Challenges and complexities of multifrequency atomic force microscopy in liquid environments.

Santiago D Solares

doi:10.3762/bjnano.5.33

Abstract

This paper illustrates through numerical simulation the complexities encountered in high-damping AFM imaging, as in liquid enviroments, within the specific context of multifrequency atomic force microscopy (AFM). The focus is primarily on (i) the amplitude and phase relaxation of driven higher eigenmodes between successive tip–sample impacts, (ii) the momentary excitation of non-driven higher eigenmodes and (iii) base excitation artifacts. The results and discussion are mostly applicable to the cases where higher eigenmodes are driven in open loop and frequency modulation within bimodal schemes, but some concepts are also applicable to other types of multifrequency operations and to single-eigenmode amplitude and frequency modulation methods.

Highlights

Multifrequency atomic force microscopy (AFM) refers to a family of techniques that involve simultaneous excitation of the microcantilever probe at more than one frequency [1]
This paper explores through simulation the implications of the low-Q cantilever dynamics within the specific context of bimodal AFM imaging
The perturbation appears to the user as a momentary variation in the phase and amplitude of the higher mode, which relaxes until the phase and amplitude reach the values they would have in the absence of the sample, just before the impact occurs

Summary

Introduction

Multifrequency atomic force microscopy (AFM) refers to a family of techniques that involve simultaneous excitation of the microcantilever probe at more than one frequency [1] The first of these methods was proposed by García and coworkers in 2004 to carry out simultaneous non-contact amplitude-modulation imaging and open-loop (phase contrast) compositional mapping of surfaces in air by exciting and controlling the first two eigenmodes of the cantilever [2]. This approach has since been extended to intermittent contact characterization using open loop and frequency modulation [3,4], imaging in liquid and vacuum environments [5,6,7,8], and to trimodal operation [9,10,11].

Methods

Results

Conclusion