Cluster-ion bombardment studies to reveal the amorphization mode in strained Si _0.8Ge _0.2

Radiation damage caused by cluster ions of different sizes is predicted to be distinctly different if materials follow disparate phenomenological models of amorphization, namely overlap and direct amorphization methods. Determination of an amorphization model for a crystalline solid can be accomplished based on its radiation response to cluster sizes of bombarding ions. In the present study, we use this approach and apply it to study radiation damage in Si _0.8Ge _0.2 caused by Ag _n clusters with the number of atoms in a cluster, n, taking values from 1 to 4. The displacements measured by using channeling Rutherford backscattering spectrometry show size-enhanced damage accumulation, which is in good agreement with the atomistic detail obtained by molecular dynamics simulations. Our studies suggest that strained SiGe, a material known to have poor radiation tolerance, follows the overlap model rather than the direct amorphization model.