3.1.3. Generation of Nanoslits and Nanoparticles

3.1.3. Generation of Nanoslits and Nanoparticles Successive sputtering due to electron irradiation induces thinning of the specimen, finally leading to the penetration of thin foils from the exit to the incident surfaces by nanogrooves and nanoholes. Figure 6a–d show the development of the nanostructure for an Au(011) foil irradiated with 400 keV electrons along [011] at 95 K. We can see that the width of nanogrooves in the pattern, which appeared in the initial stage of irradiation does not change significantly under irradiation. In Figure 6c, the penetration occurred in an area near the beam center, and then, nanoslits were formed as denoted by an arrow. In Figure 6d, the nanoslit denoted by the arrow in Figure 6c is closed, making the nanoslits beside it wider. This means the nanoslit became unstable under irradiation, probably due Successive sputtering due to electron irradiation induces thinning of the specimen, finally leading to the penetration of thin foils from the exit to the incident surfaces by nanogrooves and nanoholes. Figure 6a–d show the development of the nanostructure for an Au(011) foil irradiated with 400 keV electrons along [011] at 95 K. We can see that the width of nanogrooves in the pattern, which appeared in the initial stage of irradiation does not change significantly under irradiation. In Figure 6c, the penetration occurred in an area near the beam center, and then, nanoslits were formed as denoted by an arrow. In Figure 6d, the nanoslit denoted by the arrow in Figure 6c is closed, making the nanoslits beside it wider. This means the nanoslit became unstable under irradiation, probably due to its small size.

to its small size. The self-organized pattern of nanoslits is seen to be determined in the initial stage of irradiation. Nanogrooves tend to develop along [100] direction, finally forming nanowires between the grooves. This method of the formation of nanowires using electron-beam irradiation in an electron microscope has been used to investigate characteristic nanostructures, which can appear in small size such as nanowires stabilized by the hcp lattices of the sur-The self-organized pattern of nanoslits is seen to be determined in the initial stage of irradiation. Nanogrooves tend to develop along [100] direction, finally forming nanowires between the grooves. This method of the formation of nanowires using electron-beam irradiation in an electron microscope has been used to investigate characteristic nanostructures, which can appear in small size such as nanowires stabilized by the hcp lattices of the surfaces [25] and the ones consisting of helical atom rows coiled round the wire axis [26].

faces [25] and the ones consisting of helical atom rows coiled round the wire axis [26]. Figure 7a,b, respectively, show nanostructures of Au(001) foils irradiated with 1.25 MeV electrons at 110 K along [001] and [111] directions. The structures near the beam center denoted by X are seen to be pierced with a lot of holes produced by the irradiation and nanoparticles connected to each other. The shape of nanoparticles seen in Figure 7a,b reflects the self-organized nanostructures seen in Figure 4a,c, respectively. This method Figure 7a,b, respectively, show nanostructures of Au(001) foils irradiated with 1.25 MeV electrons at 110 K along [001] and [111] directions. The structures near the beam center denoted by X are seen to be pierced with a lot of holes produced by the irradiation and nanoparticles connected to each other. The shape of nanoparticles seen in Figure 7a,b reflects the self-organized nanostructures seen in Figure 4a,c, respectively. This method of particle formation may be useful for investigating the dependence of the characteristics of nanosized particle on size due to two advantages; one is the continuous preparation of a fresh surface under sputtering, and the other is the unique method of particle generation from thin foils.

from thin foils.

*Quantum Beam Sci.* **2021**, *5*, x FOR PEER REVIEW 6 of 20

of particle formation may be useful for investigating the dependence of the characteristics of nanosized particle on size due to two advantages; one is the continuous preparation of a fresh surface under sputtering, and the other is the unique method of particle generation

of particle formation may be useful for investigating the dependence of the characteristics of nanosized particle on size due to two advantages; one is the continuous preparation of a fresh surface under sputtering, and the other is the unique method of particle generation

**Figure 6.** Development of nanostructure on the exit surface of an Au(011) foil irradiated with 400 keV electrons along [011] direction at 95 K: (**a**) 300 s; (**b**) 480 s; (**c**) 600 s; (**d**) 750 s. **Figure 6.** Development of nanostructure on the exit surface of an Au(011) foil irradiated with 400 keV electrons along [011] direction at 95 K: (**a**) 300 s; (**b**) 480 s; (**c**) 600 s; (**d**) 750 s. **Figure 6.** Development of nanostructure on the exit surface of an Au(011) foil irradiated with 400 keV electrons along [011] direction at 95 K: (**a**) 300 s; (**b**) 480 s; (**c**) 600 s; (**d**) 750 s.

[001] direction, 1500 s; (**b**) [111] direction, 1700 s. The structures near the beam center are seen to be nanoparticles connected to each other and depend on the irradiation direction. **Figure 7.** Nanostructures of Au(001) foils irradiated with 1.25 MeV electrons at 110 K along: (**a**) [001] direction, 1500 s; (**b**) [111] direction, 1700 s. The structures near the beam center are seen to be nanoparticles connected to each other and depend on the irradiation direction. **Figure 7.** Nanostructures of Au(001) foils irradiated with 1.25 MeV electrons at 110 K along: (**a**) [001] direction, 1500 s; (**b**) [111] direction, 1700 s. The structures near the beam center are seen to be nanoparticles connected to each other and depend on the irradiation direction.

**Figure 7.** Nanostructures of Au(001) foils irradiated with 1.25 MeV electrons at 110 K along: (**a**)
