Piezoresponse Force Microscopy를 이용한 Pb(Zr,Ti)O3 세라믹의 단계적 Poling에 의한 강유전체 도메인 진화 과정 관찰

김관래 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.1

Ferroelectric material properties are strongly governed by domain structures and their evolution processes, butthe evolution processes of complex domain patterns during a macroscopic electrical poling process are still elusive. Inthe present work, domain-evolution processes in a PZT ceramic near the morphotropic phase-boundary composition werestudied during a step-wise electrical poling using piezoresponse force microscopy (PFM). Electron backscatter diffractionwas used with the PFM data to identify the grain boundaries in the region of interest. In response to an externally theapplied electric field, growth and retreat of non-180° domain boundaries wasere observed. The results indicate thatferroelectric polarization-switching nucleates and evolves in concordance with the pattern of the pre-existing domains. 강유전체의 물성들은 도메인 구조와 도메인 진화과정에 의해 결정되지만, 거시적인 폴링 과정에 의해 발생하는 복잡한 도메인 패턴의 진화과정들에 대한 이해는 아직 명확하지 않다. 본 연구에서는, 단계적인 전기적 폴링과정 중, Morphotropic Phase Boundary 근처의 PZT 세라믹에서 발생하는 도메인 진화과정들을 Piezorespnose Force Microscopy (PFM)을 이용하여 관찰하였다. 관찰하고자 하는 그레인 경계를 이미징하기 위해 PFM과 함께 EBSD를 사용하였다. 얻게 된 PFM 이미지들로부터, 외부 전기장에 의해 성장하고 물러서는 non-180° 도메인 구조들이 관찰되었다. 결과들로부터, 강유전체 분극 스위칭은 기존에 존재하던 도메인 패턴들의 진화에 의하여 진행됨을 알 수 있다.

Piezoresponse Force Microscopy를 이용한 Pb(Zr,Ti)O₃ 세라믹의 단계적 Poling에 의한 강유전체 도메인 진화 과정 관찰

김관래,Kim, Kwanlae 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.1

Ferroelectric material properties are strongly governed by domain structures and their evolution processes, but the evolution processes of complex domain patterns during a macroscopic electrical poling process are still elusive. In the present work, domain-evolution processes in a PZT ceramic near the morphotropic phase-boundary composition were studied during a step-wise electrical poling using piezoresponse force microscopy (PFM). Electron backscatter diffraction was used with the PFM data to identify the grain boundaries in the region of interest. In response to an externally the applied electric field, growth and retreat of non-$180^{\circ}$ domain boundaries wasere observed. The results indicate that ferroelectric polarization-switching nucleates and evolves in concordance with the pattern of the pre-existing domains.

Flexoelectric effect via piezoresponse force microscopy of domain switching in epitaxial PbTiO3 thin films

안윤호,손종영 한국세라믹학회 2024 한국세라믹학회지 Vol.61 No.1

The flexoelectric effect can be exploited to control the polarization and domain structure in ferroelectric materials, potentially benefiting applications, such as nanoscale electromechanical systems, memory devices, and sensors. We report ferroelectric domain switching characteristics of PbTiO3 (PTO) thin films induced by the flexoelectric effect. Epitaxially (001)-oriented PbTiO3 (PTO) thin films were deposited on single-crystal Nb-doped SrTiO3 substrates by pulsed laser deposition. Through the use of a piezoelectric force microscope and two surface electrodes, polarization domains were created vertically and horizontally within the PTO film. When subjected to a vertical external force, the domains with vertical orientation exhibited predictable switching behavior. Conversely, by imposing a vertical force during the scanning of domains oriented horizontally, we observed the formation of new domains with vertical orientation. However, in conditions where a vertical force was applied counter to the alignment of the horizontal domains, the anticipated switching of the vertical domains did not manifest. This study demonstrates that the flexoelectric effect can be harnessed to manipulate the switching of ferroelectric domains in PTO thin films using piezoresponse force microscopy.

