The Temperature-Dependent Thermal Conductivity of C- and O-Doped Si3N4: First-Principles Calculations

Abstract

Silicon nitride (Si3N4) possesses excellent mechanical properties and high thermal conductivity, which is an important feature in many applications. However, achieving the theoretically high thermal conductivity of Si3N4 in practice is challenging. In this study, we adopted a first-principles calculation method to assess the effects of doping β-Si3N4 and γ-Si3N4 with carbon and oxygen atoms. Applying geometric structure optimization combined with calculation of the electronic phonon properties generated a stable doped structure. The results revealed that carbon and oxygen doping have little effect on the Si3N4 unit cell size, but that oxygen doping increases the unit cell volume. Energy band structure and state density calculation results showed that carbon doping reduces the nitride band gap width, whereas oxygen doping results in an n-type Si3N4 semiconductor. The findings from this study are significant in establishing a basis for targeted increase of the thermal conductivity of Si3N4.