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Updated: Apr 8, 2026
A Sample Preparation Pipeline for Microcrystals at the VMXm Beamline
Published on: June 17, 2021
Nano-contact microscopy of supracrystals
Adam Sweetman1, Nicolas Goubet2, Ioannis Lekkas1
1The School of Physics and Astronomy, The University of Nottingham, Nottingham, NG7 2RD, U.K.
Background:
Highly ordered three-dimensional colloidal crystals (supracrystals) comprised of 7.4 nm diameter Au nanocrystals (with a 5% size dispersion) have been imaged and analysed using a combination of scanning tunnelling microscopy and dynamic force microscopy.
Results:
By exploring the evolution of both the force and tunnel current with respect to tip-sample separation, we arrive at the surprising finding that single nanocrystal resolution is readily obtained in tunnelling microscopy images acquired more than 1 nm into the repulsive (i.e., positive force) regime of the probe-nanocrystal interaction potential. Constant height force microscopy has been used to map tip-sample interactions in this regime, revealing inhomogeneities which arise from the convolution of the tip structure with the ligand distribution at the nanocrystal surface.
Conclusion:
Our combined STM-AFM measurements show that the contrast mechanism underpinning high resolution imaging of nanoparticle supracrystals involves a form of nanoscale contact imaging, rather than the through-vacuum tunnelling which underpins traditional tunnelling microscopy and spectroscopy.
