Electronic and vibrational properties of hydrogenated amorphous silicon nitride

The theoretical model calculations are used to study the electronic and vibrational properties of hydrogenated amorphous silicon nitride. The electronic densities of states of Si3N4 Bethe lattice, Si dangling bond (DB), SiH, SiH2, N DB, N-N DB, NH and NH2 bonds are calculated. The charges are found to transfer from Si to 14 in the Si-N bond, Si to H in the Si-H bond and H to N in the N-H bond. Si DB, N DB and N-N DB are found to have defect states in the energy gap. These defect states can be identified by the electron spin resonance. The N site of the Si2NH2 complex can be positively charged and form a defect pair with the negatively charged Si DB. The vibrational densities of states of Si3N4 Bethe lattice, SiH, SiH2, NH, and NH2 bonds are calculated. The vibrational dinsities of state of the SiD, SiD2, ND and ND2 bonds are also calculated as an aid to identify the local modes. The Si-H bond stretching frequency higher than 2160 cm(-1) is due to the asymmetric stretching mode of the SiH2 bond and the N-H stretching mode of 3450 cm(-1) is due to the asymmetric stretching mode of the NH2 bond. The asymmetric stretching modes of the SiH2 and NH2 bonds seem to be more infrared sensitive than their symmetric stretching modes.