Micro/nanotribology and its applications to magnetic media, heads and MEMS

Micro/nanotribological studies are essential to understand the interfacial phenomena on small scales and at light loads. Techniques for micro/nanotribological studies were developed successfully using the atomic force/friction force microscope (AFM/FFM). Micro/nanotribology encompasses the studies of surface topography, adhesive force, friction, scratch resistance, wear resistance, lubrication, and mechanical properties all on small scales and light loads. A friction calibration procedure was developed to measure the friction force in force units on a microscale. Mechanisms associated with friction, scratching and wear have been identified and discussed. It has been observed that, the local friction force changes with the change in the local surface slope. The resemblance between local change in the friction force and the surface slope can be explained with the help of a ratchet mechanism. The effect of surface roughness, scan size, scanning velocity, tip radius and environment on friction behavior was studied in detail. Macroscale friction tests were performed using a pin-on-disk tribometer or disk drive and results were compared with the microscale friction tests. Special AFM/FFM tips and techniques were developed to measure scratch and wear resistance of thin and ultra-thin films. To understand the material removal mechanisms, scanning and transmission electron microscopy studies were performed on the microworn single-crystal silicon. Micro/nanotribological performance of boundary layer lubricants (self assembled and Langmuir-Blodgett (L-B) monolayers and perfluoropolyether (PFPE) liquid lubricants) was studied in depth. Self-assembled double grafted {dollar}rm Csb{lcub}18{rcub}{dollar} films exhibit better friction and wear performance than L-B films. The polar PFPE lubricants exhibit better tribological performance than that of nonpolar lubricants. Lubricant film thickness plays a major role in tribological performance. Nanomechanical properties of various materials were measured for the first time at very shallow indentation depth (as low as 1 nm) using modified AFM. Using this technique the hardness of thin and ultra thin-films and monolayers can be measured. The technique of local nanoindentation is used to identify and study the soft and hard regions on specimen surfaces.; The micro/nanotribological techniques were successfully applied to study the tribological properties of magnetic media (thin-film magnetic disks, magnetic tape substrates and finished tapes), materials used in head slider construction and microelectromechanical systems (MEMS). Magnetic storage devices are generally protected by hard hydrogenated amorphous carbon coatings. Micro/nanotribological performance of hydrogenated amorphous carbon coatings deposited by various techniques was evaluated. Thin-film deposition techniques with high kinetic energy of deposition species exhibits better micro/nanotribological performance than that of low kinetic energy deposition techniques. Finally, the use of a scratching technique was demonstrated successfully to scribe fine lines and for nanofabrication or nanomachining.