Multifrequency AFM integrating PeakForce tapping and higher eigenmodes for heterogeneous surface characterization

This study introduces a multifrequency atomic force microscopy (AFM) technique that synergistically integrates PeakForce tapping mode with higher eigenmode vibrations to achieve simultaneous high-resolution topographical imaging and to access additional contrast channels for distinguishing material regions or compositions. Unlike conventional multimodal AFM, our method employs non-resonant and higher eigenmode frequencies to achieve robust topographical and compositional mapping. Our experimental results indicate that the superposition of high-eigenmode vibrations, when applied at low amplitudes, does not significantly interfere with the topographical and nanomechanical mappings obtained via the PeakForce tapping method. Furthermore, the technique's dual capability, that is, quantitative mechanics via quasi-static force curves and qualitative material-sensitive information via eigenmode vibration signals, facilitates effective compositional differentiation in heterogeneous nanomaterials while significantly simplifying the requirements for probe selection, which are typically necessary for material differentiation via the standard PeakForce tapping method. This innovation enhances the technique's practicality and extends compatibility to a wider array of probe types.