Ultra-thin a-SiNx protective overcoats for hard disks and read/write heads

This paper reports that amorphous silicon nitride (a-SiN_x) overcoats were deposited at room temperature by microwave ECR plasma enhanced unbalanced magnetron sputtering. The 2 nm a-SiN_x overcoat has better anti-corrosion properties than that of reference a-CN_x overcoats (2--4.5 nm). The superior anti-corrosion performance is attributed to its stoichiometric bond structure, where 94.8% Si atoms form Si--N asymmetric stretching vibration bonds. The N/Si ratio is 1.33 as in the stoichiometry of Si₃N₄ and corresponds to the highest hardness of 25.0 GPa. The surface is atomically smooth with RMS <0.2 nm. The ultra-thin a-SiN_x overcoats are promising for hard disks and read/write heads protective coatings.