Structural and vibrational properties of {N,N} pairs and {N,H} complexes in Si

Abstract

First-principles molecular-dynamics simulations are used to predict the structures and binding energies of interstitial nitrogen ${\mathrm{N}}_{\mathrm{i}},$ substitutional nitrogen ${\mathrm{N}}_{\mathrm{s}},$ the ${\mathrm{N}}_{\mathrm{i}}$-self-interstitial complex, the ${{\mathrm{N}}_{\mathrm{i}},{\mathrm{N}}_{\mathrm{i}}},$ ${{\mathrm{N}}_{\mathrm{i}},{\mathrm{N}}_{\mathrm{s}}}={{\mathrm{N}}_{2},\mathrm{V}},$ and ${{\mathrm{N}}_{\mathrm{s}},{\mathrm{N}}_{\mathrm{s}}}={{\mathrm{N}}_{2},{\mathrm{V}}_{2}}$ pairs (V is the vacancy). The interactions of N with H in Si are studied and the properties of several ${\mathrm{N},\mathrm{H}}$ complexes are predicted. The dynamical matrices yield many new local and pseudolocal vibrational modes associated with the impurities and their Si nearest neighbors. The unidentified ${\mathrm{N},\mathrm{H}}$-related infrared absorption line reported by Pajot et al. is assigned to the ${{\mathrm{N}}_{\mathrm{s}},\mathrm{H}}$ complex.