Single crystals were bombarded with 140keV Ar ions to doses ranging from 5 x 1014 to 5 x 1016/cm2, and were investigated by using variable low-energy positron beams, Raman spectroscopy and ion channelling. The Doppler broadening lineshape S-parameter was found to exhibit a peak as a function of the positron beam energy, and a subsequent saturation behaviour in all of the bombarded samples. The peak damage occurred at a depth of 100nm. A positron diffusion model was used to deduce the depth profiles of positron-trapping defects. The results indicated that the nature of the open-volume defects was independent of the dose, and that the predominant defects were vacancy clusters that were larger than divacancies. Raman spectroscopic studies indicated that all of the bombarded samples were amorphized. Ion-channelling studies yielded thicknesses, of the amorphized layers, which were consistent with positron beam results. The present data indicated the presence of defects at depths which were far beyond the Ar-ion range.

Study of Argon Irradiation-Induced Defects and Amorphization in Silicon using a Positron Beam, Raman Spectroscopy and Ion Channelling G.Amarendra, G.V.Rao, A.K.Arora, K.G.M.Nair, T.R.Ravindran, K.Sekar, B.Sundarvel, B.Viswanathan: Journal of Physics - Condensed Matter, 1999, 11[30], 5875-87