Growth of face-centered-cubic Fe films on Cu(100): Interdiffusion, surfactant effects, and island formation - art. no. 205422

Various factors complicating the growth of ultrathin films of gamma -Fe on CU(100)-interdiffusion, formation of surfactant layers, and island formatio n-have been investigated using density-function al calculations. It is show n that the formation of a surfactant Cu layer on top of the growing Fe film s is energetically favored over both clean Fe surfaces and the formation of ordered surface alloys. However, the exchange process leading to the incor poration of the Fe atoms in or below the Cu top layer is characterized by a barrier of 1.45 eV/Fe atom, i.e., it will be kinetically hindered at low t emperatures. In the initial stages of Fe deposition, as long as parts of th e surface of the substrate remain uncovered by Fe, island formation is ener getically preferred over the formation of atomically flat films. A surfacta nt Cu layer largely suppresses this tendency to surface roughening. Surface energies of 0.60 eV/atom for Cu(100) and of 0.84 eV/atom for gamma -Fe(100 ) have been calculated and the difference is identified as the driving mech anism behind these phenomena.