For decades, smaller and more powerful electronic components have fueled major advances in technology. Now scientists are 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, have been viewed as promising candidates for building even tinier electronic devices.
But new research from TU Wien 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 found that when 2D materials are paired with insulating layers required for electronic devices, an unavoidable atomic-scale gap forms between them. That tiny separation can significantly reduce performance and create a fundamental barrier to further miniaturization.
The findings could help the semiconductor industry avoid spending billions of dollars on approaches that may never overcome these physical limitations.
Why Interfaces Matter in 2D Electronics
“For many years, researchers have quite rightly been fascinated by the remarkable electronic properties of novel 2D materials such as graphene or molybdenum disulfide,” says Prof. Mahdi Pourfath, who carried out the research together with Prof. Tibor Grasser at TU Wien’s Institute for Microelectronics. “What is often overlooked, however, is that a 2D material alone does not make an electronic device. We also need an insulating layer — usually an oxide. And this is where things become more complicated from a materials science perspective.”
Modern transistors work by switching a semiconductor between conductive and nonconductive states. In future chips, that semiconductor could be an ultrathin 2D material. The process is controlled by a gate electrode, which must be separated from the active material by an insulating layer.
To keep devices as small and efficient as possible, the insulating layer needs to be extremely thin. However, the TU Wien team found that this creates a major issue at the atomic scale.
The Tiny Gap Creating a Big Problem
“In many combinations of 2D materials and insulating layers, the bonding between them is relatively weak,” explains Grasser. “They are held together only by so-called van der Waals forces, which provide only a weak attraction between the semiconductor and the insulator. As a result, the two layers do not come into close contact — there is always a gap between them.”
That gap measures only about 0.14 nanometers, making it thinner than a single sulfur atom. Even so, it has a dramatic effect on electronic behavior. For perspective, a SARS-CoV-2 virus is about 700 times larger.
“This gap weakens the capacitive coupling between the layers. No matter how good the intrinsic properties of the materials may be, the gap can become the limiting factor. As long as it exists, it imposes a fundamental limit on how far these devices can be miniaturized.”
According to the researchers, many studies have focused heavily on the impressive properties of 2D materials themselves while paying less attention to the interfaces formed inside complete devices. Their work shows that these interfaces may ultimately determine whether future chip technologies succeed or fail.
“Zipper Materials” Could Offer a Solution
“If the semiconductor industry wants to succeed with 2D materials, the active layer and the insulating layer must be designed together from the very beginning,” emphasizes Mahdi Pourfath.
One possible answer is the use of so-called “zipper materials.” In these systems, the semiconductor and insulating layer bond together much more strongly instead of remaining loosely connected by van der Waals forces. This tighter connection removes the problematic gap.
“Our work is good news for the semiconductor industry,” says Tibor Grasser. “We can predict which materials are suitable for future miniaturization steps — and which are not. But if one focuses only on the 2D materials themselves, without considering the unavoidable insulating layers from the outset, there is a risk of investing billions in an approach that simply cannot succeed for fundamental physical reasons.”