Reconstruction and charge ordering of epitaxial Fe3O4(0 0 1) films

Abstract Surface structure and charge ordering of epitaxial Fe 3 O 4 (0 0 1) films grown on MgO(0 0 1) were studied by scanning tunneling microscopy. The film surface exhibited a (√2×√2) R 45° reconstruction induced by ordered oxygen vacancies. The presence of cation rows running along the [1 1 0] direction revealed surface termination at B-sites. Within the cation rows, an atomic separation of 0.3 nm is resolved by using a W tip. By using a Ni tip, another feature of 1.2 nm periodic protrusions is observed on areas usually connected to surface defects such as steps and cation vacancies. These protrusions represented the static charge of Fe 2+ and Fe 3+ ions.