Electronic structure and charge transfer in α- andβ−Si3N4and at theSi(111)/Si3N4(001)interface

Using a self-consistent linear combination of atomic orbitals method based on density-functional theory in a local-density approximation, the electronic structure in the high-temperature ceramics $\alpha -{\mathrm{Si}}_3{\mathrm{N}}_4$ and $\beta -{\mathrm{Si}}_3{\mathrm{N}}_4$ and at the ${\mathrm{Si}\left(111\right)/\mathrm{S}\mathrm{i}}_3{\mathrm{N}}_4\mathrm{}\left(001\right)\mathrm{}$ interface have been calculated. The resulting charge transfer suggests that the ionic formula can be written as ${\mathrm{Si}}_3^{+1.24\mathrm{}}{\mathrm{N}}_4^{\mathrm{-}0.93}.$ For the ${\mathrm{Si}\left(111\right)/\mathrm{S}\mathrm{i}}_3{\mathrm{N}}_4\mathrm{}\left(001\right)\mathrm{}$ interface, the silicon atoms from the silicon side lose some electrons to the nitrogen atoms of the silicon nitride side forming Si-N bonds at the interface. The calculated electronic density of states spectrum of Si $2p$ core levels for this interface is in good agreement with x-ray photoemission spectroscopy experiments.