Effect of adsorbed H atoms on the Fe electronic states of Fe3O4(001) film surfaces

We report the presence of OH groups on the surfaces of ultrahigh-vacuum-prepared Fe3O4(001) films by means of x-ray photoelectron spectroscopy (XPS). In addition, the variations of Fe electronic states induced by H atoms adsorbed on a Jahn-Teller distorted Fe3O4(001) surface have been studied using in situ scanning tunneling microscopy and scanning tunneling spectroscopy (STS). The obtained XPS spectra of the films have demonstrated the presence of surface OH groups. The STS spectra measured on Fe sites with and without neighboring OH groups have indicated that adsorbed H and their neighboring Fe atoms behave as electron-donor and electron-trapping sites, respectively. This phenomenon changes the Fe atoms from a semiconducting to a metalliclike nature. These local electronic state modifications are related to the occupation of Fe 3d states just below the Fermi level, corresponding to an Fe2+-like state. The orbital occupation can be explained by the gain of electrons from the adsorbed H atoms.