Nonlinear effects in defect production by atomic and molecular ion implantation

C David and CV Anto and M Dholakia and S Chandra and KGM Nair and BK Panigrahi and PS Raman and S Amirthapandian and G Amarendra and J Kennedy, JOURNAL OF APPLIED PHYSICS, 117, 014312 (2015).

DOI: 10.1063/1.4905175

This report deals with studies concerning vacancy related defects created in silicon due to implantation of 200 keV per atom aluminium and its molecular ions up to a plurality of 4. The depth profiles of vacancy defects in samples in their as implanted condition are carried out by Doppler broadening spectroscopy using low energy positron beams. In contrast to studies in the literature reporting a progressive increase in damage with plurality, implantation of aluminium atomic and molecular ions up to Al-3, resulted in production of similar concentration of vacancy defects. However, a drastic increase in vacancy defects is observed due to Al-4 implantation. The observed behavioural trend with respect to plurality has even translated to the number of vacancies locked in vacancy clusters, as determined through gold labelling experiments. The impact of aluminium atomic and molecular ions simulated using MD showed a monotonic increase in production of vacancy defects for cluster sizes up to 4. The trend in damage production with plurality has been explained on the basis of a defect evolution scheme in which for medium defect concentrations, there is a saturation of the as- implanted damage and an increase for higher defect concentrations. (C) 2015 AIP Publishing LLC.

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