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Hybrid graphene structure enables low-power devices

Wonder material graphene can provide the building block for future transistors by using a technique known as spintronics. New materials serving as substrates able to produce a bandgap in graphene herald a new era in nano-scale electronic devices.
Hybrid graphene structure enables low-power devices
Using the electron spin as the encoding method for data, spintronics are paving the way to high-speed, low-power and smaller devices in information processing and storage technology. Computational methods are a burgeoning science that can be exploited for designing innovative materials for spintronics devices. Use of first-principle atomic-scale modelling was at the heart of the project GRAFIEST (Graphene-ferroelectric interface for electronic and spintronic technologies).

Owing to its capacity for high spin transport over relatively long diffusion lengths, graphene shows great promise for spintronics applications. By using first-principle methods, the GRAFIEST team demonstrated the possibility to produce an electronic bandgap in graphene by placing it on a suitable substrate. As an excellent conductor, graphene cannot perform logical operations and store information without a bandgap.

Over the past, materials that present coupling between ferroelectricity and magnetism have been proposed as fundamental building blocks for spintronic devices. However, ferroelectricity and magnetism are often exclusive or weakly coupled in bulk. Another route to producing spintronics devices has been to exploit the unique electronic and transport properties of graphene or carbon nanotubes. Yet, a large spin diffusion length often comes at the price of small spin-orbit coupling, limiting the possibility of manipulating electrons via an external applied field.

Based on the density functional theory, the GRAFIEST team demonstrated that placing graphene on a magnetoelectric multiferroic material helps overcome limitations when using these materials alone.

Scientists found that the velocity of the two carrier types was different, suggesting that there is spin-dependent transport. The most important result was that the spin polarisation of the insulating substrate induced significant magnetisation in the carbon network. Data in graphene-based spintronics devices could thus be encoded without current, in this case by a magnetic field, rendering low-power computing a reality. Depending on the graphene and substrate relative orientation, the hybrid system behaved as a spin injector with 100 % degree of spin polarisation or as a magnetic semiconductor.

Understanding spin injection and spin transport is crucial to optimising current devices and designing novel architectures. With this in mind, GRAFIEST findings greatly contributed to the nanoelectronics and spintronics fields.

Related information


Graphene, transistors, spintronics, bandgap, electronic, magnetoelectric
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