The computer chips inside our phones, laptops and other electronic devices contain billions of tiny switches called transistors.
These transistors are usually made from silicon, the material that has powered modern electronics for decades.
However, as companies try to make chips even smaller and more powerful, silicon is beginning to reach its physical limits.
Scientists are now exploring new materials that could work alongside silicon to create the next generation of electronic devices.
One promising group of materials is called transition metal dichalcogenides, or TMDs. These materials are incredibly thin, measuring only a few atoms in thickness.
One of the leading candidates is a material called molybdenum disulfide. It is just three atoms thick and consists of a layer of molybdenum sandwiched between two layers of sulfur atoms.
Building transistors with this ultrathin material presents a major challenge. Manufacturers often need to remove only the top layer of sulfur atoms while leaving the layers underneath completely undamaged.
Accomplishing this is extremely difficult because the entire material is only a few atoms thick.
The standard method uses plasma, a highly energized state of matter sometimes called the fourth state of matter. Plasma is found naturally in stars, including the sun, and is also widely used in modern manufacturing.
When molybdenum disulfide is exposed to plasma, some of the energetic particles strike its surface and knock sulfur atoms loose.
The problem is that there is a very narrow margin between applying enough energy to remove the top sulfur layer and applying too much energy and damaging the molybdenum layer below.
Researchers from the U.S. Department of Energy’s Princeton Plasma Physics Laboratory used computer simulations to look for a better approach.
Their findings, published in the Journal of Physical Chemistry Letters, showed that coating the material with oxygen or fluorine before plasma treatment can make the process much easier and safer.
The coatings dramatically reduce the amount of energy needed to remove sulfur atoms. On an untreated surface, about 30 electron volts of energy are required. With a fluorine coating, the amount drops to around 10 electron volts, while an oxygen coating lowers it to about 14 electron volts.
This reduction is important because the particles in plasma do not all carry exactly the same amount of energy. On an untreated surface, some particles inevitably have enough energy to damage the lower layers. By lowering the energy needed to remove sulfur atoms, the coatings create a much larger safety margin, making it easier to strip away the top layer without harming the material underneath.
The researchers say the coatings work by using chemistry rather than force alone. When plasma particles strike an oxygen-coated surface, oxygen atoms combine with sulfur atoms to form sulfur dioxide, a stable gas that can simply drift away. Fluorine works in a similar way by forming sulfur-fluorine compounds that are easier to remove.
The team now plans to investigate exactly how much damage this process may still cause and whether the same strategy could work with other ultrathin materials. If successful, the approach could help manufacturers create smaller, faster and more energy-efficient computer chips in the future.
