Naniondentation and scratch resistance testing on magnetic tape heads coated with ultra-thin amorphous carbon layers

We present results on nanoindentation and scratch testing on magnetic recor ding tape heads coated with sub-20 nm amorphous carbon layers, prepared by filtered cathodic deposition and plasma enhanced chemical vapour deposition . The hardness values of the coated devices an higher than that of the sput tered Al2O3 substrate. The coatings do not reduce friction but improve the scratch resistance of the tape heads. Hardness, which shows some correlatio n with scratch resistance is a contributing factor, especially at high load where it reduces plastic ploughing of the substrate. For low scratching lo ad, the wear seems to be influenced by the adhesive properties of the film/ substrate interface. Smoother surfaces and smaller tip radius should improv e the accuracy of the results. This could provide better insight into the f ailure mechanism of these ultra-thin overcoats. (C) 2000 Published by Elsev ier Science S.A.