Non-piezoelectric effects in piezoresponse force microscopy

Seol, Daehee,Kim, Bora,Kim, Yunseok Elsevier 2017 Current Applied Physics Vol.17 No.5

<P>Piezoresponse force microscopy (PFM) has been used extensively for exploring nanoscale ferro/piezo-electric phenomena over the past two decades. The imaging mechanism of PFM is based on the detection of the electromechanical (EM) response induced by the inverse piezoelectric effect through the cantilever dynamics of an atomic force microscopy. However, several non-piezoelectric effects can induce additional contributions to the EM response, which often lead to a misinterpretation of the measured PFM response. This review aims to summarize the non-piezoelectric origins of the EM response that impair the interpretation of PFM measurements. We primarily discuss two major non-piezoelectric origins, namely, the electrostatic effect and electrochemical strain. Several approaches for differentiating the ferroelectric contribution from the EM response are also discussed. The review suggests a fundamental guideline for the proper utilization of the PFM technique, as well as for achieving a reasonable interpretation of observed PFM responses. (C) 2016 Elsevier B.V. All rights reserved.</P>

Non-piezoelectric effects in piezoresponse force microscopy

설대희,김보라,김윤석 한국물리학회 2017 Current Applied Physics Vol.17 No.5

Piezoresponse force microscopy (PFM) has been used extensively for exploring nanoscale ferro/piezoelectric phenomena over the past two decades. The imaging mechanism of PFM is based on the detection of the electromechanical (EM) response induced by the inverse piezoelectric effect through the cantilever dynamics of an atomic force microscopy. However, several non-piezoelectric effects can induce additional contributions to the EM response, which often lead to a misinterpretation of the measured PFM response. This review aims to summarize the non-piezoelectric origins of the EM response that impair the interpretation of PFM measurements. We primarily discuss two major non-piezoelectric origins, namely, the electrostatic effect and electrochemical strain. Several approaches for differentiating the ferroelectric contribution from the EM response are also discussed. The review suggests a fundamental guideline for the proper utilization of the PFM technique, as well as for achieving a reasonable interpretation of observed PFM responses.

Distinct ferroelectric domain switching dynamics in epitaxial BiFeO3 (001) capacitors depending on the bias polarity

임소연,박민선,위상원,정진석,양상모 한국물리학회 2020 Current Applied Physics Vol.20 No.10

Understanding ferroelectric domain switching dynamics at the nanoscale is a great of importance in the viewpoints of fundamental physics and technological applications. Here, we investigated the intriguing polaritydependent switching dynamics of ferroelectric domains in epitaxial BiFeO3 (001) capacitors using transient switching current measurement and piezoresponse force microscopy. We observed the distinct behavior of nucleation and domain wall motion depending on the polarity of external electric bias. When applying the negative bias to the top electrode, the sideways domain wall motion initiated by only few nuclei was dominant to polarization switching. However, when applying the positive bias, most of domains started to grow from the preexisted pinned domains and their growth velocity was much smaller. We suggest that the observed two distinct domain switching behavior is ascribed to the interfacial defect layer.

Quantitative Analysis of the Nucleation and Growth of Ferroelectric Domains in Epitaxial Pb(Zr,Ti)O3 Thin Films

S. M. Yang,J. W. Heo,H. N. Lee,송태권,윤종걸 한국물리학회 2009 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.55 No.2

We determined simultaneously the domain wall speed (v) and the nucleation rate (N) of ferroelectric (FE) domains in 100 nm-thick epitaxial PbZr0.2Ti0.8O3 capacitors from successive domain evolution images under various applied electric fields (Eapp) by using piezoresponse force microscopy. We found that, at a given Eapp, the v and the N values decreased as the switching process proceeded. The averaged domain wall speed < v > was confirmed to follow the Merz’s law, < v > ∝ exp[–(E0/Eapp)], with an activation field E0 of about 700 kV/cm. Moreover, we found that the nucleation process played a more important role in the FE domain switching at higher fields while domain wall motion mainly contributed to the switching at lower fields.

