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Bimodal frequency-modulated atomic force microscopy with small cantilevers

Dietz, Christian and Schulze, Marcus and Voss, Agnieszka and Riesch, Christian and Stark, Robert W. (2015):
Bimodal frequency-modulated atomic force microscopy with small cantilevers.
In: Nanoscale, ROYAL SOC CHEMISTRY, CAMBRIDGE, ENGLAND, pp. 1849-1856, 7, (5), ISSN 2040-3364, [Online-Edition: http://dx.doi.org/10.1039/C4NR05907G],
[Article]

Abstract

Small cantilevers with ultra-high resonant frequencies (1-3 MHz) have paved the way for high-speed atomic force microscopy. However, their potential for multi-frequency atomic force microscopy is unexplored. Because small cantilevers have small spring constants but large resonant frequencies, they are well-suited for the characterisation of delicate specimens with high imaging rates. We demonstrate their imaging capabilities in a bimodal frequency modulation mode in constant excitation on semi-crystalline polypropylene. The first two flexural modes of the cantilever were simultaneously excited. The detected frequency shift of the first eigenmode was held constant for topographical feedback, whereas the second eigenmode frequency shift was used to map the local properties of the specimen. High-resolution images were acquired depicting crystalline lamellae of approximately 12 nm in width. Additionally, dynamic force curves revealed that the contrast originated from different interaction forces between the tip and the distinct polymer regions. The technique uses gentle forces during scanning and quantified the elastic moduli E-am = 300 MPa and E-cr = 600 MPa on amorphous and crystalline regions, respectively. Thus, multimode measurements with small cantilevers allow one to map material properties on the nano-scale at high resolutions and increase the force sensitivity compared with standard cantilevers.

Item Type: Article
Erschienen: 2015
Creators: Dietz, Christian and Schulze, Marcus and Voss, Agnieszka and Riesch, Christian and Stark, Robert W.
Title: Bimodal frequency-modulated atomic force microscopy with small cantilevers
Language: English
Abstract:

Small cantilevers with ultra-high resonant frequencies (1-3 MHz) have paved the way for high-speed atomic force microscopy. However, their potential for multi-frequency atomic force microscopy is unexplored. Because small cantilevers have small spring constants but large resonant frequencies, they are well-suited for the characterisation of delicate specimens with high imaging rates. We demonstrate their imaging capabilities in a bimodal frequency modulation mode in constant excitation on semi-crystalline polypropylene. The first two flexural modes of the cantilever were simultaneously excited. The detected frequency shift of the first eigenmode was held constant for topographical feedback, whereas the second eigenmode frequency shift was used to map the local properties of the specimen. High-resolution images were acquired depicting crystalline lamellae of approximately 12 nm in width. Additionally, dynamic force curves revealed that the contrast originated from different interaction forces between the tip and the distinct polymer regions. The technique uses gentle forces during scanning and quantified the elastic moduli E-am = 300 MPa and E-cr = 600 MPa on amorphous and crystalline regions, respectively. Thus, multimode measurements with small cantilevers allow one to map material properties on the nano-scale at high resolutions and increase the force sensitivity compared with standard cantilevers.

Journal or Publication Title: Nanoscale
Volume: 7
Number: 5
Publisher: ROYAL SOC CHEMISTRY, CAMBRIDGE, ENGLAND
Divisions: 11 Department of Materials and Earth Sciences > Material Science > Nonmetallic-Inorganic Materials
11 Department of Materials and Earth Sciences > Material Science > Physics of Surfaces
11 Department of Materials and Earth Sciences > Material Science
11 Department of Materials and Earth Sciences
Zentrale Einrichtungen
Exzellenzinitiative
Exzellenzinitiative > Clusters of Excellence
Profile Areas > Thermo-Fluids & Interfaces
Profile Areas
Date Deposited: 08 Jun 2016 09:06
Official URL: http://dx.doi.org/10.1039/C4NR05907G
Identification Number: doi:10.1039/C4NR05907G
Funders: We thank the Center of Smart Interfaces for financial support.
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