Low current MeV Au²⁺ ion-induced amorphization in silicon: rutherford backscattering spectrometry and transmission electron microscopy study

Abstract

The amorphization due to MeV Au²⁺ ion implantation in Si(1 1 1) has been studied using Rutherford backscattering spectrometry/channeling (RBS/C) and transmission electron microscopy (TEM) methods. 1.5 MeV Au²⁺ ions were implanted into Si(1 1 1) substrates at various fluences at low currents (0.02-0.04μA cm^-2) while the samples were kept at room temperature. The RBS/C results for as-implanted specimen shows the onset fluence for amorphization to be ≈5× 10¹³ ions cm^-2 which is much lower than the fluence reported earlier. Selected area diffraction (TEM) for a sample implanted at a of 1×10¹⁴ ions cm^-2 confirms the occurrence of the amorphization. Earlier, amorphization studies by Alford and Theodore, using 2.4 MeV gold ions in silicon (1 0 0) reported a threshold fluence of 1.8×10¹⁵ ions cm^-2 for amorphization when the implantation was carried out at higher currents (0.2-5 μ A cm^-2) [J. Appl. Phys. 76 (1994) 7265]. The nuclear energy loss (S_n) for 1.5 MeV gold ions in silicon is ≈13% greater than the value for 2.4 MeV and cannot be the sole reason for lower threshold fluence for the amorphization. The amorphization at a relatively lower fluence for the low current implantations could be possible due to reduction in the dynamical annealing effects.