The phenomenon of swelling (surface expansion) in low-energy self-ion implanted Si was investigated using atomic force microscopy and transmission electron microscopy, for a wide range of fluence and post-implantation annealing conditions. The swelling height in excess to that contributed by implanted ions showed approximately a cube root dependence on the Si+-ion fluence. Post-implantation annealing exhibited a marked

reduction in the swelling at 650C. Both the fluence dependence and the annealing characteristics of the excess swelling suggested the involvement of vacancy clusters in the amorphous layer. It was proposed that the excess swelling in low-energy implanted Si resulted from the migration and segregation of the displaced Si atoms from the bulk to the surface leaving behind corresponding vacancies in the lattice. It was assumed that, during irradiation, the interstitials were mobile even in the damaged layer. From the measured swelling, a density reduction of about 3.1% was estimated for the amorphous phase with respect to the crystalline phase.

Mechanism of Swelling in Low-Energy Ion-Irradiated Silicon. P.K.Giri, V.Raineri, G.Franzò, E.Rimini: Physical Review B, 2002, 65[1], 012110 (4pp)