Weak Adhesion between Contacting Rough Surfaces as Applied to Micro/Nanotechnologies

Sticking of some elements of microelectromechanical systems is a serious problem, which may arise at the stages of producing or exploiting such devices. The equilibrium distances and adhesion energies between surfaces with a normal distribution of roughness have been studied with the purpose of controlling this process. Characteristics of the studied materials, such as dielectric functions, roughness, and plasticity, which are necessary for the calculations, have been discussed. The basic force balance equation has been briefly described. Detailed calculations have been performed for a Si-Au system in air. It has been shown that the plastic properties of gold very weakly affect the adhesion energy as a function of the interfacial distance; however, they markedly influence the establishment of the equilibrium distance. The long-range dispersion forces dominate in the adhesion energy at a roughness with a root-mean-square deviation of larger than 1 nm; therefore, the energy can be calculated within the framework of the Lifshits theory.