BONDING IN HYDROGENATED AMORPHOUS SILICON

Abstract
A model for the H distribution and bonding structure in a-Si : H is presented based on new NMR and ir absorption data. The model is capable of explaining previous discrepancies in the interpretation of the ir absorption data without including oscillator strengths which vary with H density. Three types of H distributions are considered. First, the typical Si-H₂ form which has a stretching mode at 2100 cm^-1 and a bending mode at 890 cm^-1 is included. Additionally, two distributions of Si-H bonds are included ; a dilute, random distribution which has an ir stretching mode at 2000 cm^-1 and a clustered form which has its ir stretching mode near 2090 cm^-l. Local H densities and sample wide average H densities for these two forms of Si-H bonds are determined from the NMR spectrum. This NMR data is correlated with the ir absorption data to calculate a fixed oscillator strength for each of the three types of H distribution.