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

## TL;DR

This paper introduces a new AFM technique that combines two modes to improve imaging and material analysis of surfaces at the nanoscale.

## Contribution

A novel multifrequency AFM method that integrates PeakForce tapping with higher eigenmodes for enhanced surface characterization.

## Key findings

- High-eigenmode vibrations at low amplitudes do not disrupt topographical or nanomechanical data from PeakForce tapping.
- The technique enables compositional differentiation in heterogeneous nanomaterials with simplified probe requirements.
- The method provides both quantitative mechanical and qualitative material-sensitive information simultaneously.

## Abstract

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.