  The nanoinstability of single crystal Si nanowire under focused electron beam
irradiation was in-situ investigated at room temperature by transmission
electron microscopy technique. It was observed that the Si nanowire amorphized
preferentially from the surface towards the center with the increasing of
electron dose. In contrast, in the center of the Si nanowire the amorphization
seemed non-uniform and much more difficult accompanying with rotation of
crystal grains and compression of d-spacing. Such a selectively preferential
amorphization as athermally induced by the electron beam irradiation can be
well accounted for by our proposed concepts of nanocurvature effect and
energetic beam-induced athermal activation effect, while the classical knock-on
mechanism and the electron beam heating effect seem inadequate to explain these
processes. Furthermore, the findings revealed the difference of amorphization
between Si nanowire and Si film under focused electron beam irradiation. Also,
the findings have important implications for nanostability and nanoprocessing
of future Si nanowire-based devices.
