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. It is indeed important to master and reliably reproduce the chemical reactions responsible of the spin-polarization at the interface.
Here we propose an approach consisting in the insertion of an ultrathin, two-dimensional Cr4O5 magnetic oxide layer at the interface between a C60 fullerene organic semiconductor and a Fe(001) ferromagnetic metal to both maximize the spin polarization and to overcome the reproducibility issues usually present in case of direct interface between metallic layer and organic semiconductor.
C60 fullerene showed a greater surface diffusivity when growing on Cr4O5 compared to the Fe(001) case. From the first stages of surface coverage, C60 tends to form islands rather than isolated molecules, leading to a well-ordered growth at higher thicknesses (Figure 1, above).
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Figure 1. STM image 200 x 200 nm2 of the surface of a C60/ Cr4O5/Fe(001) sample with a fullerene coverage of about 0.5 ML. The image was taken at room temperature with ΔV= 1.7 V, I = 400 pA.