Amorphization processes in electron and/or ion-irradiated silicon

Amorphization has been studied in electron- ($e^{\mathrm{-}}$) and ion-irradiated Si. Si irradiated at <10 K with 1.0- or 1.5-MeV ${\mathrm{Kr}}^{+}$ became amorphous at <0.4 displacement per atom (dpa), whereas Si irradiated at 10 K to a fluence of ≊14 dpa of 1-MeV $e^{\mathrm{-}}$ in an electron microscope failed to amorphize. However, Si subjected to a simultaneous $e^{\mathrm{-}}$ and ${\mathrm{Kr}}^{+}$ in situ irradiation, at <10 K, to a ${\mathrm{Kr}}^{+}$ fluence of 1.5 dpa retained crystallinity. The critical ratio, at <10 K, of the $e^{\mathrm{-}}$ to ${\mathrm{Kr}}^{+}$ ion displacement rates to maintain a degree of crystallinity is ≊0.5. Atomistic models for these phenomena are presented.