Atomic force microscopy and x-ray diffraction studies on agglomeration phenomena of ultrathin Au/Fe bilayers

The agglomeration phenomena of a few nanometer thick Au/Fe bilayers, grown on an MgO(100) substrate, were studied by using atomic force microscopy and x ray diffraction (XRD). The authors found that the insertion of an Fe ultrathin layer between an MgO(100) substrate and a 4 nm thick Au layer promotes the agglomeration process of the Au layer, in which the bilayer structure changes into large Fe/Au islands of ∼200 nm in diameter. In addition, XRD results revealed that the Au in the agglomerated islands has only a (111)-crystallographic orientation, presumably caused by reducing the large surface energy of Au on the MgO(001) substrate. These findings are quite different from cases in which structural stabilization is achieved by inserting an Fe seeding layer of a few nanometers on an MgO(001) substrate.