Ferroelectric or Electrochemical? Artifacts in Piezoresponse Force Microscopy



报告题目:Ferroelectric or Electrochemical? Artifacts in Piezoresponse Force Microscopy

报告人:  Prof. Jiangyu LiUniversity of Washington


报告所在: 明故宫校区A18-529集会室  




Electromechanical coupling is ubiquitous in nature that underpins functionalities of both synthetic materials and biology for information processing as well as energy conversion and storage. While dynamic strain based scanning probe microscopy (ds-SPM) has emerged as a powerful tool to investigate electromechanical coupling at the nanoscale, known as piezoresponse force microscopy (PFM) for ferroelectric materials and as electrochemical strain microscopy (ESM) for ionic systems, resolving intrinsic electromechanical mechanisms as well as quantitative response remains challenging for complex media. In this talk, we introduce the basic concept of ds-SPM, highlight its various issues, and propose a number of techniques to overcome these difficulties. We show that first and second harmonic ds-responses can be used to distinguish piezoelectric and electrochemical strains, with which we reveal the co-existence of alternating polar and nonpolar domains in the emerging perovskite solar cells that correlate with photovoltaic conversion, and we shed new insight into the resistive switching in ultrathin ferroelectric heterostructures in the absence of polarization reversal. We also develop sequential excitation SPM, empowered by deep data, to determine intrinsic electromechanical coupling quantitatively at the nanoscale, wherein conventional methods fail. Finally, we present a vision for a big data SPM, wherein advanced data acquisition and analytics are coupled with machine learning and artificial intelligence to accelerate mechanistic understanding via scanning probe.



Jiangyu Li is a Professor in the Department of Mechanical Engineering, University of Washington. He obtained his B.E. degree in 1994 from the Department of Materials Science and Engineering, Tsinghua University, and Ph.D. degree in 1998 from the Department of Mechanical Engineering, University of Colorado-Boulder. Li works in the general field of mechanics of materials, focusing on advanced scanning probe microscopy and its applications in functional materials. He has published over 200 journal articles, and has been recognized by Sia Nemat-Nasser Medal from ASEM, Young Investigator Award from ICCES, and Microscopy Today Innovation Award from Microscopy Society of America. He currently serves as Associate Editor for Journal of Applied Physics and Science Bulletin.