Protective coating

A method of depositing a protective coating onto a substrate, wherein the depositing the protective coating comprises:

• depositing a first sub-layer prepared from a first precursor mixture of an organosilicon compound and no, or substantially no, O2, N2O or NO2, and comprises one of H2, NH3, N2, Ar, He and/or Kr;
• and
• depositing one or more subsequent alternating layers of:
• a first intermediate sub-layer which is a hydrocarbon polymer of formula CmHn prepared by plasma-deposition of a second precursor mixture comprising a hydrocarbon compound of formula (X), and optionally NH3, N2O, N2, NO2, CH4, C2H6, C3H6 and C3H8, He, Ar and/or Kr;
• the hydrocarbon compound of formula (X);
• wherein:
• Z1 represents C1-C3 alkyl or C2-C3 alkenyl;
• Z2 represents hydrogen, C1-C3 alkyl or C2-C3 alkenyl;
• Z3 represents hydrogen, C1-C3 alkyl or C2-C3 alkenyl;
• Z4 represents hydrogen, C1-C3 alkyl or C2-C3 alkenyl;
• Z5 represents hydrogen, C1-C3 alkyl or C2-C3 alkenyl;
• and
• Z6 represents hydrogen, C1-C3 alkyl or C2-C3 alkenyl;
• and
• a second intermediate sub-layer which is prepared by using a third precursor mixture of nitrogen-containing organosilicon compounds or an organosilicon with a nitrogen-containing co-precursor.