Atomic Intercalation for Tunable Phase Transitions in 2D Layered Materials

About This Grant

NON-TECHNICAL SUMMARY Many technologies, including sensors, electronics, and energy systems, depend on the ability to control how material behavior is affected with changes in temperature and pressure. This project, supported by the Solid State and Materials Chemistry Program in the Division of Materials Research, enables Prof. Koski and her research group at the University of California Davis to grow new layered materials, use chemistry strategies to add and remove atoms inside of these new materials (a process called “intercalation”), and to explore how to tailor these unique materials to control the behavior at high pressure and low and high temperatures. New methods for chemical intercalation are developed that will transform our abilities to manipulate thermodynamics on a molecular level. These investigations address an outstanding need of using chemistry to control 2D layered materials to access new phases and functional behavior. A method called “Brillouin spectroscopy” can study the mechanical behavior of tiny volumes of material without damaging them; the researchers use this to precisely measure new phase changes and extract physical information about the materials. This project is uniquely situated to achieve the goal of controlling thermodynamics in a 2D layered material using intercalation strategies, establishing systematic patterns for rational design of materials with desired properties. Additionally, undergraduate students receive training for careers in science and engineering. This research is open to all individuals; military veterans are recruited for participation in this research. Online resources are created in conjunction with this work, enhancing the knowledge base available for the community and the broader public. TECHNICAL SUMMARY Controlling thermodynamic phase behavior in a 2D layered material using intercalation has been highlighted as a unique strategy to achieve novel material phases and access heretofore unknown functional behaviors. There are two competing or synergistic components of an intercalation layered material that can undergo a phase change, namely the guest intercalant and the host crystal. An intercalant can undergo polytypic phase transitions or disorder-order transitions, many of which can give rise to emergent confined quantum phases. A host can have pressure or temperature driven phase transitions that can be modified by intercalation, including inducing amorphization or stabilization of phases which would not normally occur. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research, this project uses a general set of chemical methods for intercalating high densities of zero-valent elements from across the periodic table, atomic intercalation in 2D layered materials as a route to chemically tune thermodynamic phase behavior. This effort is three-fold and intertwines solid-state chemistry, spectroscopy, and high pressure/variable temperature. Specific objectives are to (i) devise new chemical methods to synthesize 2D layered materials, (ii) develop chemical intercalation strategies to intercalate and deintercalate zero-valent metals in 2D layered materials, and (iii) investigate thermodynamic properties of intercalated 2D layered materials using high pressure generated in a diamond anvil cell and variable temperature techniques. Core to this work is measurement of the acoustic phonons using Brillouin light scattering, which is central to understanding mechanical properties, thermodynamics, and phase states in a material and that can catch phase transformations that X-ray diffraction alone might miss, especially when considering closely related phases. This effort lays the foundation for accessing chemically tunable phase transitions in 2D layered materials using atomic intercalation and is crucial for accessing new functional behaviors, new materials, and understanding of material stability – all which is critical for future applied device performance. Educational and broader outreach goals include training undergraduate students for careers in science and engineering. Military Veterans are recruited for participation in research through the UC Davis Veteran Success Center. This work creates, develops and expands online tools including an online recipe guide for intercalation of metals in layered materials. It enhances and expands an online Brillouin spectroscopy database complementing similarly available databases providing the community with a unique consolidated resource for Brillouin spectroscopy. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.