Scanning tunneling microscopy and spectroscopy on thin Fe3O4 (110) films on MgO

Thin Fe3O4 (110) films, grown by molecular-beam epitaxy on MgO, have been studied by scanning tunneling microscopy and spectroscopy. A 500-Å-thick film was cleaned prior to the measurements by annealing at 850 K under ultrahigh vacuum. Tunneling images show the onset of the formation of the one-dimensional row reconstruction, which was previously also observed on surfaces of bulk single crystals cleaned by ion bombardment and subsequent annealing. Spectroscopic current–voltage curves reveal different behavior depending on the location of the tip above the row reconstruction. Most notably, when probing the filled states at negative sample bias, a larger current was found on top of the rows as compared to a tip position between two rows.