Agnès Barthélémy, Unité Mixte de Physique CNRS/Thales, France|
Title: Ferroelectric-based heterostructures
Alexei Gruverman, University of Nebraska-Lincoln, USA|
Title: Piezoresponse Force Microscopy – candid camera for the nanoferroelectric world
Jing-Feng Li, State Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing, China |
Title: Niobate-based lead-free piezoelectric ceramics
Beatriz Noheda, Zernike Institute for Advanced Materials, University of Groningen, Netherlands|
Title: Domain engineering in ferroelectric thin films
Susan Trolier-McKinstry The Pennsylvania State University, USA|
Title: Piezoelectric Films for MEMS Applications
Agnès Barthélémy is Professor at Université Paris Sud. She is also member of the Institut Universitaire de France since 2008. The heart of Agnès Barthélémy researches is to understand physical properties of nanostructures such as magnetic multilayers or tunnel junctions and particularly the new transport phenomena, Giant Magnetoresistance (GMR) or the Tunnel Magnetoresistance (TMR), that appear in these heterostructures due to the reduced physical dimensions. This research takes place in the framework of spin-electronics. Spin-electronics, also called spintronics, is born in 1988 after the discovery of a Giant Magnetoresistance effect in metallic magnetic multilayers. After a PHD thsesis under the supervision of Pr. Albert Fert, she continued to perform studies on magnetic metallic multilayers and cluster-based nanostructures. In 1998, she has reoriented her research and developed at Unité Mixte de Physique CNRS/Thales a new axis of research concerning “multifunctional oxides”. Her results have been reported in 160 papers , among them: 2 Science, 2 Nature, 8 Nature Materials, 1 Nature Physics, 1 Nature Nanotechnology, 3 Nature Communications, 1 ACS-Nano, 2 Advanced Materials, 2 Scientific reports, 18 Phys. Rev. Lett., 4 Nanoletters, 23 Appl. Phys. Lett., 21 Phys. Rev. B, 13 J. Appl. Phys, 7 book chapters, 4 review papers and 4 patents.
Abstract: Ferroelectric-based heterostructures
Ferroelectric materials with their spontaneous polarization that can be switched by an external electric field and used to modulate the properties of an adjacent layer. To study this opportunity, we combined ferroelectric materials (BaTiO3, BiFeO3 in tetragonal phase) with ferromagnetic transition metals (Fe, Co), the Mott insulator (Ca,Ce)MnO3 (CCMO) and the transition metal alloy FeRh.
In Ferroelectric tunnel junctions (FTJs) composed of an ultrathin ferroelectric tunnel barrier. In junctions of T-BFO sandwiched between a CCMO and a Co/Pt counter-electrode, the tunneling current significantly depends on the orientation of the ferroelectric polarization, resulting in large electroresistance enabling a simple non-destructive readout of the ferroelectric state. Controlling the domain configuration of the barrier allows to obtain multiple state resistance, defining an interesting system for future memristive devices. These FTJs also open the opportunity to tune the spin polarization of the ferromagnetic counter-electrode by polarization reversal resulting in a modulation of the Tunnel magnetoresistance observed in magnetic tunnel junctions.
In a field effect geometry, we observed that upon polarization reversal of the T-BFO ferroelectric gate, a CMO channel exhibits a non-volatile resistance switching by a factor of 4 around room temperature, and up to a factor of 10 at 200 K. Combining FeRh with BaTiO3 substrates, we evidenced through X-ray diffraction and various magnetometry experiments that a giant, low-voltage control of the magnetism of FeRh can be obtained. This control results mainly from the strain effect exerted on FeRh during the BaTiO3polarization reversal.
