Experimentally Constrained Molecular Relaxation: The case of hydrogenated amorphous silicon

TL;DR

This paper extends an experimentally constrained molecular relaxation method to create realistic models of hydrogenated amorphous silicon, revealing vibrational features consistent with experimental observations.

Contribution

The authors developed a new approach applying experimentally constrained relaxation to hydrogenated amorphous silicon, producing models that match experimental vibrational data.

Findings

Identified a high-frequency localized vibrational band due to Si-H vibrations.

Produced realistic atomic models with different hydrogen concentrations.

Confirmed experimental vibrational features through computational modeling.

Abstract

We have extended our experimentally constrained molecular relaxation technique (P. Biswas {\it et al}, Phys. Rev. B {\bf 71} 54204 (2005)) to hydrogenated amorphous silicon: a 540-atom model with 7.4 % hydrogen and a 611-atom model with 22 % hydrogen were constructed. Starting from a random configuration, using physically relevant constraints, {\it ab initio} interactions and the experimental static structure factor, we construct realistic models of hydrogenated amorphous silicon. Our models confirm the presence of a high frequency localized band in the vibrational density of states due to Si-H vibration that has been observed in a recent vibrational transient grating measurements on plasma enhanced chemical vapor deposited films of hydrogenated amorphous silicon.