Coverage and properties of a-SiNx hard disk overcoat

Amorphous silicon nitride (a-SiNx) overcoats are deposited on magnetic disks by rf-reactive sputtering to study their coverage and properties. According to the x-ray photoelectron spectroscopy analysis, a-SiNx has a low coverage-limit of similar to10 Angstrom compared with that of the reference a-CNx (similar to20 Angstrom). The lower coverage-limit of a-SiNx may be attributed to its high density of 3.2 g/cm(3), which corresponds to 93% bulk density. By contrast, the density of diamond-like carbon is only 54% that of diamond. This is in agreement with the results of coverage simulation, which reveal that the film coverage thickness decreases by similar to3 Angstrom per 10% increase in the relative density. Compared with 45 Angstrom a-CNx coated disks, 15 Angstrom a-SiNx coated disks have fewer pinhole defects and are more durable in the accelerated flyability test. The superior performance of a-SiNx disk overcoat may be attributed to its dense structure and high hardness (25 GPa). (C) 2003 American Institute of Physics.