Atomic force microscopy: Surface forces, adhesion and nanomechanics measurements

This paper reviews work conducted at the Naval Research Laboratory to measure surface forces, adhesion and nanomechanical properties of materials using an Atomic Force Microscope (AFM). The article portrays the AFM as an enabling technology, evolving fr om a qualitative picturing-taking tool to a quantitative probe of material!, properties. For example, surface forces can be used to reduce contact forces during imaging, improve image resolution, and change image contrast. Force-distance curves and maps can be used to correlate surface topography with the adhesion, surface energy, frictional and mechanical properties of materials. Applications presented include imaging phase-segregated Langmuir-Blodgett films, measuring molecular recognition forces between individual molecules, determining the absolute modulus of materials from nanoindentation, and studying the nucleation of dislocations. Finally, the evolution of the AFM towards, dedicated micromachined instruments and sensors for on-line process control and sensing applications is introduced.