Dr. Alexei Gruverman is a Charles Bessey Professor at the Department of Physics and Astronomy, University of Nebraska-Lincoln. He received his PhD degree in Solid State Physics from the Ural State University in Ekaterinburg, Russia. His research interests are in the field of scanning probe microscopy of functional materials, electronic phenomena in ferroics, and information storage technologies. Prior to joining UNL in 2007 he held research scientist positions at the Joint Research Center for Atom Technology in Tsukuba, Japan, and at Sony Corporation, Yokohama, Japan, and research professorship position at the North Carolina State University, USA. While working in Japan he has pioneered the SPM-based method for non-destructive high-resolution imaging of ferroelectric domains in thin films and memory devices – an approach now known as Piezoresponse Force Microscopy (PFM). He has co-authored over 160 papers in peer-reviewed international journals (including Science, Nature Materials and Physical Review Letters), which are cited more than 6000 times, a number of book chapters and review articles and has edited three books and several special journal issues on ferroelectricity. He serves as an associate editor for the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control. He is a recipient of the 2004 Ikeda Foundation Award and ISIF 2010 Outstanding Achievement Award and is a Fellow of the American Physical Society. Among his most important scientific accomplishments is the development of Piezoresponse Force Microscopy, manipulation of ferroelectric domains at the nanoscale, development of an approach for fast switching dynamics in ferroelectric capacitors, demonstration of the tunneling electroresistance effect in ferroelectrics, and nanoscale studies of electromechanical behavior of biological systems.
Abstract: Piezoresponse Force Microscopy – candid camera for the nanoferroelectric world
Explosive development of scanning probe microscopies in the early 90s of the last century has opened an era of nanoscience and nanotechnology. In the field of ferroelectrics and piezoelectric materials, it is an invention of piezoresponse force microscopy (PFM) that stimulated and enabled transition to the nanoscale realm by allowing investigation of their physical and functional properties at the reduced dimensions, unattainable by previously available techniques. Over the last 20 years, PFM has evolved from an imaging technique to a set of advanced methods, such as resonance-enhanced PFM, stroboscopic PFM and switching spectroscopy PFM, which became the prime tools for probing the static and dynamic properties of nanoscale ferroelectric structures. Application of PFM was instrumental in the discovery of entirely new classes of phenomena, such as domain wall conductivity, magnetoelectric switching, tunneling electroresistance effect and domain vertices, which besides being of fundamental interest hold much promise for future generations of novel electronic devices. As the quality of ferroelectric and multiferroic interfaces keeps improving and the size of the ferroic structures has proven to be essential to their functionality, high-resolution PFM characterization of their properties will keep growing in importance. In this lecture, I will review dramatic progress in application of the advanced modes of PFM to investigation of emergent phenomena in nanoscale ferroelectrics and will discuss future challenges in this field. One of them is related to uncritical use of PFM data for ferroelectric behavior interpretation. While generating images of the nanoscale domains has been crucial for the initial advent of nanoferroelectric research, careful analysis of the PFM image formation mechanism along with comprehensive information on structure, physics and chemistry of materials under investigation is necessary to distinguish between science and artifacts.
Jing-Feng Li is a “Changjiang scholar” distinguished professor and a vice dean of School of Materials Science and Engineering, Tsinghua University, and also serves as deputy director of Tsinghua University-Toyota research center. He graduated from Huazhong University of Science and Technology (China) in 1984 and obtained his PhD from Tohoku University (Japan) in 1991. After working in Tohoku University as assistant professor from 1992 to 1997 and then associate professor until 2002, he joined Tsinghua University as a full professor in 2002. His current research interests include piezoelectric and thermoelectric materials as well as their microfabrication technology. He has published >330 SCI-indexed papers (cited >6500, H index 43) and two books, and received several awards including young researcher award from the Japan Institute of Metals, outstanding young scientist grant from NSF of China, Journal of the American Ceramic Society Loyalty Award. Prof. Li is now an Editor-in-Chief of Journal of Materiomics and editorial committee members for several international journals including Journal of Asian Ceramic Societies and NPG Asia Materials.
Abstract: Niobate-based lead-free piezoelectric ceramics
Developing high-performance lead-free piezoelectric ceramics has been one of the most active materials research topics in the last decades. At present, a single substitute for Pb(Zr,Ti)O3 (PZT) may not be available, whereas competent lead-free piezoceramics are almost ready depending on applications in (K,Na)NbO3 (KNN) and (Bi0.5Na0.5)TiO3 as well as BaTiO3-based systems. KNN-based ceramics are especially promising for actuator applications. This talk will report the latest progress on development of KNN-based piezoceramics from fundamental issues to application prospects. At first, we will reexamine the phase structure of KNN and discuss the piezoelectricity enhancement in relation with the effects of chemical modifications and sintering processing. Then, a special focus will be placed on the temperature dependence of piezoelectric properties of KNN-based ceramics, which has been recognized as its distinct shortcoming as compared with PZT. To overcome this problem, CaZrO3-modification was revealed to be an effective solution, particularly for the converse piezoelectric output at high electric fields. Finally, we will introduce several industrial attempts of traditional piezoceramic products using KNN-based ceramics and the updated researches on some promising applications in laboratories.
