In situ oxidation of epitaxial Fe(110) films grown on Mo(110)/Al2O3(11-20) substrates

The surface morphology of in situ oxidized 200 Angstrom thick Fe(110) films grown on Al2O3 (11 - 20) substrates using a Mo(110) buffer layer was investigated by low energy electron diffraction and scanning tunneling microscopy (STM). The epitaxially grown Fe(110) films were oxidized to magnetite, Fe3O4 (111), in an oxygen atmosphere. For a low oxygen exposure of 6 L at room temperature a c(2 x 2)-O-reconstruction and for an intermediate oxygen exposure of 100 L followed by annealing at 600 K the formation of FeO(111) was observed. After high oxygen exposures (greater than or equal to 1500 L) and annealing at 800-1000 K the formation of Fe3O4 (111) films of high crystalline quality has been achieved. Atomically resolved STM images of the Fe3O4(111) surface show a hexagonal symmetry with a 6 Angstrom periodicity. The system was identified as a well-ordered epitaxial Fe3O4(111) layer on the Fe(110)/Mo(110)/Al2O3(11-20) system. (C) 2003 Elsevier Science B.V. All rights reserved.