DIAMOND-LIKE CARBON OVERCOAT FOR MAGNETIC THIN-FILM RECORDING DISKS

Diamond-like carbon (DLC), which shows excellent hardness and a low friction coefficient, has recently been used as the overcoat for magnetic thin film recording disks. The performance of the thin (about 20 nm) DLC film is highly dependent on its microstructure, surface morphology, and chemical composition, and thus depends on its fabrication process. The DLC overcoat is fabricated by d.c. magnetron sputtering of a graphite target in a gas mixture of argon and hydrogen. The hydrogen content, the gas flow and pressure, and sputtering power are found to be the key process parameters that affect the properties and characteristics of the DLC film. The chemical structure and composition are characterized using Raman spectroscopy and Rutherford forward scattering spectrometry. The film hardness, electrical resistance, optical reflectance, and plasma etch rate are also measured, and their relation to film structure and hydrogen content discussed. The final wear and stiction test on the DLC film was carried out using disk drives equipped with semiconductor strain gauges and customer designed computer-controlled hardware/software. The test results are interpreted in terms of film hardness, structure and electrical resistance.