Nanotribology and nanomechanics of ultrathin films for hard disk drives

The protective thin film overcoats on the sliders and disks in hard disk drives are used to improve the tribological performance of the head-disk interface (HDI) as well as to prevent data loss from contacts between them. Nanoindentation techniques using a Scanning Probe Microscope (SPM) type machine are one of the many methods to investigate the mechanical properties of these thin films.; This dissertation focuses on improving the current method of analysis via remodeling the contact between the indenter and the specimen and studying the substrate effects on measurements of film/substrate systems. The model requires a tip shape function to close the systems of equations derived from Sneddon's solution. Although Sneddon's solution is valid for elastic indenter, the tip shape function implicitly assumes that the indenter has the same shape on all materials.; It is truly a challenge to study the mechanical properties of modern ultra thin film overcoats with thicknesses of 5 to 10 nm due to the measurement substrate effects. Neither Sneddon's solution nor the new model provides good insight into the substrate effects, since they both consider the specimens as bulk. This dissertation provides an insight into substrate effects based on indentation hysteresis and confirms the 20% rule, that the pure film property can be obtained if the residual indentation depth is smaller than 20% of the film thickness.; The surface roughness of commercial disks is about 1 nm in standard deviation and 0.5 nm in R_a. The protective film overcoat thicknesses are about 10 nm and are expected to drop to 2 to 5 nm as the magnetic spacing continues to drop. According to the rule for avoiding substrate effects, the residual indentation depths have to be less than 1 nm, which is comparable to the surface roughness. Therefore, surface roughness is no longer negligible as assumed in Sneddon's solution. The model based on the Hertz contact theory is modified and used to study the influences of specimen surface geometry and roughness. The model is then verified on commercial disks. The results show that the model is able to predict the measurement variations (random scatter) with knowledge of the surface roughness.; Finally, cathodic arc amorphous carbon films are investigated using all of the techniques mentioned above. It is shown that the mechanical properties of the CAC films are thickness dependent, possibly due to the existence of the sp2 surface layers on top of the sp3-bonded bulk. (Abstract shortened by UMI.)...