Researchers have mapped a dense network of defects inside a superconducting titanium nitride film grown on sapphire, using a single electron-microscope scan to see how the defects connect through the film. The three-dimensional view shows some defects crossing and others rising away from the interface.
The film was made for a superconducting microwave resonator, a component being developed for all-nitride quantum circuits. Titanium nitride and sapphire have different crystal spacings, so their boundary contains closely packed dislocations: breaks in the regular arrangement of atoms. Conventional electron images compress the sample's depth into a flat view, which can hide where one defect meets another.
One scan separates defects that overlap in a flat image
The team used multislice electron ptychography, which collects patterns of scattered electrons as a beam scans across the sample and reconstructs the material in depth. In this experiment, the scan took about 15 seconds. The reconstruction covered a region 15 by 9 nanometres wide through roughly 40 nanometres of film and substrate. Its depth resolution was 3.7 nanometres, so the method does not resolve every atomic layer along that direction.
Along the interface, the researchers found dislocations about 1.6 nanometres apart on average. At one point, an interface dislocation disappeared as a threading dislocation rose in its place toward the film surface. They also saw two interface dislocations cross while keeping their original type. These connections are difficult to distinguish from a two-dimensional projection. The study was posted as a preprint on September 22.
The map is local; device effects remain unmeasured
The work shows that different defect types can be traced in a crowded crystal interface without collecting a long series of tilted images. It does not establish how those particular defects affect the resonator's electrical performance or whether mapping them will improve quantum circuits. Only a 15-by-9-nanometre region was reconstructed. The paper says the underlying data and reconstruction parameters will be made available upon publication. Testing more resonators and pairing their defect maps with electrical measurements would show whether the structures influence device behavior.
Sources
- Chung and colleagues: three-dimensional imaging of dense dislocation networks, preprint submitted September 22, 2026
- Ithepalli and colleagues: titanium nitride superconducting microwave resonators, July 2026
- Illustrative image: electron microscope photograph by Yakovlev Viktor, CC BY 4.0. It does not show the instrument used in the study.
