Novel MIT design strategy leads to discovery of new MoON

Researchers at Northwestern University have developed a novel design strategy to identify new materials exhibiting a metal-insulator transition (MIT). This rare class of materials is categorized by their ability to reversibly switch between electrically conducting and insulating states. The new strategy, reported in a paper in Physical Review Letters, could jumpstart future design and delivery of faster microelectronics with more storage capabilities, as well as quantum materials platforms for future electronics.

"Our approach uses anion substitution at the atomic scale and the recognition of key MIT properties to identify potential heteroanionic MIT materials, which have not been widely considered to this point," said James Rondinelli, associate professor of materials science and engineering and professor in materials and manufacturing at Northwestern’s McCormick School of Engineering, who led the team. "We hope by formulating these electronic structure-property relationships, new transitions in quantum materials can be designed in the future."

Using quantum-mechanical computer simulations at Northwestern's Quest High Performance Computing Cluster, Rondinelli and his colleagues designed the picoscale crystalline structure of the new material, called molybdenum oxynitride (MoON), to host the phase transition between metal and insulator. The researchers found that the MIT occurred near 600°C, revealing its potential for applications in high-temperature sensors and power electronics.

The group noted that multiple design parameters influenced MoON's phase transition. The inclusion of multiple anions in the material – in this case, negatively charged oxygen and nitrogen ions – activated the phase transition. This turned out to be due to specific electron configurations relating to the spatial orientation of electronic orbitals, supporting previous findings in other binary MIT materials. In addition, MoON's flexible rutile crystal structure ensured reversibility between the electrically conducting and insulating states.

These findings offer insight into how subtle changes on the nanoscale can be used to control macroscopic behavior – like conductivity – in materials.

"Substantial work has been done during the past decade to understand MIT materials and discover new ones; however, less than 70 unique compounds are currently known that exhibit this thermal transition," Rondinelli said. "We embodied key features of MIT materials, including particular picoscale structural features, as well as the crucial d1 electron configuration, into our design. Our project leverages a way that we and others can use key first-principle design concepts to expand the MIT phase space and effectively pursue new MIT materials."

Scientists hope that by formulating these electronic structure-property relationships, new transitions in quantum materials can be designed in the future. These compounds could prove useful as the active layer for transistors or in memory applications.

"MIT materials represent a class of phase transitions that may enable advances in information processing and storage beyond conventional complementary metal-oxide semiconductor scaling in microelectronics," Rondinelli said. "This translates to faster devices with more storage capabilities. In addition, MIT materials could enable low-power microelectronic systems, meaning you would need to charge your device less frequently, as it lasts longer because the components require less power."

This story is adapted from material from Northwestern University, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.