Conducting Atomic Force Microscopy in Liquids.
In: Tomczak, N and Goh, KEJ, (eds.)
Scanning Probe Microscopy.
World Scientific Publishing Company
Liquids confined in a narrow gap between two surfaces can form ordered layers, which may lead to oscillatory-type solvation forces, which can be measured using atomic force microscopy (AFM). However, it remains experimentally challenging to study the detailed mechanics of a single AFM contact, and in this regard conducting AFM (C-AFM) can be used to reveal subtle changes in the contact junction which are not observed in standard force measurements. Furthermore, the ability to measure conductivity allows an evaluation of the tip–sample contact area, a difficult problem in AFM. In this chapter, we present simultaneous force and current measurements as anAFM tip approaches a graphite surface in liquid and squeezes out the confined liquid. Experiments were performed on linear and branched alkanes. Solvation layering occurs for both types of liquid, but marked differences in the squeeze-out mechanics are observed, depending on whether the monolayer is ordered or disordered. It is found that continuum elastic models are well suited for describing the squeeze-out mechanism of ordered, solid-like materials. However, when the confined molecules are disordered, the data are qualitatively very different. Simple elastic models cannot be applied anymore and comparison with recent simulations suggests that some liquid molecules remain trapped within the junction.
|Title:||Conducting Atomic Force Microscopy in Liquids|
|UCL classification:||UCL > School of BEAMS
UCL > School of BEAMS > Faculty of Maths and Physical Sciences
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