Controlling the Electronic and Structural Coupling of C₆₀ Nano Films on Fe(001) through Oxygen Adsorption at the Interface

C 60 molecules coupled to metals form hybrid systems exploited in a broad range of emerging fields, such as nanoelectronics, spintronics, and photovoltaic solar cells. The electronic coupling at the C 60 /metal interface plays a crucial role in determining the charge and spin transport in C 60 -based devices; therefore, a detailed understanding of the interface electronic structure is a prerequisite to engineering the device functionalities. Here, we compare the electronic and structural properties of C 60 monolayers interfaced with Fe(001) and oxygen-passivated Fe(001)- p (1 × 1)O substrates. By combining scanning tunneling microscopy and spectroscopy, Auger electron spectroscopy, photoemission and inverse photoemission spectroscopies, we are able to elucidate the striking effect of oxygen on the interaction between Fe(001) and C 60 . Upon C 60 deposition on the oxygen-passivated surface, the oxygen layer remains buried at the C 60 /Fe(001)- p (1 × 1)O interface, efficiently decoupling the fullerene film from the metallic substrate. Tunneling and photoemission spectroscopies reveal the presence of well-defined molecular resonances for the C 60 /Fe(001)- p (1 × 1)O system, with a large HOMO–LUMO gap of about 3.4 eV. On the other hand, for the C 60 /Fe(001) interface, a strong hybridization between the substrate states and the C 60 orbitals occurs, resulting in broader molecular resonances.