Direct Observation of Domain Motion Synchronized with Resistive Switching in Multiferroic Thin Films

Lee, Ji Hye,Yoon, Chansoo,Lee, Sangik,Kim, Young Heon,Park, Bae Ho American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.51

<P>The room-temperature resistive switching characteristics of ferroelectric, ferroelastic, and multiferroic materials are promising for application in nonvolatile memory devices. These resistive switching characteristics can be accompanied by a change in the ferroic order parameters via applied external electric and magnetic excitations. However, the dynamic evolution of the order parameters between two electrodes, which is synchronized with resistive switching, has rarely been investigated. In this study, for the first time, we directly monitor the ferroelectric/ferroelastic domain switching dynamics between two electrodes in multiferroic BiFeO3 (BFO) planar devices, which cause resistive switching, using piezoresponse force microscopy. It is demonstrated that the geometrical relationship between the ferroelectric domain and electrode in BFO planar capacitors with only 71 domain walls significantly affects both the ferroelectric domain dynamics and the resistive switching. The direct observation of domain dynamics relevant to resistive switching in planar devices may pave the way to a controllable combination of ferroelectric characteristics and resistive switching in multiferroic materials.</P>

Origins of domain wall pinning in ferroelectric nanocapacitors

김윤석,Han Hee,Vrejoiu Ionela,Lee Woo,Hesse Dietrich,Alexe Marin 나노기술연구협의회 2014 Nano Convergence Vol.1 No.24

We have investigated domain wall pinning and its origins in ferroelectric nanocapacitors using piezoresponse force microscopy. Domain wall pinning of two different types was observed in the nanocapacitors. The first type of pinning originates from local point defects similar to previous reports. The second one originates from immobile local defects in the place of pristine domains. In both cases, pinning and de-pinning processes were observed without significant domain wall bowing. The results can be helpful to understand domain wall motion and improve the reliability of nanoscale ferroelectric memory devices.

Advances in Atomic Force Microscopy for the Electromechanical Characterization of Piezoelectric and Ferroelectric Nanomaterials

김관래 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.9

Given the social demand for self-powering wearable electronics, it is necessary to develop composite materials that exhibit both good flexibility and excellent piezoelectric performances. Intensive research on synthesis methods and devising characterization techniques for piezoelectric nanomaterials in various forms has been conducted. In particular, characterization techniques for piezoelectric nanomaterials require different approaches from those for conventional bulk materials. Atomic force microscopy (AFM)-based characterization techniques work based on the local physical interactions between the AFM tip and sample surfaces, making them an irreplaceable tool for studying the electromechanical properties of piezoelectric nanomaterials. Piezoresponse force microscopy (PFM), conductive AFM (C-AFM), and lateral force microscopy (LFM) are three representative AFM-based techniques used to characterize the piezoelectric and ferroelectric properties of nanomaterials. Coupled with the appearance of diverse novel nanomaterials such nanowires, free-standing nanorods, and electrospun nanofibers, AFM-based characterization techniques are becoming freer from artifacts and the need for quantitative measurements. PFM was initially developed to image the microstructures of piezoelectric materials, and well-calibrated techniques designed to realize quantitative measurements have been applied to nanomaterials. In contrast, C-AFM and LFM were initially used to measure the conductivity of diverse materials and the nanotribology of material surfaces. Over the last decade, they have proved their versatility and can now be used to evaluate the direct piezoelectric effect and the mechanical properties of piezoelectric nanomaterials. In these cases, systematic understanding with regard to the measurement principles is required for accurate measurements and analyses. In the present review article, we discuss earlier work in which AFM-based electromechanical characterization techniques were applied to nanomaterials to evaluate piezoelectric and ferroelectric properties. Also discussed is the importance of gaining a comprehensive understanding of the resulting signals.