Preparation of amorphous composites of silicon nitride and carbon layers on silica glass by chemical vapor deposition method

Amorphous Si3N4 and Si3N4–C layers were formed by the chemical vapor deposition (CVD) method on silica glass substrates using SiH4, NH3, Ar and in the case of Si3N4–C layers, C6H6. Due to considerable differences in the thermal expansion coefficients of pyrolitic silicon nitride and silica glass (about 9 times), the synthesis of uncracked layers of this material is only possible with thickness below 600 nm. Introducing about 3% carbon into the Si3N4 layer in the course of the synthesis, makes the layer crack-free even at a thickness of 3000 nm. Such thick layers do not undergo strain corrosion in contrast to the thin Si3N4 layers formed without carbon on silica glass. Samples without any layer, as well as ones with uncracked Si3N4 and Si3N4+C layer were corroded in silicon vapor at 1100°C for 3 min.