Temperature dependent vibrational spectra in non-crystalline materials: application to hydrogenated amorphous silicon

TL;DR

This paper introduces a new parameter-free ab-initio method to model and analyze the vibrational, structural, and electronic properties of non-crystalline materials like hydrogenated amorphous silicon, linking vibrational spectra to material stability and dynamics.

Contribution

The paper presents a novel, comprehensive approach combining ab-initio Molecular Dynamics with advanced signal processing to study non-crystalline materials, enabling microscopic insights and realistic modeling.

Findings

Successfully related vibrational spectra to structural stability and hydrogen diffusion.

Extracted microscopic characteristics such as hydrogen migration and bond switching.

Demonstrated the method's ability to model a-Si:H dynamics and stability.

Abstract

We present a novel approach for parameter-free modeling of the structural, dynamical and electronic properties of non-crystalline materials based on ab-initio Molecular Dynamics, improved signal processing technique and computer visualization. The method have been extensively tested by investigating hydrogen and silicon dynamics in hydrogenated amorphous silicon (a-Si:H). By comparing the theoretical and experimental vibrational spectra we demonstrate how to relate vibrational properties to the structural stability, bonding and hydrogen diffusion. We extracted microscopic characteristics that cannot be obtained by other techniques, namely hydrogen migration and related bond switching, dangling bond passivation, low hydrogen activation energy, and a-Si:H stability in general, and we show, via the analysis of a test case, that our method provides a rigorous and realistic description of non-crystalline materials. We also demonstrate that this method offers the possibility of accessing other important macroscopic characteristics of amorphous silicon and can be used to model all the aspects of a-Si:H dynamics, including the detrimental Staebler-Wronski effect.