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Achieving Higher Energy Efficiency in Electronics with the University of Groningen’s Electron-Spin Transistor

November 06, 2019 by Gaber Intihar

Moore’s law, proposed in 1965 by Intel co-founder Gordon Moore, famously states that the number of transistors in an integrated circuit doubles every two years.

The law mostly holds true even several decades later because of the continuous miniaturization of the components that make up computer processors—but the size of transistors is quickly reaching the limits of physics⁠. Which is why researchers have been trying to develop entirely new types of electronics components.


Electron Spin Transistors

One such endeavor is the attempt to develop transistors that aren’t based on a charge current— but on a current of electron spins. By taking advantage of the principles of quantum mechanics, scientists might be able to design the next generation of processors. 

Each electron can be found in one of two states⁠—it can either have an up or down spin, a “one” or a “zero”. It’s this binary nature of a magnetic moment that can be used to store or transfer information. 

Spin transistors have numerous advantages over their traditional counterparts. They should, in theory, produce less heat while offering faster performance, better power efficiency, non-volatility of data storage, and reduced component size. While this type of transistor has been proposed back in 1990, efforts to develop working prototypes have so far proved unsuccessful.


Multilayer device based on double layer graphene.

A multilayered device, based on a double later of graphene on top of a layer of tungsten disulfide. Image Credit: S. Omar, University of Groningen. 


Developing Spin Transistors

To build functional spin transistors, it’s necessary to find a way to reliably switch the spin of electrons while at the same time ensuring that the lifespan of their spins is at least equal to the time that’s needed for the electrons to travel through a circuit. Scientists from the University of Groningen have successfully tackled both of these problems.

To achieve this breakthrough, they constructed a two-dimensional spin transistor that uses a double layer of graphene placed over a monolayer of tungsten disulfide. 

Graphene, the 2D form of carbon, is an excellent conductor of electron spins but cannot be used for spin current manipulation all by itself. However, this same group of scientists has previously shown that it’s possible to control the spin of electrons by placing a graphene layer on top of another 2D material⁠—tungsten disulfide. That creates a Van der Waals heterostructure which allows for spin current manipulation via the principle of spin-orbit coupling.

The researchers ended up using a double layer of graphene to reduce the effect that metal tungsten atoms have on the spin of electrons⁠; thus taking an important step towards extending the lifetime of the spin sufficiently for use in transistors.


The Future Potential of Spintronics

Their research holds great significance for spintronic applications, especially since they were able to successfully conduct these experiments at room temperature. While there are still many hurdles to overcome before such transistors become commercially viable, spintronics is shaping up to become one of the leading alternatives to current transistor technology

While that won’t affect the ways in which consumers use electronic devices, it will change the manufacturing and design processes of basic electronic components. Whether or not the future of computing will be based on the quantum-mechanical properties of electrons, one thing is certain—we still have a ways to go before our electronic devices reach their limits.

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