Miniaturized Surface Diffraction from helium

Researchers have successfully adapted helium scattering, an ultra-gentle, surface-only measurement technique, to work on a microscopic scale [1]. Standard tools like electron microscopes can damage delicate samples and often probe too deep, confusing surface data with signals from the underlying material. While helium scattering is perfectly surface-sensitive, it was previously limited to large, millimeter-sized samples, making it impossible to study many modern materials.

Using a modified scanning helium microscope (SHeM), the team demonstrated the first-ever 2D helium diffraction patterns from a single, micron-sized spot on a crystal. This new method allows them to accurately measure the local atomic structure of tiny areas.

This breakthrough also enables a new form of imaging. By taking images while focused on a specific diffraction peak, the researchers created new micrographs with significantly enhanced contrast, revealing small-scale defects and surface variations that were previously invisible. This opens up a “vast new range” of delicate and small-scale samples, such as 2D materials, to this powerful, non-damaging analysis.

[1] PHYSICAL REVIEW LETTERS 131, 236202 (2023)