The Raman Spectra of α $$ \alpha $$ - and β $$ \beta $$ -Si3N4 and Si2N2O Determined Experimentally and by Density Functional Theory

Abstract

High-quality Raman spectra of the two silicon nitride polymorphs $\alpha$- and $\beta$-Si₃N₄ as well as of Si₂N₂O are presented here. This work significantly extends the previously available data on the Raman spectra of all three phases. For $\alpha$-Si₃N₄, a total of 34 Raman bands were confirmed, and for Si₂N₂O, a total of 19 Raman bands were observed for the first time. In the case of $\beta$-Si₃N₄, all 11 known Raman modes were confirmed. For further accuracy and comparison, the spectra of the three phases were also calculated with different density functional theory functionals. Good agreement between the experimental data and the calculated vibrational modes is shown. Between the different DFT functionals, the rSCAN functional had the best agreement with the experimental data, clearly outperforming the PBEsol functional.