Atomistic structure of amorphous silicon nitride from classical molecular dynamics simulations

TL;DR

This study uses classical molecular dynamics simulations to investigate the atomistic structure of amorphous silicon nitride across various compositions, revealing new structural features and defect types relevant for electronic applications.

Contribution

It introduces a simulation-based analysis that reproduces experimental features and identifies N--N bonds and defects affecting charge trapping in amorphous silicon nitride.

Findings

Identification of N--N bonds in the structure

Correlation between defect concentration and stoichiometry

Reproduction of experimental radial distribution functions

Abstract

By means of molecular dynamics simulations based on the Billeter et al. [S. R. Billeter, A. Curioni, D. Fischer, and W. Andreoni, Phys. Rev. B {\bf 73}, 155329] environment-dependent classical force field we studied the structural features of SiN$_x$ samples at various stoichiometries. Our results are in good agreement with experimental data and are able to reproduce some features which so far were not reproduced by simulations. In particular, we identified units containing N--N bonds, which are thought to be responsible for an unassigned peak in the radial distribution function obtained from neutron diffraction data and signals observed in electron spin resonance, X-ray photoemission spectroscopy, electron-energy-loss spectroscopy and optical absorption experiments. We have identified defects which are thought to be the responsible for the high concentration of charge traps that makes this material suitable for building non-volatile memory devices. We analyzed the dependency of the concentration of these defects with the stoichiometry of the sample.