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An atomic force microscope (AFM), with a specially prepared diamond tip, has been modified to measure indentation hardness with an indentation depth as low as 1 nm. This indentation depth is much smaller than the depth of more than 20 nm that have been reported to date. The AFM indentation technique allows the hardness measurements of surface monolayers and ultrathin films in multilayered structures at very shallow depths and low loads. The nanoindentation hardness of single crystal silicon is measured using this technique. A subtraction technique is also described which allows the actual hardness measurements of rough surfaces such as magnetic thin film rigid disks.

Ifox public release and sale; its distribution is uniimited.Read-write sliders made of silicon using integrated-circuit technology offer advantages of low-cost and high volume production. In the present study our objective is to investigate whether the friction and wear performance of bare silicon is adequate for disk drive application or whether certain coatings/treatments are necessary for low friction and wear. Macrotribological experiments have been performed with various pin/slider materials and magnetic disks in a modified disk drive.Microtribological studies have also been conducted on silicon using a friction force microscope. Based on macrotests, we found that the friction and wear performance of bare silicon is not adequate. With single and polycrystalline silicon, transfer of amorphous carbon from the disk to the pin/slider and oxidation-enhanced fracture of pin/slider material followed by oxidation of the transfer coating is responsible for degradation of the sliding interface and consequent friction increase in ambient air. With dry-oxidized or PECVD-SiO2-coated silicon, no significant friction increase or interfacial degradation was observed in ambient air. In the absence of an oxidizing environment (in dry nitrogen), the coefficient of friction decreased from 0.2 to 0.05 following amorphous carbon transfer for the materials tested. Nanoscratching/nanowear and nanoindentation studies also indicate that coated silicon is superior to bare silicon. Macro-and micro-coefficient of friction values of all samples are found to be about the same with the microvalues .ower than the macrovalues. Based on this study, we conclude that coated silicon is an excellent candidate for the construction of magnetic head sliders.

The effect of scan size (scan length) and surface roughness on microscale friction was studied using atomic force/friction force microscopy. Three silicon specimens with different surface roughnesses were studied. Surface height and friction force plots were obtained simultaneously and friction mechanisms for the correlation between them were sought. The standard deviation of surface heights increases with the scan size initially and approaches a constant value at a scan length greater than the long wavelength limit of the roughness structure. Change in the value of the coefficient of friction at different scan lengths is random. In these measurements, the sampling interval is always lower than the correlation length which is believed to be responsible for the random variation in microscale friction with the scan size. The good correlation observed between the local change in friction force and the surface slope can be explained by a ratchet mechanism.

The atomic force/friction force microscope is used to study the micro/nanotribiological properties of perfluoropolyether lubricants. Single-crystal silicon wafers were lubricated with nonpolar (Z-15) and polar (Z-DOL and Demnum S-100) lubricants. The nanowear tests show that the nonpolar (Z-15) lubricant depleted from the wear track within a few cycles, whereas polar (Z-DOL) lubricant exhibits excellent nanowear resistance with no degradation. The polar lubricant results in a lower value of microfriction as compared to the nonpolar lubricant and unlubricated silicon sample. The effect of thickness of polar lubricant is studied for the thermally bonded Z-DOL lubricant before and after wash. Unwashed polar lubricant film with unbonded fraction exhibited better resistance to wear than that of washed lubricant film. Thicker films are also more durable. Wear experiments with magnetic disks show that lubricant films on a super smooth disk is more effective in reduction of friction and wear than a smooth disk. Coefficient of friction on micro- and macroscales are compared. Variation in lubricant film thickness results in variation in coefficient of friction. Thus, friction force microscopy can be used to measure lubricant uniformity with spatial resolution on the order of tens of nm. Finally, adhesive experiments show that bonded film behaves as a soft polymeric solid.