Microscopic properties of silicon dihydride bonding in a-Si:H

We use proton nuclear magnetic resonance to probe stable silicon dihydride existing in high defect density hydrogenated amorphous silicon. The silicon dihydride line shape exhibits the well-known ‘Pake’ doublet form resulting from a dipole interaction between two protons. We simulate the line shape using the relevant Hamiltonian and broadening effects known to occur in this amorphous system and discuss the sets of simulation parameters that reproduce the experimental data. The sets share a common feature – they require the proton–proton separation to be approximately 1.8 Å, not the 2.4 Å determined by recent theoretical calculations.