  An intriguing athermal uniform elongation and accelerated radial shrinkage in
amorphous SiOx nanowire (a-SiOx NW) as purely induced by uniform electron beam
(e-beam) irradiation were in-situ investigated in transmission electron
microscope. It was observed that at room temperature the straight and uniform
a-SiOx NW demonstrated a uniform plastic elongation (without any external
tensile pulling) and a corresponding uniform radial shrinkage. According to a
new model taking into account the NW nanocurvature over its surface as well as
the beam-induced athermal activation, a kinetic relationship between the
shrinking radius and the irradiation time was established. The fitting results
demonstrated that a curvature-dependent surface energy at the nanoscale
(so-called nanocurvature effect) much higher than that predicted from the
existing theories is exerted on the elongation and shrinkage of the NW. At the
same time, the so-induced plastic flow of massive atom and surface diffusion of
atom presented as well a further direct experimental evidence for our predicted
soft mode and instability of atomic vibration as induced under energetic beam
(including e-beam) irradiation in amorphous materials The study has important
implications for the nanoprocessing or nanostability of future NW-based
structures or devices. More importantly, it further demonstrates that the
nanocurvature effect and the beam-induced atomic vibration soft mode and
instability effect, which have been normally neglected or inadequately taken
into account in the current literature, are universal concepts and applicable
to explanation of energetic beam-induced nanoinstability or nanoprocessing of
low dimensional nanostructure in general.
