Revealing Crystal Defects with Low-Dose SED and HPT‑100 Plasma Cleaning
Defects inside molecular crystals called dislocations can affect how materials perform in electronics, pharmaceuticals, or coatings. Until now, imaging these defects has been hard because the microscopes needed too much electron energy, which damages fragile organic crystals.
A team from the Bragg Centre at the University of Leeds published a Natural Materials letter on March 3, 2025, introducing a low-dose, single-exposure scanning electron diffraction (SED) technique. This method captures diffraction patterns while scanning and uses them to map lattice distortions around dislocations, without damaging the sample. The team published their findings in a letter of Microscopics crystallographic analysis of dislocations in molecular crystals.
Researchers used gentle treatment with Henniker Plasma HPT-100 to clean TEM grids before the sample transfer. That step gently removed the surface contaminants ensuring that the captured low-sode SED images are not obscured or altered by contaminants.
[Methods] The single-crystal films were transferred onto lacey-carbon-film transmission electron microscopy (TEM) support grids (EM Resolutions) by placing the grid under the film and lifting to catch the film on the TEM grid. Before the transfer process, the TEM grids were treated with an oxygen–argon (25:75) plasma for 10 s using an HPT-100 plasma treatment system (Henniker Plasma). [1]
What did the researchers find?
The researchers discovered that by using their new low-dose, single-exposure scanning electron diffraction (SED) method, they were able to directly observe and characterise individual dislocations - tiny defects like edge, screw, and mixed types, in fragile molecular crystals at approximately 1–2 nanometre resolution.
Key findings include:
-
They identified the precise Burgers vectors and slip systems of dislocations without needing prior knowledge of the crystal structure.
-
Demonstrated this technique across various organic crystals (optics, pharmaceuticals, waxes), proving its versatility.
-
Used an ultra‑low electron dose (~5 e⁻/Ų), protecting sensitive crystals from damage while maintaining image clarity.
-
The approach paves the way for routine nanoscale defect mapping, used for improving material performance in electronics, drug formulations, and more.
The Role of Henniker's HPT-100 Plasma Cleaner
The HPT‑100 plasma cleaner was used by the researchers at the University of Leeds as part of their sample preparation workflow, something that was important for the success of the study.
Researchers cleaned their TEM grids before the sample transfer using Henniker’s HPT‑100 plasma system, which:
-
Removed nanometre-thin layers of surface residue
-
Enabled true atomic-level imaging of dislocations without introducing artefacts
Without this step, the electron diffraction patterns would likely have been obscured or altered by contaminants.
Keywords
- Molecular crystals
- Dislocations
- Crystal defects
- Burgers Vector
- Slip system
- Lattice distortion
- Electro diffraction
- Scanning electron diffraction (SED)
- Single-exposure microscopy
- Nanometre resolution
References
Readers are referred to the original print, available through the provided [1] link, or click the link below for further details on the Henniker Plasma HPT-100.
[1] Microscopic crystallographic analysis of dislocations in molecular crystals
