Researchers at the University of Manchester in the UK may have cleared a significant hurdle on the path to quantum computing, demonstrating step-change improvements in the spin-transport characteristics of nanoscale graphene-based electronic devices.

The team – comprising researchers from the National Graphene Institute (NGI) led by Ivan Vera Marun, alongside collaborators from Japan and including students internationally funded by Ecuador and Mexico – used monolayer graphene encapsulated by another 2D material (hexagonal boron nitride) in a so-called van der Waals heterostructure with one-dimensional contacts. The team found that this architecture could deliver an extremely high-quality graphene channel, reducing the interference or electronic ‘doping’ caused by traditional 2D tunnel contacts.

‘Spintronic’ devices, as they are known, may offer higher energy efficiency and lower dissipation than conventional electronics, which rely on charge currents. In principle, phones and tablets operating with spin-based transistors and memories could benefit from greatly improved speed and storage capacity, exceeding Moore’s Law.

As the researchers report in a paper in Nano Letters, they measured electron mobility in the graphene channel of up to 130,000cm2/Vs at low temperatures (20K or -253°C). For comparison, the only previously published efforts to fabricate a device with 1D contacts achieved mobility below 30,000cm2/Vs. This measured electron mobility is higher than recorded for any other previous graphene channel where spin transport was demonstrated.

The researchers also recorded spin diffusion lengths approaching 20μm. Where longer is better, most typical conducting materials (metals and semiconductors) have spin diffusion lengths below 1μm. The spin diffusion length observed in this study is comparable to the best graphene spintronic devices demonstrated to date.

“Our work is a contribution to the field of graphene spintronics,” said lead author Victor Guarochico from the University of Manchester. “We have achieved the largest carrier mobility yet regarding spintronic devices based on graphene. Moreover, the spin information is conserved over distances comparable with the best reported in the literature. These aspects open up the possibility to explore logic architectures using lateral spintronic elements where long-distance spin transport is needed.”

“This research work has provided exciting evidence for a significant and novel approach to controlling spin transport in graphene channels, thereby paving the way towards devices possessing comparable features to advanced contemporary charge-based devices,” said co-author Chris Anderson from the University of Manchester. “Building on this work, bilayer graphene devices boasting 1D contacts are now being characterized, where the presence of an electrostatically tuneable bandgap enables an additional dimension to spin-transport control.”

This story is adapted from material from the University of Manchester, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

A schematic of the novel van der Waals heterostructure with graphene channel. Image: University of Manchester.
A schematic of the novel van der Waals heterostructure with graphene channel. Image: University of Manchester.