NANOINDENTATION, MICROSCRATCH, FRICTION AND WEAR STUDIES OF COATINGS FOR CONTACT RECORDING APPLICATIONS

A nanoscale monolithic slider-suspension produced by photolithography is used for contact recording. The contact pad consists of a multilaye red structure consisting of SiC, amorphous hydrogenated carbon (a-C:H) , Al2O3, Si, and Co-Nb-Zr films. In this study, we have compared hardn ess, Young's modulus of elasticity, and scratch resistance or adhesion of various coatings deposited on a single-crystal silicon wafer by na noindentation and microscratch techniques and friction and wear perfor mance by sliding against a diamond tip and sapphire ban in reciprocati ng mode. SIC coatings exhibit the highest hardness, about 27 GPa, and the highest elastic modulus, about 255 GPa. Microscratch data indicate that SiC and a-C:H coating exhibit the highest resistance to scratchi ng or debonding from the substrate. During scratching, an Al2O3 coatin g deforms like a ductile metal rather than like a ceramic. Si and Co-N b-Zr coatings exhibit ploughing of the tip into the sample surface and debris generation right in the beginning of the scratch. SiC coatings exhibit the best wear performance against a diamond tip as well as a sapphire ball. For comparisons, we also made mechanical property measu rements on bulk materials used in conventional recording: Ni-Zn ferrit e, Al2O3-TiC, and SiC (under development). The bulk Ni-Zn ferrite samp le was found to be damaged by grain pull-out during scratching even at a low load of 3 mN. Bulk Al2O3-TiC exhibits unexpected ploughing of t he sample right from the beginning of the scratch. Bulk SiC did not ex hibit any signs of significant damage up to a normal load of about 15 mN. Overall comparison of mechanical properties of bulk materials and coatings suggest that SiC is the most desirable coating in the contact pad for low wear. An SiC coating is also recommended as an overcoat f or thin film magnetic disks.