In situ oxidation of epitaxial Fe(1 1 0) films grown on Mo(1 1 0)/Al 2O 3(1 1 −2 0) substrates

Abstract

The surface morphology of in situ oxidized 200 Å thick Fe(1 1 0) films grown on Al 2O 3(1 1 −2 0) substrates using a Mo(1 1 0) buffer layer was investigated by low energy electron diffraction and scanning tunneling microscopy (STM). The epitaxially grown Fe(1 1 0) films were oxidized to magnetite, Fe 3O 4(1 1 1), in an oxygen atmosphere. For a low oxygen exposure of 6 L at room temperature a c(2 × 2)-O-reconstruction and for an intermediate oxygen exposure of 100 L followed by annealing at 600 K the formation of FeO(1 1 1) was observed. After high oxygen exposures (⩾1500 L) and annealing at 800–1000 K the formation of Fe 3O 4(1 1 1) films of high crystalline quality has been achieved. Atomically resolved STM images of the Fe 3O 4(1 1 1) surface show a hexagonal symmetry with a 6 Å periodicity. The system was identified as a well-ordered epitaxial Fe 3O 4(1 1 1) layer on the Fe(1 1 0)/Mo(1 1 0)/Al 2O 3(1 1 −2 0) system.