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Atom Diffusion and Evaporation of Free-Ended Amorphous SiO x Nanowires: Nanocurvature Effect and Beam-Induced Athermal Activation Effect

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ABSTRACT

Arresting effects of nanocurvature and electron beam-induced athermal activation on the structure changes at nanoscale of free-ended amorphous SiOx nanowire were demonstrated. It was observed that under in situ uniform electron beam irradiation in transmission electron microscope, the near surface atoms at the most curved free end of the nanowire preferentially vaporized or diffused to the less curved wire sidewall. The processing resulted in an intriguing axial shrinkage and an abnormal radial expansion of the wire. It was also observed that with the beam energy deposition rate being lowered, although both the diffusion and the evaporation slowed down, the processing transferred from an evaporation-dominated status to a diffusion-dominated status. These results are crucial not only to the fundamental understanding but also to the technical controlling of the electron beam-induced structure change at nanoscale or nanoprocessing of low dimensional nanostructures.

Electronic supplementary material: The online version of this article (doi:10.1186/s11671-016-1735-8) contains supplementary material, which is available to authorized users.

No MeSH data available.


Sequences of in situ TEM micrographs showing the typical structural evolution of the free-ended amorphous SiOx nanowires during uniform irradiation of e-beam with different current densities respectively at a 1 A/cm2 and b 10 A/cm2
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Fig1: Sequences of in situ TEM micrographs showing the typical structural evolution of the free-ended amorphous SiOx nanowires during uniform irradiation of e-beam with different current densities respectively at a 1 A/cm2 and b 10 A/cm2

Mentions: Figure 1 shows the typical in situ structural evolution of amorphous SiOx nanowire segments with single free ends during uniform irradiations of e-beam with different current densities respectively at (a) 1 A/cm2 and (b) 10 A/cm2. Before the irradiation, both the SiOx nanowires as shown in A of Fig. 1a, b represented a well-defined straight, columned segment of wire with clean and smooth surface, uniform diameter, and sharp cut edge at the free end. After an initial period of irradiation (respectively at 640 s in Fig. 1a and at 40 s in Fig. 1b), the sharp cut edges became round, and the free ends showed hemisphere shapes. Meanwhile, Fig. 1a, b demonstrated a preferential axial shrinkage from the free end and an abnormal increase of wire diameter which were also observed throughout the remaining irradiation. Normally, such increase of wire diameter or radial growth was limited within the wire segment near the free end and thus cannot be uniform along the entire wire or even the irradiated wire segment. Furthermore, both the axial shrinking and the radial increasing in Fig. 1b were obviously much faster than those in Fig. 1a with the increased beam current density (for axial shrinking rate 5.7 × 10−1 vs. 3.5 × 10−2 nm/s; for radial increasing rate 6.3 × 10−2 vs. 6.2 × 10−3 nm/s, see Additional file 1: Supporting Information 1). The similar irradiations on different wire segments under different beam current densities were repeated several times, and the structural evolution were essentially the same.Fig. 1


Atom Diffusion and Evaporation of Free-Ended Amorphous SiO x Nanowires: Nanocurvature Effect and Beam-Induced Athermal Activation Effect
Sequences of in situ TEM micrographs showing the typical structural evolution of the free-ended amorphous SiOx nanowires during uniform irradiation of e-beam with different current densities respectively at a 1 A/cm2 and b 10 A/cm2
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120135&req=5

Fig1: Sequences of in situ TEM micrographs showing the typical structural evolution of the free-ended amorphous SiOx nanowires during uniform irradiation of e-beam with different current densities respectively at a 1 A/cm2 and b 10 A/cm2
Mentions: Figure 1 shows the typical in situ structural evolution of amorphous SiOx nanowire segments with single free ends during uniform irradiations of e-beam with different current densities respectively at (a) 1 A/cm2 and (b) 10 A/cm2. Before the irradiation, both the SiOx nanowires as shown in A of Fig. 1a, b represented a well-defined straight, columned segment of wire with clean and smooth surface, uniform diameter, and sharp cut edge at the free end. After an initial period of irradiation (respectively at 640 s in Fig. 1a and at 40 s in Fig. 1b), the sharp cut edges became round, and the free ends showed hemisphere shapes. Meanwhile, Fig. 1a, b demonstrated a preferential axial shrinkage from the free end and an abnormal increase of wire diameter which were also observed throughout the remaining irradiation. Normally, such increase of wire diameter or radial growth was limited within the wire segment near the free end and thus cannot be uniform along the entire wire or even the irradiated wire segment. Furthermore, both the axial shrinking and the radial increasing in Fig. 1b were obviously much faster than those in Fig. 1a with the increased beam current density (for axial shrinking rate 5.7 × 10−1 vs. 3.5 × 10−2 nm/s; for radial increasing rate 6.3 × 10−2 vs. 6.2 × 10−3 nm/s, see Additional file 1: Supporting Information 1). The similar irradiations on different wire segments under different beam current densities were repeated several times, and the structural evolution were essentially the same.Fig. 1

View Article: PubMed Central - PubMed

ABSTRACT

Arresting effects of nanocurvature and electron beam-induced athermal activation on the structure changes at nanoscale of free-ended amorphous SiOx nanowire were demonstrated. It was observed that under in situ uniform electron beam irradiation in transmission electron microscope, the near surface atoms at the most curved free end of the nanowire preferentially vaporized or diffused to the less curved wire sidewall. The processing resulted in an intriguing axial shrinkage and an abnormal radial expansion of the wire. It was also observed that with the beam energy deposition rate being lowered, although both the diffusion and the evaporation slowed down, the processing transferred from an evaporation-dominated status to a diffusion-dominated status. These results are crucial not only to the fundamental understanding but also to the technical controlling of the electron beam-induced structure change at nanoscale or nanoprocessing of low dimensional nanostructures.

Electronic supplementary material: The online version of this article (doi:10.1186/s11671-016-1735-8) contains supplementary material, which is available to authorized users.

No MeSH data available.