Microstructure and properties of ultrathin amorphous silicon nitride protective coating

The effect of N content on the structure and properties of rf relatively sputtered α-SiNx was investigated. The N content in the α-SiNx film increases with the N2 flow rate until the stoichiometric composition (Si3N4) is reached. The refractive index asymptotically reaches 1.99 as the N/Si ratio approaches 1.33. The maximum density of 3.2 g/cm3 and hardness of 25 GPa are attained at the stoichiometric composition.