Quantification of the bond-angle dispersion by Raman spectroscopy and the strain energy of amorphous silicon

TL;DR

This paper critically analyzes the relationship between bond-angle dispersion and Raman peak width in amorphous silicon, clarifies theoretical discrepancies, and estimates the strain energy, revealing defect annihilation's limited role in relaxation.

Contribution

It provides a unified theoretical framework linking Raman spectra to bond-angle dispersion and strain energy in amorphous silicon, resolving previous discrepancies.

Findings

Discrepancies between bond-angle dispersion and Raman peak width are reduced with unified definitions.

Defect annihilation contributes minimally to structural relaxation energy.

Strain energy in defect-free a-Si can be as low as 7 kJ/mol.

Abstract

A thorough critical analysis of the theoretical relationships between the bond-angle dispersion in a-Si and the width of the transverse optical (TO) Raman peak is presented. It is shown that the discrepancies between them are drastically reduced when unified definitions for these magnitudes are used. This reduced dispersion in the predicted values of the bond-angle dispersion together with the broad agreement with its scarce direct determinations is then used to analyze the strain energy in partially relaxed pure a-Si. It is concluded that defect annihilation does not contribute appreciably to reducing the a-Si energy during structural relaxation. In contrast, it can account for half of the crystallization energy, which can be as low as 7 kJ/mol in defect-free a-Si.