(Funded by the National Science Foundation and the U.S. Department of Energy)
Researchers from Florida State University, the Shanghai Institute of Microsystem and Information Technology, and Wuhan University have revealed how various physical manipulations of graphene, such as layering and twisting, impact its optical properties and conductivity. The researchers found that the optical conductivity of twisted bilayer graphene is not heavily impacted by such manipulations and instead depends more on how the material’s geometry structure changes by interlayer twisting. To conduct the study, the team captured images of plasmons – tiny waves of energy that happen when electrons in a material move together – that appeared in various regions of the twisted bilayer graphene.

(Funded by the U.S. Department of Energy)
Researchers from New York University; the Center for Functional Nanomaterials (CFN), a U.S. Department of Energy Office of Science user facility at Brookhaven National Laboratory; and the National Institute for Materials Science in Tsukuba, Japan, have used a special robotic system to assemble very large pieces of atomically clean two-dimensional materials into stacks. These materials, called graphene heterostructures, consist of sheets just a few atoms thick, have record-setting dimensions – as large as 7.5 square millimeters, which is very large in the world of microelectronics. The robotic assembly tool helped the scientists discover a new interface cleaning mechanism that combines mechanical and thermal forces. Overall, this study opens a new opportunity to develop a more effective process to make large and clean layered heterostructure devices.

(Funded by the National Science Foundation)
Cornell University researchers have made headway into understanding how twisted bilayer graphene becomes a superconductor. In 2023, the scientists developed a theoretical formalism to compute the highest possible superconducting transition temperature in any material obtained by stacking and twisting two-dimensional materials. For the current work, the scientists applied this theoretical formalism to twisted bilayer graphene. “One of the remarkable properties of twisted bilayer graphene is the associated tunability,” said Debanjan Chowdhury, one of the scientists involved in this study. “You have unprecedented control over temperature and the twist angle – the tiny electric fields that are applied to switch the material from being an insulator versus a superconductor – making it very easy to explore all sorts of exciting regimes in this material.”

(Funded by the U.S. Department of Energy)
Flame aerosol synthesis is used to create nanoparticles that serve as key ingredients in inks and air filters. While effective, this technique has limitations, including challenges with manipulating the flame, achieving precise control over the size and distribution of nanoparticles, and cost. Two new studies, from researchers at the University at Buffalo; the U.S. Department of Energy’s Lawrence Berkeley National Laboratory, Brookhaven National Laboratory, and Lawrence Livermore National Laboratory; and the National Synchrotron Radiation Research Centre in Taiwan have addressed these shortcomings. The studies center on a unique flame aerosol system that is versatile, easy-to-use and cost-effective. In one of the studies, the system was used to create metal-organic frameworks, which are porous nanomaterials; in the other study, the researchers showed that the system could be used to create high-entropy ceramic nanomaterials.

(Funded by the U.S. Department of Defense)
Researchers from the Massachusetts Institute of Technology and the University of Udine in Italy have created a new type of three-dimensional transistor using a unique set of ultrathin semiconductor materials. It features vertical nanowires only a few nanometers wide, which can deliver performance comparable to state-of-the-art silicon transistors while operating efficiently at much lower voltages than conventional devices. The transistor’s extremely small size would enable more of these 3D transistors to be packed onto a computer chip, resulting in fast, powerful electronics that are also more energy-efficient. “This is a technology with the potential to replace silicon, so you could use it with all the functions that silicon currently has, but with much better energy efficiency,” says Yanjie Shao, the scientist who led this study.