TRIBOLOGICAL STUDIES OF SILICON FOR MAGNETIC RECORDING APPLICATIONS

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 (tribochemical oxidation) is responsible for degradation of the sliding interface and consequent friction increase in ambient air. With dry-oxidized or plasma-enhanced chemical-vapor deposition-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 microcoefficient of friction values of all samples is found to be about the same with the microvalues lower than the macrovalues. Based on this study, we conclude that coated silicon is an excellent candidate for the construction of magnetic head sliders.