Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session X04: Dielectric & Ferroic Oxides -- Structure & Functionality of Ferroic Domain WallsFocus
|
Hide Abstracts |
Sponsoring Units: DMP DCOMP Chair: Javier Junquera, University of Cantabria Room: BCEC 107C |
Friday, March 8, 2019 8:00AM - 8:12AM |
X04.00001: Electronic structure of domain walls in strontium titanate C Stephen Hellberg At low temperatures, SrTiO3 transforms from cubic to tetragonal, and twin domain boundaries form. We present density functional calculations of this system, focusing on the conduction-band states bound to the domain walls. Spin-orbit coupling strongly modifies the low-energy states. Two types of domain walls form which have different relative phases of the rotation of the oxygen octahedra in the bulk regions. The two types of domain walls have significantly different electronic states. The importance of the domain walls on electron pairing without superconductivity in this system will be discussed. |
Friday, March 8, 2019 8:12AM - 8:24AM |
X04.00002: Electronic structure of twin wall/surface intersections in CaTiO3 (001) Nicholas Barrett, Qiang Wu, Ekhard Salje, Ziyuan Zhao, Claire Mathieu, Christophe Lubin, Dominique Martinotti Domain wall engineering of functional oxides provides a new paradigm for post-CMOS electronics [1]. Domain walls are potentially the perfect structural discontinuity, maintaining the crystalline phase but defining a change in the functional order parameter. |
Friday, March 8, 2019 8:24AM - 8:36AM |
X04.00003: Nature of the Atomic Structure Underlying the Vortex Polarization Domains in Hexagonal RMnO3 Han Zhang, Sizhan Liu, SuYin Grass Wang, Yu-Sheng Chen, Sang-Wook Cheong, Trevor Tyson Hexagonal phase RMnO3 systems exhibit polarization domains with complex vortex pattern with density depending on the cooling rate from the high temperature paraelectric phase. Structural measurements are used to probe the structure on length scales commensurate with the variations in polarization. Structural measurements reveal variations on the lenghtscale of the changes in polarization. |
Friday, March 8, 2019 8:36AM - 9:12AM |
X04.00004: Towards adaptable nano-circuitry - functional domain walls and disorder engineering in improper ferroelectrics Invited Speaker: Donald M. Evans Oxide materials exhibit a broad range of tunable phenomena, including magnetism, multiferroicity, and superconductivity. Oxide interfaces are particularly intriguing. The low local symmetry combined with the sensitivity to electrostatics and strain leads to unusual physical properties. Recently, ferroelectric domain walls have attracted attention as conducting and spatially mobile interfaces. In order to ultimately design domain-wall-based devices and circuitry, however, additional functionality beyond just conduction is required. |
Friday, March 8, 2019 9:12AM - 9:48AM |
X04.00005: Probing Microwave Dynamics of Ferroelectric Domain Walls Invited Speaker: Keji Lai The past decade has witnessed the emergence and rapid development of domain wall (DW) nanoelectronics, which take advantage of the enhanced electronic conductivity at ferroelectric DWs due to the accumulation of free carriers. For practical high-speed electronics, however, the dielectric dispersion of ferroelectric materials at microwave frequencies has to be taken into account. Using a cohort of imaging techniques such as piezo-force microscopy, conductive atomic-force microscopy, and microwave impedance microscopy, we are able to determine the contribution of both mobile carriers and bound dipoles to the GHz response at ferroelectric domain walls. In LiNbO3, BiFeO3, and YMnO3, the effective microwave conductivity of certain DWs is higher than that at DC by several orders of magnitude, while other walls behave the same at both DC and AC. First-principles and model calculations indicate that the AC-conductive DWs exhibit a localized vibrational mode, which can be excited by the alternating electric fields from the tip. In addition to the DW dynamics, the local electromechanical energy transduction in ferroelectric domains can also be visualized by the microwave probe. Our work opens up a new avenue to explore various phenomena in complex materials and novel devices by near-field electromagnetic imaging. |
Friday, March 8, 2019 9:48AM - 10:00AM |
X04.00006: Microwave Conductivity of Ferroelectric Domain Walls in BiFeO3 Bulk Crystals Lu Zheng, Xiaochen Fang, Xianghan Xu, Sang-Wook Cheong, Keji Lai Domain walls (DWs) in multiferroic materials exhibit novel functionalities that may be utilized for nanoelectronic applications. In recent years, the enhanced DW dc conductivity due to the accumulation of free carriers and ac conductivity due to the excitation of wall vibration have both been reported in various ferroelectrics. Combining piezo-force microscopy and microwave impedance microscopy, we directly probe the nanoscale dielectric response of various DWs in BiFeO3 bulk crystals at microwave frequencies. Interestingly, regardless of the type of the walls (71-, 109-, or 180-degree), the neutral DWs always display high ac conductivity around 1 GHz, whereas the charged walls do not. In addition, interference of surface acoustic waves can be observed near the 180-degree walls. Our results provide a unified picture to understand the DW dynamics in BiFeO3, which is crucial for its application in high-speed nano-devices. |
