Radiation-induced mobility of small defect clusters in covalent materials

Although defect clusters are detrimental to the 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 covalentmaterial 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 yet been demonstrated. This finding was made possible by low-angle annular dark-field scanning transmission electron microscopy combined with a nonrigid 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 a ballistic collision between incoming electrons and cluster atoms. Our findings suggest that defect clusters may be mobile under certain irradiation conditions, changing the current understanding of the cluster annealing process in irradiated covalent materials.