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 α$$ \alpha $$‐ and β$$ \beta $$‐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 α$$ \alpha $$‐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 β$$ \beta $$‐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. Silicon nitride and silicon oxynitride are significant phases in ceramic materials with diverse applications. To accurately identify these phases in Raman images, high‐quality reference spectra are essential. These are presented here in comparison with spectra calculated using different DFT functionals. Multiple Raman bands of α$$ \alpha $$‐Si3N4 and Si2N2O were observed for the first time in experimental spectra.