Novel device concepts for generating spin currents in graphene

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The ultimate goal of this project is to uncover the intrinsic spin transport properties in single and in few layer graphene. Graphene, a two-dimensional crystal of carbon atoms, is a promising material for exhibiting very long spin diffusion lengths and long electron spin lifetimes, both crucial prerequisites for advanced spintronic devices. As this material only consists of surface atoms particular care and technological knowledge will be needed for addressing its intrinsic properties. To tackle this challenge, we first suggest encapsulating graphene by hexagonal boron nitride from both the top and the bottom sides to allow for best protection against ambient conditions as well as wet chemicals and solvents. In this approach, the electrical contact to graphene shall be established through the outer carbon atoms of the graphene sheet. We expect that this way will allow us to unveil intrinsic spin scattering mechanisms in graphene. Thanks to their high carrier mobility, these structures also enable to study ballistic spin transport phenomena and additionally offer to study the role of edges on spin transport. Secondly, we aim at improving the spin injection and detection barriers by suppressing the formation of conducting pinholes in the oxide barriers in bottom-up non-local spin-valve devices where the graphene layer is mechanically transferred onto predefined Co/MgO electrodes. Thirdly, we suggest exploring methods for controlling the polarization direction of the injected spin current without the need of using external magnetic fields. As electrode material we will use metals which show a strong spin Hall effect with the goal to demonstrate electrical spin injection into graphene by probing the injected spin polarization by neighboring non-local ferromagnetic detectors.