Effects of Surface Properties on the Effective Electrical Gap of Microelectromechanical Devices Operating in Contact E. K. Chan, R. W. Dutton The effective electrical gap between two conducting surfaces sandwiching a thin dielectric layer varies with applied voltage and pressure. Improved methods for measuring and modeling this variation are presented. Optical surface profile measurements of fixed-fixed beams, and capacitance-voltage measurements of a center-tethered structure that eliminates zipping are shown. A compressible contact surface model is used in 2-D simulations of electrostatically actuated beams to capture the surface effects. The simulation fit is good a low voltages but deteriorates at higher voltages. Substrate curvature and electronic effects are investigated but found to be negligible.