SiO2Si3N4

SiO2Si3N4 is not a single discrete compound but a descriptor for materials that combine silicon dioxide (SiO2) and silicon nitride (Si3N4) in a single matrix. In practice it denotes silicon oxynitride or SiO2–Si3N4 composites in which silicon is bonded to both oxygen and nitrogen. The composition can be oxide-rich, nitride-rich, or balanced, and the material may be amorphous or partially crystalline depending on synthesis.

Synthesis and structure: The material is produced by methods such as chemical vapor deposition (including PECVD), sputtering, or sol-gel processing, often followed by heat treatments to tune the O/N ratio and phase distribution. It can form thin films, bulk glasses, or multilayer stacks of SiO2 and Si3N4. The bonding network comprises Si–O and Si–N bonds; the relative abundance of these bonds controls density, refractive index, and dielectric behavior.

Properties: Refractive index and dielectric constant are tunable with composition; the material can be quite hard and thermally stable, and shows good chemical resistance. Optical transparency is achievable in the visible to near-infrared range in suitably prepared forms. The material’s thermal expansion and mechanical properties depend on the SiO2/Si3N4 ratio and microstructure.

Applications: Used as protective coatings, diffusion barriers, dielectric layers in silicon-based electronics, and optical coatings or waveguides where index contrast is required. Synthesis must balance phase stability, residual stress, and substrate compatibility.