A 2D transistor built from just one crystal could ease a long-standing problem in chip research. A team at South Korea’s Institute for Basic Science (IBS), led by Director JO Moon-Ho of the Center for Van der Waals Quantum Solids, says it has made a working transistor by chemically converting parts of a single layered crystal into the different materials a transistor needs, rather than assembling separate materials one by one.
Why a 2D transistor is hard to build
A transistor normally needs three kinds of material: a semiconductor to carry current, an insulating dielectric to control it, and metal contacts through which current enters and leaves. According to IBS, bringing all of these together gets harder as devices approach the atomic scale.
Atomically thin two-dimensional semiconductors have long been seen as promising successors as silicon nears its physical scaling limits. The institute says that after more than two decades of research, the biggest obstacle has not been the semiconductor itself but integrating it with other parts. The surfaces of 2D semiconductors offer few places for other materials to attach, which makes it hard to deposit a uniform insulator. Depositing metal directly can damage the atomically thin layer or create large contact barriers. Peeling and stacking separate 2D materials is hard to scale to mass production.
One crystal, three functions
The IBS team started with multilayer tungsten diselenide (WSe₂), a 2D semiconductor. By keeping the tungsten framework and selectively replacing the atoms around it, they changed the electronic character of individual regions without rebuilding the crystal.
The upper layers were first oxidized into insulating tungsten oxide. That oxide could then be converted through vapor-phase reactions into tungsten disulfide, an n-type semiconductor, or tungsten ditelluride, a semimetal. Regions left alone stayed as the original semiconductor. Tiny gaps between atomic layers helped stop the reaction at a chosen depth, and by adjusting temperature and gas pressure the team controlled conversion at roughly 0.7 nanometers per monolayer.
The key demonstration used the converted oxide directly above the channel as the gate dielectric, with no separate high-k material deposited. IBS says this gave an insulating layer with an effective thickness below one nanometer.
The performance numbers
In these transistors, a change of only 61.3 millivolts in gate voltage increased the current tenfold. IBS notes this is very close to the theoretical room-temperature limit of about 60 millivolts per decade, which points to highly efficient switching. The devices also reached an on/off current ratio above 10 million.
The tungsten ditelluride conversion also improved the contacts, lowering the barrier for charge injection to about one-third of that seen with direct platinum contacts. The team also built n-type molybdenum disulfide transistors with the same oxide, plus vertically stacked p-type and n-type transistors forming a complementary van der Waals inverter, a basic building block of digital logic. The successful voltage inversion, the institute says, shows the method could extend beyond single devices.
What it does not show yet
This is a laboratory demonstration. The announcement does not describe wafer-scale production, manufacturing yield or cost, and it does not compare the process with the silicon methods used in factories today. Those are the questions that usually decide whether a materials result becomes a product. Director JO himself frames the work as “a new route” toward ultralow-power, ultrascaled and vertically integrated devices, not a finished technology.
Two sides are worth keeping in view. Supporters would point out that one starting crystal could avoid many of the alignment and damage issues of stacking different materials. Cautious observers would note that a clean result on small devices does not automatically carry over to billions of identical transistors. For other recent chip research, see a brain-inspired device from IIT Guwahati and the GLS ChipForge project.
My view on single-crystal electronics
As a writer, I feel the strongest part of this work is the idea itself: stop fighting to join mismatched materials and grow the whole device from one parent crystal. Numbers close to the theoretical switching limit are encouraging, and so is the lower contact barrier. But I would be careful with the word “breakthrough”. It is a promising step in the lab, and the hard part, scaling it, is still ahead.
FAQ: 2D transistor from a single crystal
What did the IBS team build?
They built transistors from one layered tungsten diselenide crystal, converting selected layers and regions into the insulator, semiconductor and contact materials a transistor needs.
How well did the transistors perform?
A 61.3 millivolt change in gate voltage raised current tenfold, close to the roughly 60 millivolt theoretical limit, with an on/off ratio above 10 million, according to IBS.
Is this ready for mass production?
Not yet. The announcement describes a laboratory demonstration and does not report large-scale manufacturing, yield or cost.