Periodic Reporting for period 1 - Piezo2D (Piezoelectricity in 2D-materials: materials, modeling, and applications)
Période du rapport: 2023-10-01 au 2025-09-30
Piezoelectricity in two-dimensional (2D) materials is increasingly important because of its potential in realizing thin yet efficient and flexible piezoelectric devices. In contrast to traditional 3D piezo- and ferroelectrics that are prone to size effects, piezoelectricity in 2D materials may be controlled by flexoelectricity and interfaces thus providing significant piezoelectric effect in ultrathin films and crystals. Equally important, the majority of 2D layered piezoelectrics found so far possess in-plane piezoelectricity and require bending of flexible substrates to activate piezoelectric effect. This severely limits their integration with modern Si technology. This project aims at strengthening the piezoelectric activity in 2D materials via interface and stress engineering and bond control in order to reach the maximum efficiency and other relevant figures of merit. The materials list includes hafnium-zirconium oxide (HZO), transition metal thio/selenophosphates (TPS), graphene on oxide substrates, and polymer PDVF. A comprehensive investigation of piezoelectricity in these 2D materials and their relevant device performance is still at an initial stage. Piezo2D will build a technology to provide local energy generation from the nm- to the micro-scale to power nano- and microdevices. Piezo2D will do so by enhancing and deploying the combined powers of equilibrium and nonequilibrium thermodynamics and atomistic models with device physics and engineering. Research results will underpin future developments of nanoscale energy devices for decades to come. New characterization methods and metrology-based protocols aimed at future standards and their application in industry will be explored. The multidisciplinary approach of Piezo2D brings together leading teams in theoretical physics, materials science, chemistry and instrumentation.
During the reporting period, substantial progress has been achieved in relation to all major scientific and technological objectives of the project. Three representative classes of 2D materials were successfully fabricated, including HZO thin films and heterostructures, van der Waals crystals CIPS with different stoichiometries, and ultrathin polymer films. Work on large-area graphene is ongoing and continues to be developed by the responsible partner. Growth and deposition processes were carefully optimized through improvements in crystal synthesis and the transition from the Bridgman method to a chemical transport reaction technique, alongside the refinement of the Langmuir–Blodgett method for thin-film preparation.
Notable advances were made in establishing reliable methodologies for piezoelectric characterization. It was demonstrated that the conventional Berlincourt method produces inaccurate results for these emerging materials, prompting the development of a more reliable cantilever-based evaluation approach. On the theoretical side, DFT, LGD, and finite-element modeling were successfully applied to investigate ferroelectric and piezoelectric behavior, yielding new insights into phase transitions in van der Waals 2D systems.
The project also progressed toward application-oriented outcomes. Initial demonstrators for mechanical energy harvesting were fabricated using CIPS, achieving significant piezoelectric performance comparable to established materials such as LiNbO₃. Overall, the project is on track, with strong experimental, methodological, and theoretical results that collectively advance the development of next-generation 2D piezoelectric materials and their potential technological applications.
Notable advances were made in establishing reliable methodologies for piezoelectric characterization. It was demonstrated that the conventional Berlincourt method produces inaccurate results for these emerging materials, prompting the development of a more reliable cantilever-based evaluation approach. On the theoretical side, DFT, LGD, and finite-element modeling were successfully applied to investigate ferroelectric and piezoelectric behavior, yielding new insights into phase transitions in van der Waals 2D systems.
The project also progressed toward application-oriented outcomes. Initial demonstrators for mechanical energy harvesting were fabricated using CIPS, achieving significant piezoelectric performance comparable to established materials such as LiNbO₃. Overall, the project is on track, with strong experimental, methodological, and theoretical results that collectively advance the development of next-generation 2D piezoelectric materials and their potential technological applications.
The project achieved multiple scientific and technological advancements that go beyond the current state of the art in 2D piezoelectric and ferroelectric materials, while also revealing unexpected phenomena that open new research directions in this area
1. Advanced fabrication routes enabling material quality beyond current standards
The consortium successfully developed high-quality fabrication protocols for three representative classes of 2D materials—HZO thin films and heterostructures, van der Waals CIPS crystals with tunable stoichiometry, and ultrathin polymer films.
2. Breakthrough in piezoelectric characterization methodology
The project revealed that the widely used Berlincourt method produces inaccurate results for emerging 2D materials.
3. First integrated multiscale theoretical framework for 2D ferroelectrics
By combining DFT, LGD theory, and finite-element modeling, the project produced a multiscale description of polarization phenomena and phase transitions in van der Waals systems exemplified by CIPS.
New insights into ferroelectric stability, switching behavior, and electromechanical coupling in layered CIPS-type structures extend theoretical understanding beyond that previously achievable.
4. Application-driven demonstrators with piezoelectric output comparable with classic ferroelectric materials
First mechanical energy-harvesting demonstrators based on CIPS achieved piezoelectric open-circuit voltage approaching benchmark materials such as LiNbO₃. This unexpected high performance validates CIPS as a realistic candidate for low-power, flexible energy-harvesting devices, marking a clear breakthrough beyond current technology.
This comprehensive set of results demonstrates that the project not only achieved its planned objectives but also pushed the boundaries of 2D piezoelectric and ferroelectric research, uncovering entirely new phenomena with high potential for future applications.
1. Advanced fabrication routes enabling material quality beyond current standards
The consortium successfully developed high-quality fabrication protocols for three representative classes of 2D materials—HZO thin films and heterostructures, van der Waals CIPS crystals with tunable stoichiometry, and ultrathin polymer films.
2. Breakthrough in piezoelectric characterization methodology
The project revealed that the widely used Berlincourt method produces inaccurate results for emerging 2D materials.
3. First integrated multiscale theoretical framework for 2D ferroelectrics
By combining DFT, LGD theory, and finite-element modeling, the project produced a multiscale description of polarization phenomena and phase transitions in van der Waals systems exemplified by CIPS.
New insights into ferroelectric stability, switching behavior, and electromechanical coupling in layered CIPS-type structures extend theoretical understanding beyond that previously achievable.
4. Application-driven demonstrators with piezoelectric output comparable with classic ferroelectric materials
First mechanical energy-harvesting demonstrators based on CIPS achieved piezoelectric open-circuit voltage approaching benchmark materials such as LiNbO₃. This unexpected high performance validates CIPS as a realistic candidate for low-power, flexible energy-harvesting devices, marking a clear breakthrough beyond current technology.
This comprehensive set of results demonstrates that the project not only achieved its planned objectives but also pushed the boundaries of 2D piezoelectric and ferroelectric research, uncovering entirely new phenomena with high potential for future applications.