The Influence of Alkaline Earth Elements on Electronic Properties of α-Si3N4 via DFT Calculation

We used density functional theory (DFT) calculations to study the influence of alkali earth metal element (AE) doping on the crystal structure and electronic band structure of α-Si3N4. The diversity of atomic radii of alkaline earth metal elements results in structural expansion when they were doped into the α-Si3N4 lattice. Formation energies of the doped structures indicate that dopants prefer to occupy the interstitial site under the nitrogen-deficient environment, while substitute Si under the nitrogen-rich environment, which provides a guide to synthesizing α-Si3N4 with different doping types by controlling nitrogen conditions. For electronic structures, energy levels of the dopants appear in the bottom of the conduction band or the top of the valence band or the forbidden band, which reduces the bandgap of α-Si3N4.