NANO-SCALE FORCES, STRESSES, AND TIP GEOMETRY EVOLUTION OF AMPLITUDE MODULATION ATOMIC FORCE MICROSCOPY PROBES

摘要

Atomic-scale wear is one of the main factors that hinders the performance of probes for atomic force microscopy (AFM) [1-6], including for the widely-used amplitude modulation (AM-AFM) mode. To conduct consistent and quantitative AM-AFM wear experiments, we have developed a protocol that involves controlling the tip-sample interaction regime, calculating the maximum contact force and normal stress over the course of the wear test, and quantifying the wear volume using high-resolution transmission electron microscopy imaging (HR-TEM). The tip-sample interaction forces are estimated from a closed-form equation that uses the Derjaguin-Muller-Toporov interaction model (DMT) accompanied by a tip radius measurement algorithm known as blind tip reconstruction. The applicability of this new protocol is demonstrated experimentally by scanning silicon probes against ultrananocrystalline diamond (UNCD) samples. The wear process for the Si tip involved blunting of the tip due to tip fragmentation and plastic deformation. In addition, previous studies on the relative contributions of energy dissipation processes to AFM tip wear are reviewed, and initial steps are taken towards applying this concept to AM-AFM.