Realization of ohmic-like contact between ferromagnet and rubrene single crystal

We report a significant lowering of the Schottky barrier height (SBH) in nickel (Ni)/rubrene devices by the insertion of a tetrafluoro-tetracyanoquinodimethane (F4TCNQ), molybdenum trioxide (MoO3), or tetracyanoquinodimethane (TCNQ) layers at the device junction. Devices with F4TCNQ and MoO3 layers show ohmic-like characteristics, whereas the device with the TCNQ layer shows a low SBH (0.26 eV). The SBH of Ni/rubrene device without the acceptor layers is 0.56 eV. We explain the SBH lowering by the electron accepting properties of the thin layers. Such layers can be used to fabricate molecular spintronics devices with ohmic contacts for effective electrical spin injection.