Self-Assembled Lateral Multilayers from Thin Film Alloys of Immiscible Metals

Thin films consisting of alloys of immiscible metals display a unique form of compositional ordering not observed in the bulk. Utilizing scanning tunneling microscopy and low energy electron diffraction, we have examined thin films of ${\mathrm{Co}}_{\eta }{\mathrm{Ag}}_{1-\eta }$ and ${\mathrm{Fe}}_{\eta }{\mathrm{Ag}}_{1-\eta }$ grown on Mo(110) surfaces. Both of these systems are observed to form a compositionally ordered alloy of alternating, contiguous stripes of Co (or Fe) and Ag with the long axis of the stripe coinciding with the Mo[001] direction in the plane of the substrate. The average stripe periodicities are on the order of 2.0 to 2.5 nm along the $\mathrm{Mo}\left[\overline{1}10\right]$ (perpendicular to the stripes) direction depending on film stoichiometry.