Plasma Chemistry Breakthrough Could Pave the Way for Next-Generation Computer Chips

A New Path Forward for Semiconductor Manufacturing

Engineers working to push computer chips beyond their current physical limits may have just gotten a significant boost. A newly developed technique using plasma processing could make it far easier to work with the ultrathin materials considered essential for the next generation of electronics.

Researchers discovered that applying oxygen or fluorine to a material called molybdenum disulfide before plasma exposure allows manufacturers to remove just the outermost layer of atoms with far greater precision and safety. The findings were published in the Journal of Physical Chemistry Letters.

Why Silicon Alone Is No Longer Enough

Silicon has served as the backbone of computer chip manufacturing for decades. However, engineers are increasingly bumping up against the material's fundamental physical boundaries. As demand for smaller, faster, and more energy-efficient devices continues to grow, researchers are exploring ways to supplement silicon with advanced ultrathin materials.

One of the most promising categories is known as transition metal dichalcogenides, or TMDs. A standout candidate within this group is molybdenum disulfide — a material only three atoms thick, composed of a single layer of molybdenum sandwiched between two layers of sulfur.

For future transistors that integrate both silicon and TMD materials, manufacturers must be able to selectively strip away atoms from only the top sulfur layer, leaving everything beneath it completely intact.

The Challenge of Plasma-Based Atom Removal

One established method for removing surface atoms involves plasma — the high-energy state of matter present in stars like the Sun. Under precise conditions, particles within a plasma can collide with a material's surface and dislodge individual atoms.

The difficulty lies in achieving exactly the right energy level. Removing sulfur atoms from the top layer requires enough force to break surface bonds, but too much energy risks damaging the molybdenum layer underneath. The margin between success and destruction is razor-thin, making a reliable, repeatable process extremely hard to achieve.

Plasma research has been a core focus at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) for more than 75 years, and this study draws directly on that expertise.

How Oxygen and Fluorine Change the Equation

Using advanced computer simulations, researchers found that pretreating molybdenum disulfide with either oxygen or fluorine before plasma exposure substantially lowers the energy threshold needed to remove surface sulfur atoms.

The Energy Numbers Tell the Story

On an untreated surface, dislodging a sulfur atom requires approximately 30 electron volts of energy. After fluorine pretreatment, that threshold drops to around 10 electron volts. Oxygen pretreatment reduces it to roughly 14 electron volts.

This reduction is critically important because plasma ions naturally vary in their energy levels — not every particle carries the same charge. On an untreated surface, the narrow energy window between removing sulfur atoms and inadvertently damaging the molybdenum layer below means some ions will inevitably cause harm.

By lowering the removal threshold to 10 or 14 electron volts, the technique creates a far wider and more forgiving operating window, giving manufacturers significantly more control over the process.

Chemistry Doing the Heavy Lifting

Rather than relying purely on physical force to knock atoms free, the new approach harnesses chemical reactions to assist the removal process.

When a plasma ion strikes an oxygen-treated surface, two oxygen atoms can bond with a neighboring sulfur atom to form sulfur dioxide — a stable gas that naturally lifts off the surface on its own. Fluorine behaves in a comparable way, generating sulfur-fluorine compounds that detach with much less effort.

"We are not directly breaking the bonds," explained Yury Polyachenko, a Princeton University chemistry graduate student and lead author of the study, who also worked at PPPL during the summer of 2025. "We are forming some intermediate products, such as sulfur dioxide. This intermediate product is much easier to break off."

What Comes Next

The research team is already planning the next phase of investigation, aiming to quantify the degree of damage the process causes rather than simply determining whether damage occurs at all.

Beyond that, the researchers intend to test whether the same chemical pretreatment strategy works for related TMD materials — for example, substituting tungsten for molybdenum or selenium for sulfur — to determine just how broadly the technique can be applied across different material systems.

The study was conducted by Polyachenko alongside PPPL researchers Igor Kaganovich and Shoaib Khalid, as well as PPPL alumnus Yuri Barsukov. It received support from the Department of Energy's Office of Science, covering both Fusion Energy Sciences and Basic Energy Sciences, under the Extreme Lithography and Materials Innovation Center initiative. Computational work was carried out at the National Energy Research Scientific Computing Center and Princeton University's high-performance computing clusters.