Correlation of structure and hardness of rf magnetron sputtered silicon carbonitride films

Ternary nanocomposite silicon carbonitride $(SiCN)$ ceramic coatings have shown potential for wear resistance, oxidation resistance, hardness, tunable band gap, and chemical inertness applications. A systematic investigation on the deposition of $SiCN$ nanocomposite coatings by sputtering under varying deposition conditions such as chamber pressure, substrate temperature by structural, nanoindentation, and microstructural studies of optimized condition has been presented. Significant role of different deposition parameter on the mechanical and structural properties were observed. The structural characterizations of the coatings were carried out using Fourier transformed infra red (FTIR), transmission electron microscopy, Raman spectroscopy, and field emission scanning electron microscope. An increase in argon-nitrogen pressure in the range of 1–5 Pa led to lowering of particle size and surface smoothening and growth of hard phases of $β-C3N4$ and $β-Si3N4$⁠. An increase in substrate temperature from room temperature to $500°C$ led to nucleation and growth of hard phases of $β-C3N4$ and $Si3N4$ in the amorphous $SiCN$ matrix. The nanoindentation studies showed the variation in hardness and Young’s modulus from 8 to 22 GPa and from 100 to 240 GPa, respectively, dependent on the deposition conditions. The FTIR studies confirmed the presence of $CN$⁠, $SiN$⁠, $SiSi$⁠, $SiO$⁠, and $SiC$ in different films.