For decades, smaller, more powerful electronic components have driven major advances in technology. Scientists are currently searching for the next breakthrough in computer chip design, and many researchers believe 2D materials could play a key role. These ultrathin materials, made from just one or a few atomic layers, are considered promising candidates for building even smaller electronic devices.
But new research from the Vienna University of Technology suggests that many of these materials may not work as expected in real-world chip technology. The problem is not just the material itself. Scientists have discovered that when 2D materials are combined with the insulating layers needed in electronic devices, unavoidable atomic-scale gaps form between them. This small amount of separation can significantly degrade performance and become a fundamental barrier to further miniaturization.
The discovery could help the semiconductor industry avoid spending billions of dollars on approaches that can never overcome these physical limitations.
Why interfaces matter in 2D electronics
“For many years, researchers have been fascinated by the surprising electronic properties of new 2D materials such as graphene and molybdenum disulfide,” said Professor Mahdi Pourfas, who conducted the research with Professor Tibor Glasser from the Institute of Microelectronics at the Vienna University of Technology. “But what is often overlooked is that you can’t make electronic devices with 2D materials alone; you also need an insulating layer (usually an oxide). And this is where things get more complicated from a materials science perspective.”
Modern transistors work by switching semiconductors between conducting and non-conducting states. In future chips, the semiconductor could be an ultra-thin 2D material. This process is controlled by the gate electrode, which must be separated from the active material by an insulating layer.
To keep devices as small and efficient as possible, insulation layers must be very thin. But a team at the Vienna University of Technology has discovered that this poses a major problem at the atomic scale.
Small gaps cause big problems
“For many combinations of 2D materials and insulating layers, the bond between them is relatively weak,” Grasser explains. “They are held together only by the so-called van der Waals forces, which exert only a weak attractive force between the semiconductor and the insulator. As a result, the two layers do not stick together and there is always a gap between them.”
The gap is only about 0.14 nanometers, thinner than a single sulfur atom. Still, it has a dramatic effect on electronic behavior. For comparison, the SARS-CoV-2 virus is about 700 times larger.
“This gap weakens the capacitive coupling between the layers. No matter how good the material’s intrinsic properties, the gap can be the limiting factor. As long as the gap exists, it imposes fundamental limits on how small these devices can be made.”
According to the researchers, much work has focused on the superior properties of the 2D materials themselves, with less attention paid to the interfaces that form inside the finished device. Their research shows that these interfaces may ultimately determine whether future chip technologies succeed or fail.
“Zipper material” may be the solution
“If the semiconductor industry wants to succeed with 2D materials, the active and insulating layers need to be designed together from the beginning,” emphasizes Mahdi Pourfath.
One possible answer is the use of so-called “zipper material.” In these systems, the semiconductor and insulating layers do not remain loosely coupled by van der Waals forces, but are much more strongly coupled. This tighter connection eliminates problematic gaps.
“Our work is good news for the semiconductor industry,” says Tibor Glasser. “We can predict which materials are suitable for future miniaturization steps and which are not. But by focusing solely on the 2D materials themselves, without considering the inevitable insulating layers from the beginning, we risk investing billions of dollars in approaches that simply cannot succeed for fundamental physical reasons.”
