Resonance vibration of amorphous SiO2 nanowires driven by mechanical or electrical field excitation

In this work, we have used the mechanical resonance method to determine the bending modulus of amorphous SiO2 nanowires and to study an electron charge trapping effect that occurs in these nanowires. For uniform amorphous nanowires having diameter ∼100 nm and length over 10 μm, the fit modulus values cluster near 47 GPa; this value is lower than the commonly accepted value of ∼72 GPa for fused silicon oxide (glass) fibers. For some SiO2 nanowires, we observed up to three closely spaced resonances that are a result of the nanowire anisotropy. We have compared the resonance vibration of nanowires driven by mechanical and also ac electrical field loading. All of the measurements were done inside the chamber of a scanning electron microscope where the nanowires were under bombardment of a flux of ∼3 keV energy electrons. By watching the interaction between the ac electrical field and exposed nanowire when driven at resonance frequency, we have observed significant charge trapping in the nanowires. The combination of charge trapping and decay time was nonuniformly distributed along the nanowire. This suggests a nondestructive method that can be used for studying defects in certain types of nanostructures.