Eigenmodes of a quartz tuning fork and their application to photo-induced force microscopy

TL;DR

This study characterizes the mechanical eigenmodes of quartz tuning forks using simulations and experiments, demonstrating their application in multi-frequency atomic force microscopy and photo-induced force microscopy.

Contribution

It provides a detailed assignment of the first seven asymmetric eigenmodes of QTFs and shows their utility in advanced AFM techniques.

Findings

Eigenmodes assigned using FEM and experiments

QTF enables independent assessment of force components

Lateral forces measured in non-contact mode

Abstract

We examine the mechanical eigenmodes of a quartz tuning fork (QTF) for the purpose of facilitat- ing its use as a probe for multi-frequency atomic force microscopy (AFM). We perform simulations based on the three-dimensional finite element method (FEM) and compare the observed motions of the beams with experimentally measured resonance frequencies of two QTF systems. The com- parison enabled us to assign the first seven asymmetric eigenmodes of the QTF. We also find that a modified version of single beam theory can be used to guide the assignment of mechanical eigen- modes of QTFs. The usefulness of the QTF for multi-frequency AFM measurements is demonstrated through photo-induced force microscopy (PiFM) measurements. By using the QTF in different con- figurations, we show that the vectorial components of the photo-induced force can be independently assessed, and that lateral forces can be probed in true non-contact mode.