Ultrathin Iron Oxide Films on Cu(100).

In this investigation, I have focused on understanding the structure and morphology of ultrathin iron oxide films and characterizing them by STM and LEED. The room temperature Fe deposition results in a layer by layer growth. The oxidation was accomplished by annealing the sample to 810K in ambient oxygen. Two distinct oxide surface structures were observed depending on initial Fe coverage. For deposited Fe films of less than 2 ML, an oxide layer was formed with preferential growth along two perpendicular directions with a banded coarse and a hexagonal fine superstructure. As the initial Fe coverage above 2 ML, a new structure was observed consisting of uniformly thick patches of oxide with large, atomically-flat terraces. The oxide, that forms at low coverage was identified as FeO(111), while the structure at higher Fe coverage was identified as Fe3O4 on the basis of a model consistent with both STM and LEED, and thermodynamic data.