An effect of nitrogen incorporation on the structure and properties of amorphous SiC: First-principles molecular dynamics simulations

The structural, mechanical and electronic structure properties of amorphous silicon carbide and silicon carbonitride alloys were studied depending on chemical ordering, and nitrogen content, respectively, by using first-principles molecular dynamics simulations. The structure, chemical bonding, electronic structure, frequency-dependent dielectric functions, and mechanical properties (elastic moduli, Poisson ratio, bulk modulus to shear modulus ratio, ideal shear strength, Vickers hardness, Debye temperature and fracture toughness) were studied. It was established that an increase of nitrogen content in carbonitride alloys and a decrease of chemical ordering in carbide alloys cause the weakening of the Si–C network, strengthening of the C–C network, decrease in four-fold coordination and increase in three-fold coordination of Si and C atoms. All these factors lead to a deterioration of mechanical properties. The highly nitrided alloys are supposed to be wide-gap semiconductors with estimated mobility gaps in the range of 2.9–4.2 eV. The calculated data were used to elucidate available experimental results.