Unlocking Surface Secrets: Atomic-Resolution Electron Imaging Reveals Material Structures

Researchers at Nagoya University in Japan have developed a new technique using atomic-resolution secondary electron (SE) imaging. This method helps capture the atomic structure of the surface layer of materials, which is crucial for understanding chemical reactions like catalysis and corrosion. Their findings have been published in the journal Microscopy.

Materials often show “surface reconstruction,” where surface atoms are arranged differently than those below. Traditional scanning electron microscopy (SEM) struggles to capture such details, particularly for single atomic layers, because it only detects SEs emitted from shallow depths.

To overcome this limitation, the research team studied a two-layered molybdenum disulfide (MoS₂) sample. This design allowed them to distinguish between the surface and subsurface layers effectively. They found that SE imaging can reveal surface atomic arrangements with high sensitivity. The intensity of SE images from the surface was about three times greater than from the second layer, highlighting the technique’s effectiveness.

The atomic-resolution SE images displayed striking honeycomb structures formed by molybdenum and sulfur atoms. The distinct patterns indicated different atomic arrangements between the surface and the second layer. Lead researcher Koh Saitoh noted that SEs from the surface absorb or scatter from the subsurface, contributing to the method’s sensitive depth measurement.

The research team’s goal is to explore surface structures at the atomic level, including surface reconstruction. This understanding is vital for controlling the growth and properties of nanomaterials.

For further details, the full study can be found in Microscopy.