Surface Roughness and Material Optical Properties Influence on Casimir/van der Waals and Capillary Surface Forces

Theory calculations using the Lifshitz theory and atomic force microscopy force measurements show that Casimir/van der Weals dispersive forces have a strong dependence on material optical properties and surface roughness. 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, knowledge of precise optical properties of metals is very important for accurate force predictions rather than referring to idealized defect free material models. Finally, we compare the Casimir/van der Weals forces to capillary adhesive forces in order to illustrate their significance in stiction problems, which are important for motion analysis of microelectromechanical (MEMS) systems.