NANOSCALE INDENTATION HARDNESS AND WEAR CHARACTERIZATION OF HYDROGENATED CARBON THIN-FILMS (REPRINTED FROM JOURNAL-OF-TRIBOLOGY, VOL 117, PG 599-601, OCTOBER 1995)

An experimental investigation of the surface topography, nanoindentati on hardness, and nanowear characteristics of carbon thin films was con ducted using atomic force and point contact microscopy. Hydrogenated c arbon films of thickness 5, 10 and 25 nm were synthesized using a sput tering technique. Atomic force microscopy images obtained with silicon nitride tips of nominal radius less than 20 nm demonstrated that the carbon films possessed very similar surface topographies and root-mean -square roughness values in the range of 0.7-1.1 nm. Nanoindentation a nd nanowear experiments performed with diamond tips of radius equal to about 20 nm revealed a significant enhancement of the hardness and we ar resistance with increasing film thickness. High-resolution surface imaging indicated that plastic flow was the dominant deformation proce ss in the nanoindentation experiments. The carbon wear behavior was st rongly influenced by variations in the film thickness, increasing the load caused the transition from and atomic-scale wear process, charact erized by asperity deformation and fracture, to severe wear consisting of plowing and cutting of the carbon films. Both the critical load an d scanning time for severe wear increased with film thickness. Below t he critical load, the wear rate decreased with further scanning and th e amount of material worn off was negligibly small, while above the cr itical load the wear rate increased significantly resulting in the rap id removal of carbon. The observed behavior and trends are in good qua litative agreement with the results of other experimental and contact mechanics studies.