Radiation-induced mobility of small defect clusters in covalent materials

TL;DR

This study demonstrates that small defect clusters in bulk SiC can become mobile at room temperature due to electron radiation, revealing a new radiation-induced diffusion mechanism observed through advanced microscopy techniques.

Contribution

The paper provides the first direct observation of radiation-induced mobility of defect clusters in bulk covalent materials using LAADF STEM and non-rigid registration.

Findings

Small defect clusters in SiC become mobile under electron radiation.

The mobility is driven by ballistic collisions between electrons and atoms.

This radiation-induced diffusion challenges existing understanding of defect behavior in irradiated materials.

Abstract

Although defect clusters are detrimental to electronic and mechanical properties of semiconductor materials, annihilation of such clusters is limited by their lack of thermal mobility due to high migration barriers. Here, we find that small clusters in bulk SiC (a covalent material of importance for both electronic and nuclear applications) can become mobile at room temperature under the influence of electron radiation. So far, direct observation of radiation-induced diffusion of defect clusters in bulk materials has not been demonstrated yet. This finding was made possible by low angle annular dark field (LAADF) scanning transmission electron microscopy (STEM) combined with non-rigid registration technique to remove sample instability, which enables atomic resolution imaging of small migrating defect clusters. We show that the underlying mechanism of this athermal diffusion is ballistic collision between incoming electrons and cluster atoms. Our findings suggest that defect clusters may be mobile under certain irradiation conditions, changing current understanding of cluster annealing process in irradiated covalent materials.