Magnetic hard disk overcoats in the 3–5 nm thickness range

Protective properties of 3–5 nm thick carbon overcoat layers deposited on magnetic hard disks by ion beam deposition (IBD) and plasma-enhanced chemical vapor deposition (PECVD) were investigated. It is found that these overcoats are superior to the sputtered carbon films at thicknesses below 5 nm. Low-stiction performance of 3-nm-thick IBD films without any detectable wear was observed during 50 000 contact start-stop cycles at 55 °C and 10% relative humidity. Surface concentration of cobalt ions is reduced by as much as an order of magnitude as compared to the media with sputtered overcoats. Polarization resistivity values for IBD and PECVD overcoats are by an order of magnitude higher. The results show that thickness of protective carbon overcoats on magnetic hard disks can be reduced to 3–5 nm without compromising media reliability requirements. This reduction is critical for the continuing growth of storage density.