Thin film magnetic disks require protective overcoats, usually some form of carbon, to guard against corrosion and wear from interaction with the read/write transducer. In current products these films are less than 25 nm in thickness. This paper summarizes developments using scanning probe microscopes with sharp diamond tips (15 – 100 nm radius) to obtain indentation hardness tests with 5 nm deep indentations. We discuss an accelerated wear test that can measure wear at depths on the order of 1 nm. Finally material characterizations related to friction over sub-micron scans are discussed.
A novel observation has been made when studying the dependence of friction coefficient on normal load: below a critical load, which is material and tip dependent, no observable wear occurs, and the coefficient of friction is about 0.05. Above the critical load the coefficient is load dependent and increases to a value more usually associated with the materials being tested. A study of fatigue wear was made in the “no-wear” regime with three different results. For some materials, fatigue wear occurred with multiple passes, when none was apparent for a single pass. Other materials showed no fatigue wear, and one material, silicon, showed a build-up or “negative-wear” under multiple passes. Interpretations and implications of these results are discussed.