ITAMOSCINOM · Injection, transport and manipulation of spin currents in new organic materials

Injection, transport and manipulation of spin currents in new organic materials.

Spintronics is a branch of electronics that aims to take full advantage of, not only the charge, but also the spin of the electron. It is one of the areas identified by the electronic industry to represent a post-CMOS paradigm. To fulfil this impressive prediction, a two-fold objective has to be achieved: i) to introduce new spin transport materials that can surpass the ones currently used (metals or semiconductors); ii) devices with optimized performance based on these new materials have to be produced and studied. Organic semiconductors offer unique properties towards their integration in the field of spintronics, the main one being the weakness of their spin scattering mechanisms. Throughout this project we have studied how the electron spin is coherently transmitted in various organic materials and metals and have obtained fundamental parameters to understand the behavior of these materials in complex spintronic devices. At first, we have studied the integration of ferromagnetic metals with organic semiconductors from the materials science point of view in order to understand and optimize the spin injection process. This knowledge has allowed us to fabricate vertical spin valves (simple devices with an organic semiconductor as a transport spin). With the analysis of the magnetotransport properties of these devices we have been able to find both the spin coherence length in various materials and the transport mechanism. Through more complex spintronic devices, such as metal base transistors or nanometric field effect transistors, we have achieved a deeper understanding of the spin decoherence mechanisms in organic materials as well as a progressive convergence of spin with conventional electronic devices. We have also studied the spin injection and transport in metals using lateral spin valves, which are fascinating devices allowing the creation of pure spin currents, with great potential in spintronics. In this case, we have achieved a good understanding of the various contributions to the spin-flip mechanism in the spin transport of simple metals. The role of the ferromagnetic metals used for spin injection has also been carefully evaluated. Finally, we have taken significant steps in both spin manipulation in conventional metals and organic materials. For instance, we have solved several discrepancies in the current literature. We have made progress in understanding spintronics to a more sophisticated level, including the study of the spin-orbit interaction, a crucial effect needed in order to achieve spin manipulation with an external electric field in any material. If spintronics is ever going to be a viable successor to conventional electronics, new materials with optimized spin transport properties have to be found and studied in detail. Also, devices with optimized performance based on these new materials have to be produced, characterized and optimized. Organic semiconductors, which are currently being integrated in mainstream electronics (they are presently used for commercial Light Emitting Diodes and Field Effect Transistors), are ideal materials for a breakthrough in spintronics (tuneable mobility, low spin-orbit coupling). The combination of organic semiconductors with spin-based devices (organic spintronics) has been already demonstrated experimentally and there is compelling evidence of the spin transport properties of the organic materials. With this project, we have obtained precious information about the spin transport properties of organic semiconductors and how to control the electron spin in these materials. The knowledge achieved in this project will thus help bringing this discipline forward.

Data: CORDIS, © European Union