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Strain and domain structure engineering in epitaxial relaxor ferroelectric thin films

English title Strain and domain structure engineering in epitaxial relaxor ferroelectric thin films
Applicant Lippert Thomas
Number 192047
Funding scheme Project funding
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Material Sciences
Start/End 01.01.2021 - 31.12.2023
Approved amount 324'563.00
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All Disciplines (2)

Discipline
Material Sciences
Condensed Matter Physics

Keywords (5)

piezoelectric ; wafer curvature measurement ; pulsed laser deposition ; thin films; strain engineering

Lay Summary (German)

Lead
Ein Verstehen der Struktur-Eigenschafts-Beziehungen und der Domänenentwicklung in ferrolektrischen Dünnfilm-Relaxoren (RF) mit externen Anregungen ist sehr wichtig für die Anwendung dieser Materialien. Das Material, Pb(Mg1/3Nb2/3)O3- PbTiO3 (PMN-PT), ist ein typisches RF Material mit besonderen dielektrischen und piezoelektrischen Eigenschaften, die von der Koexistenz von verschiedenen Domänenstrukturen und Inhomogenitäten auf der Nanoskala an der morphotropen Phasengrenze abhängen. Die Kontrolle der epitaktischen Verformung auf atomarer Ebene und das detaillierte Verstehen der Einflüsse auf die Materialeigenschaften, macht es nötig, dass man Proben von hoher Qualität herstellen kann, die definierte Grenzschichten besitzen und die keine Pyrochlor-Fremdphasen enthält.
Lay summary

Ziel des Projekts 
Unser Ziel ist die Untersuchung des Einflusses von Verformungen und Grenzschichteffekten auf die Domänenstruktur von PMN-PT dünnen Filmen und ihr Einfluss auf das piezo- und ferroelektrische Ansprechverhalten. Unser Ansatz ist die Herstellung von PMN-PT Dünnschichten in hoher Qualität mittels gepulster Laserabscheidung, in denen die Schichten einen verschiedenen Grad an Verformung beinhalten. Die Kontrolle über den Grad der Verformung soll durch Optimierung der Abscheidungsparameter, wie zum Beispiel der Materialzusammensetzung des Targets, Schichtdicke, der Elektroden und der Substratoberfläche und der kristallographischen Eigenschaften des Substrats erzielt werden. Unsere Ergebnisse könnten einen wichtigen Beitrag zum Verstehen aber auch zur Herstellung von Nanomaterialien für Mikroelektromechanische Systeme (MEMS) und Energiespeichermaterialien leisten.

Scientific and societal context of the research project 
Wir werden einen neuen Methodenansatz verwenden um das ferroelektrische Relaxor Material, PMN-PT, herzustellen, es zu verbessern und zu charakterisieren, unter besonderer Berücksichtigung der ferroelektrischen und Energiespeicher-Eigenschaften. Das detaillierte Verstehen der physikalischen Mechanismen und der wichtigsten Parameter der Herstellung von PMN-PT könnte es erlauben neue Ansätze zur Herstellung von neuen Materialien mit verbesserten Eigenschaften zu finden.

Direct link to Lay Summary Last update: 15.04.2020

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
204103 Pulsed laser deposition of thin films for renewable energy conversion and energy storage 01.04.2022 Project funding

Abstract

Understanding of the nature of nanoscale domain structures in relaxor ferroelectrics and their evolution under external stimuli is crucial for practical application. In this project we aim to elucidate and understand the contribution of the misfit strain and domain structures on piezoelectric and ferroelectric performance of prototypical oxide Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN-xPT) relaxor ferroelectric thin films in order to develop nano-materials with high performance for microelectromechanical systems (MEMS) and energy storage devices. The idea is to use the in-plane bi-axial strain and thermal strain to stabilize a monoclinic structure at morphotropic phase boundary (MPB) with complex domain state which is known to be accompanied with anomalously dielectric and piezoelectric response in bulk PMN-xPT. The defects induced during growth processes are also an important parameter to be considered / optimized and combined with strain in thin films since a small change in the ferroelectric structure can give rise to huge change in the functional properties. The control of the epitaxial strain at the atomic level and the profound understanding of its effect on the structural characteristics require samples with very high quality, free from pyrochlore phases which is known to be challenging. Our approach is to adopt thin film processing using pulsed laser deposition (PLD) to growth differently strained PMN-xPT with compositions across the MPB on single terminated substrates, resulting in layers of high crystalline quality. PLD method allows us to engineer strain state, interface quality, and domain arrangement within the material by modifying the growth parameters, substrate, film thickness, and electrode material. Epitaxial high-quality films are known to present low leakage current (Ileak) which allows in particularly maximizing the dielectric breakdown strength (DBS) and then enhancing recoverable energy density Ureco. We will also combine the strain engineering and structural heterogeneity at nanoscale in rare-earth doped PMN-xPT thin films in order to enhance the piezoelectric response. This is 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. Another important aspect, which will be addressed in the proposed project, is to explore the effect of interfaces in epitaxial multilayers or superlattices composed of alternating thin layers of different compositions of PMN-xPT which allows tuning the physical properties by varying the number of interfaces, layer thickness and chemical modulation. Motivated by our recent advances in the atomic control of the growth of oxides on Si using PLD, the integration of PMN-PT on Si will also be explored. 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 correlated with the macroscopic dielectric, energy density and piezoelectric measurements. A special attention will be given to the real-time monitoring of stress during the growth of PMN-xPT thin films using in situ substrate curvature measurement which will help us for better understanding its effect on micro- and macroscopic material characteristics. Our expected results are believed to result in a breakthrough for the production of energy storage and MEMS devices with beyond state-of-the-art performance.
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