Breaking the Speed Limit of Chemical-Structure Imaging with Enhanced Force Sensitivity

Atomic force microscopy (AFM) with a functionalized tip can resolve the chemical structure of single molecules, but its application has been limited by slow imaging speeds and the restriction to constant-height operation. Here, we overcome these limitations by operating a Si cantilever in its second resonance mode, achieving exceptional force sensitivity. This enables robust, constant-height chemical-structure imaging at speeds up to 200 nm/s-over 60 times faster than previously reported. The enhanced sensitivity also resolves molecular bonds directly in constant-frequency-shift topographic images, a mode crucial for studying nonplanar systems. Our approach significantly expands the capabilities of AFM, opening new avenues for investigating the structure of three-dimensional molecules and tracking the dynamics of on-surface chemical reactions.