Theoretical study of hydrogen microstructure in models of hydrogenated amorphous silicon

TL;DR

This theoretical study investigates hydrogen distribution and cluster configurations in models of hydrogenated amorphous silicon, comparing simulated microstructures and NMR spectra with experimental data to understand hydrogen behavior.

Contribution

It provides a detailed theoretical analysis of hydrogen microstructure in a-Si:H models, correlating simulated configurations with experimental NMR results.

Findings

Presence of isolated hydrogen atoms and various clusters confirmed

Hydrogen cluster sizes and environments match experimental observations

Calculated NMR linewidths align with experimental spectra

Abstract

We study the distribution of hydrogen and various hydride configurations in realistic models of a-Si:H for two different concentration generated via experimentally constrained molecular relaxation approach (ECMR) [1]. The microstructure corresponding to low (< 10%) and high (> 20%) concentration of H atoms are addressed and are compared to the experimental results with particular emphasis on the size of H clusters and local environment of H atoms.The linewidths of the nuclear magnetic resonance (NMR) spectrum for the model configurations are calculated in order to compare to the experimental NMR data. Our study shows the presence of isolated hydrogen atoms, small and relatively large clusters with average proton-proton neighbor distance in the clusters around 1.6 to 2.4 Angstrom that have been observed in multiple quantum NMR experiments.