Synthesis of anticorrosion SiC and SiNx films from alkoxide solution using liquid injection PECVD

Monolithic SiC, SiNx and their duplex SiC–SiNx films were synthesized from hexamethyldisiloxane solution at 750 °C on Si wafer and SUS304 steel substrates using Ar/H2/N2 plasma enhanced chemical vapor deposition (PECVD). The films were characterized by scanning/transmission electron microscopy (SEM/TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Amorphous SiNx films were easily deposited on two kinds of substrates from thermal Ar/H2/N2 plasma, whereas crystalline SiC films synthesized using thermal Ar/H2 plasma was only achieved on Si substrate and severe etching of the steel substrate by the plasma was observed. By varying N2 flow rate from 4.5 l/min to zero at the intermediate period of the deposition process, a duplex SiC–SiNx film, consisting of a top SiC and an inner SiNx layer adjacent to the substrate, was obtained both on Si and steel substrates. The corrosive exposure test in KCl atmosphere at 650 °C indicated that the ceramic film-coated steel substrates demonstrated a much superior corrosion resistance in comparison with the uncoated one.