by varying the spacing between a partially - reflective , partially - transmissive surface and a highly reflective surface positioned behind the partially - reflective , partially - transmissive surface , an interferometric modulator selectively creates constructive and / or destructive interference between light waves reflecting off the two surfaces . the spacing can be varied by applying a voltage to create electrostatic attraction between the two surfaces , which causes one or both surfaces to deform and move closer together . in the absence of such attraction , the surfaces are in a relaxed position , where they are farther apart from one another . a actuation voltage is needed to create sufficient electrostatic attraction to cause a surface to deform . the actuation voltage can be modified by implanting ions in a dielectric layer attached to one or both surfaces . upon the application of a voltage , the ions create a baseline level of repulsion or attraction between the two surfaces , which thus require more or less voltage , respectively , to cause a surface to deform . the degree of ion implantation can be chosen to set the actuation voltage as desired , or the surfaces can be made to deform at a given voltage by appropriately selecting the degree of ion implantation .