Beatriz Noheda is full professor at the Zernike Institute for Advanced Materials (University of Groningen). She obtained her PhD in Physics on ferroelectric materials at the Autonomous University of Madrid (UAM), in Spain. Afterwards she combined a part-time position as assistant lecturer at the UAM with several post-doctoral stays in the group of M. A. Glazer at the Clarendon Laboratory in Oxford (UK) and at Brookhaven National Lab. in New York. There, in 1998, together with Dave Cox and Gen Shirane, she discovered the monoclinic phase of piezoelectric PZT and proposed the lowering of crystal symmetry as the origin of the large piezoelectric response in PZT and related materials. In 1999 she became assistant physicist at Brookhaven National Lab and local contact of the powder diffraction line of the NSLS. In 2002 she moved to the Netherlands and, after a short detour learning thin film deposition techniques and studying metal hydrides thin films at the Vrije University of Amsterdam, in 2004 she obtained a Rosalind Franklin Fellowship to initiate her own research line at the University of Groningen. In Groningen she has set a pulsed laser deposition laboratory and other facilities to investigate ultrathin ferroelectric and multiferoic thin films. Highlights of recent research include the growth and control of periodic nanodomains in ferroelastic thin films and the investigation of the distinct properties of domain walls.
Abstract: Domain engineering in ferroelectric thin films
In the last decade, strain engineering in epitaxial thin films has changed from being an attractive concept to have reached a large degree of maturity. In particular, for perovskite-like complex oxides, this amazing progress has definitely originated from the synergy between theory and experiment, as the extraordinary predictive power of first-principles and phenomenological (Pertsev-like) models, as well as the advances in thin film deposition techniques, have stimulated the highly focused and efficient search of novel phases and enhanced properties that they bring about.
An interesting side effect of the problem is the opportunity to access and control the mechanisms that facilitate the release of the strain for a sufficiently thick film or a large enough lattice mismatch. In the case of ferroic oxides, this mechanism is typically the formation of ferroelastic domains. Here I will present some of the most recent work on the understanding and control of different domain structures in perovskite-like ferroelectric thin films by using epitaxial growth (by pulsed laser deposition). I will also discuss some ways in which these different domain structures can be used to enhance the materials response, that is the ferroelectric, piezoelectric or magnetic behavior.
Susan Trolier-McKinstry is a Professor of Ceramic Science and Engineering, Professor of Electrical Engineering, Director of the Nanofabrication facility at the Pennsylvania State University. Her main research interests include thin films for dielectric and piezoelectric applications. She is a fellow of the American Ceramic Society, IEEE, and the Materials Research Society, and an academician of the World Academy of Ceramics. She currently serves as an associate editor for Applied Physics Letters. She was recently elected to Vice President of the Materials Research Society; previously she served as president of the IEEE Ultrasonics, Ferroelectrics and Frequency Control Society, as well as Keroms. Twenty people that she has advised/co-advised have gone on to take faculty positions around the world.
Abstract: Piezoelectric Films for Microelectromechanical Systems
Piezoelectric thin films are of increasing interest in low voltage microelectromechanical systems (MEMS) for sensing, actuation, and energy harvesting. They also serve as model systems to study fundamental behavior in piezoelectrics. The seminar will discuss how materials are optimized for these applications, as well as examples of the use of piezoelectric films over a wide range of length scales. The key figures of merit for actuators and energy harvesting will be discussed, with emphasis on how to achieve these on practical substrates.
For example, control of the domain structure of the ferroelectric material allows the energy harvesting figure of merit for the piezoelectric layer to be increased by factors of 4 – 10. Likewise, control of crystallographic orientation and substrate clamping enables large increases in the figure of merit for actuators. To illustrate the functionality of these films, examples of integration into MEMS structures will also be discussed, including adaptive optics for Xray telescopes, low frequency and non-resonant piezoelectric energy harvesting devices, and piezoelectronic transistors as a potential replacement for CMOS electronics.