The mechanism of ion induced amorphization in Si

TL;DR

This paper investigates how ion impacts induce amorphization in silicon, revealing that at low energies it occurs via nucleation and growth, with a higher threshold dose than simulations predict, possibly due to temperature effects.

Contribution

It provides experimental insights into the ion-induced amorphization mechanism in silicon, highlighting a nucleation and growth process and a higher amorphization threshold than previously simulated.

Findings

Amorphization occurs via nucleation and growth at low energies.

The growth process is diffusion limited with an Avrami exponent of ~1.6.

The amorphization threshold dose exceeds 17 eV/atom, higher than simulation predictions.

Abstract

Some results on damage build up in, and amorphization of, Si, induced by 25-30 keV Al$_5^-$, Si$_5^-$ and Cs$^-$ ions, at room temperature, are reported. We show that at low energy, amorphization is a nucleation and growth process, based on the direct impact mechanism. With an Avrami exponent $\sim 1.6$, the growth towards amorphization seems to be diffusion limited. A transition to a completely amorphized state is indicated at a dose exceeding 17 eV/atom, which is higher than 6-12 eV/atom as predicted by simulations. The observed higher threshold could be due to temperature effects although an underestimation of keV-energy recoils, in simulation, may not be ruled out.