Wear and mechanical characterisation on micro- to picoscales using AFM

Abstract

Atomic force/friction force microscopy (AFM/FFM) techniques are increasingly used for tribological studies of engineering surfaces at scales ranging from atomic and molecular to microscales. An AFM with a suitable diamond tip can be used to measure microscratching/microwear and nano-/picoindentation behaviour of solid surfaces and thin films. AFM has also been used for nanofabrication/nanomachining purposes. Scratch and wear properties of a variety of materials have been measured. Mechanisms of material removal on microscales are studied. Wear precursors can be detected at early stages of wear using localised surface potential measurements. Localised surface elasticity maps of composite materials with penetration depths of less than 100 nm can be obtained. Nanoindentation hardness and Young's modulus of elasticity can be measured with a depth of indentation as low as 1 nm. Scratching and indentation on nanoscales are the powerful ways to screen for adhesion and resistance to deformation of ultrathin films. These studies provide insight into failure mechanisms of materials and thin films. Furthermore, in situ surface characterisation of local deformation of materials helps to develop better understanding of fracture mechanisms and the brittle to ductile transition in materials. These studies are directly applicable to interfacial phenomena of microdevices and magnetic storage devices.