Characterization and properties of diamond-like carbon films for magnetic recording application

Abstract

An ultra-thin coating of amorphous carbon (a-C:H) or diamond-like carbon (DLC), is deposited on recording heads for improved tribological properties and corrosion protection at the head-disk interface. With the thickness of these coatings decreasing to below 5 nm for high areal density magnetic storage, it is important to understand the fundamental growth mechanism and properties of very thin films. The present work provides results of the properties of DLC overcoats deposited on n-type silicon (100) substrates, which were characterized in terms of residual stress, Raman spectroscopy, electrical resistivity and surface energy as a function of film thickness. An ion beam chemical vapor deposition (IBCVD) process using methane (CH4) as the precursor was used to deposit the DLC. The results indicate that there is considerable change in the film properties as the film grows. The residual stress gradually decreases with an increase in film thickness up to 10 nm where the stress is about 2.5 GPa. Above 10 nm film thickness, the stress increases again. The Raman intensity ratios on these films follow a similar pattern. Data on surface energy, and electrical resistivity are also presented. Implications of these measurements on the thin film growth mechanism are discussed. The results of the above techniques of DLC characterization imply that the properties of thin DLC films change as the film grows in thickness.