A method for forming an ordered alloy includes: (a) forming a layer of a first metal with a layer thickness of less than 0.3 nm over a substrate; (b) forming a layer of a second metal with a layer thickness of less than 0.3 nm on the layer of the first metal under an elevated temperature sufficient to cause interdiffusion of atoms of the first and second metals between the layer of the first metal and the layer of the second metal so as to form the ordered alloy; and (c) repeating steps (a) and (b) until a predetermined layer thickness of the ordered alloy is achieved.