Thermal stability and structure of ultrathin Co/Fe2O3 films on the Cu(110) surface

The thermal stability of very thin Co(0.9 nmapproximate to7 ML)/Fe2O3(1 nm) double layers, deposited on Cu(110), was studied by Auger electron spectroscopy, thermal energy helium atom scattering, and low energy electron diffraction. Ordering of the double layer requires annealing to 400-450 K. After annealing, the film consists mainly of Co(110). Part of the Co(110) surface shows a (3x1) reconstruction which could be related to the presence of oxygen floating on the Co film. In addition, evidence was found for the presence of c(2x2) reconstructed domains of fcc Co(100). The Co/Fe2O3 double layer is essentially stable up to 400 K. Above this temperature, the Co and Fe2O3 start to mix, resulting in segregation of Fe2O3 to the surface at around 700 K. Similar as in the case of the single layer system Fe2O3/Cu(110), copper is found to diffuse towards the surface at temperatures >600 K, but the surface itself remains covered by iron oxide up to 1100 K. Already below 1000 K, Co is completely dissolved in the bulk of the copper crystal. (C) 2002 American Institute of Physics.