Ultra-Thin SiC Membranes for Soft X-ray Beam Monitoring

Pushing SiC beam monitors into the nanometric scale

Free-standing SiC membranes offer an attractive solution for in-line X-ray beam monitoring, combining radiation hardness, electrical performance and the possibility of simultaneously measuring beam intensity and position.

As the photon energy decreases, however, transparency becomes increasingly critical. Even a few micrometers of semiconductor material can introduce significant absorption in the tender and soft X-ray range. This makes further reduction of the active material thickness essential for extending this technology towards lower photon energies.

From micrometric to nanometric membranes

Our R&D activity is focused on pushing free-standing 4H-SiC detectors well below the micrometer scale.

Previous studies investigated ultra-thin SiC membranes below 2 µm, demonstrating their potential as minimally invasive beam intensity and position monitors while also identifying some of the challenges that emerge when conventional four-quadrant geometries are scaled to extremely small thicknesses.

Building on these results, we have now successfully fabricated and tested sub-micrometric SiC membranes with a nominal thickness of approximately 220 nm and an active area of 2 × 2 mm².

That is roughly one order of magnitude thinner than the thinnest SiC membranes currently used for conventional synchrotron beam diagnostics.

First tests with soft X-rays

The first nanometric prototypes have already been tested using soft X-ray radiation at:

• PolLux, Swiss Light Source — 900 eV

• Metrologie, Synchrotron SOLEIL — 1000 eV

The measurements demonstrated that a membrane only about 220 nm thick can remain mechanically self-supported while producing a measurable X-ray-induced electrical signal. Raster scans also showed a relatively uniform transmission across the active region.

These first results are encouraging and demonstrate the feasibility of using nanometric free-standing SiC devices as active diagnostic elements in the soft X-ray regime.

What are we working on now?

Reaching the nanometric scale also introduces new engineering challenges.

Our current development activities therefore focus on optimizing:

• membrane thickness and uniformity, to maximize X-ray transmission;
• active area and device capacitance, to improve dynamic response;
• mechanical robustness and fabrication reproducibility;
• detector architectures specifically optimized for tender and soft X-ray beamlines.

In particular, experimental and simulation studies have shown that simply scaling a conventional four-quadrant XBPM geometry to nanometric thicknesses is not sufficient.

Towards transparent beam diagnostics

Our target is to develop a new generation of SiC beam monitors that can be permanently installed directly in the X-ray path, providing continuous beam information while introducing only minimal attenuation and perturbation.

The technology is currently at the R&D and beamline-validation stage. Nanometric prototypes have already been fabricated and successfully operated with soft X-rays, while further optimization is ongoing toward more reproducible and application-specific devices.

Interested in testing ultra-thin SiC detectors on your beamline?
Contact us to discuss joint R&D activities and application-specific developments.

Scientific references