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

摘要

Recent experiments on hydrogenated amorphous silicon using infraredabsorption spectroscopy have indicated the presence of mono- and divacancy insamples for concentration of up to 14\% hydrogen. Motivated by thisobservation, we study the microstructure of hydrogen in two model networks ofhydrogen-rich amorphous silicon with particular emphasis on the nature of thedistribution (of hydrogen), the presence of defects, and the characteristicfeatures of the nuclear magnetic resonance spectra at low and highconcentration of hydrogen. Our study reveals the presence of vacancies, whichare the built-in features of the model networks. The study also confirms thepresence of various hydride configurations in the networks that include fromsilicon monohydrides and dihydrides to open chain-like structures, which havebeen observed in the infrared and nuclear magnetic resonance experiments. Thebroad and the narrow line widths of the nuclear magnetic resonance spectra arecalculated from a knowledge of the distribution of spins (hydrogen) in thenetworks.