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Proceedings Paper

AFM of self-organised nanoparticle arrays: frequency modulation, amplitude modulation, and force spectroscopy
Author(s): Adam Sweetman; Peter Sharp; Andrew Stannard; Subhashis Gangopadhyay; Philip J. Moriarty
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Paper Abstract

Frequency modulation (FM) and amplitude modulation (AM) atomic force microscopy have been used to image self-organised assemblies of octanethiol-passivated Au nanoparticles adsorbed on SiO2/Si(111) samples (where the oxide is either 200 nm or ~ 2 nm thick). Imaging at negative frequency shifts - i.e. in the attractive force regime - in FM mode in ultrahigh vacuum we measure nanoparticle heights which are over 50 % larger than those measured using conventional ("repulsive mode") tapping mode imaging in air. A similar difference in nanoparticle height is observed for attractive mode imaging in air. For nanoparticles adsorbed on 200 nm thick oxide layers, force-distance (F(z)) spectra (measured in FM mode) comprise both a van der Waals component with the conventional power law (1/z2) dependence and a strong electrostatic force which is best fitted using a logarithmic function of the form ln(1/z).

Paper Details

Date Published: 28 August 2008
PDF: 11 pages
Proc. SPIE 7041, Nanostructured Thin Films, 704102 (28 August 2008); doi: 10.1117/12.796403
Show Author Affiliations
Adam Sweetman, Univ. of Nottingham (United Kingdom)
Peter Sharp, Univ. of Nottingham (United Kingdom)
Andrew Stannard, Univ. of Nottingham (United Kingdom)
Subhashis Gangopadhyay, Univ. of Nottingham (United Kingdom)
Philip J. Moriarty, Univ. of Nottingham (United Kingdom)

Published in SPIE Proceedings Vol. 7041:
Nanostructured Thin Films
Geoffrey B. Smith; Akhlesh Lakhtakia, Editor(s)

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