Watch a device being built without breaking it in the process
In laboratories spanning Germany and Israel, a collaborative research team has found a way to observe the invisible architecture of next-generation materials without disturbing what they are trying to build. Using imaging ellipsometry — a technique that reads the subtle signatures light leaves when it grazes a thin film — scientists can now monitor the health of MXene-based devices in real time, turning fabrication from a process of educated guesswork into one of continuous, non-destructive insight. It is a quiet but consequential shift: the ability to watch without touching, to know without breaking.
- For years, the only way to confirm whether a MXene thin-film device had been built correctly was to destroy it — a costly and time-consuming dead end that slowed the entire field.
- The urgency is sharpest at Tel Aviv University, where researchers stack these exotic two-dimensional nanomaterials into precision photodetectors where a single undetected flaw can erase months of work.
- Two complementary ellipsometry techniques now address the problem from different angles: one fires a focused beam at critical spots for rapid fabrication checks, while the other maps an entire device at micrometer resolution in a single pass.
- As photoresist is applied and patterns are developed, the method tracks shifts in thickness, composition, and charge transport in real time — directly linking what is seen during fabrication to how the finished device ultimately performs.
- Published in Applied Physics Letters and selected as an Editor's Pick, the work is already drawing international collaborators, signaling a transition from proof-of-concept to practical deployment across the field.
In research labs across Germany and Israel, a team led by Dr. Andreas Furchner has addressed a persistent frustration in materials science: how to monitor a device as it is being built without damaging it in the process. Their solution is imaging ellipsometry, which reads the polarization shifts that occur when light reflects off a layered material — shifts that encode information about thickness, composition, and electrical properties without any physical contact with the sample.
The stakes are particularly high for MXenes, exotic two-dimensional nanomaterials being developed for next-generation photodetectors and electronics. At Tel Aviv University, these materials are being stacked into precision backside electrodes where even minor, invisible flaws can render months of work useless. Previously, confirming whether fabrication had succeeded meant destroying the device afterward. Furchner's team found a better path.
The researchers deployed two complementary approaches. Spectroscopic micro-ellipsometry, used at The Hebrew University of Jerusalem, delivers rapid spot-checks at critical fabrication moments. Imaging spectroscopic ellipsometry, housed at the Helmholtz-Zentrum Berlin, maps an entire device at once with resolution sharp enough to distinguish features just one micrometer across — bridging the millimeter scale of a full device with the fine structure within it.
Crucially, the method works in real time. As photoresist is applied and patterns are developed, ellipsometry tracks how optical responses shift, revealing where charge transport is improving or degrading and where film thickness is changing. These observations can then be correlated with the finished device's actual performance, closing the loop between fabrication and outcome.
The work, selected as an Editor's Pick in Applied Physics Letters, has drawn attention from research groups worldwide. The Helmholtz-Zentrum Berlin team has signaled openness to collaboration, suggesting the technique is moving from demonstration into broad practical use — offering anyone building MXene-based electronics the rare ability to see clearly without breaking what they are trying to create.
In the basement labs of research institutions across Germany and Israel, a team led by Dr. Andreas Furchner has quietly solved a problem that has plagued materials scientists for years: how to watch a device being built without breaking it in the process. Their answer is imaging ellipsometry, a technique that reads the fingerprint light leaves behind when it bounces off a thin film, revealing everything from thickness to electrical properties without ever touching the sample.
The stakes are highest when working with MXenes—exotic two-dimensional nanomaterials that promise to revolutionize how we build tiny electronic and photonic devices. At Tel Aviv University, researchers are stacking these materials into the backside electrodes of next-generation photodetectors, the kind of precision work where a single flaw can render months of effort worthless. Until now, the only way to know if something had gone wrong was to destroy the device and examine it after the fact. Furchner's team found a better path.
The physics is elegant. When light reflects off a layered material, its polarization state—the orientation of its electromagnetic waves—shifts in ways that encode information about what it just bounced off. By measuring these shifts with precision, ellipsometry reveals the thickness of each layer, what it's made of, and crucially, how well charge moves through it. The optical contrast is sensitive enough to catch even tiny variations across a sample's surface, variations that might seem invisible but could doom a finished device.
The team deployed two complementary approaches, each suited to different questions. Spectroscopic micro-ellipsometry, available at The Hebrew University of Jerusalem, fires a focused beam at a single spot and reads the response in seconds. It's the tool for quick checks during fabrication, a way to sample the device at critical moments without slowing production. Imaging spectroscopic ellipsometry, housed at the Helmholtz-Zentrum Berlin, takes the opposite approach: it maps properties across an entire device at once, with a focusing optic sharp enough to resolve features just one micrometer across. This second technique stitches together the millimeter scale of a full device with the micrometer scale of its internal structure in a single measurement.
What makes this work genuinely powerful is the ability to watch changes happen in real time. As researchers apply photoresist and develop patterns—steps that fundamentally alter the device's structure—ellipsometry tracks how the optical response shifts, revealing where charge transport is improving or degrading, where the film is thickening or thinning. These spatial variations can then be correlated with how the finished device actually performs, closing the loop between what you see during fabrication and what you get at the end.
The work, published in Applied Physics Letters and selected as an Editor's Pick, has already drawn attention from research groups across the world. The versatility of the method—it works on isotropic and anisotropic materials alike, from conventional semiconductors to exotic two-dimensional systems—suggests its usefulness will only grow. The team at Helmholtz-Zentrum Berlin has made clear they welcome collaborations, a signal that this technique is moving from proof-of-concept into practical deployment. For anyone building the next generation of MXene-based electronics, the ability to see what's happening without destroying what you're building may prove to be the difference between innovation and frustration.
Notable Quotes
Local properties can be correlated with overall device functionality, which is essential for optimization and fabrication— Research team findings
The Hearth Conversation Another angle on the story
Why does it matter that you can watch the device being built without damaging it? Couldn't you just make multiple copies and destroy one to check?
You could, but MXenes are still difficult and expensive to work with. Every device is precious. More importantly, you learn nothing about why a particular device failed—you just know it did. With ellipsometry, you can correlate what you see during fabrication with how the device actually performs, which is how you optimize the process.
So this is really about feedback during manufacturing, not just quality control at the end?
Exactly. You're watching the film evolve as you apply each layer, each chemical treatment, each lithographic step. You can catch problems before they're locked in, or understand why something worked when it did.
The paper mentions two different techniques. Why not just use one?
They answer different questions. The micro-ellipsometry is fast—you can probe a spot in seconds, which is useful when you need quick answers during processing. The imaging version is slower but shows you the whole device at once, revealing spatial variations that might be invisible in a single-point measurement.
What's the actual resolution? How small a defect could you catch?
Down to about one micrometer with the imaging approach. That's small enough to catch most structural problems, though not atomic-scale defects. For MXene devices, that's usually sufficient.
Is this technique specific to MXenes, or could it work on other materials?
It's general. The team emphasizes that it works on a wide range of materials—isotropic, anisotropic, two-dimensional systems. MXenes are just the current application. The real innovation is positioning ellipsometry as a platform for device fabrication more broadly.