Structure and properties of sputtered carbon overcoats on rigid magnetic media disks

Sputtered carbon overcoats on commercial rigid disks with thin‐film magnetic media are studied using transmission electron analysis (microscopy, microdiffraction, and energy‐loss spectroscopy), Raman spectroscopy, Auger spectroscopy, ellipsometry, x‐ray diffraction, and microhardness testing. Data from transmission electron analysis, Raman spectroscopy, and ellipsometry suggest that the carbon overcoats are composed of small graphite crystallites (≤2 nm), randomly oriented, with a small percentage (0%–5%) of fourfold coordinated carbon bonds. Auger spectroscopy and transmission electron energy‐loss spectroscopy indicate the presence of a small amount of oxygen. Auger spectroscopy also shows some surface nitrogen. The optical constants, n=2.1 and k=0.78, exhibit a small wavelength dependence. In addition, the extinction coefficient k shows a dependence upon film thickness. X‐ray diffraction and microhardness testing did not yield any information concerning the carbon overcoats. There was no indication of d...