C 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/metal interface plays a crucial role in determining the charge and spin transport in C-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 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. Upon C deposition on the oxygen-passivated surface, the oxygen layer remains buried at the C/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/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/Fe(001) interface, a strong hybridization between the substrate states and the C orbitals occurs, resulting in broader molecular resonances.
Interfaces between organic semiconductors and ferromagnetic metals offer intriguing opportunities in the rapidly developing field of organic spintronics. Understanding and controlling the spin-polarized electronic states at the interface is the key toward a reliable exploitation of this kind of systems. Here we propose an approach consisting in the insertion of a two-dimensional magnetic oxide layer at the interface with the aim of both increasing the reproducibility of the interface preparation and offering a way for a further fine control over the electronic and magnetic properties. We have inserted a two-dimensional CrO layer at the C/Fe(001) interface and have characterized the corresponding morphological, electronic, and magnetic properties. Scanning tunneling microscopy and electron diffraction show that the film grows well-ordered both in the monolayer and multilayer regimes. Electron spectroscopies confirm that hybridization of the electronic states occurs at the interface. Finally, magnetic dichroism in X-ray absorption shows an unprecedented spin-polarization of the hybridized fullerene states. The latter result is discussed also in light of an ab initio theoretical analysis.
an advanced MHz-class repetition rate X-ray source for linear regime time-resolved spectroscopy and photon scattering, Nuclear Inst. and Methods in Physics Research, A (2019),
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