Mechanical Properties Studied at the Nanoscale Using Scanning Local-Acceleration Microscopy (SLAM)

Abstract
A new technique for studying mechanical properties with a lateral resolution of better than 40 nm is presented. The Scanning Local-Acceleration Microscope (SLAM) is based on the Atomic Force Microscope (AFM). The principle of the SLAM technique is to vibrate the sample with a small amplitude at a frequency above the tip-sample system's highest resonance, forcing the AFM tip to deform locally the sample's surface. This permits one to determine the sample's properties with a dramatically improved signal-to-noise ratio, from both compliant (polymer) and stiff (metal or ceramics) samples. SLAM allows one to measure the "contact stiffness" between tip and sample, which can be related to the elastic modulus of the sample. Present developments explore the possibilities of damping measurements on the same lateral resolution scale, which could lead to a better understanding of nanophased materials and interfaces. One future goal is the passage from qualitative to quantitative measurements. The SLAM instrumentation, the basis of the "stiffness" interpretation and some results from a PVC/PB polymer-blend, from a NiTi/epoxy metal reinforced polymer and from an Al₂O₃/Al Metal-Matrix Composite are presented. The current status of the damping measurements is described.