Study of low energy Si$_5^-$ and Cs$^-$ implantation induced amorphization effects in Si(100)

TL;DR

This study investigates how 25 keV Si$_5^-$ and Cs$^-$ ion implantation cause damage and amorphization in Si(100), revealing thresholds, damage saturation, and differences in defect accumulation using AFM and CRBS techniques.

Contribution

It provides new insights into damage growth thresholds, surface roughness evolution, and the effects of different ion species on amorphization in silicon.

Findings

Damage growth is nonlinear with a threshold fluence of 2.5×10^{13} ions/cm^2.

Surface roughness increases below threshold and saturates at higher fluence.

Cs$^-$ ions cause less defect accumulation compared to Si$_5^-$ ions at the same energy and fluence.

Abstract

The damage growth and surface modifications in Si(100), induced by 25 keV Si$_5^-$ cluster ions, as a function of fluence, $\phi$, has been studied using atomic force microscopy (AFM) and channeling Rutherford backscattering spectrometry (CRBS). CRBS results indicate a nonlinear growth in damage from which it has been possible to get a threshold fluence, $\phi_0$, for amorphization as $2.5\times 10^{13}$ ions-cm$^{-2}$. For $\phi$ below $\phi_0$, a growth in damage as well as surface roughness has been observed. At a $\phi$ of $1\times 10^{14}$ ions-cm$^{-2}$, damage saturation coupled with a much reduced surface roughness has been found. In this case a power spectrum analysis of AFM data showed a significant drop, in spectral density, as compared to the same obtained for a fluence, $\phi < \phi_0$. This drop, together with damage saturation, can be correlated with a transition to a stress relaxed amorphous phase. Irradiation with similar mass Cs$^-$ ions, at the same energy and fluence, has been found to result in a reduced accumulation of defects in the near surface region leading to reduced surface features.