Epitaxial growth of ultrathin Fe films on Ni(001): a structural study

We have investigated the atomic geometry of Fe films on a Ni(001) crystal in the thickness range 0-25 ML with the aim of following the transition from the fee pseudomorphic structure to the equilibrium bcc phase. The structural techniques used are primary-beam diffraction modulated electron emission (PDMEE) and low-energy electron diffraction (LEED). For film thicknesses up to 5 ML the films are fee, strained in the direction of film growth. For higher Fe coverages, the films begin a transition to the bulk bcc structure which is complete after 14 ML of Fe coverage. We have obtained evidence for intermixing between Fe and Ni in the first 3 ML. The orientational relationship between the bcc phase and the underlying fee substrate has also been investigated, finding a bcc (110) phase with four possible domains, each with one of the [111] directions parallel to an fcc [110] direction.