A lack of understanding of the fundamental mechanisms governing atomic-scale adhesion and friction creates ongoing challenges as technologically-relevant devices are miniaturized. One major class of failure mechanisms of such devices results from high friction, adhesion, and wear. This thesis presents investigations into methods by which atomic-scale friction and adhesion can be controlled. Using atomic force microscopy (AFM), friction and adhesion properties of graphene were examined. While friction between the tip and graphene depends on thickness, as explained by the "puckering effect", adhesion is independent of the thickness when measured conventionally. However, adhesion is transiently higher when measured after the tip has slid over the graphene. This effect is caused by increased adhesiveness between graphene and tip due to aging. Second, chemical modification of graphene, specifically fluorination, affects friction strongly, with friction monotonically increases with increasing degree of fluorination. As supported by molecular dynamics (MD) simulations, this dependence is attributed to the fact that attachment of fluorine to graphene greatly enhances the local energy barrier for sliding, thereby significantly altering the energy landscape experienced by the tip. Finally, through matched AFM and MD, the speed dependence of atomic friction was explored within the framework of the Prandtl-Tomlinson model with thermal activation (PTT). For the first time, experiments and simulations are performed at overlapping scanning speeds. While friction was found to increase with the log of speed in both AFM and MD, consistent with the PTT model, friction in experiments was larger than in MD. Analysis revealed that the discrepancy was largely attributable to the differences in contact area and tip masses used in experiments vs. in simulation. Accounting for the overall influence of the two with the presence of instrument noise fully resolves the discrepancy. Through those novel studies and findings, it has been demonstrated that atomic-scale friction and adhesion can be controlled and understood, assisting the development of applications where variable or constant friction and adhesion are desired.

Written by one of the most distinguished scientists and a pioneer in this field, this monograph represents a stand-alone, concise guide to friction at the atomic level. It brings together hitherto widely-scattered information in one single source, and is the first to explain the nature of friction in terms of atomistic mechanisms. In addition to his detailed description on modeling and simulation, the author stresses experimental approaches like AFM (Atomic Force Microscope) techniques for verification of theory. In this respect the book will benefit the whole nanotribology community, from graduate students who want to get the basics right up to researchers specializing in mechanical engineering, materials science, physics and chemistry.

Atomic Force/Friction Force Microscopes (AFM/FFM) were used to study tribological properties of metal-particle tapes with two roughnesses, Co-gamma Fe2O3 tapes (unwiped and wiped), and unlubricated and lubricated thin-film magnetic rigid disks (as-polished and standard textured). Nanoindentation studies showed that the hardness of the tapes through the magnetic coating is not uniform. These results are consistent with the fact that the tape surface is a composite and is not homogeneous. Nanoscratch experiments performed on magnetic tapes using silicon nitride tips revealed that deformation and displacement of tape surface material occurred after one pass under light loads (approx. 100 nN). A comparison between friction force profiles and the corresponding surface roughness profiles of all samples tested shows a poor correlation between localized values of friction and surface roughness. Detailed studies of friction and surface profiles demonstrate an excellent correlation between localized variation of the slope of the surface roughness along the sliding direction and the localized variation of friction. Atomic-scale friction in magnetic media and natural diamond appears to be due to adhesive and ratchet (roughness) mechanisms. Directionality in the local variation of atomic-scale friction data was observed as the samples were scanned in either direction, resulting from the scanning direction and the anisotropy in the surface topography. Atomic-scale coefficient of friction is generally found to be smaller than the macro coefficient of friction as there may be less ploughing contribution in atomic-scale measurements.

Combining the classical theories of contact mechanics and lubrication with the study of friction on the nanometer range, this multi-scale book for researchers and students alike guides the reader deftly through the mechanisms governing friction processes, based on state-of-the-art models and experimental results. The first book in the field to incorporate recent research on nanotribology with classical theories of contact mechanics, this unique text explores atomic scale scratches, non-contact friction and fishing of molecular nanowires as observed in the lab. Beginning with simple key concepts, the reader is guided through progressively more complex topics, such as contact of self-affine surfaces and nanomanipulation, in a consistent style, encompassing both macroscopic and atomistic descriptions of friction, and using unified notations to enable use by physicists and engineers across the scientific community.