Approximate ab initio calculation of vibrational properties of hydrogenated amorphous silicon with inner voids

TL;DR

This study uses approximate ab initio molecular dynamics to investigate how voids in hydrogenated amorphous silicon affect its vibrational properties, revealing localized low-energy vibrational states.

Contribution

It introduces a novel modeling approach for a-Si:H with voids and analyzes the impact of voids on vibrational localization and spectrum.

Findings

Voids induce localized low-energy vibrational states.

Presence of voids alters vibrational spectrum and localization.

Visualization techniques reveal nature of localized states.

Abstract

We have performed an approximate ab initio calculation of vibrational properties of hydrogenated amorphous silicon (a-Si:H) using a molecular dynamics method. A 216 atom model for pure amorphous silicon (a-Si) has been employed as a starting point for our a-Si:H models with voids that were made by removing a cluster of silicon atoms out of the bulk and terminating the resulting dangling bonds with hydrogens. Our calculation shows that the presence of voids leads to localized low energy (30-50 cm^{-1}) states in the vibrational spectrum of the system. The nature and localization properties of these states are analyzed by various visualization techniques.