From a current standpoint – Super strong and only one atom thick, graphene shows promise as a nanomaterial for everything from microelectronics to clean energy storage. But the lack of a property has limited its use. Today, researchers at Princeton University and the US Department of Energy’s (DOE) Princeton Plasma Physics Laboratory (PPPL) have overcome this problem by using low-temperature plasma, creating a new technique that opens up the door to a wide range of industrial and scientific applications for the promising nanomaterial.
Stronger than steel
Graphene, which is harder than diamond and stronger than steel, could be the foundation for next-generation technologies. But the absence of a property called bandgap in the pencil graphite that makes up graphene limits its ability to function as a semiconductor, the material at the heart of microelectronic devices. Semiconductors both insulate and conduct electric current, but although graphene is an excellent conductor, it cannot serve as an insulator without a bandgap.
“People use silicon which has a bandgap for semiconductors,” said Fang Zhao, lead author of a paper in the review Carbon which describes the new process. “The opening of a large band gap on graphene has given rise to intense studies of the use of semiconductors,” said Zhao, a physicist at the Fermi National Accelerator Laboratory (Fermilab) who wrote the article at the time. that he was a post-doctoral researcher at Princeton.
The dilemma has led scientists around the world to explore ways to produce a bandgap in graphene to expand its potential applications. One popular method has been to chemically alter the surface of graphene with hydrogen, a process called “hydrogenation.” But the conventional way of doing it produces irreversible etching and sputtering that can seriously damage the surface of graphene – known as a 2D material due to its ultra-thin nature – within seconds or minutes.
Scientists at Princeton and PPPL have now shown that a new method of hydrogenating graphene can safely open the door to many microelectronic applications. The method marks a new way to produce a hydrogen plasma that dramatically expands the hydrogen coverage in 2D material. “This process creates much longer hydrogen treatments due to its low damage to graphene,” Zhao said.
Plasma, the hot, charged state of matter made up of free electrons and atomic nuclei, makes up 99% of the visible universe. The low-temperature hydrogen plasma that PPPL developed to hydrogenate graphene contrasts with the million-degree fusion plasmas that have long been the hallmark of PPPL research, which aims to develop safe, clean, and fusion energy. abundant to generate electricity.
Ptolemy’s spin-off
The new method stems from an experiment called Ptolemy, an academic project that Princeton physicist Chris Tully developed with help from Zhao. This project uses the decay of tritium, the radioactive isotope of hydrogen, in an attempt to capture relic neutrinos that emerged just seconds after the Big Bang that created the universe. Such relics could shed new light on the Big Bang, according to the Ptolemy project.
To improve the decay detection rate, Tully turned to PPPL physicist Yevgeny Raitses, who leads low-temperature plasma research at PPPL. “PPPL’s desire to join forces and bring 2D processing properties to materials is inspiring,” said Tully. “Breaking the world record for graphene hydrogenation efficiency is a tribute to the unique capabilities of PPPL. “
Raitses and his colleagues developed a method to extend the hydrogen blanket in graphene that harbors the decay of tritium. The process greatly increases future applications of graphene. “This Ptolemy spin-off can now be used for microelectronics, QIS [quantum information science] and other applications, ”Raitses said. “The method can also be applied to other 2D materials.”
The spin-off combines electric and magnetic fields to produce a hydrogen plasma that provides a lot of hydrogen with little damage to the graphene. This gentle and well-controlled method is itself a spin-off from the research that Raitses developed while studying Hall-effect thrusters, the plasma engines of spacecraft propulsion. The technique hydrogenated graphene for up to 30 minutes in PPPL experiments, dramatically increasing hydrogen coverage and opening a bandgap that turns graphene into a semiconductor material.
All this, says the Carbon paper, creates an attractive method for making 2D materials “exciting and promising”. [sources] for large applications.
Princeton physicists Chris Tully and Andi Tan, as well as chemist Xiaofang Yang from Princeton’s Department of Chemical and Biological Engineering also collaborated on this article. Support for this work comes from the DOE Office of Science (FES) and the Air Force Office of Scientific Research.
PPPL, at the Forrestal campus of Princeton University in Plainsboro, New Jersey, is dedicated to creating new knowledge about the physics of plasmas – ultra-hot charged gases – and developing practical solutions for creating fusion energy. The laboratory is managed by the Office of Science, Department of Energy, University of the United States, which is the largest support for basic research in the physical sciences in the United States and strives to address some of the most pressing challenges of our time. For more information visit energy.gov/science.
