Enhanced feedback performance in off-resonance AFM modes through pulse train sampling

Author:

Kangül MustafaORCID,Asmari NavidORCID,Andany Santiago HORCID,Penedo MarcosORCID,Fantner Georg EORCID

Abstract

Dynamic atomic force microscopy (AFM) modes that operate at frequencies far away from the resonance frequency of the cantilever (off-resonance tapping (ORT) modes) can provide high-resolution imaging of a wide range of sample types, including biological samples, soft polymers, and hard materials. These modes offer precise and stable control of vertical force, as well as reduced lateral force. Simultaneously, they enable mechanical property mapping of the sample. However, ORT modes have an intrinsic drawback: a low scan speed due to the limited ORT rate, generally in the low-kilohertz range. Here, we analyze how the conventional ORT control method limits the topography tracking quality and hence the imaging speed. The closed-loop controller in conventional ORT restricts the sampling rate to the ORT rate and introduces a large closed-loop delay. We present an alternative ORT control method in which the closed-loop controller samples and tracks the vertical force changes during a defined time window of the tip–sample interaction. Through this, we use multiple samples in the proximity of the maximum force for the feedback loop, rather than only one sample at the maximum force instant. This method leads to improved topography tracking at a given ORT rate and therefore enables higher scan rates while refining the mechanical property mapping.

Funder

Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung

ETH Domain Open Research DATA

H2020 European Research Council

Innosuisse - Schweizerische Agentur für Innovationsförderung

Publisher

Beilstein Institut

Subject

Electrical and Electronic Engineering,General Physics and Astronomy,General Materials Science

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