Amorphization processes in ion implanted Si: Ion species effects

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Abstract
Amorphization processes in Si+, P+, Ge+, and As+ ion implanted Si have been investigated using Raman spectroscopy and Rutherford backscattering spectrometry combined with computer simulations of the initial ion-beam-induced damage profiles. The crystal Si Raman peak at 520 cm−1 decreased, broadened, and shifted toward lower wave numbers as the doses were increased from 2 to 8×1014 cm−2 for both 100 keV Si+ and P+, and from 0.6 to 1.8×1014 cm−2 for both 175 keV Ge+ and As+. The maximum peak shifts prior to amorphization were ∼−6 cm−1 in all the samples suggesting that lattice softening is responsible for amorphization in all the ion species cases. The effects of ion species were analyzed by scaling the ion dose using calculated displacements per target atom (DPA). It was found that larger DPA was necessary to obtain the same peak shifts in the Si+ and P+ than in the Ge+ and As+ implantation cases. The results suggest that amorphization is controlled by divacancies generated by ion bombardment.