Protective properties of 3-5 nm thick carbon overcoat layers deposited on m
agnetic hard disks by ion beam deposition (IBD) and plasma-enhanced chemica
l vapor deposition (PECVD) were investigated. It is found that these overco
ats are superior to the sputtered carbon films at thicknesses below 5 nm. L
ow-stiction performance of 3-nm-thick IBD films without any detectable wear
was observed during 50 000 contact start-stop cycles at 55 degrees C and 1
0% relative humidity. Surface concentration of cobalt ions is reduced by as
much as an order of magnitude as compared to the media with sputtered over
coats. Polarization resistivity values for IBD and PECVD overcoats are by a
n 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 co
mpromising media reliability requirements. This reduction is critical for t
he continuing growth of storage density. (C) 1999 American Institute of Phy
sics. [S0021-8979(99)32008-9].