Influence of random roughness on the Casimir force at small separations.pdf

Influence of random roughness on the Casimir force at small separations * P.J. van Zwol, G. Palasantzas and J. Th. M. De Hosson Department of Applied Physics, Netherlands Institute for Metals Research and Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands. Abstract The influence of random surface roughness of Au films on the Casimir force is explored with atomic force microscopy in the plate-sphere geometry. The experimental results are compared to theoretical predictions for separations ranging between 20 and 200 nm. The optical response and roughness of the Au films were measured and used as input in theoretical predictions. It is found that at separations below 100 nm, the roughness effect is manifested through a strong deviation from the normal scaling of the force with separation distance. Moreover, deviations from theoretical predictions based on perturbation theory can be larger than 100%. PACS numbers: 68.55.Jk, 68.37.Ps, 85.85.+j, 78.68.+m * Corresponding author: g.palasantzas@rug.nl 1 When the proximity between material objects becomes of the order of nanometers up to a few microns, a regime is entered where forces quantum mechanical in nature, namely, van der Waals and Casimir forces, become operative [1]. Historically, the Casimir force has been considered to result from the perturbation of zero point vacuum fluctuations by conducting plates [1]. Because of its relatively short range, the Casimir force is now starting to take on technological importance in the operation of micro/nanoelectromechanical systems (MEMS/NEMS) at separations 200 nm, e.g., micro oscillator d