Insights for void formation in ion-implanted Ge

The formation of voids in ion-implanted Ge was studied as a function of ion implantation energy and dose. (001) Ge substrates were self-implanted at energies of 20–300 keV to doses of 1.0 × 1013–1.0 × 1017 cm− 2. Transmission electron microscopy revealed clusters of voids just below the surface for implant energies ≤ 120 keV at a dose of 2.0 × 1015 cm− 2 and complete surface coverage for an implant energy of 130 keV and doses ≥ 1.0 × 1016 cm− 2. Void clusters did not change in size or density after isothermal annealing at 330 °C for 176 min. The initial void formation is discussed in terms of the vacancy clustering and “microexplosion” theories with a damage map detailing the implant conditions necessary to produce voids.