surface.*

EuO_1-x thin films deposited by pulsed laser deposition on Si(100) were studied by scanning tunneling microscopy and spectroscopy at room temperature. Oxygen vacancies in EuO_1-x are visualized through dI/dV mapping and the apparent sizes of the oxygen vacancies are found to be 1.8 nm ± 0.5 nm. These apparent sizes are considered as the spatial extension of the electron wave function originated from the oxygen vacancies. It is further argued that this observed electronic wave function might be the precursor of the bound magnetic polaron formation occurred at lower temperature. Moreover, some of the oxygen vacancies were found (1) hopping to adjacent site; (2) emerging (vacancy creation); and (3) disappearing (vacancy annihilation), indicating that the oxygen vacancies on the EuO_1-x surface at room temperature are not extremely stable.