Molecular liquid under nanometre confinement: density profiles underlying oscillatory forces
- Perret, Edith Paul Scherrer Institut, Villigen PSI, Switzerland
- Nygård, Kim Paul Scherrer Institut, Villigen PSI, Switzerland
- Satapathy, Dillip Kumar University of Fribourg
- Balmer, Tobias E. ETH Zurich, Switzerland
- Bunk, Oliver Paul Scherrer Institut, Villigen PSI, Switzerland
- Heuberger, Manfred EMPA, St Gallen, Switzerland
- Veen, J. Friso van der Paul Scherrer Institut, Villigen PSI, Switzerland - ETH Zurich, Switzerland
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21.05.2010
Published in:
- Journal of Physics: Condensed Matter. - 2010, vol. 22, no. 23, p. 235102
English
Ultrathin (<12 nm) films of tetrakis(trimethyl)siloxysilane (TTMSS) have been confined by atomically flat mica membranes in the presence and absence of applied normal forces. When applying normal forces, discrete film thickness transitions occur, each involving the expulsion of TTMSS molecules. Using optical interferometry we have measured the step size associated with a film thickness transition (7.5 Å for compressed, 8.4 Å for equilibrated films) to be smaller than the molecular diameter of 9.0 Å. Layering transitions with a discrete step size are commonly regarded as evidence for strong layering of the liquid's molecules in planes parallel to the confining surfaces and it is assumed that the layer spacing equals the measured periodicity of the oscillatory force profile. Using x-ray reflectivity (XRR), which directly yields the liquid's density profile along the confinement direction, we show that the layer spacing (10–11 Å) proves to be on average significantly larger than both the step size of a layering transition and the molecular diameter. We observe at least one boundary layer of different electron density and periodicity than the layers away from the surfaces.
- Faculty
- Faculté des sciences et de médecine
- Department
- Département de Physique
- Language
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- English
- Classification
- Physics
- License
- License undefined
- Identifiers
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- RERO DOC 20297
- DOI 10.1088/0953-8984/22/23/235102
- Persistent URL
- https://folia.unifr.ch/unifr/documents/301550
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