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Shear force distance control at different relative humitities

 

A glass substrate (hydrophillic), partially covered with a Langmuir-Blodgett film of arachidic acid (hydrophobic) was used to measure the influence of different relative humidities on shear-force distance regulation, usually used in near-field optical microscopy. At low relative humidities (left), the contaminating water layer is very thin and height difference between glass substrate and LB-film is nearly as high as expected from x-ray experiments. At higher humidities (right), the height difference decreases, due to a growing water layer on the glass substrate. The height difference between both pictures is 0,6 nm, corresponding to 2 layers of water molecules. (Sample courtesy of P. Fromherz et al., MPI Martinsried)


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Last modified: 30. Juli 1999