Polyatomic-Ion Implantation Damage in Silicon

We have investigated the number, $N_d$, of displaced lattice atoms in room-temperature implantation in Si of polyatomic-carbon-ion beams (${{\mathrm{C}}_n}^{+}$ and ${\mathrm{C}}_{n-x}{{\mathrm{O}}_x}^{+}$) for several values of $n$, using the backscattering-channeling-effect technique. For each ion species the same energy (8.8 keV) per carbon and the same atomic fluence and flux were used. $N_d$ increases rapidly with increasing $n$, indicating that the deposited-energy density within the collision cascade is a key factor in determining how much damage is created and retained.