Measuring the true height of water films on surfaces

Measuring the level of hydrophilicity of heterogeneous surfaces and the true height of water layers that form on them in hydrated conditions has a myriad of applications in a wide range of scientific and technological fields. Here, we describe a true non-contact mode of operation of atomic force mic...

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Bibliographic Details
Published in:Nanotechnology 2011-11, Vol.22 (46), p.465705-1-9
Main Authors: Santos, Sergio, Verdaguer, Albert, Souier, Tewfic, Thomson, Neil H, Chiesa, Matteo
Format: Article
Language:English
Subjects:
Atomic force microscopy
Contact
Empirical analysis
Extreme values
Hydrophilicity
Hydrophobic and Hydrophilic Interactions
Imaging
Microscopy, Atomic Force - methods
Nanotechnology
Surface Properties
Water - chemistry
Water film
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Summary:Measuring the level of hydrophilicity of heterogeneous surfaces and the true height of water layers that form on them in hydrated conditions has a myriad of applications in a wide range of scientific and technological fields. Here, we describe a true non-contact mode of operation of atomic force microscopy in ambient conditions and a method to establish the source of apparent height. A dependency of the measured water height on operational parameters is identified with water perturbations due to uncontrolled modes of imaging where intermittent contact with the water layer, or even the surface, might occur. In this paper we show how to (1) determine when the water is being perturbed and (2) distinguish between four different interaction regimes. Each of the four types of interaction produces measurements ranging from fractions of the true height in one extreme to values which are as large as four times the real height in the other. We show the dependence of apparent height on the interaction regime both theoretically and empirically. The agreement between theory and experiment on a BaF2(111) sample displaying wet and un-wet regions validates our results.
ISSN:0957-4484
1361-6528
DOI:10.1088/0957-4484/22/46/465705