Projects / Programmes
Engineering of relaxor ferroelectric thin films for piezoelectric and energy storage applications
| Code |
Science |
Field |
Subfield |
| 2.09.01 |
Engineering sciences and technologies |
Electronic components and technologies |
Materials for electronic components |
| Code |
Science |
Field |
| 2.05 |
Engineering and Technology |
Materials engineering |
Piezoelectricity, energy storage, relaxor ferroelectrics, PMN-PT, silicon, scandiates, pulsed laser deposition, misfit strain, domain structure
Researchers (11)
Organisations (2)
Abstract
Relaxor ferroelectrics are widely studied because of their outstanding dielectric and electromechanical properties in single-crystal and ceramic form, which are related to the presence of a complex domain structure near the morphotropic phase boundary (MPB). However, thin-film materials have received little attention compared to their bulk counterparts, particularly the correlations between the local nano-domain structures and the functional properties. The lack of studies relates mainly to the experimental challenge of growing high quality samples. In order to develop nanomaterials with high performance for microelectromechanical systems (MEMS) and energy storage devices, this project aims to use the strain engineering to understand and control the evolution of nano-domain structures and their contribution to the ferroelectric susceptibilities of the prototypical oxide Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN-xPT) relaxor ferroelectric. The profound understanding of the structure-property relations in such a complex material will enable us to establish the relevant keys parameters, responsible for the creation of specific local chemical and domain structure configurations with functional performance closer to that observed in the bulk materials near MPB. By adopting the thin-film processing using pulsed laser deposition (PLD), high quality single-phase films and heterostructures with compositions across the MPB will be grown on a range of single-terminated monocrystals. In addition to variation of unit-cell sizes and the thermal-expansion coefficients of the substrates, the PLD method offers a large flexibility of deposition parameters, which will allow us to engineer strain state, interface quality, and domain arrangement within the material. In combination with possible variations of the target composition, the method permits growth of epitaxial high-quality films free from defects, thus maximizing the dielectric breakdown strength (DBS) and consequently recoverable energy density Ureco. Energy-storage response and other physical properties will also be tuned by varying the number of interfaces, layer thickness and chemical modulation in epitaxial multilayers or superlattices, composed of alternating thin layers of different compositions of PMN-xPT. Motivated by the recent finding of an unexpected enhancement of the piezoelectric coefficient (up to ~4000 pC/N) for Sm-doped PMN-PT bulk single crystal, the effect of structural heterogeneity at nanoscale in rare-earth doped PMN-xPT thin films will be also addressed in the proposed project and combined with the strain engineering in order to enhance the piezoelectric response of the material. Related to our recent advances in the atomically controlled growth of oxides on Si using PLD, the integration of PMN-xPT on Si will also be explored, providing an alternative route to piezoelectric-oxides integration with semiconductors. To correlate structural and functional properties, the samples will be characterized using different advanced characterization techniques, by combining methods sensitive to the lattice strain, defects, electronic states, chemical arrangements and compositions, with local electrical and strain-mapping techniques. As-obtained results will be related to the macroscopic dielectric, energy-density and piezoelectric measurements. Selected PMN-xPT thin films will be processed and integrated into prototypes and validated on the device level. For the first time, a special attention will be given to the determination of the spatial elemental analysis of PMN-xPT targets and as-grown thin films using the Laser Ablation - Inductively Coupled Plasma - Mass Spectrometry (LA-ICP-MS), which will help us to better understand the growth mechanism of PMN-xPT thin films and to precisely determine their stoichiometry. Findings of the study are believed to result in a breakthrough for the production of energy storage and MEMS devices with performance far beyond state-of-the-art.
