Micro-wear scan test on the carbon overcoats as thin as 6 nm or less

Nitrogen-doped carbon (CNx) overcoats, ranging from 1 to 6nm in thickness, were deposited on magnetic recording disks by a DC-sputtering process. A critical load, based on the first occurrence of coating damage, was used as a semi-quantitative measure of the mechanical strength of these overcoats. It was found that the critical load decreased in a nearly linear manner with the CNx thickness from 6nm down to approx. 2nm regime. However, the 1nm thick CNx coating deviated from this trend with a significant decrease in critical load. High-resolution SEM was employed to find the critical loads as well as to reveal the details of the coating wear morphology and the CNx failure mechanism.