Researchers from the US Naval Research Laboratory (NRL) developed a new type of tunnel device structure in which both the tunnel barrier and transport channel are made from graphene. The researchers say that this device features the highest spin injection values yet measured for graphene, and this design could pave they way towards highly functional and scalable graphene electronic and spintronic devices.
The tunnel barrier is made from dilutely fluorinated graphene while the charge and transport layer is made from graphene. The researcher demonstrated tunnel injection through the fluorinated graphene, and lateral transport and electrical detection of pure spin current in the graphene channel.
The NRL researchers explain that they fluorinated the top layer of a graphene bilayer to decouple it from the bottom layer, so that it serves as a single-monolayer tunnel barrier for both charge and spin injection into the lower graphene channel. They deposited ohmic (gold) and ferromagnetic permalloy (red) contacts, forming a non-local spin valve structure. When a bias current is applied between the left two contacts, a spin-polarized charge current tunnels from the permalloy into the graphene transport channel, generating a pure spin current that diffuses to the right.