NANOTRIBOLOGY OF LUBRICATED AND UNLUBRICATED CARBON OVERCOATS ON MAGNETIC DISKS STUDIED BY FRICTION FORCE MICROSCOPY

Friction force microscopy is used to study the frictional properties of lubricated and unlubricated hydrogenated amorphous carbon overcoats deposited on magnetic disks used in hard disk drives. For carbon overcoats deposited on smooth disks, a strong correlation is found between topography and friction, with the peaks on the surface having low friction and the valleys having high friction. The correlation between friction and topography is attributed to the variation in van der Waals adhesive forces with topography. For carbon overcoats on strongly textured magnetic disks, the correlation between topography and friction is substantially reduced. For both types of disk, the addition of a perfluoropolyether lubricant film substantially reduces the magnitude and variation of the frictional forces.