Noncontact Atomic Force Microscopy - Yale School of Engineering ...

Mo-1730
Short range Casimir force measurements under ambient conditions and
liquid environments
P.J. van Zwol 1 , V.B. Svetovoy 2 , G. Palasantzas 1 , J. Th. M. De Hosson 1
1 Materials Innovation Institute and Zernike Institute for Advanced Materials
University of Groningen, 9747 AG Groningen, The Netherlands
2 MESA_Research Institute, University of Twente, PO 217, 7500 AE Enschede, The Netherlands
We briefly review ellipsometry [1] and our force measurement in the sphere plane
geometry [2,3] on smooth and rough gold surfaces, and focus specifically on the contact
point between rough surfaces, and the optical quality of the surfaces in use. Furthermore
we outline inverse colloid probe force measurements [4] in liquid environment (fig 1), for
which we found local charge variation of glass spheres resulting in varying strengths of
the electrical double layer. In addition we show that when the dielectric function of the
liquid becomes comparable to that of the surfaces, resulting Casimir forces are very
small. However sample dependence and uncertainty in the measured dielectric functions
indicate that the theory is even more uncertain than the measurements, even if measured
dielectric data is available, for all materials, over all relevant frequency ranges. In the
extreme limit this can lead to the weird situation that small variations in the dielectric
data can lead to a complete change of shape of the force, flipping between atractive and
repulsive, and multiple atractive-repulsive transitions with distance.
Figure 1: Optical image of sintered borisilicate glass spheres on glass.
[1] V. B. Svetovoy, P.J. van Zwol, G. Palasantzas, J. Th. M. DeHosson, Phys. Rev. B 77, 035439 (2008)
[2] P.J. van Zwol, G. Palasantzas, J. Th. M. DeHosson, Phys. Rev. B 77, 075412 (2008)
[3] P.J. van Zwol, G. Palasantzas, M. van de Schootbrugge, J. Th. M. De Hosson, Appl. Phys. Lett. 92, 054101 (2008)
[4] P.J. van Zwol, G. Palasantzas, J. Th. M. DeHosson, To appear in Phys. Rev. E (2009).
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