Friday, March 8, 2019 10:00AM - 10:12AM |
X04.00007: Thermal effect on domain wall roughness in epitaxial PbZr0.2Ti0.8O3 thin films with different as-grow polarization orientations Kun Wang, Jingfeng Song, Le Zhang, Xuegang Chen, Xia Hong In epitaxial ferroelectric films, the asymmetric boundary condition can lead to strong polarization asymmetry that affects the thermal stability of different polar states. We have carried out piezo-response force microscopy (PFM) studies on the thermal evolution of domain walls (DW) in epitaxial 50 nm PbZr0.2Ti0.8O3 (PZT) films grown on (La,Sr)MnO3 and LaNiO3 buffered SrTiO3, which show different as-grown polarization. We wrote stripe-domains and identified the DWs from the PFM images. The correlation function of the DW roughness depends on the distance L along the DW as L2ζ. At room temperature, the roughness exponent ζ is 0.2-0.3, consistent with 2D DWs in weak random bond disorder. The films were then heated at progressively higher temperatures till approaching TC. The subsequent PFM images show that ζ gradually increases to ~0.6, evolving to dominant thermal roughening. Both the bottom electrode type and the as-grown polarization orientation affect the T-dependence of ζ. We also compare the results obtained from in situ high temperature measurements and rapid thermal quench. Our study provides critical information about the thermal stability and size scaling limit of epitaxial thin films-based ferroelectric devices. |
Friday, March 8, 2019 10:12AM - 10:24AM |
X04.00008: Giant electroresistance effect in single-crystalline lithium niobate thin films enabled by domain wall control James McConville, Haidong Lu, Michele Conroy, Kalani Moore, Alexey Lipatov, Alexander Sinitskii, Alexei Gruverman, Ursel Bangert, Marty Gregg One of the most prominent features of ferroelectric domain walls (DWs) is their electrical conductivity, which was observed in a number of materials, such as BiFeO3, Pb(Zr,Ti)O3, ErMnO3. We combine scanning transmission electron microscopy (STEM) and local probe techniques to investigate the conduction through charged DWs in the ion-sliced single-crystalline LiNbO3 thin films with sub-µm thickness. STEM shows large inclination of the electrically-generated 180° DWs away from the polar z-axis (with angles reaching 16°) suggesting the DWs are strongly charged. Using piezoresponse force microscopy (PFM) in combination with conductive atomic force microscopy (CAFM) it was shown that head-to-head DWs have higher conductivity than the tail-to-tail DWs, suggesting an electronic type of conductance. One of the most important findings is a modulation of conductivity by an external voltage. It is demonstrated that the resistance of the LiNbO3 thin film capacitors can be changed continuously by 5 to 9 orders of magnitude by controlling the DW perimeter allowing development of multi-level resistive switching devices. Resistance states can be altered by exposure to cumulative voltage pulses, suggesting that these domain wall memristors might be useful in the context of artificial synapses. |
Friday, March 8, 2019 10:24AM - 10:36AM |
X04.00009: Dipole-dipole interaction and domain relaxation of ferroelectric triangular lattice Hye-Jin Jin, Chang Jae Roh, Janghyun Jo, Junsik Mun, Jongseok Lee, Miyoung Kim, Young-Han Shin, William Jo In ferroelectric lattices, dipole arrangements are controlled by manipulating structural formation and orientations of ferroelectric thin films are determining factor to control dipole arrangements. Herein, tetragonal PbTiO3 (PTO) thin films were obtained and triangular lattice is observed in (111)-PTO thin films. We used pulsed laser deposition and compared (001)- and (111)-PTO thin films. To confirm structural characteristics, X-ray diffraction patterns and second harmonic generations were used. In addition, dipole arrangements are investigated by using transmission electron microscopy. In particular, directions of dipoles are gradually changed and vortex-like domain structure is obtained in the (111)-PTO thin films. It is induced by tilting characteristics of polarization axes of the (111)-PTO thin films. To study domain relaxation, temporal change of domain is obtained by using piezoresponse force microscopy and a stretched exponential decay mechanism is applied. In the (111)-PTO thin films, dipole frustration is induced because of poling and redistribution of dipoles occurred to release dipole frustration. During relaxation, dipole-dipole interaction should be addressed and it gives a deep insight to understand fundamental relaxation mechanism of ferroelectric thin films. |
Friday, March 8, 2019 10:36AM - 10:48AM |
X04.00010: Designing ferroic domain states and coupling through low-energy He-irradiation Andreas Herklotz, Robert Roth, Kathrin Dorr, Yogesh Sharma, Thomas Ward The physical properties of ferroic thin films are typically dominated by their domain configurations and the response of domain walls to external fields. Domain engineering has thus developed as a powerful tool to tailor functionalities of oxide thin films. A particularly successful approach has been the use of strain fields through heteroepitaxy. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700