A hydrogenated silicon carbon nitride (SiCN:H) film is deposited onto a substrate by plasma enhanced chemical vapour deposition (PECVD) comprising: providing the substrate in a chamber; introducing silane (SiH4), a carbon-donating precursor, and nitrogen gas (N2) into the chamber; and sustaining a plasma in the chamber so as to deposit SiCN:H onto the substrate by PECVD, wherein the substrate is maintained at a temperature of less than about 250° C.