Abstract
A dynamic operation of atomic force microscopy (AFM) provides images depending on the elasticity of sample surface in addition to the topography. A resonant frequency of an AFM probe, i.e., a cantilever equipped with a force-sensor tip, depends on the contact stiffness between a sample and a tip. However, poor sensitivity often confronts us for stiff sample, e.g., ceramics and metals. We have developed a special cantilever with its mass concentrated as a way of enhancing the sensitivity to contact stiffness. A tungsten particle was employed as a concentrated mass, which is adhesively attached to the free end of a commercially available rectangular cantilever made of silicon. Measurements of the spectra and the elemental beam theory proved that the attachment of a concentrated mass provides a sufficient sensitivity even for stiff materials. We have also demonstrated a powerfulness of our cantilever in quantitative evaluation of local elasticity. In this study, we discuss an imaging technique for the mass-concentrating cantilever, and shows examples of elastic images, whose contrast is based on the elastic differences of the surface structure. So-called slope detection for contact resonance works well and produces high contrast images of elasticity for several nano-structured materials.
