Measurements of in-plane material properties with scanning probe microscopy

Scanning probe microscopy (SPM) was originally conceived as a method for measuring atomic-scale surface topography. Over the last two decades, it has blossomed into an array of techniques that can be used to obtain a rich variety of information about nanoscale material properties. With the exception of friction measurements, these techniques have traditionally depended on tip-sample interactions directed normal to the sample's surface. Recently, researchers have explored several effects arising from interactions parallel to surfaces, usually by deliberately applying a modulated lateral displacement. In fact, some parallel motion is ubiquitous to cantilever-based SPM, due to the tilt of the cantilever. Recent studies, performed in contact, noncontact, and intermittent-contact modes, provide new insights into properties such as structural anisotropy, lateral interactions with surface features, nanoscale shear stress and contact mechanics, and in-plane energy dissipation. The understanding gained from interpreting this behaviour has consequences for all cantilever-based scanning probe microscopies.