scanning localized evaporation and deposition of an evaporant on a substrate utilizes a mask assembly comprised of a series of mask elements with openings thereon and spaced apart in a stack . the openings are aligned so as to direct the evaporant therethrough onto the substrate . the mask elements are heated and the stack may include a movable shutter element to block openings in adjacent mask elements . the evaporant streams are usually vertical but some may be oblique to the substrate , and they may be of different materials .