Effect of molecular ordering on spin and charge injection in rubrene

Studies have shown that interfaces play a crucial role for efficient spin injection and transport. Here, we address the complex role of interface in spin and charge injection into organic materials by various interface-sensitive characterization tools. Inelastic tunneling spectroscopy and polarized neutron reflectometry were mainly adopted to explore the interfaces of high mobility organic semiconductor rubrene sandwiched by two ferromagnetic electrodes. The dramatic difference in the reported magnetotransport properties and charge injection characteristics in trilayer magnetic junctions has been attributed to the different growth morphology of rubrene molecules at the interface dictated by the presence or absence of a 0.6 nm alumina seed layer. The magnetic contribution of the top ferromagnetic electrode is also influenced by the morphology of the rubrene layer underneath, directly affecting the spin injection efficiency. This work highlights the importance of interface engineering in the development of organic-based spintronics devices.