Kinetic Roughening and Material Optical Properties Influence on Van der Waals/Casimir Forces

Atomic force microscopy measurements and force theory calculations using the Lifshitz theory show that van der Waals/Casimir dispersive forces have a strong dependence on surface roughness and material optical properties. 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, knowledge of precise optical properties of metals is shown to be very important for accurate force predictions rather than referring to idealized defect free material models. Finally, we compare the van der Waals/Casimir forces to capillary adhesive forces in order to illustrate their significance in stiction problems.