Microstructure, vacancies and moments of nuclear magnetic resonance of hydrogenated amorphous silicon

TL;DR

This study investigates the microstructure and magnetic resonance properties of hydrogen in amorphous silicon, revealing vacancies and various hydride configurations consistent with experimental observations.

Contribution

It provides a detailed analysis of hydrogen distribution, defects, and NMR spectra in model networks of hydrogenated amorphous silicon, highlighting the presence of vacancies and diverse hydride structures.

Findings

Presence of vacancies in the model networks.

Identification of various hydride configurations.

Calculated NMR spectra match experimental features.

Abstract

Recent experiments on hydrogenated amorphous silicon using infrared absorption spectroscopy have indicated the presence of mono- and divacancy in samples for concentration of up to 14\% hydrogen. Motivated by this observation, we study the microstructure of hydrogen in two model networks of hydrogen-rich amorphous silicon with particular emphasis on the nature of the distribution (of hydrogen), the presence of defects, and the characteristic features of the nuclear magnetic resonance spectra at low and high concentration of hydrogen. Our study reveals the presence of vacancies, which are the built-in features of the model networks. The study also confirms the presence of various hydride configurations in the networks that include from silicon monohydrides and dihydrides to open chain-like structures, which have been observed in the infrared and nuclear magnetic resonance experiments. The broad and the narrow line widths of the nuclear magnetic resonance spectra are calculated from a knowledge of the distribution of spins (hydrogen) in the networks.