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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.


Schematic illustration showing the directional surface diffusion and the preferential surface evaporation of atoms driven by nanocurvature effect: a free end with cut sharp edge case and b free end of hemisphere shape case
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Fig2: Schematic illustration showing the directional surface diffusion and the preferential surface evaporation of atoms driven by nanocurvature effect: a free end with cut sharp edge case and b free end of hemisphere shape case

Mentions: As illustrated in Fig. 2a, the starting nanowire shows a sharp cut edge at the free end, which is the most curved location relative to the cylindrical sidewall and the plane bottom. According to the nanocurvature effect of a nanowire, the most curved sharp cut edge is the most unstable location with the highest surface energy and the lowest energy barrier. So, under the activation of e-beam irradiation, the atoms at the sharp cut edge would migrate to the wire sidewall or bottom, or escape from the wire surface preferentially (see Fig. 2a) to minimize the total energy of the nanowire. As a consequence, the free end became round and smooth with a hemisphere shape of uniform positive surface nanocurvature finally (see A–C of Figs. 1a, b and 2a).Fig. 2


Atom Diffusion and Evaporation of Free-Ended Amorphous SiO x Nanowires: Nanocurvature Effect and Beam-Induced Athermal Activation Effect
Schematic illustration showing the directional surface diffusion and the preferential surface evaporation of atoms driven by nanocurvature effect: a free end with cut sharp edge case and b free end of hemisphere shape case
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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

Fig2: Schematic illustration showing the directional surface diffusion and the preferential surface evaporation of atoms driven by nanocurvature effect: a free end with cut sharp edge case and b free end of hemisphere shape case
Mentions: As illustrated in Fig. 2a, the starting nanowire shows a sharp cut edge at the free end, which is the most curved location relative to the cylindrical sidewall and the plane bottom. According to the nanocurvature effect of a nanowire, the most curved sharp cut edge is the most unstable location with the highest surface energy and the lowest energy barrier. So, under the activation of e-beam irradiation, the atoms at the sharp cut edge would migrate to the wire sidewall or bottom, or escape from the wire surface preferentially (see Fig. 2a) to minimize the total energy of the nanowire. As a consequence, the free end became round and smooth with a hemisphere shape of uniform positive surface nanocurvature finally (see A–C of Figs. 1a, b and 2a).Fig. 2

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.