Quantification of surface displacements and electromechanical phenomena via dynamic atomic force microscopy

TL;DR

This paper presents an analytical model and experimental validation for accurately quantifying surface displacements at the picometer scale using atomic force microscopy, enhancing measurement precision in various AFM-based techniques.

Contribution

It introduces a new analytical approach that accounts for cantilever shape at the first resonant contact mode, improving surface displacement quantification accuracy in AFM.

Findings

Achieved pm-scale surface displacement measurements with nanometer spatial resolution.

Validated the model experimentally on ferroelectric materials.

Enhanced understanding of cantilever dynamics in resonance-based AFM techniques.

Abstract

Detection of dynamic surface displacements associated with local changes in material strain provides access to a number of phenomena and material properties. Contact resonance-enhanced methods of Atomic Force Microscopy (AFM) have been shown capable of detecting ~1-3 pm-level surface displacements, an approach used in techniques such as piezoresponse force microscopy, atomic force acoustic microscopy, and ultrasonic force microscopy. Here, based on an analytical model of AFM cantilever vibrations, we demonstrate a guideline to quantify surface displacements with a high accuracy by taking into account the cantilever shape at the first resonant contact mode depending on the tip-sample contact stiffness. The approach has been experimentally verified and further developed for the piezoresponse force microscopy (PFM) using well-defined ferroelectric materials. These results open up a way to accurate and precise measurements of the surface displacement as well as piezoelectric constants at the pm-scale with nanometer spatial resolution and will allow avoiding erroneous data interpretations and measurement artefacts. This analysis is directly applicable to all cantilever-resonance-based SPM techniques.