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

C₆₀ 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 C₆₀/metal interface plays a crucial role in determining the charge and spin transport in C₆₀-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 C₆₀ 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 C₆₀. Upon C₆₀ deposition on the oxygen-passivated surface, the oxygen layer remains buried at the C₆₀/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 C₆₀/Fe(001)-p(1 × 1)O system, with a large HOMO-LUMO gap of about 3.4 eV. On the other hand, for the C₆₀/Fe(001) interface, a strong hybridization between the substrate states and the C₆₀ orbitals occurs, resulting in broader molecular resonances.