Probing the strain field and structural variation in shock-produced amorphous silicon by scanning nano-probe electron diffraction

Shock-induced amorphization can occur when crystalline solids are uniaxially strained in an extremely short time scale. This phenomenon also opens a new door for prototyping the exotic amorphous structures when the conventional methods failed. Taking silicon as an example, we have recovered its amorphous phase from laser shock compression experiments and illustrated the formation mechanisms by both experiments and simulations. However, one missing information is whether the amorphous silicon produced by shock wave is fully relaxed, i.e. are they structurally different than the amorphous structure produced by other techniques such as chemical vapor deposition. We use a newly developed scanning nano-probe electron diffraction technique to tackle this question. A nanometer-sized electron probe is focused onto and rastering over the electron-transparent sample and simultaneously, convergent beam electron diffraction patterns at each pixel are collected, which can be used to compute strain distribution of the region of interest. The strain field in the vicinity of the amorphous band and the radial distribution function within the amorphous domain will be discussed. A tremendous amount of structural variation can be found even within the amorphous domain.