Spin control in graphene at room temperature

Researchers have created a room-temperature spin transistor from graphene and molybdenum disulfide. A spin transistor is an essential component of future spintronic devices that will manipulate electron spin instead of charge for information processing. Using the spin degree of freedom instead of shuttling around charged carriers will lead to orders of magnitude energy savings for all our electronic devices.

Graphene has long been recognized as an interesting spintronic material due to its long spin lifetime. A research team from Chalmers University in Sweden experimentally demonstrated two years ago that graphene preserves its spin longer than any other known material, up to nanoseconds. The long lifetime  is a result of weak spin-orbit interaction. Contrary to graphene, molybdenum disulfide (MoS2), another 2D material of growing importance in recent years, has a very strong spin-orbit interaction which results in extremely short spin lifetimes. Now the same team of researchers stacked these two materials and created spin valves that control transport between the graphene and the MoS2. When the valve is “open”, carriers tunnel to MoS2 and lose their spin properties. When the valve is “closed”, carriers stay in graphene and preserve their spins. The valve is opened and closed by simple electrostatic gating. Electrostatic gate control of spin currents in 2D material devices is a milestone achievement towards practical realizations of spintronics. The research was published in the journal Nature Communications.

Coloured Scanning Electron Microscope Image of a Fabricated MoS2/Graphene 2D Materials Heterostructure Spintronic Device. Credit: Spin FET@Chalmers

The scientists are part of the Graphene Flagship, a 10-year, billion-euro project of the European Commission for bringing graphene from fundamental research to market products. It is through Flagship meetings that the researchers started collaborating with Graphenea, who provided the high-quality graphene films for this device. The MoS2 was mechanically exfoliated from large single crystal pieces and transferred on top of the graphene.

Other than use in spin transistors, the device could have imaginative new applications in electronic technology, because it contains magnetic memory elements, semiconductors and graphene, as well as having the capability of performing spintronic switching.