In-situ TEM observation of preferential amorphization in single crystal Si nanowire

TL;DR

This study used in-situ TEM to observe how single crystal Si nanowires amorphize preferentially from the surface inward under electron beam irradiation, revealing unique nanostability behaviors relevant for nanodevice processing.

Contribution

It introduces a nanocurvature and athermal activation model to explain surface-preferential amorphization, challenging classical mechanisms like knock-on effects.

Findings

Surface amorphization progresses with electron dose

Central regions show non-uniform amorphization and grain rotation

Differences observed between Si nanowire and film under irradiation

Abstract

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.