Imaging Ellipsometry Monitors MXene Thin-Film Quality During Fabrication

A German-Israeli research team has demonstrated that imaging ellipsometry can non-destructively characterize and control the quality of microstructured MXene thin films during device fabrication. This method allows for monitoring thin-film uniformity, device integrity, and functionality throughout the manufacturing process. The findings were published in *Applied Physics Letters*.

MXenes are two-dimensional nanomaterials. They serve as building blocks for microscale electronic and photonic devices, known as MXetronics. Researchers at Tel Aviv University are investigating structured MXene-based thin films for use as backside electrodes in next-generation photodetectors. Imaging ellipsometry provides a crucial non-destructive technique for monitoring these properties without damaging the device.

Ellipsometry analyzes changes in the polarization state of light reflected off a device. This provides direct, quantitative access to thin-film characteristics. These characteristics include thickness, composition, and charge-transport properties. The resulting optical contrast is highly sensitive to subtle lateral variations across a sample. This makes ellipsometry valuable for device fabrication.

The researchers used two complementary optical approaches. Spectroscopic micro-ellipsometry (SME) provides high-resolution single-spot measurements for rapid sample probing. Imaging spectroscopic ellipsometry (ISE) offers spatially resolved imaging across entire thin-film devices. ISE can map structural and functional film properties from millimeter to micrometer length scales.

The method can monitor and visualize how local properties evolve during processing steps. These changes are tracked through their impact on the optical response. This reveals spatial variations in charge-transport and structural properties without contacting the device. This capability is essential for optimization and fabrication. The Helmholtz-Zentrum Berlin (HZB) team welcomes collaborations for further research.