Electromechanical phenomena probed by AFM – the challenges and opportunities of quantification
Oak Ridge National Laboratory
Progress in many areas of science is indelibly linked to advances in techniques to investigate functional behavior on the micro- and nanoscale that have become essential in material science and device engineering. In areas such as ferroelectricity, energy storage and conversion, and information technologies, some important advancements are related to the development of atomic force microscopy (AFM) techniques which probe electro-(chemo-)mechanical phenomena, for example piezoresponse force microscopy (PFM). Current advances include multi-frequency approaches, the exploration of new measurables, and machine learning and experiment automatization. However, an underlying challenge to all these developments is the extraction of quantitative functional material properties which is necessary to compare results across AFMs, across different characterization techniques, and with theory to make AFM a truly integrated research approach leading to the physical understanding of new phenomena and materials. In this talk I want to highlight the challenges and opportunities to achieve the goal of quantitative material properties for the example of piezo- and ferroelectric but also ion conducting materials. This includes the understanding of signal origins under local electric fields to identify unwanted signal contributions as well as taking contact resonance cantilever vibrations into account. In the end, I will demonstrate the successful case of layered CuInP2S6 where PFM is used to extract the piezoelectric constant which is directly compared to theory, X-ray, and transmission electron microscopy to identify unusual ferroelectric properties in this material.
This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Science and Engineering Division. The experiments were conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.
Putting Ferroic Domains in Perspective: Multiscale and Dynamic Imaging
Technion Israel Institute of Technology
A major question in the study of solid-state materials is: how are macroscopic and atomistic properties tailored at the intermediate scale? Ferroelectrics provide us with a unique opportunity to address this fascinating question and delve into the mesoscale. Ferroelectrics exhibit domains that mediate between the atomic-scale dipole moments and the macroscopic functionality. Thus, understanding domain organization and dynamics is a key goal in the study of these polar materials. In this tutorial, we will focus on the available imaging capabilities of spatial and temporal domain organization. The main emphasize will be on the prominent imaging method, piezoresponse force microscopy (PFM). The dos and don’ts of these methods will be discussed, strengthening our confidence in domain analysis as either readers or authors of papers with PFM data. To expose the expanding limits of contemporary domain imaging, some burning challenges will be discussed, such as: How can we observe fast domain dynamics with slow imaging methods? How can we distinguish between ferroelectric and ferroelastic domains during domain dynamics? How can we observe domain switching and domain evolution during phase transitions? How does the domain structure relate to the macroscopic behavior? What can PFM tell us about the domain-wall behavior?
The tutorial is suitable for a broad audience, including those who seek to understand domain-imaging data as well as those who actively work or wish to work with domain-imaging techniques.
Introduction to piezoelectric MEMS technologies – History and recent trends
In this tutorial, I’ll present the basic concept of piezoelectric MEMS technologies, including R&D history of the application of ferroelectric thin films into MEMS. I’ll also introduce present and future commercial applications of PZT-based piezoelectric MEMS, such as inkjet printer head, gyrosenssors, HDD dual stage actuators, and acoustic and ultrasonic devices. As the fundamental technologies of piezoelectric MEMS, deposition and characterization of PZT piezoelectric thin films
will be explained.
Embedded Ferroelectric Memory at Texas Instruments: Technology, Reliability, and Applications
An overview of non-volatile, Ferroelectric Random-Access Memory (FRAM) technology, reliability, and applications will be presented. Unlike conventional floating-gate based non-volatile memories, FRAM takes advantage of the electric dipole present within the ferroelectric material PbZrTiO3 (PZT) to store information. With write speeds 100x faster than flash memory and nearly-infinite write endurance, FRAM has applications both as a standalone memory and as an embedded memory when combined with a microcontroller.
In this tutorial, the key process steps and integration approach to embed PZT-based FRAM within a CMOS process flow will be overviewed. PZT capacitor electrical properties, bit distributions, and design considerations will be described. The impact of various stress conditions, such as thermal depolarization, imprint, and cycling will be summarized. The tutorial concludes with a brief survey of PZT-based FRAM applications and some high-level considerations for Hafnium-based ferroelectric memories.
Since achieving FRAM production in 2007, Texas Instruments (TI) and its partners have qualified and released hundreds of products with applications ranging from ultra-low power micro-controllers and medial devices to automotive event data recorders.
Harvesting Energy from Mechanical Sources Using Piezoelectric Materials
University of Utah
In this tutorial I will cover the basic concepts of harvesting mechanical energy (i.e. motion and vibration) with piezoelectric materials. I will start with an introduction to mechanical energy harvesting. What types of energy are we trying to harvest? Why do we want to do this? When is it beneficial? I will then cover the basic concepts of mechanical energy harvesting separated from the specific the transduction technology (i.e. piezoelectric, electrostatic, etc.). The goal here is answer the question: how much energy could be harvested from a given source from any type of transducer? I will then move to piezoelectric energy harvesting covering two cases: static and dynamic energy harvesting. We will discuss the basic theory of piezoelectric energy harvesting for both cases. In static systems, the goal is typically to design the transducer with as much electromechanical coupling as possible. In the dynamic case, there is often a level of coupling beyond which output power saturates and a larger transducer or more coupling is not beneficial. Finally, I’ll discuss current and potential future research topics.
Theory of Polarization
This tutorial will guide you towards understanding how the electric polarization is defined, calculated and measured in bulk periodic solids.
Ferroelectric Effect in Photovoltaic Materials
Evaluating the potential of organic photovoltaics materials and devices for industrial viability is a multi-dimensional large parameter space exploration. Especially for novel multi-component materials or hetero-junctions, like in the case of ferroelectric photovoltaic semiconductors, optimization requires a too large number of experiments. Ferroelectric halide perovskites are one of the semiconductor classes, which are rapidly gaining interest for photovoltaic applications, but require complex cation engineering. The existence of regular ferroelectric domains, resulting in a macroscopic electrical field which may assist charge transport or charge separation, is researched in addition to the classical bulk photovoltaic effect. This tutorial gives a general introduction into photovoltaics and highlights the importance of the diode principle and the nature of junctions. Ferroelectric photovoltaics as well as ferroelectric effects in photovoltaic materials effects are reviewed and discussed in terms of the one-diode replacement circuit. The final section gives an outlook how research of such novel material can be accelerated by using automated experimentation. An automated platform for fabricating and characterizing complete functional devices, AMANDA, is introduced. First examples how to use such a research platform towards autonomous optimization of semiconducting materials are presented.
Fundamentals and Applications of Energy Storage
The Australian National University
Antiferroelectric materials have recently become a hot research topic due to their promising applications in energy storage. However, there are some ambiguous descriptions about antiferroelectric concept and physical phenomenon as well as structure-property relationship in antiferroelectric materials. In this tutorial, I will start from the basic concept and origin of the antiferroelectricity, distinguishing it from ferroelectric and ferrielectric property based on their average structure. I will then briefly introduce a structural analysis approach to give you a more powerful tool to picture/identify antiferroelectric phases/components. I will discuss the defect and local structure derived antiferroelectric-like phenomena, surface effect, antiferroelectric-ferroelectric phase transition and “wake-up” effect. In the end I will focus the application of antiferroelectric materials in energy storage, including some perspectives on how to design antiferroelectricity for optimal performance.