Nanoscale scratch resistance of ultrathin protective overcoats on hard magnetic disks

An atomic force microscope-based nanoscratch testing technique has been applied to evaluate scratch resistance of 100 Angstrom thick protective overcoats on hard magnetic disks. Among the overcoats prepared by de magnetron sputtering, an amorphous nitrogenated carbon (a-C:N) film showed the best performance in the tests, followed by an amorphous hydrogenated carbon (a-C:H) film and an undoped amorphous carbon (a-C) film. Substrate temperature in the overcoat sputtering process was found to be an important factor affecting the film's scratch resistance. Overcoats sputtered at lower substrate temperature were more stable against scratching. An ion beam deposition process was found to produce an overcoat with superior scratch-resistant properties as compared to the sputtered carbon overcoats. Nanoscale scratch testing results are correlated with the sp(3)-bonding character in the overcoats assessed by Raman spectroscopy. (C) 1998 American Vacuum Society.