At the forefront of graphene-based electronics – News Physics and Quantum Computing

An urgent quest in the field of nanoelectronics is the search for a material that could replace silicon. Graphene has been looking promising for decades. But its potential faltered along the way, due to damaging treatment methods and the lack of a new electronic paradigm to embrace it. With silicon nearing maximum capacity to accommodate faster computing, the next big nanoelectronics platform is needed now more than ever.

Walter de Heer, Regents’ Professor at the School of Physics at the Georgia Institute of Technology, has taken a crucial step in making the case for a successor to silicon. De Heer and his collaborators have developed a new nanoelectronic platform based on graphene – a single sheet of carbon atoms. The technology is compatible with conventional microelectronics manufacturing, a necessity for any viable alternative to silicon. In their research, published in Nature Communication, the team may also have discovered a new quasiparticle. Their discovery could lead to the manufacture of smaller, faster, more efficient and more durable computer chips, and has potential implications for quantum and high-performance computing.

“The power of graphene lies in its flat, two-dimensional structure which is held together by the strongest chemical bonds known,” said de Heer. “It was clear from the start that graphene can be miniaturized to a much greater extent than silicon – enabling much smaller devices, while operating at higher speeds and producing much less heat. This means that in principle more devices can be packed on a single graphene chip than on silicon. »

In 2001, de Heer proposed an alternative form of electronics based on epitaxial graphene, or epigraphene – a layer of graphene that was found to form spontaneously on top of the crystal of silicon carbide, a semiconductor used in high power electronics. At the time, researchers discovered that electric currents flow without resistance along the edges of epigraphene and that graphene devices can be interconnected seamlessly without metal wires. This combination enables a form of electronics that relies on the unique light properties of graphene electrons.

“Quantum interferences have been observed in low-temperature carbon nanotubes, and we expect to see similar effects in epigraphene ribbons and lattices,” de Heer said. “This important characteristic of graphene is not possible with silicon. »

Build the platform

To create the new nanoelectronics platform, the researchers created a modified form of epigraphene on a crystalline substrate of silicon carbide. Together with researchers from the Tianjin International Center for Nanoparticles and Nanosystems at Tianjin University, China, they produced unique silicon carbide chips from electronic-grade silicon carbide crystals. The graphene itself was grown in de Heer’s lab at Georgia Tech using patented ovens.

The researchers used electron beam lithography, a method commonly used in microelectronics, to sculpt the graphene nanostructures and bond their edges to the silicon carbide chips. This process stabilizes and mechanically seals the edges of the graphene, which would otherwise react with oxygen and other gases that could interfere with the movement of charges along the edge.

Finally, to measure the electronic properties of their graphene platform, the team used a cryogenic device that allows them to record its properties from near zero to room temperature.

Observation of the state of the edge

The electrical charges the team observed in the edge state of graphene were similar to photons in an optical fiber that can travel great distances without scattering. They found that the charges traveled tens of thousands of nanometers along the edge before dispersing. Graphene’s electrons in previous technologies could only travel about 10 nanometers before hitting small imperfections and scattering in different directions.

“What’s special about electric charges in the edges is that they stay on the edge and continue to move at the same speed, even if the edges aren’t perfectly straight,” said Claire Berger, professor of physics at Georgia Tech and director of research at the Center National de la Recherche Scientifique de Grenoble, France.

In metals, electric currents are carried by negatively charged electrons. But contrary to the researchers’ expectations, their measurements suggested that the edge currents were not carried by electrons or holes (a term for positive quasiparticles indicating the absence of an electron). Rather, the currents were carried by a very unusual quasiparticle that has no charge or energy, yet moves without resistance. Components of the hybrid quasiparticle have been observed to move to opposite sides of the edges of graphene, despite being a single object.

The unique properties indicate that the quasiparticle could be the one physicists have been hoping to exploit for decades – the elusive Majorana fermion predicted by Italian theoretical physicist Ettore Majorana in 1937.

“Developing electronics using this new quasiparticle in perfectly interconnected graphene networks is a game-changer,” said de Heer.

It will likely be another five to 10 years before we have the first graphene-based electronics, according to de Heer. But thanks to the team’s new epitaxial graphene platform, the technology is closer than ever to crowning graphene as the successor to silicon.

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At the forefront of graphene-based electronics – News Physics and Quantum Computing


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