Nanocasting could accelerate the discovery of new topological materials

Nanocasting of topological nanowires could accelerate the discovery of new materials for applications such as quantum computing, microelectronics and clean energy catalysts, according to a Prospects of APL Materials article co-authored by Judy Cha, Professor of Materials Science and Engineering at Cornell.

Topological materials are valued for their unique ability to possess different properties at their surfaces and edges, and these surface properties can be enhanced by designing the materials at the nanoscale. The challenge for scientists is that traditional methods of making nanowires are slow and don’t offer a high level of precision.

“Theorists have predicted that about a quarter of all known inorganic crystals could be topological,” Cha said. “We’re talking about tens of thousands of compounds, so the conventional method of making these crystals is simply incompatible in terms of screening to find test topology materials for specific applications.”

Tin telluride nanowires nanocast in an anodic aluminum oxide mold. Credit: N. Liu, Y. Xie, G. Liu, S. Sohn, A. Raj, G. Han, B. Wu, JJ Cha, Z. Liu and J. Schroers, Phys. Rev. Lett. 124, 036102 (2020); MT Kiani, JJ Cha, APL Materials 10, 080904 (2022).

But nanocasting, in which a bulk polycrystalline raw material is pressed into a nanostructured mold at high temperature to form nanowires, could provide a solution. Writing in APL Materials, Cha and postdoctoral associate Mehrdad Kiani explain that nanocasting offers several advantages over existing synthesis methods for nanoscale materials.

“Unlike traditional top-down and bottom-up fabrication methods, nanocasting requires minimal optimization of experimental parameters and can work on a wide variety of topological compounds, enabling high-throughput fabrication of topological nanowires. The fabricated nanowires are single crystal and flawless and can have high aspect ratios greater than 1,000,” Cha and Kiani write.

Nanocasting was previously used for metallic material systems, but Cha and his research group are one of the first to extend its application to topological materials. And while in principle, nanocasting offers all the features sought in a topological nanowire, it is still unclear exactly how and why the method is so successful – a knowledge gap that the Cha group is working to fill.

The Cha group’s current research projects include measuring the electrical properties of nanocast topological nanowires to compare them to nanowires produced with other techniques, and studying atomic diffusion and mechanical movements of atoms during the molding process. Cha also welcomes collaborators interested in nanofilar versions of the compounds they are looking for.

The research is supported by the Emerging Phenomena in Quantum Systems initiative of the Gordon and Betty Moore Foundation, and was also featured in an August 24 Scilight AIP.

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