irradiation; excited reaction field; transmission electron microscope; nanomaterials; manipulation; nanostructure; Al; Al2O<sup>3</sup>
