GraFIEST · Graphene-Ferroelectric Interface for Electronic and Spintronic Technologies

Graphene-Ferroelectric Interface for Electronic and Spintronic Technologies

Spintronics, or "spin transport electronics", is the new paradigm of information technology. It aims at the construction of devices based on the spin degree of freedom of the electron instead of, or in addition to, the electron charge. Spintronics is a field in which huge potentials for both innovative applications and fundamental research coexist and spur on each other's development. Since the energy scale involved in magnetic phenomena is much smaller than the electronic one, spintronic devices promise low-power consumption, high-speed operation and device downscaling. The design of efficient spin devices requires materials with high Spin Orbit Coupling (SOC) and long spin diffusion length. Traditional semiconductors meet the first requirement but not the second. Carbon-based materials (such as carbon nanotubes or graphene) exhibit very long spin diffusion length [~100μm] but at the price of low SOC. The goal of the project GraFIEST is to design novel materials for spintronics applications from first principles, i.e. by atomic scale modeling. The computational approach is fundamental in this quest, since it allows one to scan for material properties at low cost compared to experiment and to parallelize the work by looking at different materials simultaneously. In the GraFIEST project, Density Functional Theory (DFT) techniques have been used to show that it is possible to open an electronic band-gap in graphene by placing graphene on a suitable substrate. Among the possible substrate materials I have selected magnetoelectric multiferroics, i.e. materials characterized by a strong coupling between ferroelectricity and magnetism. This achievement is of crucial importance to fabricate graphene-based (spin) transistors and, hence, for nanoelectronics industry. In addition, it has been demonstrated that doping can allow one to fine tune the electronic structure of the hybrid system and make the high mobility region of the band structure accessible in a transistor configuration. In addition, the velocity of the two types of carriers is found to be quite different, so spin dependent transport is predicted in the hybrid system. The most important result is that the spin polarization of the insulating substrate induces a significant magnetization in the carbon network. Depending on the relative orientation of graphene and substrate, the hybrid system behaves as a spin injector of 100% spin polarized carriers or as a magnetic semiconductor. Both configurations are fundamental building blocks of spintronic devices. The achievements of the GraFIEST Project have the potential to advance the technologically important fields of nanoelectronics and spintronics. Understanding spin injection and spin transport is crucial to the optimization of current devices and design of novel architectures. Thanks to constant progress in the experimental techniques for fabricating interfaces and heterostructures with atomic control, first principles predictions can now be directly related to the physical properties of actual nanomaterials. The size of electronic devices is constantly shrinking, while the increased computational power and multiscale techniques allow one to model larger systems, approaching the size of real devices. The International Technology Roadmap for Semiconductors foresees ab initio simulation as the optimal tool to accelerate material evaluation, by systematically scanning the properties of existing materials and creating new improved materials by design. This is a computational Project. In the future, it is foreseen a close collaboration with experimental groups for the growth, fabrication and characterization of the simulated devices. This multidisciplinary approach is the key to advances in material optimization. Project website address: https://zeilazanolli.wordpress.com/grafiest/ Scientist in Charge: Prof. Stefan Blügel, Peter Grünberg Institut (PGI-1) and Institute for Advanced Simulation (IAS-1) Forschungszentrum Jülich e-mail: s.bluegel – at – fz-juelich.de Web: http://www.fz-juelich.de/pgi/pgi-1/EN/Home/home_node.html Marie Curie Fellow: Dr. Zeila Zanolli e-mail: z.zanolli – at – fz-juelich.de Web: https://zeilazanolli.wordpress.com/home/

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