Extremely thin transistors bring future energy-efficient chips a step closer

Modern computer chips contain billions of silicon transistors – tiny electrical switches that process, store, and move information. For decades, shrinking these transistors has been the main way to make electronics faster, more powerful, and more energy-efficient. But continuing this trend is becoming increasingly harder, as the most critical dimensions in advanced transistors are already measured in just a few nanometers. At these dimensions, silicon, the material that dominates modern electronics, begins to face fundamental material limits.

Among the most promising alternatives are atomically thin materials known as two-dimensional, or 2D semiconductors. These materials consist of a thin layer of atoms, which enables low-power electronics thanks to their excellent electrical control. Yet a major question has remained unanswered: can they still perform well at the extremely small dimensions required by future chip technologies?

The new study published in Nature Nanotechnology now provides a promising answer. The research team has fabricated transistors from two-dimensional semiconductors with channel widths as small as 25 nanometers – around 3,000 times narrower than a human hair. Despite their tiny size, the devices performed as well as much wider 2D semiconductor transistors. The nanofabrication and electrical characterisation were carried out at Stanford University in the USA, while subsequent analysis was completed at Chalmers University of Technology in Sweden.

“These are some of the slimmest high-performance transistors demonstrated in two-dimensional semiconductors,” says Anton Persson, Assistant Professor at Chalmers University of Technology, Sweden, who co-led the study. “What is particularly encouraging, and actually surprised us, is that the transistors remained well-behaved even when shrunk to dimensions relevant for future industrial technologies. That has been a major uncertainty in the field.”

New design and manufacturing approach helped overcome a key obstacle

While the exceptional thinness of 2D semiconductors has made them attractive for future electronics, researchers have struggled to reduce their width without degrading their performance. As transistors become narrower, their edges play a larger role, raising concerns that defects and damage could limit their performance. The new study shows that this limitation may be less severe than previously feared.

The researchers fabricated nanoribbon transistors using three different atomically thin 2D semiconductors. Across all three materials, the narrow transistors maintained a well-behaved switching behavior and performance comparable to larger devices.

“The 2D transistors made of tungsten disulfide were especially notable, as their current density improved by more than a hundred times compared to previous demonstrations, thanks to better material quality and improved metal contacts,” says Anton Persson.

The breakthrough was enabled by a combination of innovative device design and advanced nanofabrication techniques. The team developed a so-called “dog-bone” structure, with an extremely narrow transistor channel and wider regions under the electrical contacts to help anchor the material in place.

“Our improved nanofabrication approach was key for achieving these results,” says Tara Peña, postdoctoral scholar in electrical engineering at Stanford and co-lead author of the study. “We hope other researchers will adopt similar methods and continue optimising 2D devices at industry-relevant dimensions.”

Toward more sustainable computing

The findings strengthen the case for atomically thin 2D semiconductors as potential building blocks for future generations of electronics.

“Atomically thin 2D semiconductors have many exciting properties that give us a way to explore what may become possible beyond today’s silicon electronics,” says Anton Persson. “In the long term, technologies based on these materials could contribute to more powerful and energy-efficient electronics.”

Significant challenges remain before this technology reaches commercial production. “Our findings don’t mean that atomically thin 2D semiconductors are ready to replace silicon tomorrow,” says Eric Pop, Professor at Stanford University and corresponding author of the study. “But it shows that one of the key scaling concerns may be far less limiting than previously thought.”

More about the research:

The researchers fabricated nanoribbon transistors using three different atomically thin 2D semiconductors: molybdenum disulfide, MoS2, tungsten disulfide, WS2, and tungsten diselenide, WSe2. To prevent the delicate atomically thin material from tearing or peeling during fabrication, the team developed a so-called “dog-bone” structure. In the new design, the transistor channel is made extremely narrow while wider regions under the electrical contacts help anchor the material in place. The researchers also employed an advanced multi-patterning technique that etched the material in two steps from different directions, enabling channels as narrow as 25 nanometers.

The study, “Scaling nanoribbon transistors with monolayer transition metal dichalcogenides”, is published in Nature Nanotechnology with an associated News & Views article “2D transistor goes narrower”, also in Nature Nanotechnology.

The authors are Tara Peña, Anton E. O. Persson, Andrey Krayev, Áshildur Friðriksdóttir, Haotian Su, Yuan-Mau Lee, Young Suh Song, Kathryn Neilson, Zhepeng Zhang, Anh Tuan Hoang, Jerry A. Yang, Lauren Hoang, Shan X. Wang, Andrew J. Mannix, Paul C. McIntyre, and Eric Pop. The researchers are active at Stanford University and HORIBA, USA, and Chalmers University of Technology, Sweden.

This research was supported by the Knut and Alice Wallenberg Foundation, the U.S. Defense Advanced Research Projects Agency (DARPA), the Semiconductor Research Corporation (SRC), the U.S. National Science Foundation (NSF), Intel Corporation, Samsung Electronics, and TSMC through the SystemX Alliance. The experimental work was primarily carried out at the nano@stanford nanofabrication facilities.